ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 653 



the tendril or petiole are due to unequal growth by producing 

 unequal tension of tissues. The unequal growth is chiefly defined 

 in the vibrogen tissue, which may therefore be regarded as the seat 

 of movement. The band of unequal growth does not arise at 

 successive points of the circumference. The vibrogen tissue consists 

 of three longitudinal bands, each of which becomes more active in 

 turn, without regular order. Bending under the influence of irrita- 

 tion results from cessation of growth and condensation of structure. 

 The collenchymatous tissue is that which is chiefly concerned in 

 variations of tension under mechanical stimuli. Coiling results (by 

 contact) from cessation of growth and condensation of structure or 

 (free coiling) from increased inequality of tension due to continued 

 growth. Transmission of impulses is effected through continuity of 

 protoplasm in the active tissues. 



Ascent of Sap.* — M. L. Errera describes a series of experiments 

 on this subject, made on the large vessels of Vitis vulpina. By in- 

 jecting into the stem a solution of gelatin melting at 33° C, and 

 coloured with Indian ink, he found that in all cases, when the 

 ' experiment was carried out with all possible precautions, the in- 

 jected branch took up no water and faded in a few hours. This was 

 considered conclusive evidence against the imbibition theory of 

 Sachs, and in favour of the view that the ascending current of sap 

 takes place through the cavities of the vessels and tracheides. 



Variation of Water in Trees and Shrubs.f — According to Prof. 

 D. P. Penhallow, the hydration of woody plants is not constant for 

 all seasons, but depends on conditions of growth. It reaches its 

 maximum during the latter part of May or early in June, and its 

 minimum during January. It is greatest in the sap-wood ; least in 

 the heart-wood. The greatest hydration is directly correlated with 

 most active growth of the plant, while lignification and the storage 

 of starch and other products are correlated with diminishing 

 hydration. The amount of water in dead wood varied, in 15 species 

 of tree, between 12-9 and 19*0 per cent. In living wood, the 

 maximum percentage observed was 61 ; it is usually somewhat less 

 in the second year than in the first. 



Migration of Nitrates in Plant Tissues.! -M. G. Capus's 

 method of study was the microchemical one. Sections of various 

 plant tissues were immersed in a weak solution of Arnaud's reagent, 

 cinchonamine hydrochloride acidified with hydrochloric acid. After 

 a longer or shorter period, according to the quantity of nitrates 

 present, crystals of cinchonamine nitrate separate out ; the size, shape, 

 and position of the crystals, whether within or without the cell, also 

 afford indications of the relative abundance of nitrates in the different 

 tissues. 



The author's observations demonstrate that many plants have the 



* CR. Soc. E. Bot. Belg., xxv. (1886) pp. 24-32. 

 t Canadian Kecord of Science, ii. (1886) pp. 105-16. 



% Ann. Agronom., xii. (1886) pp. 24-42. Cf. Journ. Chem. Soc. Loud.— 

 Abstr., 1. (1886) pp. 484-5. 



