108 A TEXT-BOOK OF GRASSES 
taspis) present arcuate nerves diverging at the base and 
converging at the apex, with numerous often conspicuous 
cross-veins, thus simulating the so-called netted-veined 
blades of dicotyledons. 
Besides the various genera already mentioned as having broad 
blades are the following which also present well-marked cross-veins: 
Olyrez, Centhotheca, Senites, Orthoclada, Pariana, many bamboos, 
and a few other genera. Pharus differs in having straight parallel 
lateral nerves that diverge from the midrib nearly throughout its 
length and join with a strong marginal nerve, instead of converging 
at the apex (Fig. 29). Leptaspis resembles Pharus, but Strepto- 
cheta is intermediate. 
138. Auricles.—Some grasses bear, one on either side at 
the base of the blade, appendages known as auricles. 
These auricles are characteristic of the tribe Hordee and 
are found in certain species of other tribes. 
Wheat, rye and barley show prominent auricles. Rice and 
Festuca elatior and its allies are examples outside the Hordex. A 
very unusual development of the blade is shown in Phyllorachis 
sagittata Trim. and Spodiopogon sagittifolius Rendle. The base of 
the blade is extended into a long lobe on either side of the short 
petiole. ; 
139. Roll-leaves.—In a preceding paragraph (Par. 
136), casual mention was made of blades in which, by 
rolling in various ways, the exposed surface is reduced. 
This rolling of the blade is a xerophytic character and 
tends, by reduction of the evaporating surface, to lessen 
the loss of moisture. Such reduction of surface is charac- 
teristic of grasses of plains and desert regions, of sandy soil, 
especially along the seacoast, and of saline marshes. In 
some cases the blades are permanently rolled, in other 
cases they are flat under favorable conditions of atmos- 
pheric moisture but readily roll when the moisture 
