PROGRESS OF MICROSCOPICAL SCIENCE. 
201 
but little weight must be allowed to the phenomena as a proof of the 
absorbing capacity of the glands. Some other points in the structure 
of the plaut render it almost certain that the connate leaves are 
specially adapted to serve some useful purpose. Kerner is probably 
right in believing that the “cups” of the teasel are of use to the 
plant in keeping off nectar-stealing ants and other wingless insects ; 
but unless this is their tmly function, it seems probable that the connate 
leaves have been to a certain extent adapted for the capture of insects 
whose decaying remains are absorbed by the plant. The leaves are 
smooth and steeply inclined, and form a pair of treacherous slides 
leading down to a pool of water. 
It is worthy of note that the leaves of the first year’s growth, 
which do not form cups, are not smooth, but bristle with long sharp 
hairs ; moreover, in Dipsacus pilosus the leaves (of the second year’s 
growth) are not sufficiently connate to form cups, and they also are 
rough with hairs. These facts seem to show that the smoothness of 
the second-year leaves in D. sylvestris is a specially acquired quality. 
Another special point of structure in I), sylvestris may be noted. The 
stems are everywhere armed with sharp prickles, except where they 
are covered by the water in the “ cups ” ; and here they are quite 
smooth, so that no ladder of escape is afforded to the drowning victims. 
Even if we grant from the above considerations that the filaments 
protruded from the glands are in some way connected with the 
absorption of nitrogenous matter from the putrid fluid in the cups, we 
are far from understanding the whole of the problem ; for precisely 
similar filament-protruding glands are found on the seedling leaves of 
D. sylvestris and on the second year’s leaves of D. pilosus ; and as no 
“ cups ” are formed in either of these cases, the filaments cannot be 
connected with absorption of the products of decay. The only view 
which suggests itself is that the filaments absorb ammonia from the 
dew and rain. Eecent researches have shown that certain leaves have 
the power of absorbing an appreciable quantity of ammonia ; and this 
fact lends some probability to the view above advanced. 
To recapitulate. Protoplasmic filaments are protruded from the 
leaf-glands of the teasel ; and the only theory which seems at all 
capable of connecting the observed facts is the following : — That the 
glands on the teasel were aboriginally (i. e. in the ancestors of the 
Dipsacaceas) mere resin-excreting organs ; that the protoplasm which 
comes forth was originally a necessary concomitant of the secreted 
matters, but that, from coming in contact with nitrogenous fluids, it 
became gradually adapted to retain its vitality and to take on itself 
an absorptive function ; and that this power, originally developed in 
relation to the ammonia in rain and dew, was further developed in 
relation to the decaying fluid accumulating within the connate leaves 
of the plant. 
Is the Amoeba a Cannibal ? — Professor Leidy has asserted that the 
Amoeba is a cannibal. However, Mr. J. Michels points out, in a letter 
to the ‘American Journal of Microscopy ’ (July), that it is most 
probable that the supposed cannibalism of the Amoeba that Professor 
Leidy has noticed, is nothing more nor less than a process of repro- 
