1899] OOGENESIS IN PINUS 269 
advanced than those at the tip. In the ovulate cone, at the time 
of the division of the mother cell into potential megaspores, 
the sporangia at the base are slightly more advanced, but they 
donot develop much further. For stages figured in this paper, 
the best material is found in the middle three fifths of the cone. 
In my material, all of which was collected in the vicinity of 
Chicago, the ventral canal cell, in the season of 1897, was cut 
off about June 21, and fusion of the pronuclei occurred about a 
week later. In the season of 1896, all stages appeared more 
than two weeks earlier. 
Various fluids were used for killing and fixing. For mitotic 
phenomena the most satisfactory results were secured by allow- 
ing Flemming’s weaker solution to act for about two hours and 
then replacing it by a chrom-acetic solution (0.75% chromic 
acid and 0.25 to 100" water) in which the material remained 
for one or two days. In this way the advantages of the Flem- 
ming’s solution seem to be secured without the objectionable 
blackening. The chrom-acetic acid used alone gave excellent 
results, Carnoy’s fluid (absolute alcohol 6 parts, chloroform 
parts, acetic acid 1 part), followed by cyanin and erythrosin, 
a for tracing nuclei in the pollen tube and for differentiat, 
ees and network within the nucleus. Corrosive 
ats oa acid could hardly be recommended pats 
hiled to ea in Pinus. Hermann’s fluid and Merkel i ul 
iesti: “ee ve mg good results as the much less expensive C dies 
tation a. ayy popular safranin gentian-violet prange com é 
bet he ot definite stain for achromaes sea 26 
lowed b nai s 'ron-alum-haematoxylin used alone, or fo 
Y acid fuchsin, was better for most stages in the devel- 
pment of the oosph 
Osphere nucleus. 
i 
No atte THE VENTRAL CANAL CELL. | 2 
Stages a was made to secure a complete series of a : 
hows the a up to the condition represented in jig. Od: ea 
“<Parating is, cleus of the central cell just before the eine 
Sage there ‘¢ ventral canal cell from the oosphere. At 
p> Oen only a single nucleolus, and very seldom 
