ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 603 



seed red. If these cell- walls are examined optically by a contrivance 

 described in the paper, it is seen that when the plane of oscillation of 

 the rays of light is placed parallel to the longer asis of the actual ellipse 

 of elasticity, the smallest amount of absorption takes place, tlae largest 

 if it is placed in the direction of the shorter axis. 



C2) Other Cell-Gontents (including- Secretions). 



Sphserocrystals.* — Dr. P. Baccarini has investigated the structure 

 and properties of the spheerocrystals formed by precipitation by alcohol, 

 especially in Bignonia venusta and other species of Bignoniace^e, Gam- 

 j)anula Cervicaria, Trachelium coeruleum, Specidaria Speculum, Daphne 

 Laureola, and Anagyris foetida. In Bignonia venusta he finds them in 

 all parts of the plant, floral as well as vegetative, especially during the 

 period of flowering. They are insoluble in alcohol, in water, whether 

 cold or hot, in ether, in chloroform, in benzol, and in glycerin. Glacial 

 acetic acid, picric, citric, oxalic, and tartaric acids have no effect on 

 them. Osmic acid of 1 per cent, turns them brown, but very slowly ; 

 chromic acid of 5 per cent, causes disintegration in some hours at the 

 ordinary temperature, more rapidly when hot. Concentrated sulphuric 

 acid destroys them instantly ; dilute hydrochloric acid has no effect 

 upon them even when boiling ; dilute nitric acid has a feeble, when 

 concentrated a very powerful action. A solution of potash of from 

 5 to 10 per cent, dissolves them rapidly. The sphserocrystals from the 

 other species examined agree with those of Bignonia in their general 

 properties, but their distribution in the plant is much more limited. 



Nectar of Rhododendron.! — Sig. F. Tassi records the results of 

 analyses made by Sig. C. Grimaldi of the nectar secreted by the floral 

 glands of Bhododendron arhoreum. He finds it to consist of 92*1 per 

 cent, volatile, and 7 • 9 per cent, dry substance. The chief ingredient of 

 the latter appears to be an invert-sugar, with a divergence of 1*5° to 

 the left. This is mixed with a nitrogenous substance, and with traces of 

 calcium and potassium sulphates and chlorides. Inoculated into a frog, 

 the secretion had strong toxic properties. 



Tannin in the Crassulacese.:]: — According to Herr E. Wagner, tannin 

 is especially abundant in plants belonging to this natural order. It 

 occurs only in the parenchymatous tissue, and always dissolved in the 

 cell-sap ; but its distribution in the fundamental tissue varies greatly in 

 nearly related species. The structures which contain the largest 

 quantity are the secondary cortex, the bundle-sheath, and the epidermis 

 or one or two layers lying immediately beneath it ; it was not found in 

 the growing point, the first rudiments of the leaves, the cambium, or 

 the starch-sheath. The cells containing tannin do not usually differ 

 materially from those which surround them in size ; but there is a 

 strong contrast between them and those which contain starch, they often 

 have thicker walls than the other cells of the same tissue. In the 

 species of Crassulacege examined, it does not transfer itself from one 

 part of the plant to another, but remains in the cells where it is formed 

 until the death of the plant. 



* Malpighia, ii. (1888) pp. 1-18. 



■\ Tassi, F., ' Del liquido secrete dai fieri del Rhododendron arboreum,' 17 pp., 

 Siena, 1888. See Bot. Centralbl., xxxiv. (1888) p. 50. 



X Wagner, S., 'Ueb. d. Vorkommen u. d. Vertheilung dos Gerbstoffes bei d. 

 Crassulaceen,' 4'1 pp., Gottiagen, 1887. See Naturlbrsclier, xxi. (1888) p. 70. 



