(Araceae), Annals of the Missouri Botanical Garden

319 Pages·2016·30.49 MB·English

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Volume 78
Number 3
Volume 78, Number 3 Annals of the
Fall 1991 Missouri Botanical Garden
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THIS PUBLICATION IS PRINTED ON ACID-FREE PAPER.
Volume 78 Annals
Number 3 of the
1991 Missouri
Botanical
Garden
A REVISION OF ANTHURIUM Thomas B. Croat'
SECTION PACHYNEURIUM
(ARACEAE)1
ABSTRACT
This is the first published revision of Anthurium sect. Pachyneurium since that of Engler in 1905. Section
Pachyneurium is one of 19 sections (all but one of which were treated by Engler, 1905, in his revision of Anthurium).
The section consists of 114 species representing 126 taxa in two series. series Pachyneurium Schott, and the new
series Multinervia Croat, with 110 and 16 taxa respectively. Forty-eight taxa (including nine subspecies or varieties)
are described as new.
Section Pachyneurium is one of I 9 recognized gin rolled around the midrib and the rolled up
for Anthurium and is perhaps the most easily rec opposite margin (like a continuous coil in cross
ognizable and well-defined group in the genus. It section).
was for this reason, despite its size and taxonomic The section consists of two series with most
difficulty, that this section was chosen as a starting species in series Pachyneurium. The other series,
point for a revision of the genus. Section Pachy Multinervia, is restricted to the Andes of South
neurium is generally defined by its frequently rosu· America, especially in Ecuador. Series Pachyneu
late or "bird's-nest" habit, its short, densely rooted rium contains all the species originally included in
caudex, the commonly short-petiolate, oblanceolate grex Pachyneurium by Schott (1860), and most
to obovate, mostly coriaceous leaf blades with usu of those included by Engler (1905) in sect. Pachy
ally free-ending primary lateral veins and, most neurium. Series Multinervia contains species un
importantly, the involute vernation (rolled inward known to Schott and mostly unknown to Engler.
from both margins) of the developing leaves (Fig. The few species of series Multinervia treated by
I). All other sections of Anthurium, and indeed all Engler were incorrectly placed in sect. Polyneu
other genera of Araceae (except Lagenandra), rium or in sect. Urospadix, the latter having been
have convolute vernation (Fig. 2), with one margin employed by Engler as a rather broad "dumping
rolled inward toward the midrib and the other mar- ground." See Appendixes I and 2, respectively,
'This study was completed with support from National Science Foundation grants DEB 80·11649 and BSR
8306297. Support for publication was provided in part by National Science Foundation grant BSR.8914018.
'P.A. Schulze, Curator of Botany, Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299,
U.S.A.
ANN. MISSOURI BOT. GARD. 78: 539-855. 1991.
540 Annals of the
Missouri Botanical Garden
for the ultimate disposition of species treated in refers to the color at anthesis, i.e., when the spadix
sect. Pach yneurium by Schott and by Engler. See is producing stigmatic droplets or when fresh sta
Appendix 3 for the disposition of all currently rec mens are emerging. Colors referenced in the de
ognized Pachyneurium species and their sectional scriptions that follow are taken from the color chart
placement in the revisions of both Schott and En by Berlin & Kay ( 1969). This is hereafter cited
gler. as B & K. This color chart, available from the
University of California Press, is a reproduction of
the Munsell Color Array of 40 hues, at maximum
METHODS AND MATERIALS
saturation, with nine degrees of brightness. The B
This revision was based on field studies in Central & K color chart represents 40 hues in the vertical
America between 1967 and 1979 and in South columns and nine degrees of brightness in the hor
America in 1969 (Colombia), 1972 (Peru), 1976 izontal rows. Colors are arranged in I 0 basic clus
(Colombia and Ecuador), 1980, 1983, 1984 (west ters with four different hues per cluster, ranging
ern South America), 1984 (Venezuela), and 1986 from red through yellow, green, blue, purple, and
(western South America and Brazil). AU but 28 of finally red-purple. The four columns for each color
the 125 taxa were studied live or are under cul cluster are numbered 2.5, 5, 7 .5, and I 0. These
tivation at the Missouri Botanical Garden. Except numbers are repeated for each basic color type.
