Floristik, Geographie, Systematik etc. 277 



species involved. Onlj'- a fevv topics can be indicated herc. Compa- 

 ratively recentl}^ almost the summit area was peatcovered, and 

 tree-remains occur in all parts except the most wind-swept. With 

 retrogression of the peat as a result of climatic changes, the rock 

 and glacial deposits are being uncovered and a new Vegetation is 

 being established. The meagre alpine Vegetation is traced to two 

 sources: a) species which have survived in rocky ravines; b) species 

 ("peat-alpines") which can live on peat and on Icached alpine rocks 

 and debris. The distinction of the latter group is noteworthy; the 

 more characteristic peat-alpines are Arctostaphylos alpina, A. Uva- 

 ursi, Rubus Chmncefnoriis, Salix repens and allied spp., Betula nana, 

 Lycopodhim Selago, L. alpiniun, Enipetruni nigrum, Vaccinium 

 Vitisidaea. 



Amongst other types of Vegetation on the summits, some are 

 phases (climax, retrogressive and progressive) of moorland plant 

 associations, and these are shown to be topographically related to 

 the moorland peat associations. The debris of the mountain plateaux 

 is occupied by several associations, and this part is an important 

 contribution on a type of Vegetation not hitherto fully described; 

 the part played by mat-associations of Calluna and Rhacomitrium 

 receive special attention. Other sections are given to Vegetation of 

 corries and crags, of Springs and fiushes, and of the stream belt; 

 these include characteristic species, including many cryptogams. 



W. G. Smith. 



Cooper, W. S., Reproduction by Layering among Coni- 

 fers. (Bot. Gaz. LIL p. 369—379. Nov. 1911.) 



The author describes the reproduction of the baisam fir. Abies 

 balsamea (L.) Mill by layering on Isle Royal, Lake Superior. 

 The method is described in detail with a figure, after a brief 

 historic discussion of previous observations is presented. He finds 

 that layering may take place at any stage in the life of the tree. 

 The ecologic importance of this method of reproduction and its 

 Physiologie bearing are given. Harshberger. 



Cooper, W. S., The Climax Forest of Isle Royale, Lake 

 Superior. (Bot. Gaz. LV. p. 1— 44, 115-140, 189— 235. Jan., Feb., 

 Mch. 1913. with map and 55 figs.) 



Isle Royale in Lake Superor, when the study was pursued, 

 is situated in a region transitional between two great forest regions. 

 The account Starts with a description of previous botanic work upon 

 the flora of the island, a sketch of the topography and physiogra- 

 phic history, the climate (with tables of precipitation and temperature). 



The climax forest which is climatic for the region is made up 

 largely of three trees: Abies balsamea (L.) Mill. (baisam fir), Betula 

 alba L. var. papyrifera (Marsh) Spach (paper birch), and Picea ca- 

 nadensis (Mill) B. S. P. (white spruce). The evidence of this conclu- 

 sion is based upon 1) extreme mesophytism of the forest; 2) its 

 uniformity of development; 3) all successions lead to it; 4) mainte- 

 nance of equilibrium. The successions of Vegetation upon Isle 

 Royle are classified by Cooper, as follows: 



A. Primary succession. 



I. Xerarch successions. 



1. The rock shore succession. 



2. The beach succession. 



