THE SWALE 



293 



The dominant plants that cover consider- 

 able areas of the swale, almost to the 

 exclusion of other plants are mainly 

 grass-like plants, capable of close growth 

 above ground and nearly complete occu- 

 pation of the soil. They are such marsh 

 grasses as the panicularias (from which 

 marsh hay is made) and reed, on wetter 

 fig. 125. a heavy cius- soil ; such bulrushes as Scirpus fluviatilis ; 



ter of manna-grass 



(Panicuiaria laxa) after such other plants, as cat-tails and bur- 



Britton and Brown. _ . ^. 



reeds (rig. 16); and, over smaller areas, 

 sweet flag (Acorus calamus) arid blue flag (Iris versicolor). 

 Where these grow most compactly, there are a few lesser 

 plants intermixed, filling the niches, reaching into light 

 above and spreading roots in the superficial layers of the soil. 

 With permanent conditions, the mixture of plants will 

 remain much the same year after year. They are nearly all 

 perennials, holding their place by continuous occupancy of 

 it. Each is striving to extend its domain, but there is little 

 opportunity. In the permanent association of certain species 

 together there are some fine mutual adjustments. The 

 taller broad-leaved perennials, like swamp-milkweed and 

 joe-pye-weed and boneset, root rather deeply, and stand 

 stiffly erect. The top layers 

 of the soil are left by them 

 to such lesser things as marsh 

 skullcap, bedstraws, and 

 tear-thumbs, whose strag- 

 gling sprays reach out and 

 find the light. The annual 

 herbs of the swale are few; 

 they- are such as jewel-weed 

 and Spanish needles, that 

 depend for their opportunity 



Flower and fruit of the jewel- 



