162 



BOOKS AND CURRENT LITERATURE 



Life History of Cutleria. — -Yamanouchi has recentlj^ presented 

 the result of his work on the Mfe history of Cutleria.^ His material was 

 collected at the Bay of Naples and the investigation was carried on there 

 and at the University of Chicago. The main question dealt with in this 

 paper is whether Cutleria exhibits true alternation of generations or 

 merely polymorphism. The author finds that vegetative and germ 

 cells of Cutleria have 24 chromosomes; that the 2 x generation initiated 

 at fertilization continues until an upright column with an expanded, 

 disc-like base is formed, which becomes the plant known as Aglaozonia; 

 that all cells of Aglaozonia have 48 chromosomes; that Aglaozonia 

 produces zoospores with 24 chromosomes which germinate into plants 

 not expanded, but filamentous like Cutleria; therefore he concludes that 

 Cutleria with the zoospore that produces it is the gametophytic genera- 

 tion, and Aglaozonia with the fertilized gamete from which it develops 

 is the sporophytic generation. As further evidence that the alternation 

 of Aglaozonia with Cutleria is due to "the potential characters of their 

 germ plasm" and not to environment, the author calls attention to the 

 fact that although his cultures were grown at a depth of 15-20 cm. 

 instead of the normal depth of 1-5 m., the zoospores and the fertilized 

 gametes behaved exactly as they do in their natural habitat. Apogamy 

 was observed, but cultures from unfertilized gametes were not developed 

 to the reproductive stage. One striking difference between plants 

 from fertilized gametes and those from unfertilized gametes was the 

 slow growth of the latter. Apogamous plants had 24 chromosomes. 

 Yamanouchi believes that apogamy in Cutleria may be a "reversion 

 to the ancestral type of asexual spores which certainly existed before 

 the appearance of sexuality in the gametophytic generation." — J. G. 

 Brown. 



Influence of Ultra-violet Rays. — As the result of a series of 

 experiments Stoklasa has contributed some interesting observations on 

 the influence of ultra-violet rays on vegetation. ^ Etiolated seedlings 

 of corn, oats, barley and peas were subjected under bell-jars to ultra- 

 violet rays of different wave length. When the wave length was less 

 than SOO/Uy" there was no influence on the formation of chlorophyll. After 

 a two hours' exposure to rays with a wave length of 400 to 300/^JU the 



^ Yamanouchi, Shigeo, The Life History of Cutleria. Bot. Gaz. 54: 441-502> 

 pis. 26-35, December, 1912. 



^ Stoklasa, A. et al., Ueber den Einfluss der Ultra-violetten Strahlen auf die 

 Vegetation. Centrb. f. Bakt. 2 Abth. 31: 477, 1911. 



