24) i Nebraska State Horticultural Society. 



ground, at first to the partial exclusion of the weeds, and later to their 

 total suppression. Still later the trees overtop the shrubs, and event- 

 ually the latter may be suppressed also. While this is happening, a new- 

 weed belt is forming in advance of the best of shrubs and young trees, 

 thus the forest margin is continually advanced. 



There are many such advancing forets borders in Nebraska. In 

 fact, wherever the fires and domestic animals are kept out such an 

 advance is commonly taking place. The rate of advance varies from a 

 few feet a year to a hundred feet under favorable conditions, and in ex- 

 ceptional cases to several hundred feet. When it is remembered that an 

 advance of but ten feet a year along a forest border a mile long adds 

 a little more than an acre of woodland, even such a slow advance is 

 seen to accomplish much. In this way in the course of a century the 

 actual forest area may be greatly enlarged. While such a steady ad- 

 vance of the forest margins is now actually going on, there is another 

 mode of distribution which is even more rapid. A seed is carried by a 

 bird or other means to a considerable distance from the body of trees 

 of its kind. It springs up in its new station and eventually produces 

 seeds, and becomes a centre from which further distribution takes 

 place. A case of this kind has been brought to my attention in recent 

 appearance of the Linden tree (Tilia american) in the vicinity of Lin- 

 coln. 



In the western part of Nebraska the present spreading of the Rock 

 Pine (Pinus scopulorum) is quite noticeable. It is not uncommon to 

 find young trees considerably in advance of the older trees of the sparse 

 forests, around which are many small trees which have sprung up from 

 the young parent trees. 



