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. Meyen, 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 elasticat, and drew attention to 
some phznomena 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. 
+ Meyen’s Beitrage zur Bildungsgeschichte verschiedener Pflanzentheile. 
—Miiller, Archiv fiir Anatomie und Physiologie, &c., 1839, 255. mit 3 
Quarttafeln. 
