284 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



station gives practical assistance to the landowner or planter, and 

 also to establish in suitable centres examples of forest planting and 

 management. — A. D. W. 



Forests of North-Eastern America. By William S. Cooper (Bot. 

 Gaz., Jan. 1913, pp. 1-44 ; Feb. 1913, pp. 115-140 ; March 1913, 

 pp. 189-235, with 55 figures and map). — This paper, entitled "The 

 Climax Forest of Isle Royale and Its Development," is of great 

 importance to all who are interested in forestry and is a valuable 

 contribution to ecological Botany. 



The author begins with the geographical conditions of the district 

 when it was first abandoned by the glaciers of the Ice Age, or, 

 rather, was covered by the waters of a glacial lake, and traces every 

 stage by which the present final forest established itself. 



This climax forest consists of White Spruce (Picea canadensis), 

 Betula alba var. papyrifera, and Abies balsamea, the last forming 

 about 787 per cent. But of the larger trees (over 2*5 dm. in diameter) 

 only 33 3 per cent, belong to this species. The balsam fir is extremely 

 prolific and propagates itself not only by seed but by a process of 

 natural layering, but it is very susceptible to fungus attacks and 

 diseases, and the wood is brittle, so that the trees are often overthrown 

 by wind. The birch has a low birth-rate, but is fairly wind-firm and 

 not much affected by fungus attacks, and forms a good proportion of 

 the mature stand. The white spruce seeds about once in eight years, 

 and the seedlings require abundant light. The largest trees are of this 

 species and they are able to withstand severe winds, often towering 

 conspicuously above the general forest level. Amongst other trees 

 found in the final or climax forest are Pyrus americana, Pinus Strobus, 

 Picea mariana, Larix laricina, Populus tremuloides, and P. balsamifera. 

 The author thinks it probable that the whole of the North-Eastern 

 conifer-region is of this climax type, but the balsam fir does not extend 

 so far to the north and north-west as the other two species, and is 

 probably represented by others which may be considered ecologically 

 equivalent. To the south of Lake Superior an entirely different 

 hardwood forest, in which the beech and sugar-maple are most pro- 

 minent, replaces the white spruce-paper birch type, and may be perhaps 

 regarded as invading the conifer area just as the oak invaded the 

 territory of Scotch pine in north-western Europe. 



The original country as left at the close of the glacial period is 

 classified as follows : — 



1. Bare rock surfaces, which are occupied first by crustaceans, 

 then by leafy and finally by fruticose lichens (Cladonia and Stereo- 

 caulon), with mosses such as Rhacomitrium. Upon this mat, scattered 

 plants of Cryptogramma, Diervilla, and Arctostaphylos establish them- 

 selves. 



2. Rock crevices are soon filled by surface wash and are quickly 

 occupied by plants, of which 100 species have been noted by the author 

 as crevice plants. Junipers, Vaccinium, Arctostaphylos, and Thuja 



