The Araceae · Morphology

AROID
MORPHOLOGY

One blueprint — a stem, a leaf, a spike of flowers in a hood — and from it climbing vines, floating rosettes, underground tubers, and leaves with holes in them.

The Section

The plant is the evidence

Araceae is a family of about 125 genera built on one idea: a spike of tiny flowers wrapped in a modified leaf. What varies — enormously — is everything around that spike. This section is about the plant, not the flower: how an aroid is put together, what its parts are called, and which of those parts actually carry information.

The companion section, Aroid Reproduction, covers what the inflorescence does — the heat, the scent, the trapped insects, the crossing methods. This section covers what the plant is. Where the two meet, each points at the other.

4 types of fine venation
6× independent origins of holed leaves
5 genera with resin canals
1 free-floating species in the family

Why form is worth this much attention

Because most of what a grower can see is vegetative, and most of what a taxonomist writes down is too. A revision separates species on the angle a vein leaves the midrib, on whether two veins meet before they reach the edge, on whether a gland in a vein axil is red or pale green. Those are not ornamental details. They are the characters the names are built on.

And form is where the family's best stories live. A leaf that grows toward darkness to find a tree trunk. A vine whose juvenile leaves lie flat against bark like roof tiles and whose adult leaves hang a meter clear of it. Holes that open by programmed cell death before the leaf has unfurled. A single leaf, in one genus, that looks like a small tree.

A caution that governs the whole section

A character is not an identification. Almost every distinctive feature on these pages is shared by several genera, absent from some members of the genus it supposedly marks, or different in a juvenile plant than an adult one. The useful question is never “does it have X?” but “what combination does it have, at what stage, and what does the literature say that combination means?”

Part I

The leaf, and the four venations

Aroid leaves run from linear to gigantic, from entire to four times divided. The Genera of Araceae lists the shape range as linear through elliptic, ovate, cordate, sagittate, hastate, trifid, pedatifid, pinnatifid, pedatisect, pinnatisect and radiatisect — with bipinnatifid, tripinnatifid and even partially quadripinnatifid leaves on top¹. But the character that organizes the family is not outline. It is the fine venation: what the smallest veins do between the large ones.

Four patterns

The fine-venation types, after Mayo, Bogner & Boyce¹
Type	What the small veins do	Where
Reticulate	Net-like, superficially like a dicot leaf	Anthurium and the whole of Pothoideae; Lasioideae; most Aroideae — including Arum, Monstera and Rhaphidophora
Parallel-pinnate	Primaries and secondaries leave the midrib pinnately, then run parallel to one another to the margin	Philodendron, Aglaonema, Homalomena and Engler's old Philodendroideae; a synapomorphy of Monsteroideae²
Colocasioid	Fine veins branch at almost a right angle, arch hard toward the margin, and fuse into a sinuous interprimary collective vein	Tribes Colocasieae and Caladieae — Alocasia, Colocasia, Xanthosoma, Caladium
True parallel	Grass-type, no pinnate framework at all	Gymnostachys. One genus, in the entire family

The term parallel-pinnate was coined deliberately to keep the third pattern apart from the fourth¹ — older literature called it “striate” and Engler used it to assemble his subfamily Philodendroideae. Molecular work has since shown that grouping to be built on a character that evolved more than once², which is a useful reminder: a real, visible, repeatable character can still be the wrong thing to classify on.

Intermediates exist between most of the types, and the only large-scale comparative survey of aroid venation remains Ertl's, from 1932¹.

Peltate, and why it matters

A peltate leaf has its petiole attached inside the blade margin rather than at the edge. It appears in tribe Colocasieae, and in Anthurium, Caladium and Homalomena¹ — and in the molecular analysis, peltate leaves are the only morphological synapomorphy recovered for the Colocasia clade². It is also strongly age-dependent: in Philippine Alocasia, seedling leaves are almost always peltate while most adults are not³.

Holes

Perforated leaves occur in Monstera, Rhaphidophora, Epipremnum, Amydrium, Dracontioides, Cyrtosperma, Dracontium, and in the juvenile leaves of Anchomanes and some Cercestis^1, 4. They have evolved independently at least six times² — which is the first clue that they are doing something useful.

