290 PHYSIOLOGY [Bot. Absts., Vol. V, 



is evident in the resulting increase of the division rate. Contrasting results were obtained 

 with pituitary solution added to the basis fluid. Suprarenal extract caused an increase in 

 the rate of division. — C. R. Hursh. 



2222. Linossier, G. Sur le developpment de l'Oidium lactis en milieux artificiels. In- 

 fluence de la quantite de semence sur le poids de la recolte. [The development of Oidium lactis 

 in artificial media. Influence of the quantity of inoculum on the weight of the fungous product 

 resulting.] Compt, Rend. Soc. Biol. 82 : 240-242. 1919. 



2223. M acDougal, D. T. Hydration and growth. Carnegie Inst. Wash. Publ. 297. 17 x 

 25 cm. V+176p., 52 fig. 1920. — The author prepared biocolloids by mixing proteins, usually 

 of plant origin, such as bean or oat protein, with agar, gum arabic, prosopis gum, tragacanth, 

 or opuntia mucilage. The colloidal suspension of these mixtures in water was partially dried 

 in thin plates and the hydration (that is, the amount of water taken up when sections of these 

 plates were immersed in solutions) was measured by means of an auxograph developed espe- 

 cially for this purpose. Solutions of acids, alkalis, and salts were employed and a rather close 

 parallelism was shown between the swelling of these biocolloids and cell masses, such as sec- 

 tions of joints of opuntia, cotyledons of beans, and leaves of various plants. In this connec- 

 tion the point is brought out that vegetative cell masses, such as are responsible for growth, 

 are composed of colloids predominantly of a carbohydrate character, frequently of pentosan 

 nature. These pentosans do not dissociate and their swelling capacity is less in electrolytes 

 than in pure water. The hydration of carbohydrates is retarded by hydrogen ions. — Bio- 

 colloids behave in much the same way as do cell massses, in nutrient solutions and in bog and 

 swamp waters. Under fluctuating or alternating hydration effects, the basis of xerophily 

 and succulence, the writer details experiments in which biocolloids were subjected to alter- 

 nate treatments of acids and alkalis in solution. As a result of this treatment, an alternate 

 sxvelling and shrinking of the biocolloid was brought about. He considers these phenomena 

 as related to the structural variation of leaves of Castilleia latifolia; these leaves being thin 

 and highly acid when growing under mesophytic conditions while succulent and less acid 

 leaves in arid locations. Temperature effects and water deficit, or unsatisfied hydration 

 capacity, both in biocolloids and cell masses, are discussed. — Growth of tissues consists of two 

 fundamental features, hydration of the colloidal material of the plasma and the arrangement 

 of additional colloidal material in colloidal structures with entailed additional capacity for 

 absorbing water. The character of the hydration depends upon the character of the cell 

 colloids, proteinaceous colloids showing increases of hydration capacity with acidity, while 

 when the colloidal material is more largely carbohydrate — such as pentosans — the reverse 

 is apparently the case. Nutrient salts always modify hydration capacity. The author is di- 

 recting his studies toward an analysis of the phenomena of plant growth based on the physico- 

 chemical properties of colloid gels, especially with reference to imbibition and swelling. — Lon 

 A. Hawkins. 



2224. Seifriz, William. The length of the life cycle of a climbing bamboo. A striking 

 case of sexual periodicity in Chusquea abietifolia Griseb. Amer. Jour. Bot. 7: 83-94. 5 fig. 

 1920. — The author notes the fact that several species of bamboo display sexual periodicity, 

 flowering at intervals of a definite number of years. Chusquea abietifolia, of the Blue Moun- 

 tains of Jamaica, went through such a flowering period in 1918, during which practically 

 all individuals blossomed, produced seed and died. The next year the species was represented 

 only by seedlings, except for one small area discovered by the author in an unusually arid 

 situation where the plants were still thriving and flowerless. The only previous flowering 

 period recorded for this species was in 1885, thus establishing a cycle of 33 years, very similar 

 to that of the Indian Bambusa arundinacea, which is 32 years. — The author discusses possible 

 factors which may cause such a periodicity and shows that seasonal differences, particularly 

 in moisture, are probably insufficientto explain them, and suggests that the problem may be 

 of the same nature as that of puberty and senility in organisms. No sufficient explanation is 

 as yet forthcoming for the remarkable fact that fully 98 per cent of the individuals of the 

 species come into flower simultaneously over a great stretch of country. — E. W. Sinnott. 



