TYPHA | LFYMNACEA ‘669 
LEMNA 
uppermost. Ovaries long-stipitate, 1-celled, surrounded by num- 
erous bristles and clavate rudimentary ovaries. Styles filiform. 
Fruit nut-like, small, usually splitting on one side. Seeds linear 
striate. 
T. latifolia L. Sp. 971. Stems stout, 4-8 feet high: leaves vagy am dl 
equalling or exceeding the stem, 3-12 lines wide: pistillate spike dar 
brown or black, at length an inchin diameter; the staminate portion usu- 
ally contiguous, each 3-12 inches long: pollen grains in 4’s: pistillate 
flowers without bracts: stigmas rhomboid or spatulate. In marshes 
throughout North America, Kurope and asia, except the extreme north. 
T. angustifolia L. Sp. 971. Stems slender, 2-10 feet high; leaves 2-6 
lines wide, somewhat convex on the back: apikes light brown, the stamin- 
ate and pistillate portions usually distant, the two together sometimes 15 
inches long, the pistillate portion when mature 2-8 lites in diameter and 
provided with bractlets: pollen grains simple: stigmas linear or linear-ob- 
ong. In marshes, California and Oregon to the Eastern States and Europe. 
OrpER CII LEMNACEA Dumort. Fl. Belg. 147. (1827.) 
Very small floating stemless herbaceous plants consisting of 
flattened disk-like fronds with one or more rootlets from the 
middle below, and monoecious flowers without perianth imbed- 
ded in thefrond. Flowers consisting of 1-2 stamens or a flask- 
shaped 1-celled several-ovuled pistil. Style simple, with fun- 
nelform stigma. Fruit a 1-6-seeded utricle. Seeds compara- 
tively large, with straight axile embryo, albuminous. 
1 Lemna _ Frond 1-5-nerved, with a single rootlet. — 
2 Spirodela Frond 7-11-nerved, with several rootlets. 
1 LEMNA L. Sp. 970. 
Fronds 1-5-nerved, containing numerous acicular raphides, 
destitute of vascular tissue proliferous from a lateral slit, usually 
on each side near the base, with a single rootlet. Flowers mar- 
ginal, bracteate, diandrous. Filaments slender: anthers didymous, 
each cell bilocular by a transverse partition. dehiscing transverse- 
ly. Seeds 1-6, mostly ribbed. 
L. trisulea L. §p. 970. Fronds thin, oblong or oblanceolate, 6-9 lines 
long, attenuate at base into a slender stalk. very obscurely 3-nerved, often 
without rootlets, usually several series of offshoots remaining connected: 
bracts sac-like: seeds ovate, amphitropous, with small round operculum. 
In ponds, throughout most of North America: also in Europe and Asia. 
L. minor L. Sp. 970. Fronds round to elliptic-ovate, 1-3 lines in di- 
ameter, rather thick, very obscurely 3-nerved: seeds oblong-obovate, 
amphitropous, with prominent rounded operculum. Common in ponds in 
all parts of the world. 
2 SPIRODELA Schleiden Linn. xiii. 391. (1839.) 
Fronds 7--12-nerved. Rootlets several, with axile vascular 
tisue. Anther-cells bilocellate by a vertical partition and longi- 
tudinally dehiscent. Ovary 2-ovuled. 
S. polyrhiza Schleiden 1, c. Fronds round-obovate, 2-5 lines jongs 
thick, flat and dark green above, slightly convex and purple beneath, pal- 