How the holes form was long described as necrosis: patches of tissue dying at an early stage of leaf development, at a remarkably regular spacing of about 0.14–0.15 mm⁵. The modern account is more specific. In Monstera obliqua the perforations arise through programmed cell death, with the cell walls at the perforation site left intact and the rim cells re-differentiating as epidermis⁶ — the same outcome as the lace plant Aponogeton madagascariensis, reached by convergent evolution.

Why the holes? Nobody has settled it

Water to the roots. Proposed in 1892; Madison called it “a fanciful interpretation with no basis in reality” in his 1977 revision⁴. A later student experiment measured the opposite of what dismissal predicts — roughly twelve times more water collected beneath holed leaves than beneath leaves with the holes filled in⁷.

Cooling. Madison suggested the holes break up the still-air layer⁴; the objection is that the comparison plants are full-sun pioneers while Monstera is a shade plant, and that leaf shape had no measurable effect on the temperature of tropical understorey climbers⁸.

Wind, and herbivores. The same student experiment found no significant wind effect, and found holed leaves suffered more insect damage, not less⁷.

Sunfleck economics. The most recent proposal is that fenestration does not raise average carbon gain at all — it lowers the variance in it, which under a flickering understorey light regime raises long-run fitness⁸.

⚠ The experimental work here is a single undergraduate field study on one species, with samples of 15–30 per treatment⁷. It is the only direct test in our library, and it should be weighted as such.

Two leaves on one plant

Heteroblasty — juvenile and adult leaves differing sharply — is a feature of the climbing genera: Cercestis, Monstera, Philodendron, Pothos, Rhaphidophora, Rhodospatha, Syngonium¹. In Syngonium the juvenile blade is simply arrow-shaped and the adult is trifid to pedatisect¹ — growers keep the plants juvenile deliberately, because the adult is a different-looking plant.

The extreme form is the shingle plant: a juvenile climber with almost no petiole, blades pressed flat and overlapping against the bark like roof tiles¹. Across all flowering plants the habit has arisen in ten families, 22 genera and at least 158 species — and exactly one of those species is from mainland tropical Africa¹⁰. In Araceae it appears in Pothos, Rhaphidophora, Monstera and Scindapsus¹⁰. What it is for is again unsettled: protection of the adventitious roots from drying was the classical answer⁴, while the current favorites are trapping and recycling carbon dioxide, and capturing nutrients from water running down the trunk — with the honest note that few of the hypotheses have ever been explicitly tested¹⁰.

Part II

The stem, and the root

An aroid stem is one of four things: an underground tuber, an underground rhizome, an erect aerial stem, or a climbing stem with long internodes¹. A fifth form is not a stem at all — Arisaema and Typhonodorum build a pseudostem out of wrapped petiole sheaths¹.

The distribution is not what an older generation of botanists expected. The erect, cane-like habit of Aglaonema, Dieffenbachia, Homalomena and Schismatoglottis was once read as primitive; it is in fact concentrated in the more advanced genera, while long-internode climbing is commonest in the tribes with bisexual flowers — the older lineages¹. Underground storage organs are common in Lasioideae and especially in Aroideae¹; in the Thai flora alone, well over half the species are geophytes¹¹.

Climbing, and the two kinds of hemiepiphyte

Most Pothoideae and Monsteroideae are hemiepiphytes, and among the advanced genera the habit is confined to tribe Culcasieae, Philodendron and Syngonium¹. The two routes are worth keeping apart:

Primary hemiepiphytes begin life above the ground and send feeder roots down to the forest floor. Secondary hemiepiphytes germinate on the floor, climb a trunk, and lose their ground connection when the juvenile stem rots — then re-establish it later with feeder roots¹.

How a seedling finds a trunk in the first place is one of the family's best-known findings: skototropism, growth toward darkness rather than light, described for a Monstera in 1975¹². ⚠ The paper names its plant Monstera gigantea; Madison's revision notes the name is ambiguous and the species is probably Monstera tenuis or Monstera dubia⁴ — worth knowing before repeating the species name.

