554 ALISMACE^E. (WATER-PLANTAIN FAMILY.) 



1. ALISMA, L. WATER-PLAXTAIX. 



Flowers perfect. Petals involute in the bud. Stamens definite, mostly 6. 

 Ovaries many in a simple circle on a flattened receptacle, forming flattened 

 coriaceous achenes, which are dilated and 2 - 3-keeled on the back. Roots 

 fibrous. Leaves all from the root, several-ribbed, with connected veinlets. 

 Scape with whorled pauicled branches. Flowers small, white or pale rose- 

 color. (The Greek name ; of uncertain derivation.) 



1. A. PlantagO, L. Perennial by a stout proliferous corm ; leaves long- 

 petioled, ovate, oblong, or lanceolate or even linear, acute, mostly rounded or 

 heart-shaped at base, 3 - 9-nerved ; panicle loose, compound, many-flowered 

 (1-2 long) ; carpels obliquely obovate, forming an obtusely triangular whorl 

 in fruit. Shallow water and ditches, across the continent. Very variable as 

 to foliage, but the leaves usually more broadly cordate-ovate than in Old 

 World forms (var. Americanum, R. $ S.) ; when growing under water thin- 

 ner and narrowly lanceolate." (Eu., etc.) 



2. SAGITTAKIA, L. ARROW-HEAD. 



Flowers monoecious, or often dioecious in n. 1 and 4, and polvgamous in n. 7. 

 Petals imbricated in the bud. Stamens indefinite, rarely few. Ovaries many, 

 crowded in a spherical or somewhat triangular depressed head on a globular 

 receptacle, in fruit forming flat membranaceous winged achenes. Marsh or 

 aquatic, mostly perennial, stoloniferous herbs, with milky juice and fibrous 

 roots ; the scapes sheathed at base by the bases of the long cellular petioles, of 

 which the primary ones, and sometimes all, are flattened, nerved, and destitute 

 of any proper blade (i. e. are phyllodia) ; when present the blade is arrow- 

 shaped or lanceolate, nerved and with cross-veinlets as in Alisma. Flowers 

 produced all .summer, whorled in three?, with membranous bracts ; the sterile 

 above. (Name from nar/itta, an arrow, from the prevalent form of the leaves.) 

 1. SACrlTTARIA proper. Flowers monoecious, with the lower whorls pistil- 

 late, or dioecious; stamens few or niimc.'ous, covering the receptacle; sepals 

 spreading or rejlexcd in fruit. 



* Filaments numerous, narrow, as long as or longer than the linear-oblong anthers : 

 bracts 3, distinct ; fruiting heads larger. 



1. S. variabilis, Engelm. Scape (-4 high) angled, with one or more 

 of the lower whorls fertile ; leaves very various, almost ai.vays sagittate; 

 bracts mostly pointed ; pedicels of the fertile flowers at least half the length 

 of the sterile ones ; petals wholly white ; filaments glabrous, nearly twice the 

 length of the anthers; achenes obovate (about 1" long), winged on both mar- 

 gins, with a long curved or usually horizontal beak ^ - g its length. (S. sagit- 

 trefolia, L., var. variabilis, M. Micheli.) In water or wet places, very common ; 

 exceedingly variable in size and foliage, ordinarily with narrow halberd-shaped 

 or sagittate leaves, sometimes dioecious, with large, broad and obtuse leaves 

 (var. OBTtiSA), or monoecious, with large, broad and acute leaves (var. LATI- 

 r6LiA), or the narrow leaves with long and linear diverging lobes (var. AN- 

 GUSTIF6LIA), or with some leaves lanceolate or ovate-lanceolate, others more 

 or less sagittate (var. DIVERSIF6LIA), etc. Root propagating by stolons tuber- 

 iferous at the extremity. The European species has the fertile pedicels only 