for those so indicated, all descriptions can be as The colors from the B & K color chart are read
sumed to have been prepared from both living and by first reporting the color, then the row followed
dried material. Morphological characters were cod by the column. For example, the third color in the
ed directly into a computerized database to ensure fifth row in the red area would be called Red 517 .5.
parallel and sortable descriptions. The aroid de The second color in the eighth row would be called
scriptions database contains 228 characters thal Red 8/5.
are used to describe the morphological diversity All estimates of ecological zones given in this
expressed by Anthurium. The database also pro paper are based on either Holdridge Life Zone maps
vides a means of sorting species by characters for for most Central American countries and for Pan
writing keys, as well as for compiling lists of various ama or on the "Mapa de tipos de vegetacion de
character states. In addition, the database can be la Republica Mexicana" (Flores et al., 1971). As
put to future use for identifications and for additions yet no study has been made to correlate the veg
of new species for other treatments. The description etation types represented on the Mexican map with
file is directly tied to a nomenclatural database those of the Holdridge Life Zone system. For an
containing all species names and publication data understanding of the latter system, see Holdridge
for all A raceae species stored in T ropicos (Crosby, et al. (1971 ). For South America, maps based on
1986; Crosby & Magill, 1986). Each species is the Holdridge System were used for Bolivia, Co
represented by a unique number, which ties it to lombia, Ecuador, Peru, and Venezuela.
data in other files associated with the species. Dis Mention should be made of the distribution of
cussions and exsiccatae are also stored in separate herbarium material of Araceae under cultivation.
files, as are synonyms, but all parts are automat Herbarium material may consist of one of three
ically reassembled for the final treatment. Herbar kinds: (I) fertile original (wild) collections; (2) sterile
ium specimens can be added to the exsicca tae original collections with an inflorescence added from
database at any time and sorted in a standardized the cultivated plant of the same number (generally
manner before being printed out. Thus, exsiccatae the same individual from which the field specimens
records can be added up to the last moment, even were made); and (3) material collected entirely
when the manuscript has been completed. Species from the cultivated plant. Specimens based entirely
descriptions are decoded into narrative text auto or in part on cultivated material are clearly indi
matically from the descriptor base and require only cated as such in herbaria.
minor editing to put them in a publishable form.
Final treatments may be saved on hard disk or
ACKNOWLEDGMENTS
stored on tape, but the coded description data (which
use very little core storage space) are a part of the I acknowledge the assistance of numerous hor
permanent Tropicos database and can be used for ticulturists who provided living material, especially
other projects such as floras or ecological studies. M. R. Birdsey, C. McDaniel, J. Williford, R. Burle
The terminology and usage in the descriptions Marx, S. Mayo, M. Carmichael, J. Brenner, S.
in this paper are defined by Croat & Bunting ( 1979). Thompson, F. Fuchs, and T. Fennell, Jr., and to
The color of the spadix, unless otherwise indicated, others who provided observations on leaf vernation
Volume 78, Number 3 Croat 541
1991 Anthurium sect. Pachyneurium
and fruit color, namely J. Banta, C. Fleming, M. rium were described in the genus Pothos: Pothos
H. Grayum, and R. Sheffer. R. Sheffer also has crassinervia was described by Jacquin in l 793
assisted greatly by studying the cytology and breed and transferred to Anthurium by Schott in 1832.
ing behavior of Pachyneurium at the University The other two were Pothos solitarius Veil. Cone.
of Indiana Northwest. I thank the following insti described in 1829, and P. maxima Desf., described
tutions, which loaned or allowed me to study their in 1832. The former was transferred to Anthurium
specimens: A, AAU, B, BH, BM, BR, C, CAS, by Schott in his Prodromus ( 1860), while the latter
CAY, CHAPA, CM, COL, CR, DUKE, ECON, was transferred to Anthurium by Engler in 1905
ENCB, F, ITC, G, GB, CH, CUA, HUA, IAN, and is here treated as a nomen dubium owing to
IBE, INPA, ITIC, K, LAM, LL, M, MEDEL, the inability to place it with certainty in any cur
MEXU, MG, MICH, MY, NY, P, PMA, QCA, rently recognized species. The genus Pothos as
QCNE, R, RB, S, SEL, SI, TEX, U, UC, UCLA, now circumscribed is restricted to Africa and Asia,
UFMG, UB, US, USM, VEN, W, WIS, WAG, especially Southeast Asia. Modern suprageneric
XAL. Also acknowledged are reviewers D. H. Nic classifications do not place Pothos close to An
olson and M. H. Grayum, especially the extensive thurium. Grayum (1984) places it in a separate
work with the manuscript by Grayum. I also thank tribe, Potheae in the subfamily Pothoideae. Gray
Nicolson for his considerable help with thorny no um considers Anthurium isolated but closer to Pa
menclatural problems with Pachyneurium. thos than to any other genus. He places Anthurium
Special credit goes to volunteer workers, in in a separate tribe Anthurieae in the same subfam
cluding A. E. Westhoff and Patricia Croat, for ily. Bogner & Nicolson (in press) remove Anthur
preparation of Latin descriptions, and to the latter ium from the Pothoideae altogether and place it
for final editing; to Kay Rossmann for typing and in the subfamily Lasiodeae, leaving Pothos in the
editing all parts except the descriptions and exsic Pothoideae with only two other closely related gen
catae; to Edwina Medlock for a two-year pheno era, Pedicellarum and Pothoidium.
