534 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Buds producing male flowers only are more excited by heat than 

 females, and expand at a low temperature, under which the females 

 remain quiescent. 



A few warm days, succeeded by cooler ones, will therefore make 

 a corresponding difference in time between the opening of the male 

 and the female flowers, and possibly in the proportionate advancement 

 of the stamens and pistils in hermaphrodite flowers. 



Selenotropism of Plants.*— Ch. Musset, struck by the heliotropic 

 movements of plants, has made some experiments on the influence of 

 the moon. He sowed seeds of plants known for their phototropic sen- 

 sibilities, such as Lens esculenta, Ervum lens, and Vicia sativa. When 

 they were some centimetres in length they were placed in the dark ; 

 the branches became delicate, long, and white, while the leaves were 

 tinted a slight yellow. On the 22nd, 23rd, and 24th of February, 

 when the sky was exceptionally clear, they were exposed to the direct 

 light of the moon from 9 p.m. to 3 a.m. Almost at once the branches 

 became curved, presenting their concavity and terminal bud towards 

 the moon. The bud seemed to follow the moon, and when the plants 

 were placed at a window with a western aspect a fresh movement was 

 seen, and this continued until the moon disappeared behind the hills. 

 The author proposes to call these movements selenotropic. 



Withering of Flowers and Leafy Shoots-t — According to J. 

 Wiesner the leaves of most plants transpire more strongly than the 

 flowers ; and in cut branches, or such as are insufficiently supplied 

 with water from below, the leaves usually wither sooner than the 

 flowers. Cut flowers wither less rapidly when there are no leaves 

 attached to the shoots ; and if transpiration is prevented from the 

 leaves, the flowers remain quite fresh, showing that the transj)iring 

 leaves withdraw water from, the flowers. The same is the case with 

 plants growing in the ground when the supply of water is insufficient. 

 The growing ends of branches and flower-stalks lose water and wither 

 in the same way, not by direct transpiration, but by the water being 

 withdrawn by the mature foliage. 



The surface of the floral leaves and of young leaves is greatly 

 reduced by withering and desiccation, often as much as 50 per cent., 

 resulting partly from the cessation of tension and turgidity, partly 

 from the loss of the water of imbibition of the cell-wall. The open- 

 ing of flowers is frequently the result of transpiration. 



Cut leaves which have been placed for a time under water wither 

 more rapidly when exposed to the air than those that have not been 

 moistened, the moistening favouring transpiration. 



Leaves absorb as a rule more water through the under than through 

 the upper surface ; rain and dew do not, therefore, usually supply 

 much water directly to the plant ; but both favour transpiration after 

 the moistening has ceased. This is of advantage to the plant only 

 when the supply of water to the plant from the soil is insufficient. 



* Comptes Rendus, xcvi. (1883) p. 663. 



t Wiesner, ' Studien iiber das Welken von Bliithcn u. Laubsprodsen,' Wieu, 

 1882. 



