36 BOTANY. 



as Dry Ridge. He adds that the growth was slower, but that quite as 

 many of the trees lived. We may in many respects consider this a crucial 

 test. After three years' growth, the following percentages were alive and 

 thriving: 



Per cent. 



Silver-maple, one year old when planted 90 



Box-elder, one year old when planted 80 



Honey-locust, one year old when plan ted 100 



Ailanthus, one year old when planted 100 



Statistics from New Mexico and Arizona are meagre in the extreme. 

 There is no doubt, however, but that thousands of trees of the indigenous 

 cottonwoods, and of box-elder, Ailanthus, and China-tree, could be grown 

 along the irrigating ditches and in other moist places : enough to raise the 

 farmer in a few years beyond any immediate want for his most needed 

 woods, and to largely spare the drain on the pine forests that cover the 

 remoter mountains. It is in the highest degree probable that some of the 

 various Australian. trees, now being so successfully cultivated in California, 

 especially some of the Eucalyptus species, could be made to do well in the 

 warmer valleys of New Mexico and the warmer ones in Arizona where water 

 may be had. These trees, as rapid growers, and as making good lumber, 

 are of great value. 



We must still regard the problem a mooted one as to whether or not 

 forests actually increase the rainfall of any region. The probabilities, 

 however, appear to be against the supposition that they do. There can be, 

 I think, no reasonable doubt but that they aid in obtaining greater benefits 

 from what does fall. I am aware of recent observations in France which 

 would appear to make even this doubtful, but I think the facts are so well 

 established here that they may be regarded as above suspicion. The 

 paper by Mr. Muir, already quoted, gives a striking illustration of this in 

 the case of the Sequoia gigantca, and other instances not less apt might be 

 furnished. Mr. Cooper, of Santa Barbara, has elaborated at some length a 

 plan for obtaining larger results in agriculture from the same quantity of 

 water by making the shade of the eucalyptus diminish the excessive evapo- 

 ration of the water. The details of this will be considered elsewhere.* 



* It may be considered a question as to whether the water taken up by the roots would not equal 

 or exceed that saved from evaporation. 



