ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 303 



•that seeds will germinate in distilled water which contains no trace of 

 lime. But the growth of the root will be arrested if the water contains 

 the merest trace of copper, such as might be derived from distilling in 

 a copper retort. Growing plants are, in fact, infinitely more sensitive 

 reagents for the presence of metallic salts in the water than the most 

 delicate chemical tests. This has been found to be the case with the 

 white and yellow lupin, the castor-oil plant, wheat, and Spirogyra. 



H. Coupin * has obtained similar results with the higher, as well as 

 with the lower plants, showing, in all cases, excessive sensitiveness to 

 the presence especially of salts of silver, mercury, copper, and cadmium. 

 With sulphate of copper the limit of sensitiveness is stated to be 1 in 

 700,000,000, while with calcium chloride it is only 1 in 260. 



H. Devaux f confirms these results, and states that both Phanerogams 

 and Cryptogams are poisoned by solutions of salts of lead or copper 

 diluted to the extent of one in ten millions, or even less. The metal 

 is fixed by all parts of the cell, the cell-wall, the protoplasm, and the 

 nucleus ; the relative degree in which these different parts are affected 

 differs in different plants. He finds the sensitiveness manifested in a 

 solution diluted to 1 mgr. per hectolitre. 



(3) Irritability. 



Sensitiveness of the Nodes of Grasses.! — Dr. L. Montemartini 

 finds in the nodes of grasses, which are very sensitive to the action of 

 geotropism, a structure closely resembling that of the pulvinus of the 

 leaves of the sensitive plant. The swollen portion of the node — i.e. of 

 the base of the leaf-sheath — consists of cells which are round in trans- 

 verse, rectangular in longitudinal section, connected with one another 

 by a number of protoplasmic threads. They display the same behaviour 

 to anaesthetics as the foliar organs in Mimosa. 



Geotropism of the Roots of the Vine.§— According to J. M. Guillon, 

 different varieties of the grape-vine differ materially in the degree in 

 which their roots exhibit positive geotropism, i.e. in the angle which 

 their descending roots make with the vertical (angle of geotropism). 

 The smaller this angle the better can the plant make use of the water 

 of the soil, and the more likely is it to flourish. 



(4) Chemical Changes (including: Respiration 

 and Fermentation). 



Respiration of Plants.|| — K. Puriewitsch calls attention to the pre- 



CO 



valent error that the proportion ■■ 2 , as an expression of the production 



2 

 of carbon dioxide in the respiration of plants, is always near to unity. 



The variations in the value of this fraction in germinating seeds have 



already been pointed out, being higher in starchy and lower in oily 



seeds. The author's present observations were made on the mycele of 



Aspergillus niger, and a large number of results are tabulated, which 



* Tom. cit.. pp. 645-7. t Tom. cit., pp. 717-0. 



t Malpighia, xiv. (1900) pp. 271-4 (1 fig.). 



§ Comptes Rendus, cxxxii. (1901) pp. 589-91. 



|| Pringsheim's Jahrb. f. wiss. Bot., xxxv. (1900) pp. 573-610 (1 fig.). 



