1901. Reviews. 13 



BOG-MOSSES. 

 The European Sphagnaceae (after Warnstorf) by E. Charles 

 HORRElvL, F.E.S. Journal of Botany, May to December, 1900. 

 Since the appearance of Dr. Braithwaite's fine work on the bog-mosses 

 in 1880 nothing of importance has appeared dealing with the British 

 species. Mr. Horrell's work, which forms a pamphlet of 88 pages, and 

 appeared first in the Journal 0/ Botany, does not profess to be original, but 

 to place before British bryologists Warnstorfs latest arrangement of the 

 bog-mosses as the most natural classification yet published. 



It is however more than a mere translation. There is an interesting 

 introduction, a useful bibliography, references to British works are in- 

 serted, and numerous localities given for species and varieties, so that the 

 work will be indispensable to British students of the genus. These are 

 followed by a clavis of the European species and elaborate descriptions 

 of species and varieties. There are 41 species and no varieties numbered 

 and described, while the whole number of varieties referred to or described 

 amounts to 210. Even so., we learn that this formidable array is 

 not complete, "innumerable varieties" have been mercifully omitted. 

 The great majority of these species have been found in Britain, and a 

 lesser number of the varieties. Braithwaite's Sphagnacece recorded 20 

 species and 47 varieties as British, the London Catalogue of 1881, 16 

 species and 34 varieties, while the number in Dixon's Handbook of 1S96 

 was reduced to 12 species and 40 varieties (including sub-species). 



Irish localities are conspicuous by their absence in the long lists given, 

 and it might be supposed there was no great variety of bog-mosses in 

 the land of bogs, or that Irish bryologists had neglected the study. I 

 suppose no doubt is intended to be thrown on recent Irish records (for 

 example Sphagnum medium Limpr. and S. Auslini Sulliv. have been 

 recorded in the Irish Naturalist), but if an author only wishes to vouch 

 for specimens he has seen, this should be stated. Several important 

 works have appeared of late with accounts of the distribution of British 

 mosses in which most recent Irish records of importance are ignored. 



The Sphagnasece form a compact and natural family, but are hard to 

 divide up into natural well-defined species and varieties. The fructifi- 

 cation so useful in other families fails us here. Warnstorfs system accor- 

 dingly depends chiefly on the cell structure, and ascribes great impor- 

 tance to the position and form of the chlorophyllose cells of the branch 

 leaves, and to the form and distributiotrof the pores in the cell walls. To 

 determine the species, it is therefore necessary in many cases to make 

 sections of the leaves. Students of the old school will be sorry to find 

 that their plants cannot be determined in the field, and will not take 

 kindly to the system, but there is no doubt the older arrangements left 

 troublesome intermediate forms, often impossible to determine. It 

 remains to be seen if the new system will clear up these difficulties. 



Much work remains to be done in correlating British and continental 

 forms; many slight varieties depending only on colour, &c, will likely be 

 discarded, and others of more importance peculiar to these countries 



described, and fitted into their places. 



C. H. W. 



