Key to Families
KEY TO FAMILIES
† Treated in Vol. II.
Key
1
Plants composed of oval green platelets, not differentiated into stems and leaves, floating free on fresh water
Plants differentiated into stems and leaves or bracts, usually attached by roots but some floating free
Ovary inferior; flowers 1 to few within a bifid spathaceous bract or 2 opposite bracts
5
Flowers borne on a flattened axis permanently enclosed in a spathelike leaf-sheath; marine, intertidal to subtidal
Flowers borne on a cylindrical axis breaking out of a short leaf-sheath, or free; brackish to fresh water
6
Leaves without sheaths
HYDATELLACEAE †
7
Inflorescence a 2-flowered spike; ripened carpels long-stalked, ± umbellately arranged at top of long spirally twisting peduncle.
Inflorescence of 1–several flowers; fruits short-stalked, apparently axillary, solitary or in small clusters
9
Leaves plicate in bud; plants usually large or small trees with large palmate or pinnate leaves
Leaves not plicate in bud; plants either herbaceous or climbing or shrubby, or if trees then with linear leaves
10
Plant usually herbaceous, rarely shrubby or tree-like; leaves glabrous; flowers hermaphrodite, or unisexual and plant monoecious
Plant a tree or shrub, often with aerial roots; leaves often with serrate margins; flowers unisexual and plants dioecious
Leaves with well-developed lamina, or if reduced to sheathing bracts these few and mostly basal; plants rarely dioecious
14
Flowers grouped in simple spikelets; each flower subtended by a bract (glume) which is visible without dissection of inflorescence.
Flowers grouped in a complex spike-like inflorescence within 2–3 glume-like bracts; flowers usually enclosed in a hyaline scale only visible by dissection
15
Flowers subtended by small membranous bracts; inflorescence a much branched to condensed cyme or few-flowered or flower solitary
Flowers ebracteate; inflorescence a dense cylindrical spike, spike-like raceme, or composed of globose capitula
18
Perianth-segments 4; leaves mostly broad, if linear plant wholly aquatic and permanently submersed
Inflorescence glabrous or ± hairy, but petaloid perianth-segments always glabrous; sap not orange or red
Stamens 6 or more, 2–1; leaves not usually equitant; or stamens 3 and leaves represented only by scales
24
Stamens 2–1, borne on a central column; inner perianth zygomorphic one petal differentiated as labellum
Stamen 1, the remainder transformed into petaloid staminodia often more conspicuous than actinomorphic inner perianth
27
Stems leafy throughout; petiole usually twisted and reversing the leaf surfaces
Stems with leaves mostly at base; leaves usually sheathing at base, or petioles not twisted and leaf surfaces not reversed
28
Leaves fibrous, glabrous, but often with spiny margins; flowers usually in large panicles
29
Aquatic plants of fresh water without subterranean storage organs; leaves submersed or floating and long-petiolate
30
Plant bulbous; inflorescence with an involucre of one or more spathaceous bracts
35
Leaves mostly very fibrous; stems often woody, sometimes forming heavy trunk with terminal leaf-tufts
Leaves usually not strongly fibrous; stems usually herbaceous, rarely soft-woody, usually completely hidden within leaf-bases
36
Perianth of 3–1 sometimes bract-like segments on margin of flattened inflorescence axis; inflorescence of 2 divergent spikes
Perianth of 3 sepals and 3, rarely 0, petals; inflorescence an umbel, panicle or raceme, or flowers solitary
37
Mature carpels dehiscing adaxially; flowers often in umbels or solitary, usually involucrate with spathaceous bracts
Mature carpels indehiscent or rarely dehiscing at base; flowers in panicles or racemes, bracteate but bracts short, not spathaceous
