ONAGRACB.E. 



285 



the lower ones having leaves at their base like the stem-leaves, has 

 been considered by some as a distinct species, under the name of M. 

 alterniflorum (Eng. Bot. Suppl. t. 2854). 



2. Whorled Myriophyll. Myriophyllum verticillatum, 

 Linn. (Fig. 350.) 



(Eng. Bot. t. 218. Water Milfoil) 



In deep, clear waters the foliage is 

 precisely that of the spiked M., but the 

 flowers are all immersed in the water, in 

 the axils of the upper leaves. In shallow, 

 muddy ditches, the segments of the 

 leaves are often shorter and fewer, and 

 the flowers form a spike protruding above 

 the water as in the spiked M., but the 

 bracts or floral leaves are longer than 

 the flowers, and pinnate like the stem- 

 leaves : this form constitutes the M. 

 pectinatum of some authors, but cannot 

 be distinguished with any precision, even 

 as a variety. 



In watery ditches and ponds, with the 

 spiked M., over the greater part of its 

 geographical range, and in many coun- 

 tries as common. In Britain it appears 

 to be rather scarce, but perhaps fre- 

 quently overlooked from its flowers not appearing above the 

 all summer. 



Fig. 350. 



water. Fl. 



VI. JYIARESTAIIi. HIPPUEIS. 



A single aquatic species, distinguished as a genus from MyriopJiyll 

 by its entire leaves, and by its flowers always without petals, with a 

 scarcely perceptible border to the calyx, and reduced to 1 stamen, 1 

 subulate style, and 1 ovule and seed. 



1. Common Marestail. Hippuris vulgaris, Linn. (Fig. 351.) 

 (Eng. Bot. t. 763.) 

 An aquatic plant with a perennial rootstock, and erect, annual, simple 



