Bogner, J. 1987. Morphological variation in aroids. Aroideana 10(2)

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4 AROIDEANA, Vol. 10, No.2
Morphological Variation in Aroids
J. Bogner
Menzinger Strasse 63
0-8000 Munich 19
West Germany
INTRODUCTION
The Araceae or aroid., are a large family or roasted (or otherwise heated) to
of about 2400 species, grouped in 107 become edible. Essentially, plants have
genera and these again in nine subfami produced poisons to protect themselves
lies. The aroids are mainly a tropical from being eaten by animals. Several aroids
family and are distributed world-wide. also have uses in folk-medicine. For in
They show great variation in their mor stance, Acorus calamus has been used
phological characters, which will be de since ancient times for stomach ailments.
scribed in this paper along with some Tjlphonium blumei Nicolson & Sivadasan
other data. is used to treat diarrhea in tropical Asia
and was brought by man (probably from
India) to Africa, Madagascar and to the
USES
Neotropics (Brazil, Venezuela), where it
Many aroids are very handsome orna is naturalized today. The Indians in Co
mental plants and often cultivated, to men lombia use Urospatha antisylleptica R. E.
tion just a few: Monstera deliciosa Liebm., Schultes, Philodendron dyscarpium R. E.
Dieffenbachia maculata (Ladd.) G. Don, Schultes and Anthurium tessmannii Krause
Epipremnum aureum (Linden & Andre) for contraceptive purposes. Roots ofHeter
Bunting, many Philodendron species etc. opsis spruceanum Schott are used for
Monstera deliciosa also has a delicious basket-weaving and certain aroids as arrow
fresh infructescence tasting like pineap poisons for hunting by indigenous people.
ple. Others are important food plants, like These are just a few examples of the uses
Colocasia esculenta (L) Schott, the Taro, of aroids, about which much more is
in which the tuberous stems and the known.
leaves are eaten cooked; Amorphophallus
paeoniifolius (Oennst.) Nicolson is culti
ECOLOGY
vated for its starch-rich tubers in tropical
Asia, mainly India. Cyrtosperma merkusii The aroid., are adapted to many habi
(Hassk.) Schott var. chamissonis (Schott) tats and more than 90% are tropical. The
A. Hay is grown in Southeast Asia and a majority prefer warm and humid condi
few Xanthosoma species, originally from tions, but aroids have also conquered
tropical America, are cultivated in the periodically dry areas, where they have a
Neotropics, tropical Africa and Asia. Some resting period with dormant rhizomes,
others are also used by indigenous people, tubers or very fleshy roots (Stylochiton).
like seeds of Tjlphonodorum lindleyanum But nearly all of these prefer shady places,
Schott in Madagascar and the roasted seeds at least under trees or shrubs or between
of Montrichardia by Indians in tropical rocks. One, Zamioculcas, is a succulent
South America. Many aroids are poison plant and stores the water in its thick
ous in the fresh stage, including those petioles. Aroids also grow in very special
mentioned above which are used as food ecological niches, like rheophytic habi
plants (Colocasia, Xanthosoma, Cyrto tats; true rheophytes are Aridarum,
sperma, Amorphophallus). Their stems, Bucephalandra, Piptospatha, etc. Others
rhizomes, tubers or leaves must be cooked grow permanently submerged Qasarum,
]. Bogner, 1987 5
many Cryptocoryne species) or float on GROWTH FORMS
the water surface (Pistia). Some aroids
Aroids have many different growth
(Aglaodorum, several Cryptocoryne, e.g.
forms. Most are terrestrial plants growing
C. ciliata, tolerate brackish water and
in the soil or high climbers which can
occur in fresh water tidal zones in tropical
become disconnected from the forest floor
Asia). But no aroids occur in true deserts·
and then send down long feeding roots
some grow in very dry areas (Arum and
Eminium in Central Asia, Arum and Biarum to the soil (= hemiepiphytes). It can be
expected that all climbers exhibit skototro
in North Mrica and the Orient, Arisaema
pism, but this has so far been proven for
in the Arabian Peninsula and East Mrica
only a few species to date. There are also
a few Stylochiton species reaching th~
Sahel zone), but all of these areas have a true ep~phytes (many Anthurium species,
Remusatia), swamp plants, true submerged
certain rainy season each year, during
aquatic plants Qasarum, most Cryptoco
which they can grow vegetatively. Tem
ryne species) and a free-floating species,
perate areas are poor in aroids, but con
Pistia stratiotes L.