logical study of leaf, flower, and fruit production The epithet Pachyneurium was first used in
and for her cross-pollination program; to my tech I 860 by H. W. Schott in his first revision of the
nical staff for assisting with the project, including Araceae in Prodromus Systematis Aroidearum.
past research assistants Frances Mazanec (1980- Although no Anthurium species were treated in
1985) and Honora Murphy (1986); to the green his earlier Synopsis Aroidearum in 1856, 20 spe
house staff, Petra Malesevich and Mary N yswon cies were treated in the Prodromus. Half of these
ger, for answering repeated queries, transporting were described by Schott himself in that work or
a myriad of plants to the office, pollinating plants, in earlier works during the previous decade. Others
harvesting fruits, and keeping records on pheno were described by Karl Koch or Frederick Lieb
logical changes; and to Rob Wilds and Dan Mount mann during the same decade. In addition to the
for participating in the pollination program. four species described as Pothos mentioned above,
Most special thanks to my current research as only one species of sect. Pachyneurium, A. cras
sistants, who helped me bring the project to com sinervium (Jacq.) Schott (described as Pothos cras
pletion: to Anna Brzyski for describing plants, en sinervia in l 793), was described before the early
tering descriptions, and assembling the final 1850s. Three of the 20 names included in Schott's
manuscript for descriptions, exsiccatae and species 1860 revision, namely A. acaule (Jacq.) Schott,
excluded; to Dylan Hannon for assisting in all phases A. hookeri Kunth and A. aduncum (Veil. Cone.)
of the project, especially in generating the South Schott, were published before 1850 but these have
American species key, assembling illustrations and been excluded from Pachyneurium and placed in
final editing, and to Petra Malesevich, who assisted other sections (see Appendix l ).
in the final editing process. The revision could not Of the remaining Pachyneurium names in
have been finished without the able assistance of Schott's 1860 revision, only nine species remain.
these dedicated staff and volunteers. These include A. wagenerianum K. Koch &
Bouche, A. fendleri Schott, A. spectabile Schott,
A. crassinervium (Jacq.) Schott, A. affine Schott,
HISTORY OF SECTION PACHYNEUR/UM A. schlechtendalii Kunth, A. crenatum (L.) Kunth
The first species of sect. Pach yneurium as it is (erroneously treated by both Schott and Engler as
recognized here was described by Linnaeus (17 63) A. acaule (Jacq.) Schott (Mayo, 1982)), A. dom
in Species Plantarum as Pothos cren<tta, and was beyanum Brongn. ex Schott, and A. solitarium
transferred to Anthurium by Kunth in 1841. Three (Veil. Cone.) Schott. Still other species of sect.
other species clearly belonging to sect. Pachyneu- Pachyneurium were described in Schott's revision,
542 Annals of the
Missouri Botanical Garden
but these he included in other groups (termed A. leonianum Sodiro
"greges" by Schott). These included A. protensum A. acutifolium Engl.
Schott (included in grex Erythropodium), A. oxy A. latissimum Engl.
pum Poeppig and A. consobrinum Schott (grex A. barclayanum Engl.
Oxycarpium), and A. oerstedianum Schott (in A. ernestii Engl.
cluding its synonym, A. cuspidifolium Schott) in A. salviniae Hemsley
grex Xialophyllium. Thus, a total of 13 species A. lindmanianum Engl.
of Pachyneurium were included in Schott's revi A. martianum K. Koch & Kolb
sion, even though some were not recognized as A. selloum K. Koch
such. A. pallatangense Engl.
