420 Prof. H. Marshall Ward. The Relations between 



that the increased amount of organic acids is favourable rather than 

 otherwise to the ferment processes which lead to the conversion of 

 the starch into glucoses.* How far the protoplasm will allow the 

 watery solution of glucose to escape, owing to its increased perme- 

 ability, cannot be determined, but ifc is at least probable that some 

 may reach the cell-walls. In any case, we have the cells flooded with 

 a dilute solution of organic acids and glucose, and the controlling- 

 protoplasm becoming less and less capable of retaining the excess. 



The turgid condition of the cells, and the diminished intensity of 

 the light,f will favour growth, and, in spite of a comparatively low 

 temperature, the organs may be extending more or less rapidly or 

 slowly. If so, the tendency will be for the very watery cell-walls to 

 become relatively thinner than usual, as well as watery, because the 

 ill -nourished protoplasm does not add to the substance of the wall in 

 proportion. This being so, we have the case of thinner, more watery 

 cell- walls acting as the only mechanical protection between a possible 

 fungus and the cell contents. 



But this is by no means all that has to be considered, when the 

 conditions remain as above described. Sooner or later the glucose 

 begins to fail, either because it has been directly employed for the 

 support of the metabolic processes in the protoplasm in the immediate 

 neighbourhood, or (less probably) because it has been re-converted 

 into starch, J or other reserve carbohydrates by the leucoplasts in the 

 cells of the roots, tubers, &c, at a distance. Now, as soon as a 

 want of carbohydrates makes itself evident in the destructive meta- 

 bolic processes accompanying growth, the accumulation of substances 

 like asparagin, leucin, &c, is apt to occur, § as products of the de- 

 composition of the proteids. Under more normal conditions, as we 

 have seen, these amide-bodies would be worked up again with carbo- 

 hydrates into new constituents of living protoplasm, but they now 

 begin to accumulate. 



The net result of the foregoing changes amounts, shortly put, to 

 the following: — Under certain circumstances the parenchymatous 

 tissues of the living plant may be in a peculiarly tender, watery 

 condition, where the cell-walls are thinner and softer, the protoplasm 



* Baranetzky, ' Die Stark eumbilclenden Fermente,' 1878 ; Brown and Heron, 

 ' Journ. Chem. Society,' 1879 ; Detmer, ' Das Pflanzenphysiologische Praktikum,' 

 1888, p. 198. 



f So far as the composition of the light is altered, it will probably favour growth, 

 because the more refrangible rays are fewer when the light has to traverse a thick 

 atmosphere. 



X See Schimper, ' Bot. Zeitg.,' 1880, col. 881 ; and A. Meyer, ' Bot. Zeitg.,' 1880, 

 Nos. 51 and 52. 



§ See Palladin, " Ueber Eiweisszersetzung in den Pflanzen" (' Ber. d. Deutsch. 

 Bot. G-esellsch.,' 1 88u, p. 205) ; and for older literature, Pf effer, ' Pflanzenphysiologie,* 

 vol. 1, pp. 298 — 301, and further literature quoted. 



