770 SUMirARY OF CURRENT RESEARCnES RELATING TO 



ycllow-grccn rays D-E, under the influence of which rays also the greatest 

 amount of oxygen is evolved. Examination of the plant for Kulpluir as 

 representing the albuminoids, which must have derived their sulphur 

 from the ferrous sulphate, showed that the maximum of albuminoids was 

 attained under the influence of the rays D-E. 



Absorption of Nitrogen by Plants.* — ITerren Ilelricgel and Will- 

 furth have made some experiments in boxes in which were sown oats, 

 peas, buckwheat, &c. It was found that those of the order Papilionaceio 

 were able to grow and flourish long after all the nitrogen present in the 

 soil had been absorbed by them, whereas oats, &c., only grew as long as 

 tliere was any of the nitrogen left that had been originally contained in 

 the seed, &c 



(3) Irritability. 



Method of Studying Geotropism.t — Miss A. Bateson and Mr. F. 

 Darwin describe a method for studying geotropic curvatures. If a 

 flower-stalk remains for an hour or two pinned down to a board in a 

 horizontal position, so that no curvature can take place, a well-known 

 result is seen on its being released. The freed ends spring up with a 

 sudden geotropic curvature. The method employed by the authors is 

 based upon this fact. Geotropic stems were immovably fixed at various 

 angles, and the amounts of curvature occurring on release were taken 

 as representing the geotrojiic stimulus corresponding to each position. 

 Whatever may be the faults of the method, it has one merit, that the 

 organ is exposed to a constant instead of to a varying stimulus, as must 

 be the case if the stem is free to curve during the period of stimulation. 

 The authors then give the results of a series of experiments made with 

 the young flower-stalks of plantain (Plantago lanceolata). 



Chemotactic Movements of Bacteria, Flagellata, and VolvocineaB. 

 — Dr. W. Pfeffer in a previous work has shown that the spcrmatozooids 

 of ferns and Sclaginella are attracted by malic acid, and that this serves 

 to conduct them into the archegonial canal. In the present paper | he 

 proves that motile bacteria, colourless Flagellata, and some chlorophyll- 

 containing Volvocincfe are in a similar manner enticed or dispersed by 

 certain substances, a phenomenon which he designates by the term "chemo- 

 taxis." The method of investigation is very simple. A capillary tube 

 closed at one end, from 0*03 to 0*08 mm. wide, and 4 to 7 mm. long, is 

 furnished with a definite solution, and its open end pushed into the drop 

 of fluid containing the organisms in a state of equal distribution. To 

 obtain a striking congregation of bacteria for instance, it sufijces to 

 introduce a capillary tube charged with a 2 to 4 per cent, meat sc tion 

 in a drop containing B. tcrmo. In a few seconds there is air iy a 

 marked confluence of the bacteria, and in from 1 to 2 minute _ the 

 anterior part of the tube is thickly filled with them. 



The author worked out completely the c\\cmoi&xi& oi Bacterium termo. 

 Spirillum undula, and Bodo saltans ; Bacillus suhtilis, Spirillum rubrum, 



* Bied. Centr., 1888, pp. 228-30. See Journ. Chem. Soc. Lond., Abstracts, 1888, 

 p. 742. 



t Ann. of Bot., ii. (1888) 6.^^-8. 



t Untersuch. Bot. Inst. Tubingen, ii. (1888) p. 582. Cf. this Journal, 1884, p. 412. 



