1914] ROBERTS— PLANT SUCCESSIONS OF HOLYOKE RANGE 439 



a place for more rapid accumulation of soil; junipers, pines, and 

 grey birches come in, while on the north face Tsuga canadensis gets 

 a foothold in the crevices. 



, The pines and the hemlock seem to represent a temporary 

 climax until the edaphic situation becomes altered. 



TALUS SUCCESSION 



At the west side of the Mount Tom Range the talus is made up 

 of trap flakes alone, while on the north side of the Mount Holyoke 

 Range it is composed of trap and glacial drift. In each case trees 

 and undergrowth are established on the entire talus except where 

 patches of rapidly weathering rock have covered all but tree growth; 

 in such places birch or butternut may be seen growing in the midst 

 of an island of trap chips. At the base of Mount Holyoke, where 

 the glacial drift is associated with trap chips, the soil is far more 

 stable and is covered with herbaceous forms. 



Shrubs and vines advance up the slope at the base of the cliff, 

 with the assistance of a little lichen or moss growth. At the top 

 of the talus, which is made up of clean trap chips, an interesting 

 advance is made by the plants with creeping stems and rootstocks, 

 Rhus Toxicodendron, Psedera quinquefolia, and Vitis aestivalis. 



The talus on the north side of Mount Holyoke presents an 

 almost unbroken slope except at the top. As the fault lines extend 

 across the trap face, short ravines have been formed at the head 

 of the ravines of the trap slope. Here the drainage divides to the 

 north and south and the north face receives more moisture below 

 these short ravines. This unequal amount of moisture together 

 with the greater amount of shade, due to the projecting sides of the 

 trap ravines, affects the vegetation for about 50 feet along each 

 fault, and below this the talus assumes a uniform aspect. 



In a short ravine facing north are found : Spermatophy ta : trees 

 over a foot and a half in diameter, Tsuga canadensis, Betula alba, 

 B. lutea, and B. lenta; trees about an inch in diameter, Ostrya 

 virginiana, Quercus rubra, Q. alba, and Carya ovata; there are 

 a few seedlings of Acer saccharum; and scattering shrubs of Eama- 

 melts virginiana, Acer spicatum. and Viburnum acerifolium are 

 found. The spermatophytic herbs are Maianthemum canadense, 