Roots do two different jobs

Aroid roots are always adventitious, and in climbing hemiepiphytes they are dimorphic¹: short anchor roots that grip the bark, and long feeder roots that run to the soil. The difference only appears once the plant is about a meter up and the stem is 7–10 mm thick. Anchor roots reach 20–30 cm in Monstera; feeder roots in the same genus may extend 30 meters to the forest floor^1, 4. Some climbers — Scindapsus pothoides among them — never make the distinction at all¹, and Syngonium anchor roots may lack root hairs and appear cemented on by dried mucilage¹.

Geophytes have their own specialization: contractile roots, which pull the stem back down when it creeps too near the surface, in Arisarum, Arum, Biarum and Cryptocoryne¹.

Water

Rheophytes — plants of swift streams, flooded to the waterline — are recognizable as a form: narrow leathery leaves on a firmly attached, usually rock-gripping stem¹. In Araceae they are concentrated in the Schismatoglottideae, with Homalomena, Anubias, Holochlamys and rarely Anthurium¹.

Fully submerged aquatics are rarer: Jasarum steyermarkii, with linear leaves in blackwater streams, and many Cryptocoryne¹. And of the whole family, exactly one species floats free — Pistia stratiotes, a rosette of spongy wedge-shaped leaves with no midrib and a curtain of feathery roots beneath¹.

The module

One last piece of architecture, because species descriptions lean on it constantly. A flowering aroid stem is almost always a sympodium: a chain of articles, each beginning with a two-keeled prophyll, continuing through a run of leaves, and ending in an inflorescence¹. The continuation shoot arises at the second node below the spathe — except in Orontioideae, where it arises at the first¹. Cataphylls, when they persist, become a visible character in their own right: membranous in some species, a mass of net-fibres in others, and conspicuously mottled in Arisaema and some Alocasia^1, 9.

Part III

Inside the tissue

Three internal characters are used across the family, and one of them is the reason an aroid leaf can hurt you.

Raphides — the needles

Calcium oxalate crystals are abundant throughout Araceae, and needle-shaped raphides are always present¹. They are twinned, H-shaped in cross-section and often barbed along their length. They sit inside specialized cells: thin-walled idioblasts, and thick-walled biforines that eject their contents through a pore at either end — about 50 × 150 µm in Colocasia and 40 × 90 µm in Alocasia, which is unusual in ejecting the entire mass of crystals and mucilage together¹.

The needles are the delivery system, not the poison

“Raphides alone are harmless… Raphides, however, are only the vehicles of irritating substances”¹. The crystals wound; something else carried with them does the burning.

Laticifers and resin canals

Most aroids carry laticifers — latex-bearing canals — and their form is taxonomically loaded. Anastomosing (branching and rejoining) laticifers are limited to the tribes Caladieae, Colocasieae and Zomicarpeae; articulated non-anastomosing ones occur in Calla, Orontium and nearly all Aroideae¹. Engler defined his subfamilies Pothoideae and Monsteroideae partly by their lack of laticifers¹. Tribe Cryptocoryneae was long reported to lack them too — until they were found in the stems, roots and cataphylls (though not the foliage leaves) of both Cryptocoryne and Lagenandra¹.

Resin canals are far rarer. A survey of 91 genera found them in the roots of five: Culcasia, Cercestis, Homalomena, Furtadoa and Philodendron¹. In Culcasia and Philodendron they are visible in the leaf without magnification. The same resin has a job at flowering time: in Philodendron it glues pollen onto the pollinating beetle¹. (Note for currency: Furtadoa has since been sunk into Homalomena, which reduces that list to four genera as currently circumscribed.)

And the genus that has none of it

Acorus — long treated as an aroid, now placed in its own family Acoraceae as the sister to all other monocots — lacks both laticifers and raphides¹. In a family where raphides are otherwise universal, their absence is one of the clearest signals that the plant was never really one of us.

A naming trap worth knowing

Rhaphidophora is not named for raphides. Hasskarl named the genus in 1842 on the basis of trichosclereids — needle-shaped sclereids, a different structure entirely — which he had illustrated correctly and labelled confusingly¹.

