Botany. 153 



diffusion ; but it is not so easy to tell why, after taking the form 

 of sugar, these carbhydrates do not return to the leaves again, in 

 virtue of the very same laws of diffusion. Since uniformity does 

 not exist between the chemical composition of cell-contents in 

 different parts of the plant, diffusion must be assumed to be 

 balanced by some other force. The author regards this as a 

 simple question of osmotic balance. Applying the doctrine of 

 osmotic equivalents to the special case in hand, he states that the 

 saccharose in the root, to satisfy the demands of existing condi- 

 tions, should be, in concentration, double that of the reducing 

 sugars found in the leaves. Further, a similar equilibrium may 

 be supposed to exist between the root and the soil. Maquenne's 

 recorded results are suggestive from many points of view. From 

 them he enunciates the following law, which he regards as of 

 general applicability to Physiology, — any immediate principle 

 can accumulate whenever its formation gives rise to a reduction 

 of osmotic pressure. It is interesting to notice that this sub- 

 stantially restates a law applied by Deherain to the appropria- 

 tion of mineral matters and the transfer of elaborated substances 

 in plants. G. l. g. 



5. Guide to the British My cetozo a; by Arthur Lister, pp. 42, 

 fig. 44. — This little book is the second of the botanical series 

 intended to serve as a guide to specimens exhibited in the British 

 Museum. It gives a condensed account of British Mycetozoa 

 taken irom the author's monograph of the Mycetozoa, ol which a 

 notice was given a few months ago, preceded by a short account 

 of the general structure and development of the order. The col- 

 lection of British Mycetozoa and the series of colored drawings 

 explaining their structure, now exhibited in the botanical gallery 

 of the Museum, were presented by Mr. Lister, as well as over 

 eight hundred mounted slides kept in a cabinet of the crypto- 

 gamic herbarium. This valuable collection, taken in connection 

 with Mr. Lister's guide, will make it comparatively easy for 

 students to recognize British species of this difficult order. 



w. G. F. 



6. The Norwegian Forms of Lithothamnion; by M. Foslie, pp. 

 180, 8°, pi. 23. Trondhjem, 1895. — In this elaborate monograph the 

 author gives a critical study of the species of Lithothamnion and 

 Lithophyllum of northern Europe, with occasional references to 

 species of North America. Our knowledge of the confused species 

 of the Corallinacese comprised in the Lithothamnion group has been 

 much increased in recent years owing to the writings of Kjellman, 

 Rosen vinge, Stromfelt and Foslie. The present paper is a revis- 

 ion of previous papers in the light afforded by fresh material from 

 America as well as Europe. The writer reduces Lithophyllum 

 to a subgenus of Lithothamnion, instead of regarding it as most 

 closely related to Melobesia, where it was placed by Batters and 

 ourselves ; and the subgenus Eulithothamnion he divides into two 

 sections, Innatae, with innate, and Evanidge, with superficial 

 sporangial conceptacles. The definition of species in algaa of this 



