508 SUMMARY OF CURRENT RESEARCHES RELATING TO 



some of the lamellae is not apparent under natural conditions is prob- 

 ably because the refractive properties of the crystalloid substance so 

 nearly resembles that of the associated colloid. The use of certain 

 reagents causes an imbibition of water by colloidal portions with conse- 

 quent swelling of the grain, and hence a contrast in refractive power 

 with the more insoluble crystalloid substances. 



Action of Freezing on Plant-Cells.* — D. Matruchot and M. 

 Molliard, as the result of a long series of experiments, come to the 

 following conclusions. Freezing of plant-cells or tissues causes an 

 attraction of water to the outside of the cell, produced in aquatic plants 

 by freezing of the surrounding liquid, in aerial plants by freezing of 

 the thin layer of water which covers the external surface of the cell-mem- 

 branes. There results a rapid general exosmosis of water, and not only 

 from the cell-sap but also from the cytoplasm and the nucleus, in the 

 latter cases by a vacuolation of the living matter. In the case of the 

 cytoplasm there is no evident morphological modification, but with the 

 nucleus there results not only a diminution of volume but also profound 

 modifications in texture. The one or more directions- in which the 

 water-attracting force acts is indicated by a uni- to multi-polar orientation 

 in the nucleoplasm ; the poles are the points at which the water finds 

 easiest outward passage, they are always more watery and therefore less 

 chromatic than the rest of the nucleus. The position of the poles is 

 always in relation to the proximity of a large cytoplasmic vacuole. 

 Plasmolysis effects the same cytoplasmic and nuclear modifications as- 

 freezing. 



Molisch's theory of death by freezing finds a direct cytological con- 

 firmation in the results of these experiments : death by freezing is really 

 death by desiccation. 



Starch-Grains in the Root-Cap of the Onion.f — Gr. Husek gives 

 an account of the occurrence, production, and reactions of starch in the 

 root-cap of Allium Cepa. He discusses the influence of temperature 

 and light on its formation and also describes the regeneration of the root- 

 cap after cutting off and the development of the leucoplasts. 



Acocantherin : an African Arrow-Poison.J — E. S. Faust has iso- 

 lated a new poisonous alkaloid, acocantherin, from the " Shushi " arrow- 

 poison which is prepared from Acocanthera abyssinica. It has the 

 formula C 32 H 50 O 12 and is precipitated in yellow flakes on addition of 

 ether to its alcoholic solution. It is a homologue of ouabain and 

 strophanthin and is possibly dimethyl-ouabain. Its physiological action 

 resembles that of the Digitalis alkaloids. 



Structure and Development. 



Vegetative. 



Foliar Origin of the Stem.§ — Leon Flot concludes that the general 

 plan of organisation at the stem-apex which is found in plants snowing 



* « Modifications produites par le gel dans la structure des cellules ve'ge'tales.' 

 Paris, 1902, 55 pp. (3 pis.). Extracted from Rev. Gen. Bot., xiv. (1902). 



t S.B. k. Bohm. Ges. Wissensch., xli. (1902) p. 10. 



X Arch. exp. Path. Pharm., xlviii. pp. 272-S1. See also Journ. Chera. Soc, 

 lxxxiv. (1903) i. p. 191. § Comptes Rendus, xxxvi. (1903) pp. 774-6. 