Part IV

The tell: genus by genus

One character per genus — the vegetative feature a taxonomist reaches for first. None of these is an identification on its own, and several are shared. They are starting points, not verdicts.

Vegetative signature characters, after *The Genera of Araceae*¹ unless noted
Genus	The tell
Anthurium	A geniculum — a distinct joint at the top of the petiole that lets the blade swivel. Plus reticulate fine venation.
Philodendron	Parallel-pinnate venation, a petiole only rarely geniculate, and intravaginal squamules. Resin canals visible in the leaf.
Monstera	Neotropical, reticulate-veined, elaborately perforated. The only fenestrate climber in the New World tropics.
Rhaphidophora	Palaeotropical counterpart of Monstera; stem often square in cross-section; leaves distichous.
Epipremnum	⚠ Vegetatively near-inseparable from Rhaphidophora. The genera are divided on seed structure, not on the leaf.
Scindapsus	The climber that never fenestrates: adult blade always entire.
Pothos	The petiole itself is winged and blade-like, geniculate and often auriculate at the top.
Alocasia	Colocasioid venation, wax glands in the vein axils, blade peltate as a juvenile and usually sagittate as an adult.
Colocasia	Peltate at every stage, posterior lobes rounded and partly to almost wholly fused.
Xanthosoma	The New World one: cordate to sagittate to pedatisect, and only rarely peltate.
Caladium	Peltate and usually variegated, on a small tuber. Separated from Xanthosoma chiefly by that peltation.
Dieffenbachia	Erect green cane with conspicuous annular leaf scars; sheath more than half the petiole.
Aglaonema	The Old World cane: same habit as Dieffenbachia, but parallel-pinnate venation.
Spathiphyllum	An acaulescent rosette herb that still has a geniculate petiole — an unusual combination.
Syngonium	Textbook heteroblasty: arrow-shaped juvenile, trifid to pedatisect adult.
Homalomena	Crushed tissue is aromatic (terpenoids)¹³.
Schismatoglottis	Superficially the same plant — but not aromatic¹³, and often with a long apical ligule on the sheath.
Amorphophallus	Usually a single dracontioid leaf: one petiole, one trisect blade, further divided — a whole crown on one stalk.
Arisaema	Pedate or radiate blade on a pseudostem of petiole sheaths; sex expression shifts with the plant's condition¹³.
Zantedeschia	Spongy petiole; blade often marked with pale translucent windows of diaphanous tissue.
Cryptocoryne	Stoloniferous aquatic with convolute leaf ptyxis — rolled, where Lagenandra is involute.
Anubias	Thick creeping rhizome, leathery leaves, geniculate petiole. An African rheophyte, not a true aquatic.
Pistia	The only free-floating aroid: a pubescent rosette, no midrib, feathery hanging roots.

The comparison everyone actually needs

Alocasia, Colocasia and Xanthosoma are the three big-leaved genera that get confused with one another in every plant shop on earth. All three share colocasioid venation, so the fine veins will not separate them. What does:

Three genera, one silhouette
	Alocasia	Colocasia	Xanthosoma
Peltate?	Juvenile yes; adult usually not (peltate in some species)	Yes, always	Rarely
Adult blade	Sagittate, less often hastate or cordate	Ovate-cordate to sagittate-cordate, posterior lobes rounded and fused	Cordate, sagittate, hastate, trifid or pedatisect
Vein-axil glands	Wax glands present in the axils of the primaries¹⁴	—	—
Native range	Asia to the Pacific	Asia	Neotropical
Fine venation	Colocasioid in all three — this character cannot separate them

The rule we could not source

You will read everywhere that Alocasia holds its leaves pointing up and Colocasia points them down. It may well be a useful field impression. But we could not find it stated in any taxonomic source in the Aroidpedia library — not in The Genera of Araceae, not in the Flora of China, not in the Flora of Thailand, and not in Hay's revisions of Alocasia. Until it can be cited, treat it as a growers' heuristic rather than a diagnostic character, and reach for peltation and the vein-axil glands instead.

