ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 573 



determined on cloudy days. The harmonising of the rhythms of ab- 

 sorption, exudation and tension of fluids, and the rate of growth is 

 suggestive of the vital character of transpiration. Variations of a few 

 per cent, in the humidity of the atmosphere produced no sensible 

 change in the amount of transpiration, but an increase of 8 per cent, 

 resulted in a marked drop in the rate. The curve in the dark was 

 sometimes in keeping with the rhythm found under constant illumina- 

 tion, but was more frequently characterised by variations quite out of 

 keeping with the periodicity of light. There is evidently a cessation 

 of the vital action of the plant, and the retardation of the rate and its 

 greater regularity accords with the loss of tone manifest in the plant. 

 The considerable volume transpired in the dark indicates that the 

 stomata may be sufficiently open to allow the escape of vapour. Only 

 in the case of Cycas revoluta was the amount of transpiration in keeping 

 with the ratios determined for cuticular transpiration. The physio- 

 logical character of transpiration is also indicated by the periodicity of 

 the opening and closing of the stomata. They are more responsive to 

 the stimulus of light in the morning than in the afternoon. 



Transpiration of Evergreen Trees in Winter.* — Shunsuke Kusano 

 gives an account of a large series of experiments on the transpiration 

 of evergreen plants at the latitude of Tokyo, during winter. Details 

 of the experiments which were made under various external conditions 

 of temperature, light, time of day, &c. are tabulated. The author 

 shows that not only is transpiration continued, but also that photo- 

 synthesis takes place without intermission in winter, though much 

 feebler than in summer. The time of minimum transpiration coincides 

 with that of minimum temperature (end of January). The amount of 

 water trauspired by foliage evergreen trees was in average cases one 

 and a half to twice as great as that transpired by conifers. The author 

 concludes that many of the evergreen trees in Japan have their stomata 

 more or less open even in the depth of winter ; a condition which is 

 probably the most important factor in winter transpiration. 



Relations of Calcium and Magnesium to Plant-Growth.f — W. 

 May experimented with various plants grown in water, sand, and 

 ordinary soil, and manured with calcium and magnesium as sulphates, 

 nitrates, and carbonates. A great excess of magnesium was found to 

 be very injurious, while excessive amounts of calcium check the growth. 

 The best relations of calcium to magnesium are 7 : 4. 



Accumulation of Mineral and Organic Matter in Woody Plants.f 

 — G. Andre has studied the variation in the amount of mineral and 

 organic matter in the branches of the current year in the horse-chest- 

 nut, starting from the time when the branch has finished its elongation 

 to the fall of its leaves. The nutritive materials accumulated serve to 

 nourish the terminal bud which will develop next year. He finds a 

 gradual increase through the period of experimentation (from July 29 

 to November 16) in the phosphoric acid, potash, and nitrogen. The 

 amounts of carbohydrate saccharifiable by dilute acids, and the cellulose 



* Journ. Coll. Scl. Imp. Univ. Tokyo, xv. pt. 3 (1901) pp. 313-6G (I pi.). 

 t U.S. Dept. Agr. Bull., 1901, No. 1, pp. 37-53. See also Journ. Chcm. Soc, 

 Ixxxii. (1902) ii. p. 347. t Comptes Rendus, exxxiv. (1902) pp. 1514-7. 



October loth, 1902 2 q 



