148 COMMON CANADIAN WILD PLANTS. 



3. AMS'MA, L. WATKK-I'LANTUX. 



A. planta'gO, L., var. America'nuiH, <iray. Leaves long- 

 petioled, mostly oblong- heart-shaped, but often narrower, 3-9- 

 nerved or ribbed, and with cross veinlets between the ribs. 

 Flowers small, white, in a large and loose compound panicle. 

 Low and marshy places, often growing in the water. 

 4. SAGITTA'RIA, L. AHHOW-HEAD. 

 * Filaments narrow, as long as the anthers. 



1. S. Varia'bilis, Engelm. Very variable in size and in the 

 -shape of the leaves. Scape angled. Common everywhere in 

 shallow water. 



* * Filaments very xhort, loiih enlarged mostly yland'diir bate. 

 -. S. heterophylla, Pursh. Scape weak and at length pro- 

 cumbent. Leaves lanceolate or lance-ovate, entire, or with one 

 or two narrow basal sagittate appendages. 



3. S. gramin'ea, Michx. Scape very slender, erect. Leaves 

 varying from ovate-lanceolate to linear, scarcely ever sagittate. 



ORDER XCV. HYDROCHARIDA'CE^E. (FROG'S-BIT F. ) 



Aquatic herbs, with dioecious or polygamo-dicecious flowers on 

 scape-like peduncles from a kind of spathe of one or two leaves, 

 the perianth in the fertile flowers of 6 pieces united below into a 

 tube which is adherent to the ovary. Stigmas 3. Fruit ripening 



under water. 



Synopsis of the Genera. 



1. Aiitich'aris. Growing under water, the pistillate flowers alone coining to 



the surface. Stem leafy and branching. Perianth of the fertile (lowers 

 with a 6-lobed spreading limb, the tube prolonged to an extraordinary 

 length, thread-like. Leaves crowded, pellucid, 1-nerved, sessile, wh >rlcil 

 in threes or fours. Stamens 3-9. 



2. Vallisiie'ria. Nothing but the pistillate flowers above the surface, these 



on scapes of great length, and after fertilization drawn below the surface 

 by the spiral coiling of the scapes. Tube of the perianth not prolong. 1. 

 Leaves linear, thin, long and ribbon-like. 



(In both genera the staminate flowers break off spontaneously and float on 

 the surface around the pistillate ones, shedding their pollen upon them.) 



I. AlVACH'ARIS, Kichard. WATKU -\VKI;I>. 



A. Canadensis, Itichard. (Klu>l<'<i <'<in<nl<-nxix, 1'lanchoii, in 

 Macoun's Catalogue.) Common in blow waters. 



