424 Meyen's Report for 1839 on Physiological Botany. 



XLIX. — Report of the Results of Researches in Physiological 

 Botany made in the year 1839. By F. J. Me yen, M.D., 

 Professor of Botany in the University of Berlin*. 



[Continued from p. 336.] 



I have given a special description of the development of 

 structure in the leaves of Ficus elasticaf, and drew attention to 

 some phcenomena visible in this and in similar plants. I 

 showed the development of the cuticular glands and their 

 stomata, and found that the whole respiratory system, viz. the 

 intercellular passages, with the more or less regular air-cells 

 and respiratory cavities in the substance of the leaf, are first 

 developed when the stomata make their appearance, and that 

 as these are more fully developed the glandular hairs (which 

 at an early stage are seen on the whole surface of the leaves 

 of Ficus elastica) die off. All these subjects are fully ex- 

 plained by a series of drawings. The large masses of crystals 

 which one finds in the large cells, chiefly under the epidermis 

 of the upper surface of the leaves of Ficus elastica, are formed 

 in a most peculiar manner on the surface of a club-shaped 

 mass of gum, which is developed in the epidermal end of those 

 large cells, and which grows downwards into the centre of the 

 cell. These bodies, which I call for the sake of distinction 

 "Gum-clubs" (gummikeulen), are of very different forms in 

 the different species of Ficus ; in some they are found only just 

 under the upper surface, in others on the lower surface, and 

 in some, indeed, they are found exclusively in that position. 

 The delineations give the most exact description of the form, 

 development, &c. of these formations. The species of the 

 genus Ficus have generally firm and shining leaves, and the 

 epidermis is then generally composed of several layers of cells ; 

 they are, however, all formed out of the outer layer which 

 covers the leaf at the time when the formation of the cuticular 

 glands and stomata commences ; in one species a simple di- 

 vision of these cells takes place, in others the division is re- 

 peated, but one soon sees that all these layers belong together 

 and form the true epidermis, on which account I should pro- 

 pose in such cases the name epidermal layer. It is thus ex- 

 plicable why the epidermal layer on the leaves of some spe- 

 cies of Ficus have only two layers of cells, and that the layer 

 on the lower surface, as, for instance, in Ficus bengalensis, 



* Translated from the German, under the direction of the Author, and 

 communicated by Henry Croft, Esq. 



f Meyen's Beitrage zur Bildungsgeschichte verschiedener Pflanzentheile. 

 — Miiller, Archiv fur Anatomie and Physiologie, &c, 1839, 255. mit 3 

 Quarttafeln. 



