MOISTURE AND EXPOSURE 



215 



materials. Note how rank the plants are in low places. 

 Observe how the weeds grow about the barn where the 

 soil is not only rich but where moisture is distributed from 

 the eaves. Contrast with these instances the puny plants 

 that grow in dry places. In dry countries irrigation is 

 employed to make plants grow vigorously; or the moisture 

 may be stored in the soil by means of deep preparation and 

 frequent surface 

 tillage and other 

 dry-farming meth- 

 ods. In moist and 

 rich soil plants 

 may grow so fast 

 and so tall as not 

 to be able to with- 

 stand the wind, as 

 in Fig. 382. 



374. Plants are 

 Influenced by the 

 Exposure of the 

 Place In Which 

 They Grow. The 

 particular site or 

 outlook is known 

 as the exposure or 

 aspect. The ex- 

 posure, for example, 

 may be southward, 

 eastward, bleak, warm, cold. A favorable exposure for 

 any plant is one that supplies the requisite warmth, room, 

 sunlight, moisture and nutrients, and immunity from severe 

 winds and other destructive agencies. Against the edge of 

 a forest (Fig. 383) or at the base of a cliff, certain plants 

 thrive unusually well. Note the plants of any kind grow- 

 ing in different exposures : observe that they vary in stature, 



381. A tree that shows which way the wind blows. 

 Oklahoma. 



