ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
305 
In some mosses, especially in species of Bicranum , the leaves exhibit 
the same directions of growth as the shoots in those already described. 
In a large number of mosses, light, which contributes to the develop- 
ment of the plagiotropic growth in the above-named species, has no 
influence on the direction of growth of the lateral shoots ; positive 
geotropism playing the principal if not the only part. The leaves of 
Bicranum scoparium are, in the same way, positively geotropic. 
While, therefore, the orthotropous mosses, represented by Poly- 
trichum, owe their direction of growth chiefly to light, that of the 
plagiotropic species is mainly influenced by geotropism in conjunction 
with moisture. 
Oil in Mosses.* — As the result of a large number of analyses, Herren 
B. Jonsson aud E. Olin state that a larger or smaller amount of oil is 
generally present in mosses, forming, with carbohydrates and nitro- 
genous substances, the material for metastasis. The amount is small in 
those species which, like Sphagnum, grow in wet places, larger in the 
xerophilous species ; in Bryum roseum it amounts to 18 per cent. It is 
more abundant in the resting condition than when assimilation is 
energetic. In some families, e. g. the Bryineae, oil is the chief or the 
sole basis for metastasis ; in the Mnieae it is accompanied by a greater 
amount of starch. In Bryum roseum all the cells of the mature part of 
the stem contain oil. The medullary tissue, the central bundle, and the 
outer cortical tissue, are the parts where it is chiefly found. 
Classification of Pleurocarpic Mosses. t — Herr N. C. Kindberg holds 
that, in the classification of Mosses, too much stress has been laid by 
systematists on the form of the capsule, which may vary even within 
narrow limits of affinity. From the study especially of tropical forms, 
he proposes the arrangement of the pleurocarpic genera under three 
tribes the Tricholepideae, the Dicholepideae, and the Symphyolepideae. 
To the 1st belong the Cryphaeaceae, Anomodontaceae, Fabroniaceae, 
Pilotrichaceae, and Pterobryaceae ; to the 2nd the Hypopterygiaceae, 
Phyllogoniaceae, Neckeraceae, Leptodontaceae, Leskeaceae, Entodontaceae, 
Hookeriaceae, Meteoriaceae, Eriodontaceae, Spiridentaceae, Cyatho- 
phoraceae, Racopilaceae, Helicophyllaceae, Climaciaceae, Mniadelphaceae, 
Thuidiaceae, and Hypnaceae ; while the 3rd tribe comprises the Fonti- 
nalaceae only. A complete classification of the genera under these 22 
families is given. 
The Hypopterygiaceae have amphigasters, while the Phyllogoniaceae 
have not. The Spiridentaceae are distinguished from the rest of the 
Pleurocarpae by their sheathing leaves. In the Cyathophoraceae the 
capsule is straight, the calyptra cap-shaped, and the peristome double. 
In the Racopilaceae the capsule is curved, the calyptra unilateral and 
cap-shaped, the peristome double, and the leaves more or less papillose. 
The Helicophyllaceae should possibly be placed among the Acrocarpae. 
The Mniadelphaceae are distinguished by their cap-shaped calyptra ; 
the capsule is straight ; the stem not arborescent. 
Br ait h waite’s British Moss-Flora.f — Proceeding with the family 
Hypnaceae, Dr. R. Braithwaite has now completed his account of 
* Lunds Univ. Arsskr., xxxiv. (1898) 42 pp. and 1 pi. (German). 
t Bot. Centralbl., lxxvi. (1898) pp. 83-8; lxxvii. (1899) pp. 49-55, 385-95. 
j Pt. xix., 1899, 32 pp. and 6 pis. Cf. this Journal, 1898, p. 327. 
