Sagittaria ALlSMACEAE-HYDROCHARITACEAE Hydrilla 



Lvs. hastate or sagittate: plant 1-8 dm. tall 2. S. sagittifolia 



var. leucopetala 



1. Sagittaria pygmaea Miq. (E.P.IV. 15: 44). Erect, 10-15 cm. high; fls. white, 

 VIII; pistillate fls. 1, sessile; fr. IX. Japan, Korea, China; locally in Hun., Ki. 

 Flooded rice fields. 



2. Sagittaria sagittifolia Linn. var. leucopetala Miq. Old World Arrowhead (Tz'u 

 Ku; Mother-of-Tubers) (E.P.IV. 15: 48). Erect perennial, to 0.7 m.; fls. white, 

 VI-VII; fr. VIII-IX. Eurasia; locally in An., Che., Hun., Hup., Ki., Ku. Pond 

 margins, ditches. Fig. 397. 



There are wide extremes of variation in leaf form in S. sagittifolia and varieties have been 

 described for these. Since, however, the variation in leaf form in a single plant is often quite 

 striking it seems best to denote these extremes simply as narrow-leaved forms and broad-leaved 

 forms. In the typical form of S. sagittifolia, the petals are tinged with purple at the base 

 (Hegi I. t. 20, f. 1) while in the Asiatic var. leucopetala they are pure while. 



176. BUTOMACEAE f\W% ( M ao Sao K'o) 

 Marsh herbs with scapose erect stems (ours), or submersed plants, with latex (ex- 

 cept Butomus): fls. perfect: fr. of several follicles. 6 genera with 9 species, mostly 

 in tropical America; 2 genera and as many species in Eurasia, one in China. 



1. Butomus Linn. %MM (Mao Sao Shu) 



Glabrous erect marsh herbs with creeping rootstocks, and without latex: fls. pink, 

 in simple bracteate umbels; perianth segments all colored and marcescent: stamens 9; 

 fr. of 6 beaked many-seeded follicles. One species, in Eurasia. (Greek meaning "ox" 

 and "cut", referring to the sharp leaves, which cut the mouth of cattle.) 



1. Butomus umbellatus Linn. f&Jt (Mao Sao) (B.M. 96). Erect herb, to lm. ; fls. 

 pink, V; fr. VII-VIII. Eurasia; locally in Ku. Streamsides. 



177. HYDROCHARITACEAE Frog's Bit Family y^MPc (Shui Pieh K'o) 

 Aquatic herbs, submersed or floating, with simple entire lvs. and unisexual or 

 polygamous regular petaloid fls. arising from a bracted spathe: sepals and petals 3; 

 stamens 3-12, distinct or united: ovary inferior, syncarpous, 1-3-celled, ripening under 

 water, indehiscent. 14 genera with 40 species; 9 genera and as many species in China. 



Key to the Genera 



A. Plants with elongated submerged brg. stems and verticillate lvs 1. Hydrilla 



AA. Plants stemless or with creeping rootstocks. 



Lvs. long and narrow, ribbon-like: perianth single 2. Vallisncria 



Lvs. especially the floating ones, broad: perianth double. 



Fls. white: If. blades mostly orbicular-cordate 3. Hydrocharis 



Fls. bluish: If. blades mostly linear, lanceolate or ovate 4. Ottelia 



1. Hydrilla L. C. Rich. MMM (Hei Tsao Shu) 



A slender branched submersed herb with thin narrowly oblong verticillate lvs. and 



small unisexual fls. : staminate fls. escaping from their sheaths and floating free on 



the water; stamens 3, with large reniform anthers: pistillate fls. sessile and persistent; 



ovary one-celled, with 2-3 oblong seeds. One species: temperate and tropical parts 



426 



