CHAPTER ii 



THE STRUCTURE AND GENERAL ECONOMIC IMPORTANCE 

 OF GRASSES 



The grass family, Graminaceoe, is the most important family econom- 

 ically speaking in the whole vegetable kingdom. It includes several 

 thousand species, all of them with a few exceptions (see ante) being with- 

 out any deleterious properties. The vegetational associations where 

 grasses control the faces are known as meadows, prairies, pampas, steppes 

 and savannahs. 



Habit. The grass family includes low, erect herbs. A few, such as 

 the bamboos, are shrubs, or trees. Some grasses are creeping, others 

 trailing, semi-erect, erect and unbranched, or very freely branching from 

 the base (Fig. 46). Several, although perennial, are monocarpic, flower- 

 ing and fruiting but once. In duration grasses are annuals, winter 

 annuals, living through the winter and sending up flower stalks the 

 next spring, or are perennials. 



Roots. Their roots are fibrous, and secondary, that is, there is never 

 at any time a primary root.. The roots in such grasses as maize may be 

 divided into the horizontal, feeding roots penetrating the soil at no great 

 depth, the deep roots (3^ feet in corn) for anchorage and the prop roots 

 which develop as aerial roots from the lowermost nodes of the upright 

 stern and later enter the soil bracing the stem during storms of wind. 

 Occasionally, the deep roots draw upon the deep-seated supplies of water, 

 especially in arid countries, where such grasses, as the buffalo grass 

 (Buchlo'e), grow to a depth of seven feet. Ordinarily in the grasses with 

 horizontal underground stems, the roots spring freely from the nodes and 

 from tufts of short spreading character. The interlacement of the 

 subterranean roots and stems is so compact in areas where grasses domi- 

 nate in herbage, that shrubs and trees are unable to establish themselves 

 in competition with the grasses and this is one of the cogent reasons for 

 the treelessness of prairies and other characteristic grasslands, such as 

 the pampas of South America. 



