ti(J4 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Influence of Light and Colours on Yeast.*-- J. E. Purvis and 

 Gr. R. Warwick have experimented with different species of Saccharomyces 

 in order to show the inllnence uf ravs of light of different refrangi- 

 bility upon the appearance and production of spores. Red, green, and 

 blue screens were used, and the yeast was kept in an Incubator at 

 24-25 c C. In four series of experiments the results show that while 

 blue and violet retard sporulation in a most marked manner, and green 

 to a less extent, red rays produce the same effect as darkness. Ultra- 

 violet rays produce the greatest retardation. The influence of radium 

 was also tested, and found to destroy the vitality of the cell. In 

 general, it is found that rays of low refrangibility accelerate spore 

 formation, and vice versa. Experiments made on the influence of light 

 and colours upon fermentation of hopped wort show that fermenting 

 solutions are not seriously influenced by these factors. 



Chemical Changes. 



Effects of Poisonous Gases on Plants.f — W. J. V. Osterhout has 

 made experiments on various plants, both wild and cultivated, in order 

 to ascertain whether it is possible to distinguish the effects of poison- 

 ous gases from those due to drought, root-injury, and other natural 

 causes. All the experiments confirm the opinion that, while drought 

 and natural causes result in the fading of the leaves, beginning from 

 the oldest, various poisonous gases, e.g. sulphur dioxide, cause the young 

 leaves to fade long before the old ones. Also the young rind of stems 

 is quickly injured by drought, but endures the action of sulphur dioxide 

 for a considerable time. 



Value of Sodium to Plants. % — The same author has experi- 

 mented with plants grown in water-cultures and in soil, with the view of 

 discovering whether sodium can be used as a protective agent to plants. 

 Experiments were made with various flowering plants, liverworts, algae, 

 and fungi, and tend to show that sodium can protect plants against the 

 toxic action of potassium, ammonium, magnesium, and calcium. The 

 sodium has no nutritive function, but is only protective ; moreover, 

 both chlorides and nitrates give similar results. These results show a 

 striking similarity between the behaviour of plants and animals, and may 

 prove of great value in agriculture. 



General. 



Origin of Parasitic Plants.§— C. A. White has studied parasitic 

 Seed Plants with the view of discovering something as to their aggre- 

 gate origin. He divides them into seven groups. Group I. includes 

 partial parasites which prey upon the roots of host-plants for part of 

 their nourishment. Group II. includes complete parasites, which, how- 

 ever, are nearly normal in structure, e.g. Mistletoe. Group III. contains 



* Joura. Inst. Brew., xiv. (1908) pp. 214-33. f Tom. cit., pp. 339-40. 



t Univ. Californ. Bot. Publications, iii. (1908) pp. 331-7. 

 § Amer. Nat., xlii. (1908) pp. 98-108. 



