74 Scientific Intelligence. 
nodes just ee — the bud; the thickening of the walls of the 
ligneous and cortical cells, which characterizes adult stems is 
here wholly poo This thickening, indeed, is Saas by bonds 
which are not yet very wasn understood to the presence of leaves 
on the internode. In darkness the leaves not being developed, the 
cells retain the primitive pean of their membranes. 
“ This being understood, the elongation of the etiolated stems 
is easily explained, thanks to the intervention of two factors. In 
the peripheral layers that itis it ; in youn 
jected to a tension strong enough to cause them to shorten con- 
siderably when they are isolated. But in proportion as their 
walls become thickened the resistance becomes more effective, and 
we see this in the fact that their contraction, when they are separ- 
ated from the rest, becomes less and less. In darkness their 
walls do not thicken, and nothing is opener to the elongation of 
the ped ery cells. This is the first fac 
Vith regard to the pith itself, M. RS 6s already shown, 
in a former work (Botan. Zeit., 1867, Nos. 17, 18), that it has 
the property of het ip solely by the interpoution of aqueous 
molecules between the cellulose molecu is interposition 
may take place in the etiolated as in the seul Gat: ; the pith 
is, therefore, the only part of the plant which continues to grow 
actively in ‘the dar is growth is precisely the second factor 
e jak gi ps - os internodes ; and by combining it with 
the absence o nce in the peripheral ys we can under- 
recent observations —— relate to the ‘action of cold upon 
plants, iota j r, have been already referred to in 
se pages, see Michel 8 abstract of Schreeder’s researches upon the 
of the Maple ” we will reproduce :— 
The pin has paid attention to all the successive aoa 
ie ee works which, even when they do not contain any Vv 
ults, are, nevertheless, very useful to read and py bie ; 
but it is is difficult to give a clear notion of them in a few words. 
glance at the course pursued by M. Schreder will show the great 
number of facts which group themselves within a frinework| such 
as he has adopte 
“ The first part is entirely devoted to the study of the sap, its 
ascent and its composition. The maple, under the latitude of 
in its composition. It always contains sugar, a transitory p 
of the transformation of the starch accumulated in the. aca 
oy, 
4 
es 
