200 THE .TOUEXAL OF POTAXY 



not easy to digest at the first reading, but it is severely logical and 

 ])resents a fascinating study of the origin and progression of plant life 

 and all that it involves, which will be welcomed and enjoyed by all 

 students of biolog3\ 



A. G. 



A 3Io7iograj)h of the Gemis Alaria. By Professor K. Yexdo 

 (Journal of the College of Science, Imperial University of Tokyo, 

 vol. xliii. 1919 : 145 pages, 19 plates). 



Thts is a valuable addition to our knowledge of the Brown Algae. 

 In addition to submitting the species to a critical revision and reducing 

 them to 15 — some 32 have been described since Greville established 

 the genus in 1830, — the author discusses in his introduction several 

 matters of great interest in relation to the anatomy, morphology, 

 habit, and life-history of Alaria and its allies among the Laminariaceae. 

 The shape of the lamina is untrustworthy as a systematic character 

 for its width varies with the environment ; so also does its thickness 

 and toughness ; and the rapidity of growth pf the frond is astound- 

 ing ; in three or four months the frond of such a colossal plant as the 

 N. Pacific A. Jistulosa may attain a length of as much as 60-80 feet 

 or even more. This species is remarkable for its hollow midrib 

 septated at irregular intervals, which serves as a float for the 

 lamina. A close study of the development of the sporophylls has 

 led the author to divide the species into two groups, Holosoria 

 and Metasoria. In the former the sporophylls are thick and coria- 

 ceous from the first and become covered with sori. In the latter, 

 to which our one British species belongs, the sporophylls are 

 membranaceous at first ; and this part remains sterile and more or 

 less gets worn away, while a new and thicker growth ai'ises below it 

 and becomes soriferous. The meaning of the cryptostomata has been 

 much discussed. Prof. Yendo sums up our knowledge of these 

 structures in the different families of Brown Alga? and concludes that 

 in the Laminariaceae the hair- tufts can safely be regarded as a sort of 

 al)sorptive organ. The presence of mucilage glands in the various 

 species of Alaria is described ; but mucilage canals are absent. 

 Occasionally monstrosities occur such as duplication of the lamina or 

 ramification of the stipes, <S:c. 



In treating of the development and life-history of Alaria, Prof. 

 Yendo discusses two questions about which there has been much 

 disagreement, namely, whether Alaria is perennial, and whether it 

 sheds its lamina annually. His own observations lead him to the 

 conclusion that the plant is biennial. Germinating in the late autumn, 

 the plants grow to a great length by the following October, the 

 lamina then becoming worn away almost to the base ; quite early in 

 the following year the lamina starts growing again from the base 

 rapidly, soon shedding the remnant of last year's blade, and quickly 

 attaining its greatest length becomes soriferous and is washed away 

 from its substratum before the end of October. There is, he says, 

 little difference in the life-histories of Alaria and Laminaria on the 

 coast of Japan. In a diagrammatic table he figures the comparative 



