114 Journal of Agricultural Research voi. iii. No. j 



GROWTH AND LOSS OP FORAGE SBEDLINGS DURING SECOND AND SUBSEQUENT 



SEASONS 



During the second year nearly all species make vigorous growth, both 

 above and below ground. Plate XVI shows the deep and spreading 

 character of the roots of 2-year-old mountain bunch-grass (natural size) 

 at the end of the second season. It \vill be seen that the roots are much 

 longer than the leaf blades. The vertical roots reach well beyond the 

 dry substratum during the most critical period of drought. The leaf 

 blades, which number about 70 or 80 on the more vigorous individuals, 

 are all basal, with an average length of about 4 inches, about half that 

 of the deepest roots. This splendid root and herbage development pro- 

 vides the plant with abundant food-storage tissue, so that in the following 

 season vigorous growth begins promptly. 



During the third year the development of the plant is quite as marked 

 as during the two preceding seasons (cf. Pis. XVI and XVII). Both 

 roots and herbage grow rapidly from the first, though the growth of the 

 former still greatly exceeds that of the leaf blades. Such development 

 is essential, for the roots absorb moisture slowly, and where transpira- 

 tion is great, nothing short of a well-developed root system can supply 

 the plant with the moisture it requires. Owing to the depth and spread 

 of the roots, the question of available soil moisture is not a serious one, 

 since an ample supply exists 3 inches below the surface layer. At the 

 start of the growing period there is a superabundant supply of moisture, 

 and plants whose roots are well beneath the surface soil continue to 

 extend them more deeply until the innumerable root hairs have worked 

 themselves through the capillary spaces among the soil particles, thus 

 insuring the plant against drought. 



By the end of the third year mountain bunch-grass and other species 

 complete their life cycles, and cease to be seedlings. Flower stalks and 

 seed are then produced, as shown in Plate XVIII. At this time the 

 plants are often as tall as older individuals. The specimen shown 

 in Plate XVIII exhibits the maximum development attained, the 

 average growth being shown in Plate XVII. The flower stalks (there 

 are seldom more than three) of the 3-year-old plants as a rule are 

 put forth a few days later than those of the parent or older plants. Con- 

 sequently the seeds are not matured as early as are those of the longer 

 established individuals, though the variation rarely exceeds five days. 

 So extensive is the development of the plants by the second year of 

 growth that the loss during that and subsequent seasons owing to cli- 

 matic factors is negligible. 



The facts derived from the study of the life history of the vegetation, 

 which are important as a basis for a rational and practical grazing sys- 

 tem, may be summarized as follows: 



