226 NEBRASKA STATE HORTICULTURAL SOCIETY 



lack of soil moisture. This is no great direct loss, however, because they 

 would never have amounted to much, unless freed by cutting the dormant 

 trees overtapping them. Their chief function was the indirect one of 

 protecting the soil from the drying influences of sunlight and air. The 

 presence of this large quantity of killed trees in the forests will tend to 

 increase the insects that live in dead wood, and in states with more ex- 

 tensive timbered tracts would increase the fire danger, which, however, 

 is not great in Nebraska. Soil conditions become suitable for forest 

 trees, because more sunlight and more circulating air will tend to destroy 

 the leaf mold. 



DROUTH-RESISTING TREES. 



The richer the soil and the more vigorous the tree the greater will 

 be its endurance in drouths; yet certain species are naturally better 

 adapted than others for drouthy condition. They even inherit the quali- 

 fications to endure drouth. The writer compared a white pine with a 

 western yellow pine seedling. Both were of the same age and the seeds 

 of both were planted under the same conditions of soil, warmth, and 

 moisture in a hothouse. An abundance of moisture was provided them. 

 The western yellow pine seedling did not expend much energy in stem 

 growth, but it put down comparatively long roots. The white pine sent 

 up a comparatively long stem and a short spreading root system. Each 

 seedling was demonstrating inherited tendencies. The western yellow 

 pine in its natural habitat has to grow deep roots in order to make sure of 

 moisture during drouth intervals; the white pine is indigenous to a 

 region of comparatively heavy and frequent rains and does not need to 

 send down quickly long roots. 



The drouth-resisting trees are those which have adapted themselves 

 to arid conditions. Just what physical or morphological characteristics 

 render certain trees drouth-resisting has not been studied deeply, so far 

 as the writer is aware, and a fertile field is open for investigation along 

 these lines. 



A study of the leaves of the green ash shows that the leaves of ash 

 growing under drouthy conditons are thicker than those- where soil 

 moisture is more abundant. It is possible that an extended study would 

 show leaf, bark, and root peculiarities which render certain trees better 

 adapted to endure drouth. Among the drouth-resisting species may be 

 mentioned western yellow pine, jack pine, American elm, hackberry, Rus- 

 sian olive, sand cherry, honey locust, red cedar, white spruce (usually 

 locally known as the Black Hills spruce). C. S. Harrison is authority 

 for extending the above list with the following: Russian tamarisk, tree 

 lilacs. 



In the western part of the state and especially in the rine Ridge, 

 Colorado blue spruce should succeed in sheltered places. 



Norway spruce is not adapted to drouth, and white pine is likely to 

 have small portions of its cambium killed by heat or drouth. Its bark is 

 very thin for a pine, and portions of it simply die, due to the drying of 

 portions of it. 



