298 BOTANICAL GAZETTE. [ November, +; | 
3 
On thin longitudinal sections the continuity of the air-spaces 
in the larger air-channels of the internode, in the inter- 
~ 
cellular cavities of the node, and, finally, in the interior of 
the sacs, can be traced distinctly. I would, therefore, call 
these sacs, not trichomes, but reduced, or rather trans- 
formed phyllomes, transformed in order to fulfil a special 
function, z. ¢., to give the apex of the stem necessary 
buoyancy, so that the leaves may receive light and air, and 
the pistils and stamens the visits of insects or the currents of 
the air 
At no stage could any secretion exuding from the sacs be 
noticed. The protoplasm contained in the cells, although 
plainly visible at the early stages, is too insignificant to indi- 
cate that intense activity which is going on in secretory or- 
gans; besides, the comparative isolation of the cells, which 
are really simply epidermis cells, speaks against such a func- 
tion. But I would call attention to the peculiar fan-shaped, 
or rather palm-shaped hairs found at the nodes in consider- 
able numbers, which most likely produce some kind of secre- 
organs, the sacs included, just begin to differentiate, leaves 
hardly any doubt that they serve for the protection of those 
points that are most in need of i 
or systematic botany the question is of great interest, 
whether each, the pistil and the stamen of Callitriche, is to 
be considered a separate flower or not. In most text-books® 
the flowers are described as moneecious. In my opinion, the 
histology of the inflorescence ought to decide the question. 
4Cf. DeBary, Comp. Anat. Engl. ed., p. 64. 
5e. 9., Gray’s Manual, Eichler’s Syllabus, 
