ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 449 



and the general phenomena of development depend upon the degree of 

 maturity of the individual gemma ; the plane of dorsiventrality is fixed 

 within 10-20 hours after the sowing of the gemmi^. The plagiotropic 

 orientation is the expression of a function which is influenced by 

 illumination, and is the result of the combined action of diaheliotropism 

 and negative geotropism. When growing in greenhouses Machantia 

 reproduces itself by gemmaj only ; but, if the light be decreased and the 

 moisture increased, neither gemms nor sexual organs are produced ; if, 

 however, the intensity of light be increased and the plant be grown in 

 direct sunshine, then, whether the moisture be increased or not, the 

 formation of sexual organs is abundant, being entirely dependent on 

 intense and prolonged illumination. When submerged, the plant 

 produces neither gemmre nor sexual organs. When growing in conditions 

 favourable to a purely vegetative state, neither gemmai nor sexual organs 

 are produced, and vice versa. The gemnne of every plant, male or 

 female, tend to reproduce plants of the same sex. Growth in length of 

 the pedicel of the inflorescence, mode of branching of the thallus, and 

 production of stomata, are mainly controlled by outward factors. 

 Fertilisation occurs mostly during rain by the splashing of water from 

 the antheridial inflorescence. 



Thallophyta. 



* Algae. 



(By Mrs. E. S. Gepp.) 



Sylloge Algarum.* — A. Forti completes another volume of this 

 important work, namely, the part which deals with the Myxophyce*. 

 The arrangement is on the same lines as that of the preceding volumes, 

 which were compiled by De Toni. They dealt with Chlorophyce^e, 

 Bacillari^, Phajophyceffi, and Floridea3, and the present volume pre- 

 sumably completes the series. 



Algae of the West Coast of Sweden.t— H. Kyhn publishes the 

 result of his studies on the algal flora of the west coast of Sweden, in 

 which he records the species collected by himself in various parts and 

 those in the Upsala herbarium, making altogether a valuable flora of that 

 region. Several new species are described, and critical notes are made 

 concerning many other records. The author then proceeds to the second 

 part of his work, viz. " General Observations on the Algal Flora on the 

 West Coast of Sweden," and this he treats of under the headings : 

 (1) External conditions, including salinity and temperature of the water, 

 and the formation of the coast and sea bottom ; (2) algse regions and 

 alg» formations ; (8) comparison between the algal vegetation of the 

 Bohuslan and Halland coasts ; (4) position of the flora as regards 

 geographical distribution, including composition of the flora, comparison 

 with neighbouring floras, and suggested reasons for the present com- 

 position and distribution of the flora ; (5) biological observations. The 

 book is illustrated by plates and text figures, 



* Syll. Algarum, v. (1907) 761 pp. 



t Studien iib. d. Algenflora der Schwedischen Westkiiste (Akadem. Abhandl.). 

 Upsala, 1907, 288 pp., 1 map, 7 pis. and 41 figs, in text. 



