Walter Gardiner. 
(52 
ver treatment with Jodine and Ghlor-Zinc-Jod. demonstrates that the swollen 
sides of the pits are quite free from, and do not embrace the delicately 
drawn out protopfasmie processes That part of the process abutting on lo 
the pit-closing-membrane bas either a broad apex, or it may be drawn lo a 
line point. In two opposite pits the proloplasmic processes may either both 
have broad ends, or both pointed ends, or finally a broad-ended apex niav 
have opposite il one whose termination is drawn out lo a delicate point, 
all these various appearauces depending upon the degreo of action of the 
acid. The middle lamellae remain but little actedupon, and appear as a 
delicate network marking out the limits of the cells. By proper treatment 
with Glycerine all the staining may be dissolved from them, and after being 
mounted for some time in strong Glycerine they may be rendered so incon- 
spicuous as not lo interfere with suceessful observation. 
Ilaving thus stated in detail the various phenomena presented by the 
eell-wall and the general cell-protoplasm, I now coine to the most important 
pari of the subject which deals with the evidence as to the occurrence of a 
continuity of the protoplasm between one cell and another. The only Sug¬ 
gestion that we have hitherto had of such proloplasmic continuity was the 
remarkable fact of the hanging on of the protoplasm to the pit-membrane, 
l)ut this fact allhough it may be taken to afford some indication of the pro¬ 
bable existence of a communication between adjacent cells, of itself actually 
proves but little; for it is the existence of protoplasm in the cell-wall which 
has to be demonstrated and protoplasm may equally well be present traver- 
sing the pit-closing-membrane whether the proloplasmic processes adhere to 
the pit-wall or whether they contracted away. This is an important point. 
Thus it is the pit-membrane which must be carefully examined. In 
a well prepared section of the j>ulvinus of Mimosa there appear after treat¬ 
ment with acid at first to be several ways in which the continuity of the 
protoplasm between adjacent cells is established. In some instances il 
appears as if fairly thick proloplasmic processes traverse the pits bodily, so 
that the proloplasmic mass of one cell is directly continuous with that of its 
neighbour as if in fact the pits were open, and possessed no closing mem- 
brane. ln other instances it appears as if each process had become drawn 
out in the pit into a very delicate Strand and that the two opposite alte- 
nuated Strands efleet a junction by means of a small Perforation in the pit- 
closing-membrane. Lastly it appears as il a sieve plale arrangement occurs- 
1 propose lo consider these cases in some detail, and beforc so doing 1 think 
il is necessary that I should state some of the difficulties which altend ihr 
observation of such struclures, and also some of the precautions which must 
be taken in order to avoid a false interpretalion of the appearauces which 
I have described above. Firstly the tenuity of the processes, and the tbinnesS 
of the pit-membranes necessitate the use of high powere, which must neceS- 
sarily be mnnipulafed with very great care. Again, owing to the action o* 
