163] FLORA OF COLUMBIA AND VICINITY 21 



the palustrous or riparian floras. The plant-growth is usually 

 slight; it looks weedy and is often filthy. Owing to high water 

 this vegetation has no, or but slight, vernal development. It 

 is best seen in late summer, while in autumn protracted drouths 

 allow a weedy uliginose vegetation, consisting of species of 

 Polygonum, Coreopsis and Bidens, to hide it mostly from view. 

 Obviously a limose plant is subjected to great and violent ex- 

 tremes. Hence the vegetation mainly either grows in dense 

 wiry tufts, or consists of succulent creeping plants. In spite of 

 the plants being under water for a part of the year, they exhibit 

 certain xerophytic adaptations. The mud of the shore bakes 

 into hard lumps in times of drouth, and the vegetation, till au- 

 tumn, is seldom shaded much from the sun. Omitting the au- 

 tumnal uliginose plants, there are six limose associations: 



a. Limosae heleocharidoides. The spike-rush associ- 

 ation consists of low densely tufted leafless plants with wiry 

 culms and of a peculiar dark green color. They stand often in 

 shallow water, the larger species being truly amphibious plants. 

 They are as follows : 



Heleocharis acuminata H. palustris 



H. tenuis H. Engelmanni 



H. intermedia H. ovata 



H. glaucescens 



b. Limosae cyperoides. The galingale association of 

 limose sedges and grasses consists of somewhat larger plants 

 than those of the preceding. In late summer the larger galin- 

 gales {Cy perns spp.) are especially prominent. Excluding these 

 as being, rather, uliginose species, the following are character- 

 istic : 



