132 ILLINOIS ACADEMY OF SCIENCE. 



REPRODUCTION BY LAYERING IN THE BALSAM FIR 

 AND OTHER CONIFERS. 



By William S. Cooper, 

 University of Chicago. 



(Abstract.) 



During ecological studies on Isle Royale, Lake Superior, many 

 balsams were found which were producing young trees by the 

 layering of the lower branches. The process was found to be 

 usually as follows. A lower branch, becoming more or less soil 

 covered, produces roots from its under side, and the tip then 

 becomes erect and takes on radial symmetry. The erect portion 

 derives practically all of its sustenance from its own root system, 

 the portion connecting it with the parent not developing further. 

 Connected groups of several were frequently seen, and the com- 

 monness of the habit is partially responsible for the great pre- 

 ponderance of balsam in the young growth. The young tree-like 

 branch may sooner or later be detached from the parent, and when 

 this takes place the former becomes an independent tree. One 

 case was seen in which the tip of a lower branch had taken the 

 erect position without the production of roots. The habit was 

 also observed, though less commonly, in all the other coniferous 

 species growing on Isle Royale. 



There is here an excellent opportunity for investigation of the 

 causes of orthotropism and plagiotropism, and their mutual rela- 

 tions. 



Discussion. 



Mr. Cowles. — "This is interesting from two or three stand- 

 points. In the first place, it casts discredit on a great many eco- 

 logical works of the past, in that we have not been subterranean 

 enough in our habit. We have got to use the spade a great deal 

 more than we have been doing. Another point of interest is that 

 here we find the possibility for a greater lease of life for our forest 

 succession — much greater than we had believed possible. A plant 

 which would give so much shade that the seedlings did not germi- 

 nate is naturally limited, and one that can reproduce by layering 

 of this sort is naturally much better provided for." 



Mr. Hessler. — 'T have seen that similar method of reproduction 

 in Arbor Vitse." 