In Engler's 1905 revision, 62 names were in A. linguifolium Engl.
cluded in sect. Pachyneurium (Appendix 2). Of Until recent times, relatively few taxa of Pachy
this total, only 18 species were actual Pachyneu neurium had been described subsequent to Engler's
rium species not already included in Schott 's re revision. A list of the names published subsequent
vision. Fourteen of the names included by Engler to Engler's time and prior lo the beginning of this
(in reality only 12 species, since two were syn work is presented here:
onyms), including A. hookeri Kunth, A. hacu
A. agoyanense Sodiro = A. dombeyanum Brongn.
mense Engl., A. weberbaueri Engl., and all species
ex Schott
numbered 52 through 62, have subsequently been
var. agoyanense ( 1905) = A. dombeyanum
proven to be non-Pachyneurium (see Appendix 2).
Brongn.
Ten names included by Engler were synonyms of
var. eleutheroneuron. Sodiro (1905) =A. dom
earlier names in Schott's revision, three names
beyanum Brongn.
were synonyms of older names in Engler's own
A. angustilaminatum Engl.
revision and four names have been excluded be
var. albidum Sodiro (1906) = A. angustilam
cause of confusion in the nomenclature (see Species
inatum Engl.
Excluded section). These are A. maximum ( Desf.)
var. brevipes Sodiro ( 1 906) = A. angustilam
Engl., A. cymatophyllum K. Koch & Sellow, A.
inatum Engl.
agnatum Schott, and A. tricarinatum Sodiro.
var. crassum Sodiro (1906) = A. angustilam
In addition to the 18 species that Engler added
inatum Engl.
to those Schott had included in his grex Pachy
var. gladiatum Sodiro (1906) = A. angusti
n.eurium, Engler included the following elsewhere:
laminatum Engl.
A. oxycarpum (sect. Oxycarpium), A. pallatan.
A. atropurpureum R. Schultes & Maguire
gense Engl. (sect. Polyneurium), A. oerstedian.um
var. atropurpureum ( 1953)
Schott (including A. cuspidifolium Schott, in sect.
var. apertum R. Schultes (1954) = A. bon.
Urospadix, series Obscureviridia), A. linguifoliu.m
plandii R. Schultes & Maguire subsp. bon
Engl. (sect. Urospadix, series Flavescentiviridia),
plandii
and A. spathiphyllum N. E. Br. (sect. Episeio
A. bonplandii Bunting (1975)
stenium). Of these, only A. pallatangense and A.
A. concolor K. Krause ( 1932)
linguifolium had not been treated by Schott.
A. fasciale Sodiro (1905)
Thus, in the 45 years between the publication
A. giganteum Matuda (1950) = A. salviniae
of Schott's revision in 1860 and Engler's treatment
Hemsley
for Das Pjl.anzenreich in 1905, an additional 22
A. guayanum Bunting (1975) = A. bonplandii
valid species were described, bringing the total
Bunting subsp. guayanum (Bunting) Croat
number of Pachyneurium species to 33. The spe
A. lanjouwii Jonker & Jonker (1966)
cies included by Engler, but not by Schott, in the
A. maguirei A. Hawkes (1948)
present concept of sect. Pachyneurium were as
A. ottonis K. Krause (1932)
follows (in the order presented in the revision):
A. rodrigoi A. Hawkes ( 1948) =A. paraguayense
Engl.
A. pendulifolium N. E. Br.
A. superbum Madison (I 978)
A. paraguayense Engl.
A. tessmannii K. Krause ( 1932) A. uleanum
A. josean.um Engl. (= A. protensum Schott)
Engl.