tainsome old isolated genera (Calla, Symplo
carpus, Orontium, Lysichiton, all of which
MORPHOLOGY
are swamp plants). Calla and Lysichiton
are distributed northwards to the subarc Vegetative Parts (shoots, vegetative
tic zone (Calla to northern Scandinavia propagation)
Lysichiton to Alaska). A few of the othe;
Aroids are herbaceous, perennial herbs,
mainly temperate genera (Arum, Arisaema,
some very large, or subshrubby climbers
Pinellia) grow on the forest floor or at
with somewhat woody older stems. The
least in shady places under trees or shrubs,
leaves are arranged in rosettes or the
but in all these cases their rhizomes or
internodes may be long, especially in the
tubers are dormant during the cold season.
root climbers, where some groups (Mon
Some aroids go high up into the Andes
stereae, Cercestis) flagelliform shoots
(Gorgonidium ca. 3000 m) or Mrican
mountains (Arisaema ruwenzoricum up ( = flagelles), with very long internodes
and cataphylls only, also occur. Some
to 3200 m on the Ruwenzori), where a
aroids have upright short stems with the
warm temperate climate exists. The high
leaves at their apex (Alocasia, Xantho
est altitude is reached by the genus Ari
saema in the Himalaya, where Arisaema soma sect. Xanthosoma), pseudostems (Ty
phonodorum), creeping rhizomes or
lobatum Engler andAjacquemantii Blume
tubers; rarely they may be tree-like (Mon
are growing up to an elevation of 4500
trichardia with stems up to 6 m, some
m, Arisaema flavum Schott up to 4400 m
species of Xanthosoma with trunks to 3
and for some other species an altitude
m tall and some species of Alocasia such
up to 4000 m is reported. Some aroids
grow under semi-epilithic conditions, with as A portei Becc & Engl., A macron-hiza
~heir stems, rhizomes or tubers growing (L.) G. Don,A odora C. Koch). The ramifi
cation of aroids is usually sympodial, rarely
10 humus deposits in holes or crevices of
monopodial (Potheae). Vegetative propa
steep rocks (limestone hills in Malay pen
gation usually occurs. There are shoots,
insula with Colocasia gigantea Hook. f.,
often specially formed as long runners
Amorphophallus; washed out holes in lime
(stolons) with a rosette of leaves (Crypto
stone in Madagascar with CarJephyton,
coryne) or a tuber at their apex (some
Colletogyne; or granitic hills in Eastern
Alocasia, few Amorphophallus). Some pro
Brazil with a few hard-leaved Anthurium
duce underground runners several metres
sI?ecies). The rheophytes grow mostly
long (Lasiomorpha senegalensis Schott),
directly on rocks under very humid con
ditions. quickly occupying large areas. The flag
elles (with their very long internodes) of
6 AROIDEANA, Vol. 10, No, 2
Fig, 1 AridclI'/llII nico/sollii Bogner, r\ t\-picli rheoph\Te gnw,ing on sandstone rocks
at Sllngai Tamhak, ;\ It. Santllhong, Sara\\'ak, J Bogner
Fig. 2 Crlplocor)'ne /Joillederiljolia Schott growing in a Nlpaji'ulical/s swamp near
T~lbakis, Sllm~ltra, Incionesia,.J. Bogner
fig, 3 Lagel/andra ol'ala (L.) Th\\'aites, in Sri Lanka (Ce\'lon), J. Bogner
fig, -i Lasia COl7cilllla V ,A. \' R, This ven' rare amid from Kalimantan, grmving in the
Keblll1 I~a\'a, /3ogor (.1<I\'a), \XI. Herrmann
J. Bogner, 1987 7
several Monstereae and Cercestis enable stereae). There is often a great difference
them to quickly reach another branch or between juvenile and adult leaves. In most
tree. Peculiar erect or horizontal above cases, the first foliage leaf (of a seedling),
ground shoots with many small bulbils is entire; subsequent leaves may become
also occur in Remusatia and Gonatanthus. increasingly divided, sometimes ending
One bulbil is produced on the upper part up highly compound; between the ex
of each petiole in Pinellia temata Makino tremes, all intermediate leaf-forms exist.
