272 SUMMARY OF CURRENT RESEARCHES RELATING TO 



siderable importance, since the latter relationsliip had hitherto been 

 observed in Monocotyledons only. 



Gliding Growth in the Formation of the Tissues of Vascular Plants.* — 

 The term " gliding growth " (gleitendes Wachsthnm) is applied by Herr G. 

 Krabbe to that mode in which the cell-walls of neighbouring cells become 

 pushed or glide one over another ; and he points out the importance of this 

 process in the differentiation of tissues. Any increase in the tangential 

 diameter of vessels can, he maintains, take place only on this supposition. 

 A very simple instance of this mode of growth occurs in the formation of 

 the cambium-ring. The author believes also that it assists in the forma- 

 tion of vascular cells, sieve-tubes, tracheides, libriform, and bast-cells. 

 When cells increase in volume in this way, no increase in turgidity need 

 be assumed, the cause of growth being an active growth or specific activity 

 of the cell-wall where it is in contact with the j)rotoplasm. This view is 

 inconsistent with the hypothesis of a universal continuity of protoplasm 

 from cell to cell. 



Influence of an Aquatic Medium on Amphibious Plants. — M. E. Mer,f 

 replying to the objections of Costantin,+ adheres to his conclusion that 

 modifications which survive in the form and structure of amphibious pLints 

 in consequence of a change of medium — the only ones on which it is 

 possible to experiment, because they are the only ones which can survive 

 in either air or water — must be considered as the result— not of a direct 

 influence, but of a slow and prolonged action of the medium, transmitted 

 by heredity. He supports this view from the structure of the very plants 

 which Costantin relies on to prove the contrary. 



To this M. J. Costantin replies, § adducing instances in which he con- 

 ceives that no other explanation can be offered of the alteration of structure 

 in organs caused by complete submersion than that it is the direct result 

 of the action of the medium on the organs. 



(6) Movement. 



Transpiration. |1 — Herr F. G. Kohl enters in great detail into the 

 phenomena attending this function. In opposition to the statements of 

 Haberlandt and Wiesner, he finds that cut plants when moistened wither 

 less rapidly than when dry. Moistening with water causes the stomata to 

 close or not, according to the structure of the neighbouring epidermal 

 cells. When the guard-cells are the only epidermal cells which contain 

 chlorophyll, the stomata open in light ; but if the other cells of the 

 epidermis also contain chlorophyll, the effect is slight or none at all. 

 With regard to the influence of temperature on the stomata, the author 

 confirms the observations of Schwendener and Sorauer that a rise in tem- 

 perature favours transpiration, whether of the air or of the ground. Plants 

 destitute of stomata, as Trichomanes radicans, transpire less in the dark than 

 in diffused light. 



A number of experiments were undertaken in order to ascertain the 

 effect of stronger or weaker transpiration on the development of tissue. 

 As a general result it is stated that plants grown in dry air exhibit a 

 tendency to stronger thickening and cuticularizing of the outer walls of 



* Krabbe, F., 'Das gkitende Wachsthum bei der Gewebebildung d. Gefasspflauzen,' 

 100 pp. aud 7 pis., Berlin, 18SG. See Bot. Centralbl., xxix. (1887) p. 3. 



t Bull. Soc. Bot. France, viii. (1886) pp. 169-77. 



X See this Journal, 1886, p. 474. § Op. cit., pp. 192-6. 



II Kohl, F. G., ' Die Transpiration d. Pflanzen, u. ihre Eiuwirkung auf d. Ausbil- 

 dung pfianz. Gewebe,' 124 pp. and 4 pis., Braunschweig, 1886. See Bot. Centralbl,, 

 xxviii. (1886) p. 292. 



