1916] AGEICULTUEAL BOTAKY. 225 



Some factors determining the presence of fat as a food reserve in woody- 

 plants, E. W. SiNNOTT {Abs. in Science, n. ser., 43 (1916), No. 1105, p. 328). — 

 Reserve fat is said to occur most abundantly in those woods in which the rays 

 and parenchyma cells are comparatively thin-walled and well provided with 

 pits, and to be particularly well developed in the cells immediately adjacent to 

 the vessels. The fat is said to be practically absent in species with thick- 

 walled, slightly pitted parenchymatous tissue. 



These facts are claimed to suggest that the occurrence of fat in wood and 

 Its distribution may depend on the easy diffusion of some fat-forming ferment. 

 Experiments show the presence of a fat-splitting ferment in the leaves and bark, 

 which varies greatly in amount according to species and season but which is in 

 general most abundant in the spring in those species in which reserve fat is 

 most abundant in winter. It is suggested that this fat-splitting ferment may 

 be reversible in its action, and during late summer and fall it may be diffused 

 downward through the wood and bast, converting into fat the food reserve to 

 which it has access. 



On the properties of a chromogen generally present in plants, J. Wolff and 

 Nadia Rouchelmann {Com.pt. Rend. Acad. Sci. IParis], 161 (1915), No. IS, pp. 

 399-401). — The authors, having extended their study as previously reported 

 (E. S. R., 34, p. 32) to a number of plant families, state that the chromogens 

 exhibit, besides their great .sensitiveness to the action of laccase and hydriodic 

 acid, a large number of characters in common, some of which are here enumer- 

 ated, indicating that they should probably be regarded as one and the same. 

 The brown coloring matters that form in various plants or organs may be re- 

 garded as products of oxidation, as observable in case of the brown pigment of 

 cut or injured potatoes, horse chestnut, dead leaves, and macerated green plants 

 when subjected to the action of a laccase. 



Lipolytic action in germinating teliospores of Gymnosporangium juniperi- 

 virginianae, G. H. Coons (Abs. in Science, n. ser., 43 (1916), No. 1105, p. 327).^ 

 A study was made of the teliospores from mature telial horns of G. juniperi- 

 virginiance, which seemed to indicate that in the germinating spores lipase is 

 present. This places the rust fungi in the list of organisms now known to 

 possess lipase. Attention is called to the occurrence of oil in rust spores, and 

 the conversion of the globules of oil into soluble products, brought about by the 

 lipase, is considered a factor in the rapid germination process. 



Acidity and gas interchange in cacti, H. M. Richakds (Carnegie In.^t. Wash- 

 ington Pub. 209 (1915), pp. 107, figs. 6).— The author gives an account of the 

 methods and results of his work as carried out with cacti at the Desert Botani- 

 cal Laboratory at Tucson, Ariz., along three main lines, namely, the determina- 

 tion of the acidity of the tissue as regards the expressed juice and the total 

 amount of acid present, the determinations of carbon dioxid evolution to fix 

 the diurnal periodicity in relation to normal temperature changes and to 

 ascertain the effects of various agencies upon the rate, and the study of the 

 gas interchange in darkness between plants and the atmosphere. The results 

 are given in considerable detail and discussed in their bearings. 



It is stated that with rising acidity in the tissues, the total acid increases 

 more rapidly than does the concentration of the juice. Light, the most im- 

 portant factor in the diurnal decrease of acidity, is less effective at the lower 

 temperatures. Rising temperature, especially above 30° C, decreases acidity 

 when this is initially high, but does not wholly inhibit its production. Acidity 

 tends to decline with excess of oxygen and to increase with deprivation thereof. 

 While excess of oxygen raises the carbon dioxid-oxygen ratio, this ratio re- 

 mains stationary or decreases in its absence. Wounding causes an increase 