(synP. tuberifera Ten. and a few on the There are species, for instance in the
leaf-blade of Amorphophallus bulbifer genera Syngonium and Xanthosoma, in
(Roxb.) BI. Much more common are tu which juvenile and adult leaves are always
bercles produced sometimes in large quan entire, yet other species in the two men
tities around the apex of an old tuber tioned genera have compound (pedate)
(Dracontium), or in lower numbers in leaves in the adult stage. But there are
many other tuberous species (Arisaema, other genera, like Gonatopus and Amor
JYphonium). Another unusual type ofvege phophallus, in which the first foliage leaf
tative propagation is by broken leaflets, (of a seedling) is already divided; they
in Zamioculcas and Gonatopus; the leaf never have entire leaves.
lets fall down by a slight touch, then root Leaf venation in aroids is parallel or
in the soil and form a tubercle from which reticulate, but in both types we can find
a new leaf will develop. some variation in certain groups, like
Pothos or Colocasioideae; also somewhat
intermediate types exist, where the (pri
Leaves
mary) lateral veins of the first order are
Aroid leaves show very great variation. parallel, but the lateral veins of the second
The leaves are usually arranged spirally, order are reticulate (some Monstereae,
only rarely distichously or solitarily (Am Spathiphyllum). One (or two) collecting
orphophallus, Dracontium). The petiole veins running along the margin of the
is usually well developed and has a sheath, leaf-blade are quite common, where the
which protects the young, still furled leaf; lateral veins of the first order turn up
only rarely are leaves subsessile. Some wards and then connect (anastomose)
aroids (Anthurium, Monstereae) have a along the margin.
geniculum which enables them to move
Aroid leaves, as well as all other parts
the leaf-blade into an optimal position
of the plant, are usually glabrous, but
relative to the light.
hairy leaves aare also known. These are
Although ensiform leaves (unifacial in mostly pubescent, tomentose, villous or
Acorus, bifacial in Gymnostachys) rarely with trichomes on the petioles and the
occur, most leaf-blades range from fili veins on the lower surface of the leaf
form (certain stages in Cryptocorne retrospi blade only. Pistia stratiotes is well known
ralis Kunth and C. consobrina Schott), as a hairy species; the other species with
linear Oasarum), elliptic, ovate, oblong trichomes occur in disparate, often com
to sagittate, hastate and tripartite; com pletely unrelated genera (Schismatoglot
pound leaf-blades also occur and may be tis, Cryptocornye and· Lagenandra, Ari
of the pedate, radiate or the dracontioid saema, Stylochiton, Xanthosoma, Philo
type, the latter with three main parts, each dendron). Spiny petioles occur in many
of which can be divided two or three Lasioideae. Some aroid species have leaves
times again. True pinnate leaves (Zamiocul that are naturally colored, either on the
cas, somewhat intermediate in Gonato entire lower or upper surfaces or as spots
pus petiolulatus (Peter) Bogner and or stripes. These species have been used
Anaphyllum), are-also known, as well as especially for selection and crossing of
pinnatifid to pinnatisect and laciniate leaf nicely colored cultivars (some Aglaonema
blades, sometimes with holes (many Mon- Caladium, Dieffenbachia).
8 AROIDEANA, Vol. 10, No.2
Development, juvenile and adult Spathes
stages
The aroid spadix is subtended by a
Cataphylls are leaves in which the blade modified leaf or bract, the so-called spathe.
is not developed or is reduced, and in The spathe has undergone great modifi
certain cases (stolons), all intermediates cations in its evolution, from an incon
can be found, beginning with a minute spicuous green, leaf-like organ to a col
blade at the apex of the cataphyll, and so ored, spreading and very showy one. The
on. Cataphylls can be found on stolons, most highly specialized spathes are con
flagelles, seedlings or on adult shoot.. in stricted between the female and male
association with ramification. Cataphylls flowers or above the fertile flowers, with
are usually membranaceous, though some a tube below and a showy lamina above.
times weathering to fibers perSisting for But spathes may also be partly (Stylochi
a long time on the stem (some Philoden ton, Sauromatum) or for most of their
dron, Anthurium).; usually however they length marginally connate and forming a
rot away qUickly, soon drying or falling kettle' enclosing the flowers (Lagenan
off. Seedlings start with one or a few dra, Cryptocoryne). Usually the spathe is
cataphylls before the first foliage leaf ap adnate below the spadix, but in two genera
pears. Sympodial ramification terminates (Lysichiton, Orontium) the spathe goes
in an inflorescence and the new shoot down to the rhizome and only encloses
always starts with one or a few (depend (not adnate) the peduncle; this is an unique
ing on the group) cataphylls. In several and, in my mind, another primitive char
cases (Anthurium, Philodendron, Crypto acter.
coryne) cataphylls appear but not inflo
rescences, which are actually suppressed.
