IV. On tlie contiiiuity of tlie proloplasm tlirougli llie walls of vegetable cells. §5 
described. Here and there Stretching across the tissue, or between the 
contents of neighbouring cells were a number of what one niighl fairlv call 
slime strings, produced apparently by the violent aclion of tlie acid upou the 
proloplasm, and although in roany cells the middle lamollae were alniost 
invisible, in other parts of the tissue they appeared swollenup, and beeame 
stained with .todine, or Carmiue, although less so with Picric Hoi fmanx’s blue, 
ln nearly every instance, and certainly in the great majority of instances, no 
trace of any direct continuity could be detected. In others the close ap- 
proximation of two attenuated processes at first sight seerned to suggest 
such an appearance as Mr. üu.uiouse has described, but eareful focussing 
usually determined, either that no actual union occurred, or that the pro¬ 
cesses camc from cells which overlapped and were not in the same plane, 
ln fact in no one clear and undoubted instance was I able to satisfy mvself 
of the existence of a direct continuity, but it appeared to me that the pro¬ 
cesses ended at the pit-membrane. 
I then proceeded to treat sections according to my method, mounting 
thern either in Canada balsam or in glycerine as occasion seerned to require. 
Such treatment as far as I could observe, proved conclusively, that in all the 
tissues examined the processes entering the pits could only be followed as 
far as to the pit-closing-membrane and that they were clearly and distinctly 
bounded, by that structure, although in every case the processes of adjacent 
cells were connected through the pit-membrane by a lighter stained area. 
ln Prunus and Aucuba, this area presented the well known form of a flat- 
tened sphere,'and in it distinct threads could be seen. Henc.e here a sieve 
arrangement is present. In Acer merely a doubtful striation could be de¬ 
tected, and in Ilex and Aesculus merely a staining in pit-membrane. 
Consequently as it seems to me, the one point which is satisfactorily 
proved in Mr. Hillhoose’s paper, is that in Prunus lauro-cerasus a continuity 
between the contents of adjacent cells is established by means of delicate 
protoplasmie filaments which in the manner of a sieve-structure perforate 
the pit-closing-membrane. 
As regards the occurrence of a direct continuity, both in Prunus and in 
the other tissues, I can neilher confirm his results nor do 1 believe them 
capable of eonfirmation: and although by his own researches he has not 
demonstrated the existence of a continuity of the protoplasm in Ilex, Acer 
and Aesculus, I have shown that such a continuity does exist and that it is 
niade possible by means of delicate filaments which in the manner of a 
sieve-structure traverse the pit-closing-membrane. There is a minor point 
that the threads do not appear to me to go as Mr. Hiilhoise draws them, 
straight through the closing membrane so as to cause the whole thread com- 
plex to assume the form of a cylinder, but they bend in the way I have so 
°ften described so as to assume the form of a flattened sphere. 