And where the leaf genuinely runs out

Two of the most-searched genera on this list cannot be separated vegetatively at all. Rhaphidophora and Epipremnum are divided on the structure of the seed — ovule number and seed shape — and not on anything you can photograph on a houseplant¹. Typhonium and Arum are, in Mayo's treatment, separated from their tribemates on the sterile flower zone rather than the leaf.

That is not a failure of the method. It is the method telling you the truth: some questions the leaf cannot answer, and the honest next step is the inflorescence, the seed, or the sequence.

The Genera

Morphology, genus by genus

Each guide reads one genus the way a revision reads it — the characters that carry information, the ones that only look as though they do, and the point where the plant stops answering.

Read now
Alocasia

Colocasioid venation · wax glands · peltate juveniles

The leaf read character by character — Hay's A–N diagram on real leaves, the venation hierarchy from costa to secondary vein, and two case studies where a vein a few millimeters from the edge is the whole diagnosis.

Read the guide
In preparation
Anthurium

The geniculum · reticulate venation

The largest genus in the family, and the one with the clearest joint at the top of the petiole. Blade shape runs from linear to orbicular, which means outline is almost useless here and the small characters carry everything.
In preparation
Philodendron

Parallel-pinnate venation · resin canals

One of only a handful of genera with resin canals visible in the leaf without a lens — the same resin that glues pollen to a beetle at flowering time. Cataphyll behavior splits the subgenera.
In preparation
Monstera

Fenestration · skototropism · heteroblasty

Holes opened by programmed cell death, juveniles that grow toward darkness to find a trunk, and shingle-stage leaves pressed flat to the bark. Why the holes exist is still argued.
In preparation
Rhaphidophora

Square stems · a name that misleads

The Old World answer to Monstera — and not named for raphides at all, but for trichosclereids its author illustrated correctly and labelled confusingly.
In preparation
Epipremnum

Separated on the seed, not the leaf

The genus that proves the point of this whole section: vegetatively near-inseparable from Rhaphidophora, and divided from it on ovule number and seed shape.
In preparation
Scindapsus

Always entire

The climber that never makes a hole, and whose anchor roots may not differentiate from feeder roots at all.
In preparation
Colocasia

Peltate at every stage

Taro, and the type of colocasioid venation. Peltate from seedling to adult — the character that most reliably separates it from the Alocasia it is constantly confused with.
In preparation
Xanthosoma

The New World cousin

Sagittate rather than peltate, neotropical rather than Asian, and sharing the venation type that makes the three big-leaved genera so hard to tell apart at a glance.
In preparation
Caladium

Peltate, variegated, tuberous

Where leaf variegation becomes the thing the plant is grown for — and where peltation does the work of separating it from Xanthosoma.
In preparation
Amorphophallus

One leaf that looks like a tree

A single dracontioid leaf on a single petiole, dividing into a crown that can stand taller than a person. The most structurally extraordinary leaf in the family.
In preparation
Arisaema

Pedate blades · a pseudostem

No true aerial stem — the trunk is a column of wrapped petiole sheaths. Sex expression shifts with the plant's condition from one year to the next.
In preparation
Syngonium

Two plants in one

Arrow-shaped as a juvenile, trifid to pedatisect as an adult. Growers keep it juvenile on purpose, because the adult is a different-looking plant.
In preparation
Aglaonema

The Old World cane

Same erect, annular-scarred habit as Dieffenbachia, on the other side of the world and with a different fine venation.
In preparation
Dieffenbachia

Annular leaf scars · a long sheath

The green cane of the New World understorey, and one of the best-studied plants in the family for what happens at flowering.
In preparation
Homalomena

Aromatic when crushed

The character is chemical, not visual: crush a leaf and it smells of terpenoids. Its lookalike Schismatoglottis does not.
In preparation
Schismatoglottis

Not aromatic · ligulate sheath

The other half of that pair, plus the long apical ligule that marks much of the tribe — and a concentration of rheophytes.
In preparation
Cryptocoryne

Convolute ptyxis · truly aquatic

How the young leaf is rolled in the bud separates it from Lagenandra, which is involute. One of very few genera in the family that lives submerged.
In preparation
Spathiphyllum

A rosette with a joint

An acaulescent herb that nonetheless carries a geniculate petiole — an unusual pairing, and a reminder that habit and character do not travel together.