But it is then easy to see that such a plant Flowers
has already reached the adult stage, even
Aroid flowers are nearly always sessile
if juvenile and adult leaves are not differ
(except shortly pedicelled in Pedicel
ent. For example, if a Philodendron with
larum), usually densely arranged on the
uniform leaves (some have different leaf
spadix and are always lacking a bract
forms in the juverfile and adult stage)
below each flower. Such bracts are always
produces one foliage leaf after another
present in the Liliiflorae, which are espe
then it is in juvenile stage; if foliage leaves
cially interesting in that they may imitate
and cataphylls are produced alternately
aroids in having densely flowered spikes
then it is in the adult stage, but this does
(Rohdea, Gonioscypha). The primitive
not automatically mean that such a plant
spadix in aroids is covered with perfect
will produce inflorescenes. The length of
flowers up to its apex. Then, an evolution
the sheath also usually changes from the
ary tendency toward reduction of flowers
juvenile to the adult stage.
appears. The upper flowers may become
sterile and, in highly advanced spadices,
we find a long terminal appendage with
In.t1orescences
out any sign of floral rudiments. Often
The flowers of aroids are usually very sterile flowers appear between the male
numberous and small, rarely few by re and female parts of the spadix, and these
duction, and are generally arranged on a have a characteristic form in different
fleshy axis, the spadix, only rarely in a groups. There is great variation among
(non fleshy) spike (Pedicellarum, some sterile flowers, too. The female flowers
Pothos). Not much is left of the spadix in are always situated on the lower part of
the very reduced Pistia, and in the related the spadix, the male ones above them,
Lemnaceae, the Duck Weed.. , the spadix except in Spathicarpa where male and
is completely lacking. female flowers are arranged in longitudi-
J Bogner, 1987 9
-
fig. ') Cn1JtoCOrl'lle ciliata (I~():\h.) SChOll. shmYing the limh of spathe \yith :1 ciliate
margin; from Celehes. J Bogner
fig. 6 AIII.1'drilIlJ/ blllJ/ile Schott, in tlO\yer from the ,\LtI:I\' Peninsuh J Ilogner
rig. 7 rlllap/Jl'Ilopsis (//J/eriC(//lCl (Eng!.) A. H~I\' in tlO\yer from rrench Gu\·ana. I
Bogner
rig. H Nobdea j(ljJOlliccl (Thunh.) A. \\'. I{oth r\ memher of the Li I iaceae first
descrihed as an amid (Orolitillllljapollic/lJ/I) Iw Thunherg. J Bogner
10 AROIDEANA, Vol. 10, No.2
nal rows with the spadix and spathe com structure, very thick and truncate (Anthu
pletely connate. But in the related genus, rium, Dracontium, Urospatha) to mem
Spathantheum, in which the spadix is also branaceous (Anadendrum, in which they
entirely adnate to the spathe, the female are also shorter than the ovary and incon
flowers are below and the male ones spicous). Tepals may either be free, partly
above, as in typical aroids. The spadix in connate (some Pothos) or completely con
other aroids is free, but in some genera nate and forming a cup (Pedicellarum,
there is a partial adnation of the lower Spathiphyllum sect. Massowia, Holoch
(female) part to the spathe. lamys). The number of tepals of the perigon
The flowers themselves undergo a great in the genera Urospatha and Dracontium
evolutionary reduction from perfect flow is inconstant. Urospatha sagittifolia (Rudge)
Schott has flowers with four, sometimes
ers to naked bisexual flowers to· naked
five or six tepals as well as stamens on the
unisexual flowers, with several intermedi
same spadix. The same situation is found
ate forms. Plants with unisexual flowers
in the genus Dracontium, where up to
are usually monoecious, but in Arisaema
eight tepals may occur and often the same
most species are paradioecious. Paradio
number of stamens, though the latter may
ecious means that sexuality is not geneti
have up to nine or twelve, and then do
cally fixed, but depends on environmental
not correspond with the number of tepals.
conditionsj stronger and bigger plants
produce female flowers only, whereas This example shows that the question of
weaker or younger plants produce male whether aroid flowers are basically di-or
flowers only. Since the tubers are formed trimerous should not be overemphasized.
