ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 623 



tbey are being formed, the cells concerned of the soft bast are divided 

 by periclinal and anticlinal longitudinal walls, so that they are broken 

 up into several elongated j)rismatic cells, with a nearly square base. 

 But these cells become gradually more and more rounded off, their 

 cell-walls becoming thickened at the ends, like collencbymatous cells. 

 Delicate central lamellte are then more or less clearly seen, which, 

 however, finally entirely disappear, probably by deliquescence, so that 

 the needle-shaped cells lie loose side by side, retaining, however, 

 somewhat of their original arrangement. These structures have at 

 present been observed not only in the Acanthacete, but in many plants 

 belonging to that order. They are especially numerous in the root 

 and leaf-stalks of a species of Buellia and in Sancliezia picta ; in 

 Justicia picta only in the stem ; in Fittonia giganiea and ApJielandra 

 aurantiaca only in the root ; in Hexacentris mysorensis only in the 

 leaf-stalk. They were not detected in species of Erantliemum or in 

 Aphelandra cristata. 



Structure of Stomata and Glands.* — In a very elaborate paper 

 on these organs, M. Licopoli gives a very full description of the 

 complicated glands found, for example, on EJiipsalis, where the special 

 cells are bordered on the inside, and are surmounted by cells which 

 partially close the opening, and which he calls " labriform excres- 

 cences." The special cells he states to be invariably limited to two 

 in number ; where more have been described, it is because writers 

 have mistaken for them epidermal cells which take part in the 

 constitution of the stoma. Not only are the special cells liable to 

 become more or less completely cuticularized — sometimes to such an 

 extent as to resist the action of acids — but the cuticle, which descends 

 from the upper surface across the pore, expands in the stomatic 

 chamber below the special cells, forming a vesicular organ of such a 

 character that the exchange of fluids between the interior of the plant 

 and the atmosphere which takes place by the stoma must be effected 

 across a dialyzing apparatus. 



Calciferous glands are classified by M. Licopoli into two categories; 

 one connected with the fibrovascular bundles, as those of Polypodium 

 vulgare, Crassula lactea, and the section Aizoon of Saxifraga ; the 

 other with the parenchyma, as those of the Plumbagine^e. 



Pilosism in Plants.j — Botanists, M. Ed. Heckel says, have im- 

 properly designated by the single name oi pilosism all the physiological 

 or teratological manifestations of exaggerated development of the 

 pilose system. It is easy to see, however, that these phenomena present 

 a graduated series from the simple physiological fact to the most 

 complex teratological state, which the author calls deforming pilosism, 

 because it ends in completely disfiguring the species. Although 

 hitherto all teratologists have considered pilosism to be unimportant, 

 the author thinks it is evident that it represents a higher signification 



* Atti E. Accad. Sci. fis. et mat. (Naples), iii. (1879) 72 pp. (7 pis.). See Bull. 

 Soc. Bot. France, xxvii. (1880) p. 151 (Eev. Bibl.). 

 t Comptes Eendus, xci. (1880) pp. 349-51. 



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