246 MR. F. E. WEISS ON THE CAOUTCHOUC-CONTAINING 
et appartenantes au système laticifére primitif. On ne constate jamais l'apparition de 
nouvelles initiales aprés les premiers stades du développement embryonnaire.” 
In Eucommia, however, the caoutchouc-containing cells, whether they exist іп the 
embryo or not, are continuously formed anew in all new secondary growths. In the 
very young buds and in the youngest parts of older shoots, t. е. therefore in all meri- 
stematic regions, no trace of these cells will be found. They first make their appearance 
in the cortex of a rapidly growing internode. Тһе cortical tissue growing very rapidly 
here, we find a large number of transverse divisions to each initial cortical cell, the 
lateral walls of which have already attained some considerable thickness, and the tissue 
presents the appearance of a number of cells divided up by thin transverse walls (see 
figs. 1, 5, 8). 
This appearance of young tissues is figured by Sachs in his text-book in the case of 
the hypocotyledonary portion of the stem of the Sunflower (fig. 56), and in fig. 94 of his 
Lectures for the rapid tangential growth of the cortical cells. 
In the cortical cells at this stage longitudinal divisions take place in cells which are 
noticeable by their very granular protoplasm, which completely fills the cells, whereas 
the surrounding cortical cells have large vacuoles at this stage (fig. 1). Тһе cortical 
cells also contain several plastids, which are absent in the cells referred to. These 
initial cells occur most frequently about midway between the epidermis and the fibro- 
vascular bundles, in a region where the cortical cells are loosely packed and intercellular 
spaces abound, and are of considerable size; they may, however, occur only three cells 
beneath the epidermis, where the intercellular spaces are much smaller. 
The longitudinal division of these cortical cells may take place either by radial or 
tangential walls. In radial longitudinal section, such as those from which figs. 1 & 4 
are drawn, the two daughter cells have arisen by tangential division of the mother cell. 
Fig. 6 is a drawing of a transverse section of an internode at a somewhat later stage 
of development, but it shows two young stages of division before any further elongation 
has taken place, or, at any rate, that part of the cell which has not elongated, and 
therefore they have the same appearance as а young stage. They are characterized by 
the larger diameter of the cells, by the presence of nuclei, and by the straight dividing 
wall. In the case in whieh this wall is anticlinal, I could not but compare the appear- 
ance of the daughter cells at this age with Chauveaud's figures of transverse sections of 
some embryos of Euphorbia. The figures in question are those of Euphorbia exigua 
(pl. i. fig. 2), of Euphorbia Peplus (pl. ii. figs. 6 & 7), and of Broussonetia papyrifera 
(pl. vii. fig. 8). In all these cases the initial cells, which develop into the latex cells, 
occur in groups of two, and suggest an origin (by longitudinal division of a mother cell) 
similar to that of the caoutchouc-containing cells of Eucommia. 
А number of other species of Euphorbia (E. falcata, E. helioscopia, E. Lathyris) ате 
figured by Chauveaud with a ring of latex-cell initials, and these too may have been 
derived in pairs from a mother cell. 
The same origin of the caoutchouc-containing cells of Eucommia occurs in the cells of 
the pith (fig. 3), but takes place here in somewhat older internodes, therefore at a later 
period than in the cortex. The caoutchouc-containing cells in the pith are of very much 
