ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 455 



to the primary root, and the author concludes that the secondary roots 

 behave in a corresponding manner to the primary. As far as his experi- 

 ments go, he finds that rheotropism is neither gained nor lost in the 

 development of a plant from seedling to near maturity. 



Influence of X-Rays on the Plant Organism.* — H. Seckt has in- 

 vestigated the action of these rays on the streaming movement of proto- 

 plasm, and on leaf-movements of Mimosa and Oxalis. For the former 

 purpose he used objects such as staminal hairs of Tradescantia, in 

 which, under normal conditions, there is a well-marked circulation. He 

 finds that exposure to the rays distinctly favours the movement, a result 

 previously attained by Lopriore. Movement which had been slow, or 

 even non-existent, before exposure became rapid after ^ to f of an hour's 

 exposure to the rays. The radiation also exerted a favourable influence 

 on the duration of the movement, which often persisted with un- 

 diminished activity for 2 to 3 hours. When the tube of the apparatus 

 was placed too close to the object a greater or less tendency to plasnio- 

 lysis appeared. This, the author suggests, may be due to the harmful 

 action of other electric waves, a supposition which was strengthened by 

 the behaviour of Spirogyra, which shows great susceptibility to electric 

 currents, and in which plasmolysis rapidly appeared (in 5 to 10 minutes) 

 when the tube was placed 10 to 20 cm. from the specimen). 



In experiments with Mimosa and Oxalis corniculata the distance of 

 the tube from the object was not an essential factor ; generally the dis- 

 tance was from £ to h metre. The influence of the rays was generally 

 remarked after 20 to 30 minutes, when in the case of Mimosa the leat 

 had assumed the position as usual after stimulus. In 20 to 25 minutes 

 more the normal position was resumed. 



Chemical Changes. 



Reaction and Nature of Oxidising Ferments.f— J. H. Kastle and 

 O. M. Shedd suggest that phenolphthaliu, from the fact that it is readily 

 oxidised to phenolphthalein, a substance readily lending itself to colori- 

 metric measurements, might prove a valuable reagent in the study of 

 the oxidising ferments. They have investigated its action on the 

 oxidising ferment of the potato, and find that it operates in a manner 

 similar to tincture of guaiacum. They also show that extract of potato, 

 on standing at ordinary temperature, rapidly loses its power to oxidise 

 either phenolphthalin or guaiacum, owing to the instability of the 

 oxidase in aqueous solutions. They find that the oxidase is distributed 

 throughout the substance of the potato, occurring in small quantities 

 even in the skin. The oxidation of the phthalin proceeds much more 

 slowly than that of guaiacum, and it has one advantage over many of 

 the reagents hitherto proposed from the fact that the rate of oxidation 

 can be easily and accurately determined by colorimetric comparisons 

 with alkaline solutions of phenolphthalein of known strength; the 

 amount oxidised is found to be proportional to the time of its remaining 

 in contact with the oxidase. The colour ranges from light pink to 

 dark red. The authors find the same or a similar oxidase present in a 



* Ber. Deutsch. Bot. Ges., xx. (1902) pp. 87-93. 

 t Amer. Chem. Jouru., xxvi. (1901) pp. 526-39. 



