448 JOURNAL OF FORESTRY 



be smothered. Even four-year-old transplants which were planted as 

 an experiment to determine the feasibility of reforesting these swamps 

 were smothered out by the moss in many instances. 



How then does the black spruce perpetuate itself in these muskeg 

 and spruce swamps and maintain itself as the dominant and con- 

 trolling species? The writer discovered in 1910 that black spruce 

 perpetuates itself in these swamps by layering. This vegetative system 

 of layering is quite rare in conifers and is a striking example of the 

 law of perpetuation. In the formation of the peat swamps the spruce 

 gradually migrated from the outer edge inward as the moss took the 

 ■place of grass and sedges. The lower branches of the spruce were 

 covered by the rising moss, and these branches in the water-laden 

 substratum produced adventitious roots which with the help of the 

 food derived from the parent tree stimulated the growth of the branch. 

 The end of the branch assumed an upright position, while the roots 

 on the branch became more extensive. Finally the connection with 

 the parent tree became severed or the old tree died and an independent 

 tree was formed. The lower branches of this tree go through the 

 same cycle and in this way migration and establishment of the species 

 is carried on. 



In many cases when the moss was dug away the old branch con- 

 nection for four generations was still linked together under the peat. 

 The sapwood in all cases had decayed and only a part of the heart- 

 wood was left. In some cases severed branches were found which 

 had rooted, and many instances were found where the branches of a 

 prostrate tree which had been partly buried in the moss were growing 

 and had developed roots, while the stem or bole of the windthrown 

 tree was dead. 



On the moss-covered rock of northeastern Minnesota, where black 

 spruce is found and to which reference was made in the first part of 

 this paper, the same method of reproduction has been found. 



Whether or not it is possible to artificially reproduce black spruce 

 vegetatively, our experiments are not yet conclusive. 



