IV. On the continuity of the protoplasm through the walls of vegetable cells. 57 
To obviale tlio difliculties 1 have rncntioned above I attempted lo usc 
die same modification as I had doue ia Ihe case of Sulphuric acLd vis«. lo 
Ircal first with Chlor-Zinc-Jod. and, having well washed out the section, to 
slaiu with Hoffmann’s blue. In this however, like Tangl, 1 was at first un- 
succossful, for allhough by the Jodine and Chlor-Zinc-Jod. treatment, well 
defined threads were plainly seen, yet on staining, no colouration whatever 
was produced. However from a number of experiments that I instituled 
in order to acertain why this occurred, I observed that when such sections 
were treated with Solutions of well coloured crystalline bodies, such as 
picric acid, gold chloride, chromic acid, something of the threads could bo 
seen. fhis led me lo believe that I had lo deal merely with a phenomeuon 
of did'usion, for my aniline dyes were essentially colloidal in character, and 
it seemed not improbable the solution of such colloidal substances would 
not difluse into the delicate Strands of colloidal protoplasm. Consequcntly 
I adopted the modification of dissolving the Hoffmann’s blue in a 50% solu¬ 
tion of alcohol saturated with picric acid and on washing out 1 found the 
threads well stained — the picric acid bodily carrying, as it were the solu¬ 
tion of the dye into the fine proloplasmic Strands. Picric acid has also 
another valuable property in that it tends to prevent the staining of cell- 
wall by dyes which, allhough possessing an especial aflinity for the proto¬ 
plasm, will stain the cell-wall also uuless soine such restraining reagent 
be used. 
I am now in a position lo give my melhod with Chlor-Zinc-Jod. in full. 
Sections are stained with Jodine and mounted in Chlor-Zinc-Jod. Thon if 
the material is favourable one may sce something of the threads, or at any 
rate obtain some information as to their probable presence or absence. After 
being exposed lo the action of Chlor-Zinc-Jod. for about 12 hrs. the sections 
are well washed; stained with Picric Hoffmann’s blue, washed again in 
Waler, and finally mounted in glycerine, or what is ofteu beiter still, plaeed 
*u alcohol, first di Inte, und at lenglh absolute; cleared with clove oil, and 
mounted in Canada balsam. In those cases where the tissue rapidly swells 
Under the action of the reagent, as in the endosperm of Strychnos nux- 
Vointca, Bauhinia and Turnus, the action noed not be so prolongcd, and the 
°xcessive swelling must be prevented by the use of alcoholic Jodine at the 
°ulset, and in a similar mannor it may be washed with alcohol instead of 
with water, otherwise the threads will be so displaced and altered as to be 
f| lmost or enlirely invisible. 
These tlien are the two principal methods. As regards the management 
(, f the reagents, and the lenglh of time they must be allowed to act in order 
b* obtain a salisfactory result, it is clear that the manipulation must be 
v aried lo a certain exteut lo suit the requirements of the various kinds of 
bssue, as it is Ihin wallod or thick, easily swollen or swollcn with dil’li— 
cu, ly- The use of Sulphuric acid is atlended with by far the greater amount 
