ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 695 



alkaline earths exercise a pyisonous effect on plants in proportion to tlio 

 atomic weight of the metal, — calcium, strontium, barium. Most of tho 

 salts of barium and strontium are poisonous ; barium chlorate especially 

 so ; as also are tbe chlorates of potassium and sodium. 



Action of Carbon dioxide on the Movements of Water in Plants.* 

 — From a series of experiments made on Phaseolus vulgaris, Dr. P. 

 Kosaroff concludes that carbon dioxide exercises a strongly depressive 

 effect on the movements of water in plants. Under the influence of an 

 excess of C0 2 , the amount of water absorbed is decreased, whether the 

 plants be uninjured or the leaves be removed. The injurious action of 

 carbon dioxide is especially marked where it comes into contact with 

 living elements. This action is due both to direct injury and to the loss 

 of oxygen. The withering of plants on long exposure to carbon dioxide 

 is due to the reduction of transpiration. 



Transpiration in the Tropics and in Central Europe, f — Hen* E. 

 Giltay gives details of further experiments to elucidate the questions 

 arising out of this subject, and replies to the criticinms of Haberlandt 

 on his previous publications. 



Bleeding of Cornus macrophylla4 — Among Japanese trees this is 

 one in which the phenomenon of bleeding is most strongly displayed. 

 M. M. Miyoshi found the greatest pressure represented by a column of 

 mercury 109 cm. high. The bleeding displays a daily periodicity, the 

 maximum pressure occurring about 6 a.m. in the summer, or between 

 that and noon in the winter, the minimum between 4 and 8 p.m. 



(3) Irritability. 



Geotropism. — Herr F. Noll § criticises Czapek's explanation of gco- 

 tropic curvatures, controverting some of his conclusions. He thinks 

 that Czapek places too much reliance on klinostat experiments, since the 

 klinostat does not prevent all geotropic irritation. He further states 

 that the reactions of the cell-contents described by Czapek in geotropi- 

 cally irritated apices of roots are not closely connected with the reception 

 of the irritation. 



Mr. E. B. Copeland || confirms Czapek's statement that the growing 

 hypocotyl of Cucurbita displays no polarity ; similar results were obtained 

 also in the case of other seedlings, and with roots. If a stem is split into 

 two longitudinal halves, and laid horizontally, the lower half, which has 

 the split surface upwards, will increase in length more rapidly than the 

 upper half ; while with split roots the reverse is the case. 



Rheotropism of Roots. — Herr A. Berg % has adopted three different 

 modes for determining the rheotropism of growing roots : — Dipping the 

 roots in running water ; causing the roots to move in still water by the 



* Eot. Centralbl., lxxxiii. (1900) pp. 138-44. 



t Pringsheirn's Jahrb. f. wiss. Bot., xxxiv. (1900) pp. 405-24. ( 'f. this Journal. 

 1S99, p. 179. 



% Arb. Bot. Inst. k. Univ. Tokio. See Bot. Centralbl.. lxxxiii. (1900) p. 347. 



§ Pringslieim's Jahrb. f. wiss. Bot., xxxiv. (1900) pp. 457-500. Cf. this Journal. 

 1899, p. ISO. 



|| Bot. Gazette, xxix. (1900) pp. 185-96. 



f Lund's Univ. Arsskr., xxxv. (1899) 35 pp. and 1 pi. See Bot. Ztg., lviii. (1900) 

 2«» Abt., p. 169. 



