246 NEBRASKA STATE HORTICULTURAL SOCIETY 



to the fact that it sets forth analytically what the problem is, and thus 

 may suggest how it may be attacked. 



There are three regions in every tree so far as the present inquiry 

 is concerned, viz., I, the Root System; II, the Stem System, including 

 the trunk and its branches; III, the Leafy or Foliage System. And we 

 may direct our inquiry to these in succession, as follows: 



I. THE ROOT SYSTEM. 



1. Deep Roots appear to be more likely to withstand prolonged 

 drouth than roots that spread nearer the surface, and this is generally 

 conceded by plant physiologists. And yet it is well-known that in 

 regions of deficient rainfall many plaruts spread their roots out in a rela- 

 tively thin layer of the upper soil, the only part that is ever wet at all 

 by the occasional rains. To what extent our trees do the same needs to 

 be determined by examination and experimentation. Is it true with our 

 trees that the deep-rooted species can endure drouth better than the 

 shallow-rooted species, or do the shallow-rooted species profit by the 

 lighter rains so much more quickly that they actually endure the drouth 

 better than those with deep roots? 



• 2. Finely Branched Roots, by being able to penetrate the finer in- 

 terstices of the soil, as well as to come more closely into contact with 

 the moist surfaces of the soil particles, are better able to furnish an 

 adequate supply of water to the tree, and no doubt this is true in the great 

 majority of cases. Yet here again I am in doubt whether this can be 

 taken as an infallible guide. Certainly it is necessary to take into con- 

 sideration other things than the fineness of the roots, as their depth in 

 the soil as discussed above, the coarsness and fineness of the soil, the 

 individual activity of the roots, their supply of root-hairs, mycorhiza, etc. 

 Here again practically the whole question needs careful scientific investi- 

 gation. 



II. THE STEM SYSTEM. 



1. Effective Bark. The moist tissues of the trunk and branches are 

 covered with a protective mass of bark, which is more or less effective 

 in preventing the loss of water by evaporation. It is a matter of common 

 observation that the bark of some trees forms a continuous layer or 

 series of layers of porous tissues that must be very effective in pre- 

 venting water-loss, while that of others is so deeply fissured as to expose 

 the inner moist layers of the bark. At once we may surmise that in 

 the former case the protection is greater, and in the latter case much 

 less, and yet we have to admit that direct experimental data are nearly 

 wanting. A close and critical study of the various types of bark is much 

 needed, and will have to b'* undertaken before a definite pronouncement 

 can be made as to the part taken by the bark in enabling the tree to 

 withstand dessication. 



2. Spreading Tree-top to Shade the Trunk. In the forest the tree- 

 trunks arc sliadod frnin the intense lu^it of tlie sun. but in trees that 



