324 SUMMARY. OF CURRENT RESEARCHES RELATING TO 



otherwise precisely similar, but in darkness, gave only 27 mgrm. In 

 light the cells are small, in a state of active multiplication, and con- 

 tain no starch-grains. "When living in the dark they are large, with 

 thick walls, and evidently sluggish ; they were, moreover, crowded with 

 starch. The absence of starch-grains in the light is explained by the 

 fact that starch being a temporary reserve, the plant was growing too 

 rapidly to be able to store any carbohydrate. 



Chemauxism of Copper Salts on Penicillium glaucum.* — Dr. 

 Le Eenard describes the influence exerted by soluble copper salts on 

 the growth of Penicillium in the presence of carbohydrates. The writer 

 finds, as did Nageli in his study of oligodynamics, that the presence of 

 copper salts in infinitesimal quantities in the culture medium is fatal to 

 the organism. A more concentrated solution excites the growth which 

 increases by leaps up to a certain strength ; after the maximum is reached 

 the copper again becomes harmful to the growth of the plant. 



Resistance to Salt Solution. - ]" — F. Cavara publishes his investiga- 

 tions of the extraordinary physiological resistance offered by Mierocoleus 

 ehtonoplastes Thur. to salt water of varying degrees of concentration. 

 The plant is a cyanophyceous alga, and plays an important part in the 

 separation of pure salt from sea-water. The author gives an account of 

 the process adopted in the evaporation tanks and of the benefits derived 

 from the presence of the alga, which greatly assists in the purification of 

 the brine. He describes the experiments he made for determining the 

 maximum and minimum strengths of solution in which the alga can 

 f^row, and his microscopical observation of the changes which result in 

 the filaments and cells. He finds that the plant can even maintain life 

 for a year or two in the heaps of extracted salt. 



Irritability. 



Action of Temperature on the Absorption of Minerals in Etio- 

 lated Plants.^ — Gr- Andre experimented with etiolated plants of maize 

 and haricot growing at temperatures of 15° C. and 30° C. He finds a 

 remarkable increase in the proportion of silica in the dry weight at the 

 higher temperature. Calcium carbonate, on the contrary, was absorbed 

 in less quantity, and the amount of potash was not increased. The pro- 

 portion of phosphoric acid was unchanged. The amount of nitrogen 

 was only feebly influenced by the rise in temperature. Among hydro- 

 carbons, vasculoso was present in considerably larger proportions at 

 30° C. than at 15° C. 



Light and Spore-Germination. § — N. Schulz treats of the germina- 

 tion of the spores of Mosses, Ferns, and Equisetacese, and shows that in 

 all but a few cases light is indispensable for promoting the assimilation 

 of the food stored in the spores of Mosses and Ferns. The spores of 

 Equisetaceae contain no food-stores and can only obtain nourishment 

 from carbonic acid in the presence of light. 



* Journ. de Bot., xvi. (1902) pp. 97-107. 



t Nuov. Giorn. Bot. Ital., nuov. ser. ix. (1902) pp. 59-80 (t. 2). 



X Compt. Rend., exxxiv. (1902) pp. 668-71. 



§ Beiheft. Bctan. Centralblatt, xi. (1901) pp. 81-97 (8 figs.). 



