(J 1-1 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(2) Nutrition and Growth (including Movements of Fluids). 



Influence of Light on the Growth of Leaves.*— Sig. G. Arcangcli 

 discusses this subject from a matbcmatical point of view. He is of 

 opinion that the statement that the size attained by leaves is propor- 

 tional to the intensity of the light to which they have been subjected is 

 too absolute. While some plants arc heliophilous, i, c. are dependent on 

 light for the full dcvcloiiment of their foliage, others are sciaphilous, or 

 thrive best, and their leaves assume a full dark-green colour, only when 

 the light is not too intense. This he found to be esjiecially the case 

 with Euryale ferox and Camellia japonica. It has been shown by 

 Wiesner that in many plants at least the direct rays of the sun act 

 injuriously on the chlorophyll, and hence on the power of assimilation ; 

 and the dcveloj)mcut of the palisade-tissue, the increase in the number 

 of rows of cells of which it is composed, and their elongation in the 

 direction of the incident rays, not merely facilitate the transport of the 

 assimilative substances, but also offer a means for the chloroplasts and 

 the protoplasm to withdraw from the too intense radiation which would 

 act injuriously upon them. The plaiting of the leaves of Euryale and 

 of other plants has a similar purpose. 



Supply of Food Constituents at Different Periods of the Growth 

 of Plants. t — Herr G. Liebscher advances a new theory as a basis for 

 the science of manuring. Each day the root should supply a certain 

 amount of food to the plant ; this amount varies more or less at different 

 stages of growth, and further, these variations differ in case of different 

 plants ; thus, one species requires a fairly uniform daily supply through- 

 out its period of growth, whilst another requires much more at one stage 

 than at another. Thus, for a plant requiring a uniform daily supply, a 

 slowly decomposing and lasting manure is appropriate, wliilst an easily 

 soluble one should be given to a plant whose demand is large during a 

 short period. 



(8) Irritability. 



Power of Contractility exhibited by the Protoplasm of certain 

 Cells.]: — Mr. W. Gardiner gives the results of experiments made on the 

 power of contractility exhibited by the i)rotoplasm of certain plant-cells. 

 In Mesocarpis, we have a cell which reacts in a most powerful manner 

 to the stimulus of temperature, of light, of electricity, and of poisons, 

 and this reaction, which may be watched under the Microscope, is 

 attended by a diminution in size. In the author's opinion, there is in 

 every cell a sufficient quantity of osmotically active substance to insure 

 turgidity, but the increase or decrease of turgidity depends essentially 

 on the contraction or relaxation of the parietal utricle. All the ex- 

 periments tend to show that it is the ectoplasm which mainly determines 

 the state of turgidity of the cells. The power of contractility which the 

 author has established for the irritable cells of Brosera and Mimosa, and 

 for the less specialized cells of JSIesocarpus, is a i)roperty which is 

 possessed in a greater or less degree by all the actively living cells 

 which constitute the tissues of plants. 



* Nuov. Giora. Bot. Ital., xx. (1888) pp. 331-41. Cf. this Journal, ante, p. 84. 

 t Bied. Ceutr., 1887, pp. 658-60. See Jouro. Chem. Soc. Lond., 1888, Abstr., 

 p. 382. X Ann. of Bot., i. X1888) pp. 362-7. 



