ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 679 



the experiments on this subject of MM. Bonnier and Mangin,* have 

 arrived at somewhat different results. They describe the apparatus 

 used, the plant experimented on being Euonymus. Instead of the 



CO 



value of -p-? being usually less than unity, they found it to vary from 



0*96 (in February) to 1'20 (in April), being most often greater than 

 unity. The cause of this difference the authors suggest to be that the 

 carbon dioxide measured by MM. Bonnier and Mangin included a 

 portion of that formed by respiration. They consider the facts 

 observed to show that in the plant examined a portion of the carbon 

 dioxide given off is the result of internal combustion similar to that 

 which takes place in fermentation. 



Commenting on this paper, M. Th. Schloesing t considers the 

 results obtained by MM. Bonnier and Mangin to be very well authen- 

 ticated, and points out the singular fact, which he does not attempt to 

 explain, that the proportion of hydrogen in the plant is larger than 

 might be expected to result from the fact that it becomes fixed in the 

 plant along with oxygen in the proportion in which the two together 

 constitute water. 



Variation of Respiration with Development.^ — As the result of 

 further experiments on the relation between the amount of oxygen 

 inhaled and of carbon dioxide exhaled by plants, Messrs. G. Bonnier 



and L. Mangin state that the value of the fraction -p— is not constant 



for the same species in different stages of development ; but that at 

 the same stage of development it is always constant whatever the 

 temperature. This corresponds to the law already established by the 

 authors for the relationship between the gases absorbed and exhaled 

 by leaves in darkness. 



Thermotropism of Roots.§— New experiments on the pheno- 

 menon to which Dr. J. Wortmann has given this namc,li made on 

 seedlings of Ervum lens, Pisum sativum, Phaseolus multiflorus, and Zea 

 Mai8_ have led him to the general conclusion that not merely the tip, 

 but the entire growing region of the root, is sensitive to heat striking 

 it on one side. By the application of higher temperatures, decapitated 

 roots displayed the same energy in their thermotropic movements as 

 normal roots. A similar sensitiveness was shown by the secondary 

 roots of the scarlet runner. 



Air in "Water-conducting Wood.lT— Dr. M. Schoit lays down tho 

 following propositions on this subject:— So long as the cell-walls are 

 moiHt, as is the case with living plants under normal conditions, no 

 air can diffuse through the tracbeids ; for it can bo demonstrated that 

 even under pressure, lasting for weeks, greater than that which is 



♦ See this Journal, iv. (1884) p. 591 ; ante, p. 488. 



t Comptc-8 Rendus, c. (1885) pp. 12.3G-8. 



j Ihid., pp. 1092-5. See this Journal, ante, pp. 94, 488. 



§ Bot. Ztg., xliii. (1885) pp. 19.3-200, 209-lC, 225-.35. 



II See thifl Journal, iii. (188H) p. 873 ; iv. (1884) p. 588. 



i Jenaiflch. Zeitschr. f. Naturwiss., xviii. (1885) pp. 463-78. 



2 V 2 



