250 МВ. Е, E. WEISS ON THE CAOUTCHOUC-CONTAINING 
elastie. If a young developing leaf be treated in this way, the contents may be pulled 
out before the complete fusion of the granules has taken place, and threads will be seen 
presenting a jagged outline owing to the granules protruding along the side of the thread. 
By the time the fusion has taken place it is impossible to demonstrate any protoplasmie 
contents to the cells, and we must assume that all further growth ceases. 
CONCLUDING REMARKS. 
From the foregoing description of the caoutchouc-containing-cells of Hucommia, it 
will be seen that, while reminding one in many particulars of the latex cells of the 
Euphorbiacez, yet in some very essential points they differ from them. 
They agree with the latex cells in their occurrence in the inner portion of the cortex, 
in the secondary phloem, and to some extent in the pith. They elongate enormously, 
and make their way by a sliding growth into the growing regions and largely into the 
leaves. They contain at the commencement numerous large caoutchouc granules in their 
protoplasm, though these granules afterwards become welded into a homogeneous mass 
of caoutchouc. They differ, however, chiefly from latex cells— 
(1) In remaining unbranched and containing only a single nucleus. 
(2) In arising de novo in all secondary growths, such as the secondary phloem and in 
new shoots and leaves. 
As far as this secondary difference is concerned they would in this agree with the 
latex cells of the Cannabinese, of Urtica, and of Vinca, in which the latex cells do not 
arise from specialized cells of the embryo, as they do in the Euphorbiex. 
Chauveaud has, therefore, also distinguished the latter, as “ tubes continus primitifs," 
from those of Urtica, which he calls *tubes continus ultérieurs.” бо, too, they might 
be called in Ewcommia, were it not for the fact that their contents, except possibly at a 
very early stage, are very different indeed from what is usually termed latex. They 
seem to contain only the one substance, which I have taken to be caoutchouc, and never 
present fats, oils, or starch. I have, accordingly, preferred to call them merely what 
they seem to me to be, 4. е. caoutchouc-containing cells. 
Yet, morphologically, they may be equivalent to the cells usually termed latex cells, 
but are less specialized and less elaborate in structure than these, and I think we may 
therefore venture to assume that latex cells of a more organized type may have been 
derived from cells similar to those of Eucommia, and possibly our conclusions may 
support the views of some observers who have dealt with the relationship of the various 
forms of laticiferous tissues. 
Pax *, in his paper on the Anatomy of the Euphorbiaces аз affecting their classifi- 
cation, takes the separate closed sacs containing latex which are found in some of 
the Ricinocarpeze and in the Acalyphe аз the starting-point in the evolution of the 
latex cells of Euphorbiaceze. In the group of the Johannesi:e the individual cells of the 
articulated sacs are of different length, some of considerable length, and if, as Pax 
* Engler's Botanische Jahrbücher (1884), pp. 384-421. 
