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 
1. 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 
Fic. 125. A heavy clus- soil; such bulrushes as Scirpus fluviatilis; 
(Panicularia laxa) after Such other plants, as cat-tails and bur- 
Britton and Brown. 
reeds (fig. 16); and, over smaller areas, 
sweet flag (Acorus calamus) and 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 
Fic. 126. Flower and fruit of the jewel- 
weed. 
