ALISMACE^;. 



795 



Besides the common species, there are several from North and South 

 America, and eastern Asia. 



1. Common Arrowhead. Sagittaria sagittifolia, Linn. 



(Fig. 957.) 



(Eng. Bot. t. 84.) 



A perennial, with a creeping rootstock, 

 forming bulb-like tubers. Leaves ra- 

 dical, rising out of the water on very 

 long stalks ; the blade 6 to 8 inches 

 long, sagittate ; the lobes of the base 

 nearly as long as the terminal one, all 

 pointed, but varying much in width. 

 Flower-stem leafless, erect, longer than 

 the leaves, bearing in its upper part 

 several distant whorls of rather large, 

 white flowers ; the 3 inner segments 

 of the perianth twice as long as the 3 

 outer green ones; the upper flowers 

 usually males, on pedicels \ to 1 inch 

 long ; the lower ones females, on shorter 

 pedicels. 



In watery ditches, and shallow ponds 

 and streams, dispersed over the greater 

 part of Europe and central and Russian 



Asia to the Arctic regions. Represented in North America by a slight 

 variety now said to be a distinct species. In Britain, limited to Eng- 

 land and Ireland, with the exception of a single station near Paisley, 

 in Scotland. FL summer and autumn. 



Fig. 957. 



III. ALISMA. ALISMA. 



Aquatic herbs, erect or rarely floating, with radical, long-stalked 

 leaves ; the flowers either in a terminal umbel, with or without whorls 

 of pedicellate flowers below it, or in a panicle with whorled branches 

 each bearing a similar umbel. Perianth of 3 outer, small, herbaceous 

 segments, and 3 much larger inner ones, petal-like, and very delicate. 

 Stamens 6. Carpels numerous, small, and 1-seeded, either arranged 

 in a ring round the axis, or irregularly in a globular head. 



A genus now known to comprise a considerable number of species, 



