ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 455 



fraction of the conducting tissue is needed if the wood-cells of the 

 portion in question are living ; while the whole of the conducting tissue 

 does not transmit sufficient water if these cells have been destroyed. 



Function of Silica in the Nutrition of Cereals.* — A. D. Hall and 

 C. G. T. Morison, as the result of investigations on barley, conclude 

 that silica, although not an essential constituent of plant food, plays a 

 part in the nutrition of cereals, such as barley, which contain normally a 

 considerable proportion of silica in their ash. The effect of a free 

 supply of soluble silica is manifest in an increased and earlier forma- 

 tion of grain, and is thus similar to the effect of phosphoric acid. 

 The silica acts by causing an increased intake of phosphoric acid, to 

 which the observed effects are directly due. There is no evidence that 

 the silica within the plant causes a more thorough utilisation of the 

 phosphoric acid that has already been assimilated, or itself promotes the 

 migration of food-materials from the straw to the grain. 



Physiology of Germination of Pollen .f — L. Jost finds that ger- 

 minating pollen-grains may be placed in three classes. (1) Those re- 

 quiring nothing but water for germination, much mineral matter being 

 injurious. To this group belong Grasses, which can only germinate 

 in minute quantities of pure water. (2) Those requiring a very dilute 

 solution of a definite chemical substance, which is contained in the 

 stigma. In a few cases this substance is laavulose, in others organic 

 acids, but in most cases it is unknown. (3) Those which germinate 

 only in a sugar solution of definite concentration. In this case it is 

 still unknown whether the sugar is nutritive, or whether it prevents 

 excessive absorption of water owing to its osmotic properties. It may 

 act like laevulose, or it may neutralise the poisonous effects of certain 

 mineral substances, or it may exercise both these functions. 



Similar results may be expected in connection with the germination 

 of fungus spores. 



Effect of Calcium Salts on Sphagna. J — H. Paul gives a preliminary 

 account of his observations on the effect of lime-salts upon Sphagna. 

 He reviews the work of previous authors, notably that of C. A. Weber, 

 from whom he differs entirely. Weber holds that calcium salts are not 

 inimical to the nutrition of Sphagna, but that he has found them to 

 flourish, and one species to fruit, even when irrigated with water rich 

 in calcium carbonate. Paul, on the other hand, finds Sphagna very 

 sensitive to solutions of calcium carbonate, though the species vary in 

 this respect. Calcium sulphate they can tolerate in fairly large quantities. 

 Details of Paul's experiments are promised in a further paper. 



Fungi in Relation to Atmospheric Nitrogen. §— Berthold Heinze 

 has conducted a series of experiments with various fungi on artificial 

 culture media to test their power of assimilating nitrogen from the air, 

 and so aiding in the enrichment of the soil. He comes to the conclusion 



* Proc. Roy. Soc, Series B, lxxvii. (1906) pp. 455-77. 

 t Ber.Deutsch. Bot. Gesell., xsiii. (1906) pp. 504-15. 

 j Op. cit., xxiv. (1906) pp. 148-54. 

 § Ann. Mycol., iv. (1906) pp. 41-63. 



