404 
Osterhout . — On the Life- History of 
Methods. 
The best results were obtained from material which was 
fixed in a saturated solution of picric acid in sea-water, washed 
fifteen to twenty hours in running sea-water and preserved in 
sea-water, to which was added plenty of camphor broken up 
into small pieces. Material so treated is still in excellent 
condition after standing for over a year. Material killed in 
chromic acid (i °/ o in sea-water), or picric acid and preserved 
in formalin (2 °/ o in sea-water), is also very satisfactory, while 
material placed directly in 2 °/ o formalin without previous 
treatment retains its colour for some time and is kept in 
excellent condition. The addition of 1 °/ chrome-alum to 
the formalin seems to be an advantage. 
At the commencement of the work hand-sections were 
made with a razor ; but as it soon became evident that some 
more efficient method of sectioning was necessary, the material 
was embedded in paraffin and serial sections were cut. The 
shrivelling of the tissue in all except very young parts of the 
frond was so great that this method was abandoned. Freez- 
ing by means of ether was then tried, and excellent results 
were obtained ; but this method of freezing proved so trouble- 
some, that in looking about for a better one, the writer began 
experimenting with ice and salt, with the result that an 
apparatus was finally devised which could be operated with 
very little trouble and which proved very efficient, a descrip- 
tion of which appeared in the Botanical Gazette for May, 
2896 (vol. xxi. p. 195). It was found that large frozen 
sections when cut very thin, easily broke in pieces in the 
region of the medulla. To avoid this the material was 
placed before sectioning in 50 °/ o gelatine 1 for a short time ; 
1 This is prepared as follows : The best gold-label gelatine is carefully brushed 
clean and used according to the following formula : — 
Gelatine . . . .100 grm. 
Distilled water . . . 100 c.c. 
Thymol .... Trace. 
Mix over a water-bath, and add the white of one egg to clarify. 
