OF THE MATTO GROSSO EXPEDITION, 1891-92. 475 
distance, and may even pass over into ordinary pitted pith-cells ; their contents would 
seem to be placed in continuity by means of fine threads passing through minute pores in 
the intervening septa. An extreme case of septation of a latex-tube is shown at fig. 7 of 
the cited plate; upon its right side are pith-cells, to the left is a row of cells with 
contents contracted and turned red by boiling in caustic soda, these cells passing below 
into ordinary pith-cells. Similar cells accompanying latex-tubes may also be seen at the 
outer part of the bast, and more rarely in the cortex. What may be the relation, if 
indeed there be any at all, between these rows of cells and the latex-tubes, I am not 
prepared to say. 
The epiderm of the leaf's upper side (fig. 7) is either one or two cells deep ; below it 
lies the well-marked palisade tissue and the spongy mesophyll, the latter having but few 
interspaces, and these very small. Only on its lower face can stomates be seen. Slender 
latex-tubes accompanied by cells similar to those above alluded to are found chiefly in the 
vascular bundles of the leaf (fig. 9 shows a tube with a septum across it); the contents 
of many of the leaf-cells, and their walls as well, are turned a fine brick-red after lying a 
little time in glycerine. 
The latex-tubes can best be seen in the tissues of the embryo, and especially in the 
cotyledons (fig. 10). The cells of the latter organs are crammed with small starch-grains, 
and coursing among the cells are very numerous freely-branehing non-septate latex-tubes. 
But one concludes at once that the latex is not confined to the tubes, since many of the 
cells are seen to contain latex in addition to starch. I imagine there must be some 
connection between these cells and the latex-tubes: indeed, the tubes can sometimes be 
seen to be terminated by a cell, or a group of cells; hitherto, however, I have not 
succeeded in satisfactorily demonstrating continuity. Other laticiferous cells may be 
seen in close relation with the tubes in their course (fig. 12 , & fig. 10 9 ), though most of 
the cells lying in proximity to the tubes have no latex. Such a drawing as that shown 
in fig. 12 is very suggestive of connection between tube and cells, a short string of the 
latter clearly seeming to actas a continuation of the tube. The presence of latex in 
cells as well as in tubes, which latter may be simple or branched and septate or non- 
septate—that is, the exhaustion of all possibilities in one and the same species—is, I 
venture to think, a matter of some slight interest. 
The latex consists for the greater part of fine granules, in which I failed to detect stra- 
tification. Seeing that dried material alone is available, it has been thought better not 
to attempt further study of this substance, though an opportunity of doing so may 
possibly occur in the future, as what few seeds could be spared have been sent to 
Dr. Trimen, of Peradenia Gardens, Ceylon, with a view to germination. The economic 
importance of a good rubber plant isa fact patent to all, and I think it not impossible 
that Brosimopsis may prove to be of some value in this relation. 
The ripe seed is contained in a thin erustaceous membrane—the persistent ovarian 
wall To this membrane the seed, after maturation, is found still attached close to its 
hilum, so that, in extracting the seed, portions of the envelope are very apt to be left 
behind, fixed to the edge of the prominent hilum. The testa is of a pale brown colour 
d is very thin. 
as y 3Q 2 
