ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 281 



of starch in the leaves was glucose, and that this glucose is transported 

 into the leaf-stalk and stem. This transformation into soluble sugar 

 is undoubtedly due to a diastatic ferment. Further experiments 

 showed thf^t the veins are the sole conduit through which the trans- 

 port of glucose takes place, and that it occurs almost exclusively in 

 the " conducting sheath " or tissue which encloses the finest ramifica- 

 tions of the vascular bundles as a single layer of cells, the stronger 

 bundles as a tissue composed of several layers. The chlorophyll- 

 grains in this sheath possess only to a small degree the power of 

 forming starch. The transport is the direct consequence of darkness, 

 and the current of assimilated substances takes place practically in 

 the veins, but chiefly in their conducting sheath. The sugar begins 

 to disappear after the complete transformation of the starch ; first 

 from the mesophyll and finer veins, then from the stronger veins, 

 gradually from the apex to the base. The cells of the conducting 

 sheath are adapted for their function by a much stronger attractive 

 force for dissolved carbohydrates than those of the mesophyll. 



In Impatiens the formation of starch is comparatively feeble. 

 Totally different results are obtained from a number of plants where 

 the changes go on with such energy that the glucose is temporarily 

 again transformed into starch in all the cells through which it passes. 

 An extreme case of this is furnished by Sydrocharis morsus-ranse. 

 Here the sheaths of the thicker bundles are found to retain the starch 

 the longest. 



With regard to the transport of food-materials by the laticiferous 

 vessels, as assumed by Schwendener * and others, experiments of 

 the author on Euphorbia Peplus and E. lathyris are quite opposed to 

 the hypothesis. 



In a Hepatica, Plagiochila asplenioides, the transformation of 

 starch into sugar was also determined. Details are given with regard 

 to the formation of starch and sugar in a number of other plants. 



Functions of Chlorophyll.! — Herr C. Timiriazeff sums up the 

 evidence in favour of the view which he has advocated that the 

 decomposition of carbonic acid in the light is effected by the heat- 

 rays of the spectrum, and that their maximum and that of the 

 decomposition of carbonic acid corresponds with the absorption-band 

 of chlorophyll in the red. He criticizes the opposing conclusions of 

 Draper, Pfeffer, N. J. C Miiller, and others. 



Temperature of Growing Fruits.^ — Interesting experiments have 

 been tried on the temperature of growing fruits by Dr. W. M. Ord. 

 He used a slender-pointed thermometer, which could be easily thrust 

 into the fruit. The trials were made on cucumbers in a hot-house, 

 and the variations due to fluctuations were indicated by the tempe- 

 rature of a bottle of water suspended at the side of the fruit. A 

 difference of one or two degrees was found between the temperature 



♦ See this Journal, v. (1885) p. 1022. 



t Bull. CoBgres Internat. Bot. St. Petersburg, 1884, pp. 103-34. See 

 Comptes Rendus, c. (1885) p. 851, and Bot. Centralbl., xxiv. (1885) p. 264. 

 t Brit. Med. Journal, 1885, ii. p. 784. Cf. Bot. Gazette, x. (1885) p. 430. 



