420 
* * Styles 2 to 4, with dilated lobes: pod large, often thick, subylobose to ovate-oblong, 
2 to 4-valved: bracts mostly glabrous: stamens GU or more: seeds 2 to 4mm, long. 
2. P. monilifera Ait. (COTTONWOOD, NECKLACE POPLAR.) Tree 20 to 40m, high: 
leaves broadly deltoid, with numerons crenate serratures and narrow very acute 
acumination, sometimes ovate, rarely cordate, on clongated tlattened petioles: 
scales lacerate-fringed, not hairy: pods on slender pedicels, in long catkins, oblong- 
ovate, 3 to 4-valved (Incl. P. angulata Ait.)—Extending into the mountains of 
western Texas. 
3. P. Fremonti Watson. A large tree, with gray cracked bark: leaves broadly 
deltoid (or somewhat reniform), with a broad acute apex and more or less of asinus 
at base, few serratures (4 to 12 on each side), on petioles 2.5 to 7 em. long: aments 
with glabrous rhachis and bracts; the staminate loose, with pedicels 16 to 20 mm, 
long and the conspicnons disk 6 to 8 mm. broad; the fruiting 7 to 10 em. long: pod 
6to 8mm, long, on short stout pedicels, the disk 6 mm, broad; valves 3, thick 
coriaceous: seeds white.— Along water courses throughout the State. Var. (?) 
WISLIZENI Watson, of the Rio Grande valley from El] Paso to the Gulf, has sharply 
acuminate leaves truncate or slightly cuneate at base, staminate aments with 
shorter pedicels and less dilated thin disks, pistillate very slender (5 to 15 em. 
long), disk 4 to6 mm, broad, and ovate to ovate-oblong somewhat angled 3 
(usually 4)-valved pods (8 to 10 mm.) long on slender pedicels. 
CERATOPHYLLEA. (HorNworr FAMILY.) 
Aquatic herbs, with whorled finely dissected leaves, minute axillary 
sessile moncecious naked flowers, but with an 8 to 12-cleft involucre 
in the place of calyx, the fertile a simple l-celled ovary with a sus- 
pended ovule, and the seed filled by a highly developed embryo. 
1. CERATOPHYLLUM L. (Horxworr.) 
Herbs growing under water, with the sessile leaves eut into thrice- 
forked filiform rigid divisions, sterile flowers of 10 to20 stamens of sessile 
anthers, and the achene beaked with the slender persistent style. 
1. C.demersum L. Fruit smooth, marginless, the long style with a short spine 
or tubercle at the base on each side.—Var. ECHINATUM Gray, found in slow streams 
and ponds across the continent, has the fruit mostly larger (6 mm. long), rough- 
pimpled on the sides, the narrowly winged margin spiny-toothed, 
