242 



DRY FARMING CONGRESS. 



DRY LAND ARBORICULTURE. 



(By Silas C. Mason, Arboriculturist, Plant Life History Investigations,. 

 Bureau of Plant Industry, Department of Agriculture.) 



Outline of Work of Arboriculturist. 



With the establishment of the office of Dry Land Arboriculturist as 

 a part of the work of the Bureau of Plant Industrj^ a year ago, it was 

 frankly admitted that the title was not one easily susceptible of defini- 

 tion. While the work was intended to be an accompaniment of dry land 

 agriculture it must avoid the field of the forester on the one hand and 

 that of the old line hotticulturist and pomologist on the other. It was 

 scarcely anticipated that this work would be directed to the cultivation 

 of tree crops wholly without irrigation, but the expectation was that the 

 chief study would be devoted to such trees and shrubs as would produce 

 valuable products, either of fruits or for other economic purposes aside 

 from forest products, with the minimum use of water. Thus far the work 

 has been undertaken onl}^ with plants possible of culture in the arid 

 southwestern region where the rainfall is light and canal or artesian water 

 must be used with great economy and where the, climate is so warm that 

 plants of the warm temperate and semi-tropical regions maj^ be grown. 

 It is, however, b}' no means the intention that the v/ork shall be confined 

 to these regions, as there are many possibilities lor the development of 

 dry land arborial crops in the plains region of the great west and south- 

 west. 



Structure of Desert Plants. 



That no tree or woody plant can survive except it receives some sup- 

 ply of water is a question which needs no discussion. As one leaves 

 the ^Mississippi Valley region on the east and passes out into the semi- 

 arid and arid plains there is a notable change in the character of the 

 vegetation. Plants of the same species may be found so changed in their 

 habit-s of growth as to be scarcely recognizable. Plants of the same fam- 

 ilies and genera become developed into strange new species, having a 

 special adaptation to the conditions found in the land of little rain. 



Suppression of the Leaf System. 



One of the most common changes observed in native plants is the " 

 suppression of the leaf system. 



Families of plants, some of whose members possess broad and deli- 

 cately constructed leaves are found to be equipped with leaves greatl}- re- 

 duced in size and changed in character to a thick, leathery structure, or 

 perhaps covered with a dense hairiness or pubescense. All of these char- 

 acteristics are very evidently a defense against the too rapid transpira- 

 tion of such moisture as the plants may receive from- the soil through 

 the roots. Few whose lives have been spent in the eastern states, fa- 

 vored with an abundance of rain, have any realization of the d^ssicating 



