€00 SUMMARY OF CUItRENT RESEARCHES RELATING TO 



Embryog-eny in Euphorbia."— W. Weniger has studied the develop- 

 ment of the embryo-sac and embryo in^. Preslii and E. splendens. The 

 author finds that in both species the cyathium-papilla arises between two 

 bracts, and gives rise to staminate flowers, involucre, ovules, carpels, 

 and finally to secondary staminate flowers. The megaspore mother - 

 cell arises in the sub-epidermis ; an axial row of four megaspores is 

 formed, the lowest of which forms the embryo-sac, while three disintegrate. 

 The inner integument develops first, but is soon outgrown by the outer. 

 When mature, the long, narrow embryo-sac is deeply embedded in the 

 nucellus. In E. Preslii the structure is that of a typical angiosperm 

 but it seems probable from certain peculiarities that in E. splendens the 

 four antipodal nuclei undergo a second division. The obturator arises 

 from the placenta, filling the beak-like prolongation of the nucellus, and 

 disintegrates as the embryo develops. At the first division of the egg of 

 E. Preslii, endosperm-nuclei lie between it and the micropylar end of the 

 embryo-sac. The embryo is a round mass of cells, which elongates to 

 form two cotyledons and a root-cap. The ripe embryo is straight and 

 embedded in endosperm, except at the tip of the root-cap. E. splendens 

 has a short suspensor, but E. PresUi has none. 



Physiology. 

 Nutrition and Growth. 



Environment and Nectar Secretion.! — L. A. Kenoyer has studied 

 the influence of environment on the secretion of nectar. After a brief 

 historical summary of previous investigations, the author gives an 

 account of his experiments conducted under various conditions of 

 humidity, rainfall, temperature, atmospheric pressure, light, fertility of 

 soil, flowering period, and age of flower. He finds that an increase in 

 humidity causes increase in the water secreted by the nectaries ; excess 

 of water causes reduction of sugar-surplus ; rain causes much loss of 

 nectar-sugar. The rate of secretion of sugar and water increases with 

 temperature up to a certain optimum, but the accumulation of sugar 

 varies inversely as the temperature. Alternations of high and low 

 temperatures cause the maximum secretion of sugar. Variation in 

 pressure has no marked effect on secretion, but darkness diminishes 

 sugar-secretion. The amount of sugar secreted varies directly with 

 conditions of growth and vigour of the plant. Nectar is most abundant 

 early in the flowering season, while accumulation and secretion of sugar 

 are greatest near the time of the opening of the flower. 



Irritability. 



Mechanism of Movement in Drosera rotundifolia.:|: — Henry D. 

 Hooker has studied the movements of the leaf tentacles of Drosera 

 "which he describes as growth phenomena. 



The osmotic concentration in cells of D. rotundifolia tentacles 



* Bet. Gaz., Ixiii. (1917) pp. 266-^1 (3 pis.). 



t Bot. Gaz., Ixiii. (Iyl7) pp. 249-65. 



X Bull. Torrey Bot. Club, xliv. (1917) pp. 389-403. 



