ee 
Cuar. XIV.] ALDROVANDA VESICULOSA. 261 
Directly after reading Prof. Cohn’s memoir, I received 
through the kindness of Dr. Hooker living plants from 
Germany. As I can add nothing to Prof. Cohn’s excellent 
description, I will give only two illustrations, one of a 
whorl of leaves copied from his work, and the other of a leaf 
pressed flat open, drawn by my son Francis. I will, how- 
ever, append a few remarks on the differences between this 
plant and Dionza. 
Aldrovanda is destitute of roots and floats freely in the 
water. The leaves are arranged in whorls round the stem. 
Their broad petioles terminate in from four to six rigid 
projections,* each tipped with a stiff, short bristle. ‘lhe 
bilobed leaf, with the midrib likewise tipped with a bristle, 
stands in the midst of these projections, and is evidently 
defended by them. The lobes are formed of very delicate 
tissue, so as to be translucent ; they open, according to Cohn, 
about as much as the two valves of a living mussel-shell, 
therefore even less than the lobes of Dionæə ; and this must 
make the capture of aquatic animals more easy. The 
outside of the leaves and the petioles are covered with minute 
two-armed papillæ, evidently answering to the eight-rayed 
papille of Dionza. 
Each lobe rather exceeds a semi-circle in convexity, and 
consists of two very different concentric portions ; the inner 
and lesser portion, or that next to the midrib, is slightly 
concave, and is formed, according to Cohn, of three layers of 
cells. Its upper surface is studded with colourless glands 
like, but more simple than, those of Dionxa; they are 
supported on distinct footstalks, consisting of two rows of 
cells. The outer and broader portion of the lobe is flat and 
very thin, being formed of only two layers of cells.{ Its 
upper surface does not bear any glands, but, in their place, 
smail quadrifid processes, each consisting of four tapering 
projections, which rise from a common prominence. These 
* There has been much discussion 1850) and Caspary (‘Bot. Zei- 
by botanists on the homological nature 
of these projections. Dr. Nitschke 
(‘ Bot. Zeitung,’ 1861, p. 146) believes 
that they correspond with the ftim- 
briated scale-like bodies found at the 
bases of the petioles ot Drosera, 
t [According to Cohn (¢Fiora,’ 
tung,’ 1859), the two layers of cells 
are so combined as to produce the 
effect of a single layer. The three 
layers of which the central part is 
made up consist of external and 
internal epidermic layers, and a single 
layer of parenchyma.—F. D.] 
