394 LILY HUIE. 
tissues being examined by the methods about to be detailed ; 
but none of my drawings have been taken from material of the 
fourth series, because plants kept for a few days in a green- 
house frequently show, as Darwin pointed out, a loss of the 
bright red colour peculiar to them under natural conditions, 
and they are therefore affected to some extent by their 
artificial surroundings. 
Meruops. 
I used the four following fixing fluids: 
1. One per cent. chromic acid solution, as recommended 
by Gardiner. 
2. Absolute alcohol. 
3. Mann’s picro-corrosive alcohol.? 
4. Mann’s weak watery picro-corrosive fluid. 
The effects of these fluids were very different. 
The chromic acid caused the controls (unfed leaves) to close 
up as if powerfully stimulated ; and on subsequent histological 
examination the glands presented the appearance of having 
been stimulated for a short time,—for example, the nuclei of 
the third layer of gland cells had become ameeboid, or irregular 
in form, The whole tissue was cloudy, and stained with no 
precision. 
The two alcoholic fixing agents preserved the control leaves 
in a beautifully expanded condition, but instantly made the 
glands white and transparent-looking, as if some substance 
had been extracted. Sections of such glands showed more or 
less distortion or slight collapse of the cell walls, and great 
vacuolation of the contents of the apical gland-cells. By the 
picro-corrosive alcohol, however, the large chromatin bodies 
1 Gardiner, W., “On the Phenomena accompanying Stimulation of the 
Gland-cells of Drosera dichotoma,” ‘Proc. Roy. Soc. London,’ 1885. 
2 Mann, G., “On a Method of preparing Vegetable and Animal Tissues 
for Paraffin Embedding, with a few Remarks as to Mounting Sections,’ 
‘Trans. Bot. Soc. Edin.,’ vol. xviii. 