A. jenmanii Engl.
A. wurdackii Bunting (1975)
A. uleanum Engl.
A. tarapotense Engl. Of the 21 names listed above, 10 still represent
A. cubense Engl. valid taxa, while the remainder have here been
Volume 78, Number 3 Croat 543
1991 Anthurium sect. Pachyneurium
synonymized. This ra·ises to 46 the number of taxa prevalent in ~reas where there is a pronounced dry
of sect. Pachyneurium at the time this researcher season, especiaUy in areas of tropical moist forest.
began working with the Araceae (in approximately While species in sect. Pachyneurium occur in most
I 97 6 ). Subsequent to I 97 6, an additional 16 spe life zones, most occur in tropical dry, premontane
cies of sect. Pachyneurium have been described. dry, and tropical moist forest. Relatively few spe
In "The Genus Anthurium (Araceae) in Costa cies occur in tropical wet, premontane wet, or
Rica," Croat & R. A. Baker (1979) described six montane wet forest life zones. No Pachyneurium
additional species: A. brenesii, A. prolatum, A. species is known from pluvial tropical forest.
schottianum, A. seibertii, A. standleyi, and A. In habit, especiaUy in terms of their short stems,
upalaense. Two more species were described in short, densely rooted internodes and mostly erect
preparation for a revision of Anthurium for Pan leaves held in a tight rosette, Pachyneurium spe
ama, namely A. luteynii and A. purpureospathum cies resemble most closely species of sect. Por
(Croat, 1981); two species, A. halmoorei and A. phyrochitonium. Indeed, some members of that
salvadorense, were described in "A Revision of section, for example Anthurium hacumense Engl.
the genus Anthurium for Mexico and Middle Amer (placed in sect. Pachyneurium by Engler), are
ica" (Croat, 1983) and two more, A. nervatum often confused with Pachyneurium (Fig. 5). Still,
and A. pseudospectabile, were described in "A species of Porphyrochitonium differ by having
Revision of the Anthurium of Panama" (Croat, dark glandular punctations on one or both leaf
1986). In addition, a number of Venezuelan species surfaces, and in having convolute, not involute,
have been described by Bunting ( 1986, 1988, vernation and berries which are often depressed
1989) since this project began. These include A. apically with two or more seeds per locule. In
xanthoneurum and A. quanchezii (1986), A. vi addition, sect. Porphyrochitonium is ecologicaUy
nillense ( 1988, along with three others introduced very different, inhabiting some of the wettest life
into synonymy), and A. iramirezae ( 1989). Fi zones such as pluvial rainforest. The Choco region
naUy, one species, A. plowman ii, was described of Colombia, for example, which is one of the
during the preparation of the treatment of the wettest places on earth with more than 500 inches
Araceae for the "Flora de Paraguay" (Croat, l 987). (2,272 mm) of rainfaU per year, is the center of
The current work includes a total of 114 species, diversity for sect. Porphyrochitonium. Possibly
representing l 26 taxa, 48 of those being described also a member of sect. Porphyrochitonium is An
for the first time. This is 14 7% more species than thurium hookeri Kunth, which resembles sect.
were recognized at the outset of the work. Pachyneurium more than any other non-Pachy
neurium (Fig. 6). It differs from typical Porphy
rochitonium in being much larger and in having
SECTIONAL RELATIONSHIPS WITHIN AN11WRIUM
scalariform secondary lateral veins and perhaps
Section Pachyneurium is one of 18 sections belongs in a section of its own.
recognized by Engler ( 1905). While Schott ( 1860) Much more easily confused with sect. Pachy
recognized 28 groups (and this probably will prove neurium than sect. Porphyrochitonium is a rel
to be closer than Engler to the actual number of atively small group of species which also has the
needed sections in Anthurium), he was dealing with "bird's-nest" habit and shares similar oblong to
only a small percentage of the species known to oblanceolate or obovate leaf blades, but without
Engler. Engler no doubt found it necessary to involute vernation (a feature considered an absolute
broaden the concepts of the subgeneric groups in requirement regardless of habit or blade shape).
