2J2 Shaw.— The Fertilization of Onoc/ea. 
For fixing 1 the prothallia they were placed whole in \ °/ o 
or i °/ chromic acid. The best results were obtained by 
leaving the specimens in \ °/ o chromic acid for eight to twenty- 
four hours. In most cases dilute sulphurous acid was used 
for removing the last traces of chromic acid. 
Most of the material was stained with Czokor’s alum- 
cochineal, in which the prothallia were allowed to remain 
for eighteen to twenty-four hours. Some of the plants were 
stained in alum-carmine, and others in diluted Delafield’s 
haematoxylin. Some of the sections of plants which were 
stained in toto in alum-cochineal were counter-stained on the 
slide with Bismark brown. A few sections were restained 
on the slide with Flemming’s triple stain 2 , safranin-gentian 
violet-orange G, and a few others with Heidenhain’s iron- 
haematoxylin. 
The prothallia were sectioned in paraffin. At first turpen- 
tine was used as a medium between alcohol and paraffin, but 
it was soon discarded, and xylene used according to the 
method recommended by Zimmermann 3 in his handbook. 
The wings were cut off with a razor before the prothallia 
were imbedded. The sections were cut io/x thick on a Minot 
microtome of the older style. They were cleared with clove 
oil and mounted in Canada balsam. 
Investigation. 
The spermatozoids, which were usually held in large num- 
bers in the slime before the mouth of the archegonium, 
remained unchanged for a long time, and were favourable 
objects for study. They were in a position to be acted upon 
very quickly by the fixing agent, and also by the stain. 
Those fixed after fourteen, eighteen, and twenty-four hours 
had the same appearance as those fixed after a few minutes. 
They had all lost the nutritive vesicle, and become a little 
1 For fixing the series of 0. Strut hi o^teris most of the agents given in Zimmer- 
mann’s Botanical Microtechnique were used. 
2 Zimmermann ’93, p. 186. 
3 1. c., pp. 32-33- 
