46 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the surface; and the formation of cork. It is probable that direct 
division of the nucleus always takes place in the phellogen resulting 
from a wound. The spread of the irritation caused by a wound is 
slow; dead elements, as vessels and fibres, do not conduct it. The 
author believes that a chemical process always underlies the propagation 
of the irritation. In Nuphar and other water plants, cavities near to 
the wound are filled up by freshly formed cells. The formation of 
cork is promoted by the drying up of the surface of the wound. 
Mucilaginous Epiderm of Leaves.* — Herr 0. Kruch has investigated 
the frequent occurrence of mucilage in the epiderm of Dicotyledons. 
This takes the form of a mucilaginous layer on the inner or on both the 
inner and outer walls of the epidermal cells. The author has paid 
special attention to the examples occurring in the order Rosaceae, where 
the phenomenon is frequent in nearly all the families. 
The formation of mucilage appears to have a distinct connection 
with assimilation, since it occurs only in cells which are in direct con- 
tact with assimilating cells. It never takes place on the lateral walls 
of epidermal cells ; and when the epiderm consists of several layers, it 
is confined to the inner walls of the lowermost layer. The property 
is never common to the whole of the epidermal cells, but belongs only 
to certain cells with very variable distribution. In the Rosacese the 
mucilage always takes the form of a secondary thickening of the wall, 
separated from the protoplasm by a layer of cellulose. 
The author regards the mucilage layer as a reservoir of water pro- 
tecting the surface against excessive transpiration. 
Development of the Leaf and Origin of the Foliar Vascular 
Bundle.! — Herr V. Deiniga has studied this subject, which he sub- 
divides under the following heads : — (1) The development and the 
course of the bundles in typical monocotyledonous plants; (2) Dicoty- 
ledonous plants with monocotyledonous venation ; (3) Monocotyledonous 
plants with abnormal venation ; (4) Dicotyledonous plants with typical 
reticulate venation ; (5) The development of palm leaves. Under (2) the 
plants chiefly studied were Eryngium and Bupleurum falcatum ; under (3) 
Itichardia sethiopica , Xantliosoma , Caladium, and Dioscorea. brasiliensis. 
As a general result, the author states that the development of the 
vascular bundle depends on the form of the leaf. The bundle which 
is first formed runs straight to the apex; the others curving according 
to the degree of development of the two halves of the lamina. In all 
the plants examined, however complicated the branching and anastomos- 
ing of the veins in the mature leaf, the venation can always be traced 
back to the simplest type where all the bundles are independent and 
unbranched. 
Stem of the Beet4 — According to M. G. Fron, the increase in 
thickness of the stem of the beet is not effected, as in the root, by the 
formation of successive generating layers, but by the gradual shifting 
outwardly of a single layer. This layer, at first of normal origin, 
becomes later partly normal and partly pericyclic, and finally completely 
* Anuuar. r. 1st. Bot. Bomu, vi. pp. 191-274 (2 pis ). See Bot. Centralbl., Ixxvi. 
(1898) p. 16. f Flora, lxxxv. (1898) pp. 439-98 (1 pi., 22 figs.). 
X Comptes Bendus, cxxvii. (1898) pp. 397-400 (3 figs.). 