Why so many at once

The genus pages are written from the same library, so the comparative material already exists — what each one needs is photography of real leaves, which is the slow part. If you grow any of these and can photograph a leaf properly, front and back, that is exactly the missing ingredient: get in touch through the contact page.

Reference

The words, plainly

Every term used across this section, in the sense the taxonomic literature uses it.

Adaxial / abaxial: Upper surface / lower surface of the blade. Many characters differ between the two, so descriptions always say which.
Anterior lobe / posterior lobes: The forward part of a divided blade, and the two basal lobes behind the petiole insertion.
Costa: The main rib of a lobe. A divided aroid leaf has an anterior costa and two posterior costae.
Colocasioid venation: Fine veins leaving the primaries at nearly a right angle, arching to the margin and fusing into a sinuous collective vein. Tribes Colocasieae and Caladieae.
Parallel-pinnate venation: Primaries and secondaries leaving the midrib pinnately, then running parallel to the margin. Called “striate” in older work. Not the same as grass-type parallel venation.
Reticulate venation: Net-like fine venation, superficially like a dicot leaf.
Interprimary collective vein: A vein formed where secondary veins meet between two primary lateral veins. Whether it forms at all can be diagnostic.
Marginal / intramarginal / submarginal vein: A vein at the very edge; one running a short distance inside it; one that the major venation runs into some way in from the edge. Different structures — and some species have more than one.
Geniculum (pulvinus): A swelling or joint at the top of the petiole that lets the blade move independently. Nearly universal in Pothoideae and Monsteroideae.
Peltate: Petiole attached within the blade margin rather than at the edge.
Sagittate / hastate / cordate: Arrow-shaped with lobes pointing back; spear-shaped with lobes pointing out; heart-shaped.
Pedate / pedatisect: Divided with the side segments themselves branching outward, like a bird's foot; pedatisect means divided all the way to the axis.
Dracontioid: The Amorphophallus-type leaf: trisect, with the primary divisions themselves pinnatisect or further divided.
Fenestrate: Perforated. In Araceae the holes open during early leaf development, by programmed cell death.
Heteroblasty: Juvenile and adult leaves differing markedly on the same plant.
Shingle plant: A juvenile climbing stage with almost no petiole and blades pressed overlapping against the bark.
Hemiepiphyte: Primary: germinates above ground, sends roots down. Secondary: germinates on the ground, climbs, loses the ground connection, then re-establishes it.
Skototropism: Growth toward darkness — how a seedling climber finds a tree trunk.
Anchor root / feeder root: Short roots that grip bark; long roots that run to the soil. Climbing hemiepiphytes make both.
Rheophyte: A plant of swift streams, flooded to the waterline: narrow leathery leaves, firmly attached stem.
Sympodium, prophyll, cataphyll: The stem as a chain of articles; the first (usually two-keeled) leaf of each article; a scale leaf without a blade.
Ptyxis: How a single young leaf is folded or rolled in the bud. Convolute in Cryptocoryne, involute in Lagenandra.
Raphides, biforines: Needle-shaped calcium oxalate crystals, always present in Araceae; and the thick-walled cells that eject them.
Laticifer / resin canal: Canals carrying latex, present in most of the family; canals carrying resin, in only a handful of genera.

Sources

The books and papers behind this section

This hub is a synthesis, and one book carries most of it. Where a claim is contested — and several here are — the competing readings are given in the text rather than resolved silently.

