ee 
+. 
1897 | THE LIFE HISTORY OF SALIX 149 
December collections were made to determine the histological 
character of the winter buds. 
At first I per cent. chromic acid was used for killing and 
fixing, but experience proved that better results could be obtained 
by adding a little acetic acid to counteract the tendency to 
shrink. The material was left in the fixing agent 12 to 24 hours, 
then washed in water for 24 to 36 hours, and after passing through 
successive grades of alcohol was left in 70 per cent. alcohol until 
needed for use. Flemming’s fluid proved excellent, and the same 
must be said of Merkel’s and Hermann’s, but these are rather 
expensive. Picric acid with a trace of acetic is also to be recom- 
mended. To insure rapid fixing the tops of many of the pistils 
were cut off down to the level of the ovules. 
Xylol proved the best clearing agent. The transfer from 
absolute alcohol to xylol was made gradually by adding small 
quantities of xylol to the alcohol until the mixture contained 
about three parts of xylol. The mixture was then poured off, 
and pure xylol was substituted. As soon as the material was 
cleared, a lump of paraffin was added, and thus the transfer 
from xylol to paraffin was made gradual. One to three hours 
in the bath is sufficient after such treatment. 
Serial sections were cut with a Thoma microtome. Mayer's 
albumen fixative in connection with the water method was used 
for fixing the sections to the slide. Cyanin and erythrosin was — 
the best combination for embryo sacs. Delafield’s hematoxylin 
was good for embryos and the early stages of anthers. Safranin 
and gentian violet, cleared in clove oil, seems to be the best com- 
bination for the pollen grain. 
The celloidin method was tested, but did not give as s good 
_ results as paraffin, and besides was’ unnecessarily tedious. 
All drawings were made with an Abbé camera lucida. A ae 
Bausch and Lomb immersion was used for a the aeeee except 
a of pl. XVITI and fig. 66a. 
ORGANOGENY OF THE FLOWER. 
a Ne attempt was made to secure a perfect series of stages in 
e . the development 0 of the floral — one nea were col- 
