ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 613 
to Dicotyledons, and asserts that in their cambium also there is no 
one cell which is distinguished from the rest by its greater or less 
capacity for division. There is a layer of meristematic cells correspond- 
ing to the meristem in the apex of a stem. The same law governs the 
growth of the meristem of the medullary rays. The author points out, 
moreover, that these observations are prejudicial to Krabbe’s theory of 
“ gliding growth.” 
Increase in Thickness of Palm-stems.* * * § — Herr G. Kraus states that 
in Oreodoxa regia (in Java) there is, in the course of a few months, a 
quite appreciable increase of thickness in the whole of the stem. The 
zone of the trunk in which the greatest increase takes place appears to 
differ in different palms. He further asserts that this increase is not 
derived from a cambium layer, but to by far the greatest extent from 
a secondary increase of the original fundamental tissue and of the 
sclerenchyme of the vascular bundles. It is, in fact, comparable to the 
mode of growth of a leaf or of a fruit, rather than to that of the stem of 
Dicotyledons. It especially resembles the former in its more limited 
character. 
Gum-canals of Carludovica.| — M. H. Micheels has studied the for- 
mation of the gum-canals in Carludovica plicata , belonging to the 
Cyclanthaceae. They are of schizolysigenous origin. The root is 
entirely destitute of these canals. In the young leaf they occur only 
in the low r er region of the lamina; in the adult leaf they are found in 
the sheath, the petiole, and the lamina. They are present also in the 
spathe and in the floral organs. 
Water Storage in Senecio praecox.f — Dr. J. W. Harshberger de- 
scribes the peculiar structure of the stem and root of this plant growing 
on a lava-formation in Mexico. The stem possesses a very watery firm 
pith, a small cylinder of wood, and a wide cortex with chlorophyll and 
receptacles from which exudes a resinous or balsamic substance. The 
pith serves as a storage for water. 
Fall of the Leaf and Cicatrisation of the Wound.§— According to 
M. A. Tison, the separating layer formed at the base of a leaf ready 
to fall does not always result from a secondary meristem ; it is often 
composed of two or three layers of primary tissue. The detachment 
is frequently the result of a doubling of the wall between two layers of 
the separating tissue. A certain thickness of this wall, comprising the 
primary cell-wall and the adjacent secondary layers, becomes trans- 
formed into pecto-cellulose-mucilage, which swells and gelatinises. 
After this dissolution the cells are isolated from one another, their pro- 
toplasm being enveloped only by a thin internal membrane, the remains 
of the primitive wall. The cells of these two layers elongate towards 
one another, and, by their mutual pressure, rupture the vascular system, 
and detach the leaf. Cicatrisation may take place either by a sclero- 
suberous modification in the walls of one of the cell-layers of the 
cushion ; or by the formation of a peridermal layer histologically re- 
* S.B. phys.-med. Gesell. Wurzburg, 1899, pp. 62-8. 
t Bull. Soc. R. Bot. Belgique, xxxvii. (1898) C.R., pp. 95-100 (1 pi.). 
X Contrib. Bot. Lab. Univ. Pennsylvania, ii. (1898) pp. 31-40 (2 pis. and 1 fig.). 
§ Comptes Rendus, cxxviii. (1899) pp. 1530-2; cxxix. (1899) pp. 125-7. 
