18 THE BIOLOGY OF HARDING COUNTY 



seasons, of much over a foot and practically none reach two feet. 

 The vast majority have most of their bulk within six inches from 

 the surface. The conspicuous place held in the flora by the Com- 

 positae points to compactness of flowering parts. Even the 

 grasses, (Grama, buffalo, wheat, etc.) have the spikelets relatively 

 compactly arranged instead of loose as is the case of many prairie 

 and v/ood land grasses. 



(3) Root system specialization: 



Since there are, in time of drought, frequently only slight 

 showers which do not soak in, there are many plants, notably the 

 short grasses which have a shallow, wide-spreading root system 

 developed. The buffalo and grama grasses have their roots nearly 

 confined to within a foot from the surface. In contrast to these 

 there are such deep-rooted plants as Psoralea which has almost 

 all of its roots at a depth greater than four feet, and in some cases 

 penetrates hard sub-soil as deep as six feet. 'Certain species 

 notably Artemisia and Gutierrizia have both well developed lateral 

 roots and rather deep tap-roots. The plants showing storage are 

 chiefly the bush morning glory, the blazing star (Lacinaria) and 

 the Indian turnip (Psoralea). The cacti are the only ones that 

 store considerable amounts of water above ground. 



(4) Prevalence of narrow, small or resin-covered leaves : 

 Almost all the plants have either small or narrow leaves. The 



prairie pink (Lygodesmia) and Gutierrizia are almost leafless. 

 Abundant species with resin are the cone flowers, gum-weed, 

 Psoralea, etc. 



(5) Wind dispersal including the tumble weed habit: 

 The "tumble weed habit" is developed chiefly by plants of 

 the wind-swept plains. Several species belong to the different 

 groups such as the Russian thistle (Salsola pestifer) a Chenopod; 

 Psoralea, a legume; the tumble-weed (Amaranthus) a member of 

 the Amaranthaceae, have this habit. 



(6) A short growing period not closely confined as to season: 

 The climate of plains is irregular. In some years the vege- 

 tation is several weeks ahead of normal and the next year it may 

 be as far behind. Delays in the coming of the rains occasionally 

 cause surprising late flowering. We found flowers of the Pasque 

 flower and of the prairie rose in August, following July rains. 



