INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 295 



of water takes place as long as the plants are growing, decreasing as 

 soon as growth in length ceases. 



A series of experiments related to the causes of geotropic and 

 heliotropic curvatures. In negatively geotropic organs the proportion 

 of water is greater in the convex nodes than in the concave upper side 

 of the curvature. In the curved parts of a young root the proportion 

 is greater in the convex upper than in the concave under side. Before 

 curvature takes place, the proportion of water increases in the upper 

 side. 



Finally, attention was paid to the distribution of water in con- 

 nection with the tension of the bark, with the following results : — 

 As the tension of the bark changes during the day, a corresponding 

 change takes place in the amount of water contained in the bark, an 

 increase of tension being accompanied by an increase in the amount 

 of water. As the stems of trees are exposed to a higher temperature, 

 it was found that the tension and thickness of the bark, and the amount 

 of water contained in it, also increased. These changes take place 

 without the diameter of the wood being sensibly increased, and without 

 any increase in the total amount of water in the branch. From this 

 it follows that an increase of temperature drives the water out of the 

 wood into the bark. 



Sugars of Vegetation.* — The saccharine matters found in plants 

 belong to two great groups — the saccharoses and the glucoses ; the 

 former constituting the reserve materials which are not directly 

 assimilable, while the latter can be directly utilized by the plant. 

 In order for a saccharose to be made use of, it must first be trans- 

 formed into a glucose, the process being one of hydration, effected by 

 a soluble nitrogenous principle known as an inverting ferment. M. 

 Bonnier has extracted a similar soluble ferment from the tissues of 

 sacchariferous phanerogams, as Helleborus, Hyacintluis, Primula, &c. 

 This ferment has the power of transforming into a glucose sixty 

 times its volume of a saccharose, siich as cane-sugar. 



The saccliariferous tissues are developed especially in the root, as 

 in the beet and carrot, in the rhizome, as in Cyj'erus csridenfiis, or in 

 the woody stems, as in Acer and SyrvKja. In the flower, near the 

 ovary, is frequently found an accumulation of saccharoses, accom- 

 panied by glucoses. The most fi-o(|uent saccharose, CioH.vjO,,, is 

 that of cane-sugar ; less often melezitose is found, as in the larch, 

 maunitose in tlie pith of the ash, oak, and elder. The most widely 

 distributed glucose, C„H,^0,.,, is grape-sugar, almost always accom- 

 panied by levulose ; tlie glucose known as sorbin occui's in Sorbns, 

 Amyfjdalus, Cydonia, itc. Mannite, C,;H,,0,;, already known in abne 

 and iungi, has been found by Bonnier in the leaves of Acer. 



Tlie following is the method emidoycd by Bonnier for obtaininf^ 

 the three kinds of sugar, saccharose, glucose, and levulose, in a pure 

 state from the sacchariferous tissues of flowers. The mixture is first 

 treated with absolute alcohol ; the insoluble cane-sugar (saccharose) 

 crystallizes out. Tiie crystals are dissolved in water and reerystallizeil, 



* ' Hull. S.M'. b..t. Fniiice," xxvi. (ISTD) p. 20S. 



