IV. Oii Wie conlinuity of the protoplasm through the walls of vegetable cells. 59 
Willi regard lo olher manipulative details 1 should menlion tlial besides 
a plalinum 1 ifter, I also used platinum needles and thal 1 w as careful to 
thoroughly brush all Ihe sections wilh a camel-luiir-brush, both, alter the 
aclion of the acid, or of Chlor-Zinc-Jod. and aller staining. This I regard 
as a detail of some importance. 
In order to prove that the threads traversing the cell-wall were in reality 
proloplasm, 1 employed wilh suceess a solution of Molybdic acid in strong 
Sulphuric acid, which has the advantage of swelling the cell-wall and at the 
same time colouring the proloplasm. lf Molybdic acid be dissolved in strong 
Sulphuric acid a colourless solution is obtained which, wilh Alcohol or maiiy 
other substances of an organic nature, gives a beautiful blue colour. So 
delicate is this reaction that the blue colour is dcveloped even when the 
liquid is kept in a stoppored boltle in consequenoe of the previous iulro- 
duetion of some foreign matter of an organic nature. I found that such a 
solution while not affecling the cell-wall for some time gave a fine blue 
colouration at once Willi the proloplasm. lf then a section of some living 
endosperm such as Turnus be treated wilh this reagent, it will swell up the 
cell-wall and will commence to dissolve the protoplasm; the liue threads 
porforating the walls will remain for some time unacted upon, and while 
the main protoplasmic mass w ill assume an intense blue, the threads in ad- 
dition will be perceptibly coloured. 
At an early stage in this research 1 was strack witli the peeuliar pro- 
perties of the pit-membrane as compared wilh those of the rcsl of the 
cell-wall. 
For instance, after staining with .lodine and Chlor-Zinc-Jod., whereas 
the general cell-wall assumes the usual blue tint, the pil-mcinbrane is but 
slightly coloured, and indeed when the membrane is somewhal thin may 
not appear to colour at all, although the examination of a fine transverse 
section of the pit w ill prove that a definite staining has taken place. But 
the depth of the staining certainly appears less llian one would expect in 
Proportion to the thickness of the membrane. 
Methylene blue slains both the wall and the pil-membraues a fine 
light blue, and after the aclion of Sulphuric acid the swollen wall assumes 
a much lighler tint, owing to the fact that the quantity of the dye taken up 
by the cell-wall is uow distributed over a rclatively largor spare, lf a 
section be cautiously treated with Sulphuric acid, washed and stained, 
il w ill be seen that whereas the general swollen wall is coloured a light 
blue, the bolloms and the sides of the pits will still assume the darker blue 
colour of the unsw ollen cell-wall, and w ill Ihus be clcarly marked out. If 
bowever anolhcr section be treated for a longer time wilh acid, or il the 
same section be a seeond time exposed to its aclion, il will be seen on 
staining that no special colouration of the bolloms and sides of the pits can 
be dctectcd, but that tlic whole sw ollen wall is of an uniform light tint. 
