Meyen’s Report for 1839 on Physiological Botany. 425 
Ficus pyriformis, consists of a single stratum of cells. We 
see by this that the type of formation remains the same in all 
the species of a genus, and that the modifications exhibited 
by different species in their structure are only to be explained 
by the more or less advanced degree of development ; the 
same is seen in the hairs and glands on the leaves of the va- 
rious species of Ficus; in some they remain during the whole 
life of the plants; in others, on the contrary, they fall off 
earlier or later. : 
At the same time I brought forward a series of exam- 
ples, to show that in different plants and in different parts, 
cellular formations entirely different may be developed. The 
cell formation, on occasion of the development of the spores 
out of the original spore (motherspore), will be specially men- 
tioned hereafter, as also the formation of the large cells by 
the appearance of transverse partitions in the embryo-sac of 
Viscum album; but besides these I mentioned the following 
cases :—During the formation of both cells of the cuticular 
glands, a longitudinal partition passes through the middle of 
the mucous nucleus, which is seen in the middle of the pri- 
mitive cell of the future gland, and after the production of 
both cells a nucleus is formed in the middle of each of them. 
During the formation of the glands on the young leaves of 
Ficus elastica, 1 observed the radial arrangement of the cells 
lying near the primitive cell of the glands (mothercell) ; more- 
over, the further changes up to the perfect development of 
the gland with its stoma, the cavity belonging to it, &c. &c., 
were observed and delineated. In the club-formed and 
glandular hairs with which the~young leaves of Ficus are 
covered, I observed that the formation of cells, by means of 
partitions, was preceded by separation or dissolution of the 
growing masses in the interior; but in some cases I saw that 
a partition passed through such a mass, and that sometimes 
cells were formed in the interior of the hair without the pre- 
sence of such masses. In the tubes of Mucor mucedo I saw 
spiral formations as in the Spirogyre, but in the case of Mu- 
cor they are colourless and extremely tender, and moreover 
not always present. Sometimes a portion of these spiral de- 
posits separates from the sides and forms a bladder, which, at 
first, lies loose in the cavity of the tube, but afterwards at- 
taches itself to the side, and partly causes its absorption, so 
that at last the new cell appears as a perfectly independent 
one connecting the neighbouring ends of the tubes. 
Moreover, observations were made on the development of 
the Ceramium diaphanum, which are perhaps not altogether 
devoid of interest, but of which an extract cannot well be 