order to include aU the new species. In doing so, Typical of this group is A. michelii Guill. (Fig. 3),
some groups lost definition. This is particularly true once considered to be a member of Pachyneurium
in the case of the species he placed in sections (Croat, 1983). These species, with epunctate, ob
Belolonchium, Urospadix, Polyphyllium, and lanceolate to oblong-eUiptic blades and generaUy
Xialophyllium, aU of which (and especiaUy the short stems with short internodes are mostly smaU
first) contain what appears to be a wide variety of plants not easily confused with typical Pachyneu
seemingly unrelated species. A discussion of these rium species, but some of the larger ones, such as
groups, their typification, and proposals for some A. michelii, are in fact easily confused with Pachy
realignment wiU be the topic of a future paper. neurium. This group of plants has not been placed
Section Pachyneurium is distinct in its ecolog with certainty in any group, though it is tentatively
ical requirements and is the most edaphically adapt placed in a new section including A. decurrens
ed of aU the sections to xeric growing conditions. Poeppig, placed by Schott ( 1860) in his grex Ox
Because of this, the taxa in the section are most ycarpium. Since only three species, A. decurrens
544 Annals of the
Missouri Botanical Garden
Poeppig, A. oxycarpum Poeppig, and A. conso rium has independently evolved the cordate con
brinum Schott were included in Schott' s grex Ox dition rather than having independently acquired
ycarpium, and since the two latter species are now involute vernation. The reasoning here is that leaf
placed in sect. Pachyneurium (along with the ep vernation is a conservative ontogenetic character
ithet sect. Oxycarpium, which is now synonymous whereas leaf blade shape in the genus is a highly
with sect. Pachyneurium) only A. decurrens re plastic one. Indeed, leaf shape may be highly vari
mains. The name for this new section will be pro able even on individual plants (see section on leaf
posed in a future paper. This new section is the blades under Morphology).
only section (other than sect. Urospadix) with short The Central American species of An.thurium are
internodes and elongate, epunctate leaf blades with now well known, and all suspected species have
convolute vernation. Section Urospadix is, I be been screened for the presence or absence of in
lieve, distinct from the latter section based on gen volute vernation. Despite the fact that the endemic
erally closer, more uniform primary lateral veins South American Pachyneurium species are less
and its more restricted geographical distribution, well known, many cordate South American species
mostly in southeastern Brazil. have been studied in cultivation, and no Pachy
Section Urospadix (Fig. 4) is the next most neurium species have been found among them.
likely group to be confused with Pachyneurium. Thus the phenomenon of subcordate-or cordate
These two are probably not closely related owing leaved Pachyneurium seems lo be largely a Central
to their lack of involute vernation (although one American and West Indian one. It is in these regions
probable species of sect. Urospadix has hybridized where some cordate Anlhurium species with short
with a Pachyneurium- see section on breeding stems, short internodes and blades with free-ending
behavior). Given that this character state, a con veins (a relatively common feature in many cor
servative ontogenetic feature, is present onJy in dale-leaved Anthurium) might be confused with
sect. Pachyneurium and in only one other genus sect. Pachyneurium. Engler placed a number of
in the family, lagenandra, it seems apparent that these species in his sect. Pachyneurium (Appendix
sect. Pachyneurium has no close relatives. Nev 2). These included A. longispathum Carriere(=
ertheless, sect. Urospadix has many features in A. grandifolium), A. grandifolium (Jacq.) Kunth,
common with Pachyneurium, especially the short A. boucheanum K. Koch (= A. cartilagineum
stems, close internodes, frequently rosulate habit (Desf.) Kunth), A. liebmannii Schott (= A. um
and the presence of elongate, often short-petiolate brosum Liebm.), A. umbrosum Liebm., A. cor
leaf blades. In gross morphology they differ from datum (Willd.) G. Don, A. andicola Liebm., A.
members of series Pachyneurium in their generally cartilagineum (Desf.) Kunth, A. brownii Masters,
closely spaced and moderately obscure primary A. appunianum Schott(= A. cartilagineum), and
lateral veins. Some members of sect. Urospadix A. seleri Engl. Except for A. seleri, most have
are very similar to members of series Mullinervia, many of the general features of sect. Pachyneu
a group mostly restricted lo the Ecuadorian Andes. rium and are 'in many ways similar to Central
From species of series Multinervia they differ prin American and West Indies cordate-leaved species
cipally in having supervolute vernation, and in be of Pachyneurium, except that they lack involute
ing geographically isolated in the geologically more vernation. Thus, it is nol surprising that Engler,
ancient parts of eastern South America, namely apparently unaware of the important character of
Brazil. Section Urospadix ranges principally from involute vs. supervolute vernation, placed these
the state of Bahia to Sao Paulo with al least two species in sect. Pachyneurium. On the other hand,
outlying species (tentatively placed in this section), using general characters such as leaf shape, short
one in the Venezuelan highlands (A. yutajense stems, and short internodes alone, many additional
Bunting) and one from the Cordillera de la Costa species from the West Indies, Central and South
(A. lilacinum Bunting). America might well have been placed by him in
Some other groups of Anthurium, especially sect. Pachyneurium.
species currently placed in sect. Belolonchium in In general, South American species are either
Central America and in the West Indies, have not subcordate-leaved, or their blades are decidedly
species that are similar to those few species of elongate with merely the bases being subcordate
Pachyneurium with cordate or subcordate blades, (e.g., A. fendleri).
e.g., A. venosum, A. ranchoanum, A. sclwttian The remaining sections of Anlhurium are not
um, A. standleyi, A. colonicum, and A. cotobrusii. at all similar to members of Pachyneurium and
It is believed that this latter group of Pachyneu- need not be discussed.
