Several genera containing about 10 species, mostly of warm regions. 



1. Hydrocleys Rich. 



Characteristics of family. Four species, all native to Brazil. 



1. Hydrocleys nymphoides (Willd.) Buch. Water-poppy. Fig. 70. 



Rhizomes rooting at the nodes; leaves alternate, long-petioled; leaf blades 

 broadly ovate, cordate at base, rounded at apex, 5 cm. long or more, entire, glossy 

 on upper surface, somewhat spongy along the midrib and sparsely pubescent on 

 lower surface, usually floating; flowers axillary on long peduncles, raised well 

 above the water and lasting only one day; petals light-yellow, obovate, 2-3 cm. 

 long; stamens numerous, the outer ones sterile, fertile stamens purple or violet- 

 color; pistils usually 6, gradually tapering into the style. 



Cult, in ponds and pools in s. U.S., including e. Tex., and becoming somewhat 

 naturalized, summer; nat. of Braz. 



Included here on the basis of Muenscher's report of its occurrence in Texas; 

 we have seen no specimens. 



Fam. 23. Hydrocharitaceae Juss. Frog's-bit Family 



Fresh- or salt-water herbs, partly or wholly submerged, dioecious to poly- 

 gamo-monoecious, with terrestrial or floating roots; leaves radical and crowded 

 or dispersed on elongated stems, alternate to opposite or whorled; flowers regular, 

 usually unisexual, arranged in a bifid spathaceous bract or within 2 opposite 

 bracts, the staminate usually more than 1, the pistillate solitary; spathe sessile 

 to long-pedunculate, the peduncle sometimes spirally twisted; perianth segments 

 free to the base, 1- or 2-seriate, 3 or rarely 2 in each series, the outer often green 

 and valvate, the inner imbricate and petaloid; stamens 1 to numerous; anthers with 

 2 parallel cells that open by longitudinal slits; rudimentary ovary present in the 

 staminate flowers; staminodes sometimes present in the pistillate flower; ovary 

 inferior, sometimes beaked, 1 -celled, with 3 to 6 or rarely more parietal placentas 

 that sometimes protrude nearly to the middle of the ovary; styles as many as 

 placentas, entire or 2- or 3-branched; ovules numerous on the placentas; fruit 

 globose to linear, dry or pulpy, rupturing irregularly; seeds numerous, without 

 endosperm; embryo straight, with a thick radicle and usually inconspicuous 

 plumule. 



About 16 genera and 80 species, mainly of tropical and warm temperate 

 regions. 



1. Fresh-water plants that are pollinated at or above the surface of the water; 

 pollen spheroid (2) 



1. Marine plants that are pollinated beneath the surface of the water; pollen 



confervoid or united in strings (5) 



2(1). Plant floating; leaves broadly ovate to reniform, distinctly petiolate, 



emersed or floating; spathe composed of 1 or 2 free bracts 



1. Limnobium 



2. Plants attached to bottom; leaves linear or straplike, without a petiole, sub- 



mersed; spathe composed of 2 bracts connate into a tube (3) 



3(2). Leaves clustered at the base, straplike, more than 15 cm. long; petals rudi- 

 mentary and much smaller than the sepals 2. Vallisneria 



3. Leaves opposite or in approximate whorls on an elongated stem, less than 



5 cm. long; petals well-developed and much larger than the sepals 

 (4) 



156 