Mayo, S. J., Bogner, J. & Boyce, P. C. (1997). The Genera of Araceae. Royal Botanic Gardens, Kew. The spine of this section. The venation types and the coining of “parallel-pinnate”; the blade-shape range; peltate genera; the stem and habit types; the hemiepiphyte definitions; anchor and feeder roots; contractile roots; rheophytes and aquatics; the sympodial module; raphides, biforines, laticifers and the five resin-canal genera; the geniculum's distribution; the absence of raphides in Acorus; the Rhaphidophora naming trap; and most of the genus signature table.
Cusimano, N., Bogner, J., Mayo, S. J., Boyce, P. C., Wong, S. Y., Hesse, M., Hetterscheid, W. L. A., Keating, R. C. & French, J. C. (2011). Relationships within the Araceae: comparison of morphological patterns with molecular phylogenies. American Journal of Botany 98(4): 1–15. The character-by-character audit of which morphology tracks the molecular tree. Source for fenestration having arisen at least six times, aculeate petioles at least five, peltate leaves as the only synapomorphy of the Colocasia clade, and the finding that Engler's striate-venation subfamily was built on a homoplasious character.
Hay, A. (1999). The genus Alocasia (Araceae–Colocasieae) in the Philippines. Gardens' Bulletin Singapore 51(1): 1–41. Seedling leaves almost always peltate while most adults are not — the clearest ontogenetic caution in the section.
Madison, M. (1977). A revision of Monstera (Araceae). Contributions from the Gray Herbarium 207: 3–100. The shingle-plant description, the 30-meter feeder roots, the dismissal of the water-drip hypothesis as “a fanciful interpretation with no basis in reality,” the cooling hypothesis, and the correction that the skototropism paper's Monstera gigantea is probably Monstera tenuis or Monstera dubia.
Melville, R. & Wrigley, F. A. (1969). Fenestration in the leaves of Monstera. The classical necrosis account, and the 0.14–0.15 mm hole spacing the authors read as a diffusion-reaction pattern.
Gunawardena, A. H. L. A. N. et al. (2005). Programmed cell death and leaf morphogenesis in Monstera obliqua (Araceae). Replaces necrosis with programmed cell death: TUNEL-positive nuclei, intact cell walls at the perforation site, rim cells re-differentiating as epidermis — convergent with the lace plant.
Lubenow, C. (2011). Experimental tests of hypotheses for leaf fenestration in Monstera deliciosa. CIEE Monteverde. ⚠ An undergraduate field study on one species, with 15–30 replicates per treatment. It is the only direct experimental test in this library, and it is cited as such: ~12× more water beneath holed leaves, no significant wind effect, and more herbivore damage on holed leaves rather than less.
Muir, C. D. (2013). How did the Swiss cheese plant get its holes? The American Naturalist 181(2): 273–281. The variance-reduction model: fenestration does not raise mean carbon gain, it lowers the variance under sunflecks. Also the objections to the cooling and camouflage hypotheses, and the observation that there are no fenestrated trees.
Boyce, P. C. & Wong, S. Y. (2012). Araceae of Malesia I: The Genera. Malayan Nature Journal 64(1): 33–67. The modern Malesian recasting of the generic characters — the tessellate venation state, the cataphyll and ligule examples, and the hapaxanthic shoot option that the 1997 treatment does not carry.
Zona, S. (2020). Shingle-leaf climbers. The cross-family census of the shingle habit — ten families, 22 genera, at least 158 species, with only one species in mainland tropical Africa — and the statement that few of the functional hypotheses have ever been explicitly tested.
Boyce, P. C., Sookchaloem, D., Hetterscheid, W. L. A., Gusman, G., Jacobsen, N., Idei, T. & Nguyen, V. D. Araceae. In: Flora of Thailand. The geophyte proportion of a regional flora, and a second glossary treatment of colocasioid venation that hedges Mayo's wording.
Strong, D. R. & Ray, T. S. (1975). Host tree location behavior of a tropical vine (Monstera gigantea) by skototropism. Science 190: 804–806. The original description of growth toward darkness. See reference 4 on the species identity.
Li, H. et al. (2010). Araceae. In: Flora of China, Vol. 23: 3–79. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis. The aromatic/non-aromatic split between Homalomena and Schismatoglottis, the Alocasia wax glands, and paradioecy in Arisaema attributed to nutrition.
Hay, A. (1998). The genus Alocasia (Araceae–Colocasieae) in West Malesia and Sulawesi. Gardens' Bulletin Singapore 50: 221–334. The Alocasia leaf-blade diagram and terminology that the Alocasia guide is built on.

AROID MORPHOLOGY