Volume 78, Number 3 Croat 545
1991 Anthurium sect. Pachyneurium
MORPHOLOGY OF VEGETATIVE STRUCTURES especially the size of the petiole bases, the stem
diameter is highly irregular from node to node with
GROWTH PATTERN
the petiole bases conspicuously swollen while the
The shoot organization of Anthurium sect. very narrow intervening areas between them are
Pachyneurium has been characterized by Ray devoted entirely to cataphylls and roots. The ab
( 1986, 1987, 1988). Though appearing un scission scar of the petiole is generally broader than
branched, the stems of most anthuriums are in facl high (i.e., broadest laterally, perpendicular to the
highly branched with a growth pattern described axis), though the shapes of the scars are usually
as triphyllous sympodial (Ray, 1988). Each article not as variable throughout the section as is the
(or segment) of the shoot includes a sylleptic pro range of variation of petiole cross sections. Petiole
phyll (P) and mesophyll (E) (both of which are abscission scars are generally rounded abaxially
cataphylls) as well as a sympodial leaf (S) (a foliage and broadly rounded adaxially. The abscission scar
leaf) and a solitary, terminal inflorescence (I). Veg is typically inclined inward to the axis at an angle
etative buds are formed only on the sympodial of 110-140° from the axis of the stem. Unlike
segment and on the peduncle base (which is axillary many Anthurium species with longer internodes,
to the mesophyll and the foliage leaf). This growth Pachyneurium has leaf scars that are usually not
pattern can be summarized as follows (after Ray, easily visible but remain obscured by the persistent
loc. cit.). cataphyll fibers and roots (Fig. 7).
The stems of Pachyneurium are generally short,
usually less than 20 cm long, and rarely more than
30 cm long except in very large old plants. Stem
diameter varies from as little as 1.5 cm in some
of the smaller species to about 7 cm diam. in the
{P - E - S - I) larger species, generally averaging 3-4 cm diam.
Stem diameter is in part also a matter of age, but
mostly increases only slightly during the life of the
plant.
Usually the oldest part of the stem rots away
except for that portion contained in the living root
Studies by Tom Ray (pers. comm.) have defined mass. Older parts of the stem are frequently at
the shoot organizations and growth patterns. In this tacked by root borers, which enter through the
regard sect. Pachyneurium is identical to thal of softer central portion of the stem and bore up into
all species of Anthurium with the exception of sect. the younger portions. However, perhaps because
Polyphyllium. It is the sylleptic prophyll which is of the seasonally dry habitats and the generally
termed the cataphyll throughout this work and massive root ball, which provides protection to the
previous works by this author on Anthurium (Croat, stem, sect. Pachyneurium exhibits fewer cases of
1983, 1986). The stem thus consists of a series infestation by root borers than perhaps any other
of units (articles), each of which comprises a branch section of Anthurium.
with a single foliage leaf subtending (eventually) a Only rarely do Pachyneurium species have no
continuation shoot and a terminal inflorescence. ticeably elongate internodes. Some species, such
as A. consobrinum, tend to grow rapidly when
young, producing internodes to several centimeters
STEMS
long, before reverting to a slower growth with short,
The stems of Anthurium sect. Pachyneurium broad internodes. Some species may revert to a
are characterized primarily by being generally short growth pattern with slightly longer internodes when
and densely rooted. While most members of other disturbed or dislodged from their positions in trees,
sections of Anthurium (excluding Xialophyllium especially when they land on their sides or land
and Tetraspermium) have short lo moderately short upside down. This reversion to longer internodes,
internodes as well, few sections ever have species so common in other genera and even in other
with such extremely short internodes. Typically, sections of Anthurium, is not common in Pachy
those of sect. Pachyneurium are several times neurium, and even when reversion to production
broader than long. Moreover, the caudex differs in of longer internodes does occur, the duration of
being much more densely rooted than in other long internode production is always very brief.
