554 ALISMACE^. (WATEK-PLANTAIN FAMILY.) 



1. A L ISM A, L. Water-Plantaix. 



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 hack. — Roots 

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

 Scape with whorled panicled 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, oblojig, 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. SAGITTARIA, L. Arroav-head. 



Flowers monoecious, or often dioecious in n. 1 and 4, and polygamous 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 threes, Avith membranous bracts ; the sterile 

 above. (Name from sn(/itla, an arrow, from the prevalent form of the lea^-es.) 

 § 1. SAGITTAEIA proper. Flowers monoecious, icith the lower ichorls pistil- 

 late, or dioecious; stamens fev^ or numerous, covering the receptacle; sepals 

 spreading or re flexed in fruit. 

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

 Irracts 3, distinct ; fruiting heads larger. 



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

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

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

 of the sterile ones ; petals Avholly Avhite ; filaments glabrous, nearly tAvice tlie 

 length of the anthers; achenes oboA'ate (about V long), Avinged on both mar- 

 gins, Avith a long curA-ed or usually horizontal beak ;J- J its length. (S. sagit- 

 ta?folia, L., A^ar. variabilis, M. Micheli.) — In Avater or Avet places, very common ; 

 exceedingly variable in size and foliage, ordinarily Avith narroAv halberd-shaped 

 or sagittate leaves, — sometimes dioecious, Avith large, broad and obtuse leaves 

 (var. OBTtJSA), or monoecious, Avith large, broad and acute leaA-es (A-ar. lati- 

 f6lia), or the narroAv leaves with long and linear diverging lobes (var. an- 

 gustif6lia), or with some leaves lanceolate or ovate-lanceolate, others more 

 or less sagittate (A-ar. diversif6lia), etc. Root propagating by stolons tuber- 

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



