CELLS OF EUCOMMIA ULMOIDES, OLIVER. 251 
suggests, we consider the number of these cells reduced to one, and that one endowed 
from its first formation with a very pronounced power of elongation, we arrive at the 
ordinary latex cell, such as we find it in the group of the Euphorbiez. 
Chauveaud * inverts this order and considers the long, branching, but undivided cells 
of the Euphorbieze as the most primitive form of latex tissue (“ tubes continus primitifs "), 
just as the unicellular or non-cellular Бірһопеге represent а more primitive form than the 
multicellular plants. The fact, also, that the latex cells of the Euphorbiew arise in the 
embryo itself seems also to strengthen Chauveaud in his conclusion, and he lays great 
stress on three cases in which the embryo presents the continuous latex cells, whereas in 
the adult plant the laticiferous system is represented by a series of closed sacs, though 
be has no direct observations to show that the latter have arisen by a dividing of the 
continuous cells of the embryo. The plants alluded to are Aleurites triloba, Jatropha 
Curcas, and Jatropha multifida. 
My own observations оп Eucommia tend in no way to support. Chauveaud's theory of 
the relationship of the different forms of laticiferous tissues, but illustrate, I think, 
another step in the series of forms through which Pax would lead us to the highly 
specialized inarticulated laticiferous tubes. Рах” suggestions have been provisionally 
accepted by Dr. Scott f, in his valuable paper read before this Society, in which he shows 
how, starting from the same primitive condition of closed laticiferous saes, we might also 
derive the articulated laticiferous vessels of Manihot and Hevea. The fact that these 
two different systems, the non-articulated cells of the Euphorbieze proper and the 
articulated vessels of Manihot and Hevea, can be derived from the closed secretory sacs, 
such as those found in the Ricinocarpem, by a development towards the same end, 
namely, towards continuity, seems to me to be a strong claim for the correctness of Pax's 
suggestion; whereas, according to Chauveaud, the “ tubes continus primitifs ” become 
discontinuous by dividing into a number of separate cells, such as are found in Cnesmone 
and Dalechampia, only to become continuous again in the case of the articulated vessels 
of Hevea and Manihot. 
It is not, however, my object in this paper to discuss the origin of the articulated 
vessels, as in Ewcommia; my observations bear only on non-articulated cells. 
I consider that we are dealing here with a primitive, though not the most primitive, 
form of a latex cell. Тһе caoutchouc-containing cells of Еисопита are, I think, similar 
to the closed latex sacs described by Pax in the group of the Johannesieze, but are 
somewhat more specialized, and therefore, in some respects, more like the latex cells of 
the Euphorbiez proper. Their specialization shows itself in the fact that the initial cell 
divides into two before elongation takes place, so that we have always two daughter 
cells in the place of the primitive mother cell. This division of the initial cell into two 
reminds one, as I have stated previously, of the appearance of the initial cells figured in 
some of the Euphorbian embryos by Chauveaud, so that I do not regard it as improbable 
that this division into two may have been a step in the evolution of the non-articulated 
latex cells of Euphorbia. 
* Annales des Sciences naturelles, Série vii. tome xiv. (1891) pp. 1-160. 
+ Journal of the Linnean Society, vol. xxi. (1885) pp. 566-573. 
SECOND SERIES.— BOTANY, VOL. III. 2N 
