AGRICULTUKAL BOTANY. 731 



observable there. The movement of sap of low acidity from center to periphery- 

 has little effect upon the variations of acidity of these tracts, as compared with 

 the conjoint effects of light and temperature in this respect, as seen in the 

 outer portions. 



Why certain plants are acrid, W. R. Lazenby (Sci. Mo., 1 (1915), No. 3, pp. 

 272-277). — The author reports an examination of a number of species of plants 

 noted for acridity, stating that the taste varies greatly among the plants tested. 

 The acrid principle is not always volatile and was not found to be soluble in 

 ether. Tests show that the acridity of several members of the Arum family 

 is connected with the abundant presence of needle-shaped calcium oxalate 

 crystals. 



The absence of the acrid effect in case of some plants, the cells of which are 

 crowded with raphides, is ascribed to the fact that in such cases the crystals 

 are covered or embedded in an insoluble mucilage, which prevents their coming, 

 into contact with the tongue. 



The study of plant enzyms, particularly with relation to oxidation, A. D. 

 Hall, E. F. Aujistrong, et al. (Abs. in Rpt. Brit. Assoc. Adv. ScL, 84 (1914), pp. 

 108, 109). — This is a summary of the third report of the committee on this sub- 

 ject (E. S. R., 32, p. 523). 



It is stated that in the flowers of certain white-flowered races of Primula 

 sinensis which breed true to whiteness the peroxidase has a definite zonal dis- 

 tribution, and that such races, on crossing with colored forms, yield in the 

 F2 generation a certain number of plants the flowers of which show a similar 

 zonal character. This pattern is referred to a lack of uniformity in distribu- 

 tion of the peroxidase constituent of the color-forming mechanism, not of the 

 chromogen. 



Partial success has been achieved in the discovery of agents indicative of 

 the presence of reductases. 



The conception that in life interaction takes place between substances In 

 pairs, the one being oxidized and the other reduced, is considered to simplify, 

 materially the study of the oxidative changes in plants. 



The formation of red pigments from yellow flowers by reduction and sub- 

 sequent oxidation has been further studied, the experiments having been 

 extended to quercetin, which has been reduced under a variety of conditions. 

 As a rule colorless compounds are formed which become red on exposure to 

 air or the addition of hydrogen peroxid. 



A study has been made of the rates at which various carbohydrate solutions 

 decolorize methylene blue in alkaline solution. 



A study of the behavior of lipase in relation with water shows that the 

 presence of even a small proportion of the latter greatly favors the action of 

 the former in the reverse direction. 



Studies in permeability. — I, The exosmosis of electrolytes as a criterion of 

 antagonistic ion action, W. Stiles and I. Jorgensen (Ann Bot. [London], 29 

 (1915), No. 115, pp. 349-367, figs, i^).— The authors have investigated by the 

 methods of physical chemistry the exosmosis of electrolytes from plant tissue, 

 using disks of potato tuber and also living bean plants, as related to the com- 

 position of different external solutions. 



From the results as given, they conclude that within certain limits the rate 

 of exosmosis is a measure of toxicity. A decrease in this rate on addition of 

 certain ions to solutions containing poisonous ions might be due, it is thought, 

 to the so-called antagonism. It is claimed to have been shown that in some in- 

 stances the phenomena are more complex than is generally assumed. The 

 authors emphasize the necessity of examining and analyzing each case sep- 

 arately. 



