146 A TEXT-BOOK OF GRASSES 
to collect in depressions or drainage basins where the 
water from showers remains longest. 
185. Halophytic grasses are those that grow in soil 
containing an excess of mineral salts. In general they are 
known as salt-marsh plants. They are found in the salt- 
marshes of the seacoast and of interior alkali regions. 
The soil that supports halophytes may not be lacking in 
water, but the presence of soluble salts increases the 
density of the soil-water and hence renders it less easily 
absorbed by the root-system of the plant. Although 
erowing in water or wet soil, the plants have difficulty in 
obtaining the necessary water-supply and consequently, 
to avoid injury from loss of water through evaporation, 
xerophytic characters have been developed. Among these 
characters may be mentioned harshness due to the pres- 
ence of mechanical tissue, roll-leaves, and succulence. 
Familiar examples of halophytic grasses are Spartina 
glabra Muhl. of the Atlantic coast salt-marshes and 
Distichlis spicata (L.) Greene of the interior alkali plains. 
186. Hydrophytes are water plants. They grow in 
the water, either submerged or from soil that is perma- 
nently saturated. Only a few grasses, such as Hydrochloa 
caroliniensis Beauv., are nearly or quite submerged. But 
there are many that inhabit permanent fresh-water or 
brackish marshes. To this group belong Zizania palustris 
L. (Indian rice), Zizaniopsis miliacea (Michx.) Ddll & 
Asch., Paspalum dissectum L. and P. repens Berg. Pani- 
cum elephantipes Nees and Echinochloa sabulicola Nees 
of the American tropics are succulent hydrophytes, grow- 
ing in several feet of water. Paspalum repens, of Pan- 
ama, forms long runners that float upon the surface of 
the water, buoyed up by their inflated sheaths. 
Swamp-grasses as distinguished from marsh-grasses 