sections. Depending on the size of the stem and Of the two series of Pachyneurium, series Mul-
546 Annals of the
Missouri Botanical Garden
tinervia has a stronger tendency to produce longer into the basket often formed by the rosulate habit
internodes. This no doubt owes to their generally and the short-petiolate leaves (Figs. 7, 8, 14). The
more mesic habitats at higher elevations, where uppermost roots are the most active in terms of
the closer, more compact stems have less advan growth, and generally act as feeder roots.
tage (and perhaps some disadvantage since the Even in such situations, still other roots, usually
more typical plants in series Pachyneurium would those further down on the stem, act more for an
probably become waterlogged and rot in such cool chorage and support. These are also generally lon
er, wetter environments). ger, stouter, and less well ordered, being instead
Pachyneurium stems are tough and moderately more frequently intertwined. They are nevertheless
inflexible, perhaps owing to the presence of nu equally capable of entrapping debris and are, at
merous coarse fibers. Only the central or older least near the periphery of the living root mass,
parts of the stem are soft, offering one of the few debris-infested. Because long-petiolate species are
avenues for predation (the other being through the less likely to be efficient at catching debris, they
soft area of the abscission scar where the old pe are more likely to have their roots directed down
duncles have rotted away). ward rather than upward (Fig. 9).
Pachyneurium stems are typically erect, wheth The root masses of most species are extremely
er habit is terrestrial or epiphytic. In a few rare compact, the roots generally being completely con
cases stems may be repent, e.g., in A. lindman tiguous with one another near the surface of the
ianum. This is presumably an ecological adapta stem in most species of series Pachyneurium (Fig.
tion, providing the plant with a better means of I 0). Some species, especially many members of
survival. Anthurium lindmanianum usually occurs series Multinervia, have less densely aggregated
in seasonally dry areas as a terrestrial plant along roots. This compact nature of the root system not
the edges of watercourses. In cultivation, the spe only enables the plant to adapt well to dry condi
cies will grow well in a standing pool of water on tions, allowing it to absorb quickly virtually all of
rocks or bricks above the water level. Its roots the rainwater that passes through in brief rain
extend into the water and the typical rosulate habit showers, but also is effective in keeping phytoph
is still maintained because the petioles are turned agous insects, especially root borers, away from
sharply at right angles to the stem and are held the stem.
erect. Other Pachyneurium species, especially the ter
Despite the obvious ecological advantage of re restrial ones, frequently have their roots directed
pent stems in drier areas, this habit has not evolved downward along the stem and into the ground.
frequently in Pachyneurium. More commonly, even These species, despite the fact that they too often
in extremely dry habitats, the stem and leaves are have the typical rosulate habit with short stems,
stiffly erect. are frequently growing under conditions where they
Stems may be horizontal to almost pendent in are less likely to accumulate debris from falling
A. pseudospectabile, which grows suspended from leaves, etc., and often grow out in the open or
a few roots. Potted plants of this species may grow under low forest, which does not yield such high
in a curve until the apex is again directed more or quantities of debris. Some terrestrial species, such
less downward. as A. atropurpureum var. alropurpureum, A.
pachylaminum, or A. bonplandii, often occur on
white sand soils, which are notoriously poor in
ROOTS
nutrients, and are either found growing in open
Perhaps more than any other section, Pachy areas or growing beneath typically evergreen trees
neurium shows considerable variability in root dis on white sand soils. In such situations, roots di
position. Depending on the habitat and the species, rected into the soil appear to be an adaptation to
some species, especially short-petiolate ones, may take better advantage of nutrients present in the
produce most of their roots so that they are directed soil, which might not be available from accumulated
upward or downward or spreading. Typically, in debris. On some species, e.g., A. linguifolium,
epiphytic species in mesic habitats that experience from a very arid area, the uppermost feeder roots
a pronounced dry season, at least the uppermost are much reduced and directed upward rather than
roots are directed upward and are frequently nar downard.
rowed and pointed at the ends as well (Fig. 8). This The roots themselves, usually 3-8 mm diam.,
provides a clear advantage for collecting falling are initially covered with a dense layer of root
debris and precipitation around the roots (Figs. 7, hairs, so dense as to appear as a smooth and con
13). These uppermost roots frequently even grow tinuous layer. Artificial drying of the stems, which