50 



The g-eneral appearance of the association, including especially 

 the color-tone and number of secondary plants, depends almost en- 

 tirely upon the specific peculiarities of the bunch-grasses represented 

 and upon the density of the covering. Most bunches are so distinct 

 in size, density, or other features that they are easily recognized, even 

 when sterile. In doubtful cases minor morphological characters may 

 be used, such as pubescence, the stiaicture of the ligule, and other 

 similar vegetative features. Some of the most important bunch- 

 forming species are the following. 



1. Koeleria cristata. — Bunches regular, compact, about one foot 

 (3 dm.) in maximum diameter and eight inches (2 dm.) high, with 

 a considerable accumulation of dead leaves beneath them, forming an 

 elevated central tuft and radiating on the sand; leaves six to ten 

 inches (15-25 cm.) long, mostly straight and erect, glaucous-green 

 or canescent with fine pubescence. 



The regular close bunches of Koeleria have an appearance of 

 trimness and neatness in which they excel any other species. The 

 gray-green color and the shining spikelike panicles make the grass 

 very conspicuous, especially during the aestival aspect when it is in 

 bloom, or at any season when the dew is still on it in the early 

 morning. The bunches are rarely confluent and tend to leave a con- 

 siderable uncovered area between, especially when not associated with 

 other species. 



2. Leptoloina cogiiafiiin. — Bunches 8-12 inches (20-30 cm.) wide 

 and about eight inches (20 cm.) high, very compact, close and dense, 

 flat-topped, frequently confluent in large irregular patches ; leaves 

 short, all erect or radiating, and freely mixed with the dead leaves 

 of the preceding' season, giving the whole bunch a yellow-gray ap- 

 pearance. The short leaves are more irregiflarly arranged than those 

 of Koeleria cristata, and the dead leaves and culms remain for a 

 long time mixed with the living. In the serotinal season the large, 

 but very lax, red-flowered panicles appear and impart a distinct red- 

 dish hue to the consocies in which the plant grows. 



3. Stipa sparfea. — Bunches loose, few-leaved, but regular in size, 

 1-1.5 feet in diameter and about the same height, with a slig-ht ac- 

 cumulation of dead leaves and culms on the sand beneath. The flow- 

 ering culms rise to a height of three feet (i m.). Of all the bunch- 

 forming species of grass in the association this species fonns the 

 loosest and most indefinite bunches. 



4. Panicnm pscndopubescens (PI. Ill, Fig. 2). — Bunches irregu- 

 larly circular in outline, depressed, i-r.5 feet (3-5 dm.) in diameter, 

 four to six inches (1-1.5 dm.) high; culms and leaves radiating from 



