ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 815 



is excreted, and it is entirely wanting in lysigenous glands ; the 

 latter are usually surrounded by partially absorbed cells which are 

 not sharply distinguishable from the surrounding tissue. 



In glands which originate from the epidermis (Amorpha, Myrtus, 

 and Eugenia), it is not uncommon that instead of growing into the 

 parenchyma, they become glandular, warty, or conical trichomes ; 

 which appears to indicate that internal epidermal glands originate 

 as trichomic glands ; the latter being phylogenetically the older. 



The schizogenous glands of Hymenea and Tracliylobium contain 

 copal ; the hard copal of Tracliylobium having undoubtedly a similar 

 origin. In Ardisia crenulata are peculiar schizogenous secretory 

 organs, formed locally out of the medulla of the veins of the margin 

 of the leaf, and which contain an albuminoid substance ; of these a 

 careful examination was made. The same species also possesses 

 secretory organs, which from their origin and structure must be 

 regarded as a coalescence of secretory tubes. 



The mucilage-tubes of Abies possess albuminoid crystalloids in 

 the interior of the mass of mucilage formed in the protoplasm. A 

 description is given also of the origin, structure of the wall, and 

 nature of the contents of the secretory tubes of Evodia glauca, 

 Rhamnus, JEonium tortuosum, Mesembryantheimm, Physostegia vir- 

 giniana, Calycanthus, Gozsalp'mia echinata, &c. Oil and mucilage-tubes 

 also occur in the wood of some Laurinese. 



Sphero-crystals * — G. Kraus records the discovery of sphero- 

 crystals in Ptelea trifoliata, Gonium maculatum, and JEthusa, 

 apparently identical in composition with those previously detected in 

 Cocculus laurifolius. In Ptelea they occur in the leaf only ; in Gonium 

 also in the stem, flower-stalks, fruits, &c. ; but in all cases in the 

 epidermis only. They usually have the form of hemispheres attached 

 to the wall ; and are radiate or even spined. As in Cocculus, they are 

 not found in every epidermal cell, but in groups in adjoining cells, and 

 attached to the adjacent transverse walls. They are insoluble in cold or 

 boiling water, and in dilute mineral or organic acids ; soluble in 

 concentrated sulphuric acid with a golden yellow colour, and in 

 potash-ley or hot nitric acid. The reactions indicate a probability 

 that they are composed of hesperidin. Their insolubility in alcohol 

 shows that they cannot consist of any compound of conia. 



Respiration of Detached Shoots.f — It is an established fact that 

 a sprig of a plant, if placed for some hours in an atmosphere of car- 

 bonic acid and then removed and placed in the dark, exhales a more 

 than normal amount of carbonic acid. This has been stated to be 

 due simply to the giving up of carbonic acid which has been taken in 

 in excess, but not assimilated. J. Borodin combats this conclusion 

 with the following arguments: — 



The activity of respiration of a detached twig is not constant, even 

 when the conditions are constant ; it becomes less in the dark. This 



* Ber. Naturf. Ges. Halle, 1881, pp. 41-3. 



t Mem. Acad. Imp. Sci. St. Petersbourg, xxviii. (1881) No. 1. Cf. Natur- 

 forscher, xiv. (1881) p. 463. 



3 i 2 