anew in each vegetative period, it may
happen that a small tuber is produced Unisexual flowers
due to poor nutrients or the destruction
Unisexual flowers with a well devel
of the leaf early in its growthj such a plant,
oped perigon are found in the genera
if it flowers at all, may produce male
Zamioculcas and Gonatopusj both have
flowers only. Arisaema species are nor
female flowers without rudiments of the
mallyeither monoecious or paradioecious,
other sex, but the male flowers have a
but occasionally in certain usually paradi
pistillode in the center. In Zamioculcas
oecious species plants can be found with
the stamens are free, whereas in Gonato
female and male flowers on the same
pus the stamens are connate with the
spadix.
fused filaments forming a ring around the
As already mentioned, in the evolution
pistillode. The unisexual flowers of Furta
of aroids there has been an across-the
doa are nakedj each male flowers consist')
board trend toward reduction in flower
of single stamen and one pistillode and
structures. Perfect (bisexual) flowers with
each female flower of a pistil with one
a perigon become naked bisexual flowers
staminode. Thccarum and Gorgonidium
(Monstereae, Pycnospatha) or unisexual
have male flowers with completely or
flowers with or without a perigon, with
panly connate stamens, but the central
or without rudiments of the other sex. A
pan of each synandrium is clearly of
few examples should suffice to demon
pistillodial origin. Most species of Sty
strate thisj first, perfect flowers are con
lochiton have a small, inconspicuous pis
sidered.
tillode in the center of the male flower,
but their male flowers have free stamens
Perfect flowers
with filiform fiJaments and each male
Perfect flowers in aroids usually have flower is surrounded by a saucer-like
four or six tepals, in two whorls of two perigonj each female flower is surrounded
or three, as well as the same number of by a cup-like perigon covering the whole
stamens. The tepals are of a medium-thick ovary, and staminodes never present. The
J. Bogner, 1987 11
flowers of the Arophyteae are naked and other characters, and the same can be said
the very similar cup-like organ around in the ca..'ie of Zantedeschia aethiopica or
the pistil of the female flower is clearly Amorphophallus cirrifer. At first, upon
of staminodial origin, as it is proven by seeing A cirrifer with its long filiform
the existence of bisexual flowers between staminodes around the pistils, one thinks
the female and male flowers in some in terms of a separate genus, but a com
species; other species have sterile flowers parison of other characters reveals that it
( = sterile male flowers) of the same struc is closely related to other species. I think
ture in this region and form a so-called that this species is worthy of subgeneric
synandrodium (lacking the anthers). A or sectional rank; Stapf, who described it,
similar situation can be found in the genus has already established the subgenus Metan
Asterostigma sea. Rhopalostigma, in which drium for Amorphophallus cirrifer.
the staminodes around the pistil are con
nate. Usually, the staminodes are free and
Staminodes
surround the pistil; they are mostly four
or six in number, but there is some vari Generally, staminodes and sterile male
ation. In the genus Homalomena there is flowers are quite variable in form, and
usually only one staminode beside the both are used for cla..'isification. Stami
pistil, or else staminodes are lacking alto nodes can be free or partly or completely
gether. The staminode in Homalomena connate; their form varies from filiform,
can be a..'i long as the pistil, in which case cylindrical, clavate or spathulate to scale
It is often clavate, but in many cases it is like. These kinds of staminodes can sur
much smaller and more or less conical round the pistils or lie between the female
or conoidal or sometimes minute or com and male flowers, or above the male
pletely lacking. Other examples are the flowers. Quite often synandrodia arise
genera Zantedeschia and Amorphophal from connate staminodes or: from synan
Ius. Zantedeschia aethiopica (1.) Spreng. dria, become steril, and are situated be
has several staminodes around the pistil tween the female and male flowers or on
of each female flower, wherea..'i all other the (apical) appendix. They are also vari
species of this genus are completely lack able in form, often resembling the synan
ing such staminodes. Another ca..'ie is Am dria, but without thecae and appearing
orphophallus cirrifer Stapf, which has fili elongate or subrhombic in shape (viewed
form staminodes around the pistil, all from above) and truncate in Caladieae.
other species lacking any staminodes in Synandrodia in the Arophyteae are empty
the female flowers. Some Amorphophal only in the center where there is usually
Ius species have staminodes between the a pistil (in bisexual flowers, between the
female and male flowers. Two species (A. female and male flowers). But synandro
margaritiferus Kunth and A mysorensis dia can be also wart-like, flat, knob-like
c.
