ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 837 



in trees; and that the medullary rays are especially adapted for 

 driring up water to the highest branches. 



"Bleeding" of Parenchymatous Tissues.* — Dr. C. Kraus states 

 that " bleeding " takes place from all parenchymatous tissues as the 

 result of osmotic forces when the turgidity is sufficiently high, when 

 there is no mechanical resistance, and when the parenchyma is in the 

 right condition. The composition of the sap thus excreted varies, 

 and is often different from that of the cell-sap. While the cell-sap 

 is usually decidedly acid, the excreted fluid may be neutral or very 

 slightly acid or even strongly alkaline ; sometimes it is even more 

 acid than the cell-sap. The bleeding is not brought about by trans- 

 verse sections alone, but also by tangential and radial wounds. 

 Bleeding often takes place from the leaves of cut branches, but 

 usually only when the leaves are young ; also from the surface of 

 the epidermis of young roots ; and acid drops have been observed to 

 exude from the apex of root-hairs. The reaction of the parenchy- 

 matous sap appears to vary in the same plant. 



Physiological and Pathological Effect of Camphor on Plants.^ — 

 Dr. A. Burgerstein has determined, from a large series of experi- 

 ments, that when cut and withered shoots of various plants are placed 

 in cami>hor-water, they recover more rapidly, and again become turgid 

 sooner, than if placed in distilled water. At the same time camphor- 

 water increases the transjjiration from the shoot. If, however, the 

 absorption of camphor-water is continued for a longer period, from 

 two to five days, the plant is injured and at length killed. If made 

 to swell in camphor-water, seeds will absorb water more rapidly and 

 in greater quantity than if placed in distilled water. 



Chemical and Physiological Action of Light on Chlorophyll. J — 

 M. C. Timiriazeff, in order to avoid errors due to the unequal dis- 

 persion of a prism, adopted the method of decomposing portions of 

 the previously dispersed light. By means of the cylindrical lens and 

 prism of small angle used in experiments on complementary colours, 

 two images, complementary in colour, were thrown at the same timo 

 either on two test-tubes containing a 30 per cent, solution of carbonic 

 anhydride in which was placed a small branch of Elodea, or on a 

 plate coated with collodion containing a small quantity of chlorophyll. 

 When the spectrum was divided into two equal parts with respect to 

 the normal spectrum, the two images were of course respectively 

 yellow and blue. The maximum chemical and physiological effect 

 was exerted by the yellow, whilst the effect of the blue rays was 

 scarcely ai)preciable. The blue-violet portion of the spectrum being 

 cut oflF by a screen, the less refrangible portion was divided into two 

 equal parts, red and greenish yellow. The maximum chemical and 



• Bot. Cenlrulbl., xxi, (1885) pp. 212-7, 245-9, 274-8, and 373; also 

 Wolluy'H FortHchr. a. d. Gob. d. Agriculturphys,, vii. (1884) pp. 136-71. See 

 thin Journal, i v. (1881) pj). 5'Jl, 777. 



t V.rh. K. K. Zw)l.-lJ(,t. GcHoll. Wicn, xxxiv. (1885) pp. 513-U2. 



J Coinptcri l{(;ii(liiH, c. (1885) pp. 851-4. 

 Her. 2 —Vol,. V. 3 I 



