80 A TEXT-BOOK OF GRASSES 
the water-requirement. It also affects directly the growth 
of crops. There is an optimum temperature for each 
crop at which it thrives best. The temperature through 
the growing season is of the most importance, though for 
perennials the minimum winter temperature may be a 
limiting factor. 
110. The timothy area.—This area extends from New 
England to the southern boundary of Virginia and farther 
south in the mountains and west to Minnesota and east- 
ern Kansas, approximately to the 96th meridian. In 
general this is the humid area. The rainfall is sufficient 
on the average for the growing, without irrigation, of 
the common meadow- and _ pasture-grasses, timothy 
and blue-grass, and the legume, red clover. The 
rainfall is distributed through the summer or growing 
season. 
There are other humid regions in the United States 
in the mountains of the western portion, isolated areas 
where the rainfall is sufficient and the altitude not too 
great. Timothy can be raised in Colorado up to about 
9,000 or even 10,000 feet altitude. At higher latitudes 
the altitudinal limit is lower. The most important humid | 
region of the West is the upper Pacific coast region lying 
west of the Cascades and extending from Puget Sound 
south into northern California. This differs from the 
eastern humid region in having cooler summers and milder 
winters with considerable rainfall. This region is emi- 
nently adapted to pasture crops because of the mild, moist 
winters. It is not so well adapted to hay crops because 
of the difficulty of curing hay in the moist climate. (See 
Farmers’ Bulletin No. 271.) 
In the northern part of the timothy area, the Canada 
field pea is much used (Par. 67). In the eastern part along 