E. Barnes & E. C. Fischer) have peculiar or prismatic; these kinds are mostly found
pearl-like organs in this position. Most on appendices.
species of Amorphophallus have an (apical)
appendix without any sign of staminodes,
Male Flowers
but a few unrelated species have an ap
pendix with more or less well developed Male flowers are also distinctively
staminodes. The conclusion is that the formed in the different groups. The male
presence or absence of one or more flowers of Zamioculcas and Gonatopus
staminodes, a..'i in the above mentioned have already been mentioned; these still
examples, should be not overemphasized. retain a perigon. In other cases, male
Those species of Homalomena without a flowers are naked. The stamens are free
staminode in the female flower are closely or all partly or completely connate, and
related to other species on the basis of then forming a synandrium. Free stamens
12 AROJDEANA, Vol. 10, No.2
may be in groups of two, three, four or six Pistils
in a male flower, but they can also be
The aroid pistil usually has a slightly
solitary, which means that each male flower
narrowed stylar region below the stigma,
consists of only one stamen. The fila
but long styles and sessile stigmas are also
ments of the stamens may be filiform, but
known. The stigma is always wet and
are more often flat. They may be fused
covered with copious secretion during
only basally or higher up, and there is
the receptive phac;e, and dries afterwards.
often much variation on the same spadix,
The stigma is capitate to disc-like, or
ac; in Gorgonidium mirabile Schott. But
lobed to star-like, The ovary is unilocular
mostly the filaments are completely con
to plurilocular, though unilocular ovaries
nate and the thecae are arranged laterally
are pseudomonomerous, Two- or three
or apically, or even marginally on the
locular ovaries are common, and some
synandrium. These synandria are mostly
species have ovaries with numerous 10-
truncate, but may be mushroom-like, cy
cules, There are one to many ovules per
c1indric or of other shapes. Synandria can
ovary or locule, in some species up to one
also be reduced to one stamen only (Col
hundred in an ovary. Great variation also
letogyne). In Ariopsis, all male flowers
exists in the type of placentation, Axile,
are connate and form a single mass.
parietal, apical, basal or bac;al and apical
The anthers always consist of two thecae,
placentation all occur in aroids. The ovules
each of which consists of two pollen sacs.
can be orthotropous, hemiorthotropous,
The thecae open by means of a lateral slit
amphitropous, hemianatropous or anatro
or an apical pore or slit; the opening of
pous.
each pollen-sac separately is rare, Some
(Cryptocoryne, Lagenandra, Aridarum)
have horned thecae, ending in a more or
less long tubule with poricidal dehiscence.
The stamens of Aridarum are peculiar: the
thick filament is excavated and the two
Fruits
thecae are situated inside or outside of
the cavity, depending on the species. The fruits of aroids are usually berries
with plenty of juice, rarely nearly juice
less, closely packed in the infructescence,
Generally, the berries are free, but form
an indehiscent syncarp in Syngonium and,
Pollen grains
in Cryptocoryne, a syncarp which opens
The pollen grains of aroids are of dif apically. The berries are usually indehis
ferent types and their morphology is very cent (not opening), the ripe berries of
useful for the classification of genera or Lagenandra open basally at maturity and
higher taxa, The pollen grains are usually release the seed or seeds. Aroid berries
shed in monads, but Xanthosoma and contain one to many seedc;. The spathe
Chlorospatha have tetrads. The most primi can be deciduous after anthesis, drying
tive aperture is the monosulcate type; a or rotting away, or may be completely or
few genera have dicolpate (Calla, Rhaphido partly persistent, In many cases, the lower
phora, Heteropsis), periporate (Anthu part of spathe (tube) protects the young
rium), or extensive-sulcate or zonate developing fruits, then decays at maturity
sulcate poll~n grains. Inaperturate pollen or actively opens (A1ocasia) to present the
grains are, however, quite common. The colored berries, The berries in aroids are
ornamentation of the exine also shows vividly orange to red or purple-red in
great variation: smooth, rough, reticulate, color, white (many Philodendron species,
foveolate, striate, echinulate (spiny), ver Stenospermation), sometimes green or
rucose (warty), areolate and baculate, yellow (Typhonodorum),
J. Bogner, 1987 13
Fig. 9 Pollen grain or Pislia slralioles L. \X'. BanhJoll
Fig. 10 Pollen grain oJ' COI/ClIOpUS /Joil'illii (Decne.) Hook. f. \V BanhJott
Fig. 11 Pollen grain of C)' JII l/oslrlch)'s Cll/ceps R. Ik \'\'. 13anhlotl
Fig. 12 Pollen gr:lin or H(/jxt/il/e broll'llii I-look. f. \V Banhlott