1887.] - MICROSCOPICAL JOURNAL. 195 
translucent to admit of examination by transmitted light under low powers. 
Cut off a small branch and place the end of the stem in a bottle or other ves- 
sel containing the coloring solution. Place the vessel conveniently near the 
microscope, so that one of the leaves of the cutting may be laid out over the 
stage, as is done with the foot of a frog in the examination of its circulation. 
Then watch the absorption of the coloring matter as it passes from cell to 
‘cell- 
In selecting specimens for use in this experiment the newest shoots will be 
found most satisfactory, because the absorption of the coloring matter is more 
rapid and, consequently, more easily watched. As the preparation is not a 
permanent one, it is unnecessary to give it the careful preliminary treatment 
required in mounting. 
Some coloring matters are more readily absorbed by the living plant than 
others. The various coal-tar derivatives are taken up very slowly, and so is 
the ordinary carmine and cochineal if simply dissolved in water. The most 
satisfactory, simply because they are the most rapid, are the colored writing 
fluids of commerce, more especially the scarlet and purple. -With some of 
these the leaf is thoroughly stained in the course of fifteen minutes, making 
a beautiful object even to the naked eye. 
The study need not be confined to leaves, as the flowers may also be sub- 
jected to the same operation and the mode of circulation be observed even in 
the organs of reproduction: In the leaves the stronger and more prominent 
veins do not take up the color readily while the plant is living, but the finer 
veins and cellular tissue are readily colored. 
These coloring fluids may be injected into the stem of the rooted plant, but 
greater care and patience are necessary than by the method of cuttings. 
Hereafter will be described some of the results obtained by this method of 
studying circulation, more particularly ia the vital organs of various plants. 
O 
The Cell Question.—Prof. Schafer took the lead in a discussion at the 
British Association upon ‘ The Present Aspect of the Cell Question.’ He 
said the typical cell is a protoplasmic body surrounded by a net-like substance, 
with a central nucleus. Contrary to the view taken by many observers, he 
held that the essential part of the cell was not the reticular substance, but that 
which was contained within it, which was really the protoplasm of the cell, 
the substance upon which what was used to be known as the vital functions 
depended. In support of this view he referred to the amceba, which pre- 
sented, he believed, no reticular structure, and, in a more important sense, to ° 
the white corpuscles in the blood. These corpuscles, viewed under a higher 
power of the microscope, presented the reticular structure, but the movements 
of the corpuscles were produced, not by this substance, but by the contained 
protoplasm, which was extended in pseudopodia-like processes. Prof. A. 
Weissman read a paper on ‘ Polar Bodies’ as a contribution to the discussion. 
He said that the polar globules might be regarded as insignificant rudiment- 
ary organs as long as they were only known in a few groups of the animal 
kingdom. But as their existence was now proved in nearly all classes of ani- 
mals, and as they appeared in all of them in the same manner, they were 
compelled to assume that they possessed at least some physiological signifi- 
cance. Prof. Lankester drew attention to a statement made by the president 
of the Association in his opening address. Sir Henry Roscoe had stated that 
protoplasm was not a chemical substance, but a structure. Although this 
statement must shock the susceptibilities of many biologists, he (Prof. Lan- 
kester) had no hesitation in saying that it was perfectly correct. The term 
‘ protoplasm’ was originally applied by Von Mohl to the whole of the slimy 
structure within the vegetable cell wall. But nowadays biologists were more 
