206 
Agnes Robertson. 
I have great pleasure in thanking Professor Oliver, at whose 
suggestion the work was undertaken, for the help and advice which 
he has most kindly given me throughout. 
I hope in a future paper to describe the structure of the seed 1 
in its second year of development. 
II.—Methods. 
During the seven weeks from August 3rd to September 19th of 
this year material was fixed at the tree, as a rule once in three 
days. To ensure good penetration of the fixing fluid, the four 
thick green bracts which surround each ovule, and the free part of 
the arillus, were removed with a scalpel, and the nucellus laid bare 
as completely as possible by cutting away the adherent part of 
arillus and integument. The small conical cap formed by the free 
apex of the integument was generally removed with a needle. 
Flemming’s weak solution was the fixing fluid chiefly used, but 
Flemming’s strong solution, weak and strong chrom-acetic solutions, 
1% chromic acid, Juel’s fixative, and absolute alcohol were also 
employed to some extent. Flemming's weak solution followed by 
Flemming’s triple stain, and fuel's fixative, followed by either 
Heidenhain’s haematoxylin or Flemming’s triple stain, gave much 
the best results. Juel’s fixative 1 (2 grs. zinc chloride, 2 cc. glacial 
acetic acid, 100 cc. 45-50% alcohol) is particularly convenient for 
use, as it is a clear liquid unaffected by light. Material fixed in 
Flemming’s strong solution, or strong chrom-acetic, was very apt to 
crumble to pieces in the paraffin. Except in the case of absolute 
alcohol, the dissected ovules were suspended at once in small muslin 
bags in a jar of the fixative, where they were left for twenty-four 
hours. After solutions containing chromic acid the ovules were 
washed for a day with many changes of water, and then passed up 
in the dark through graded alcohols to methylated spirit, and thence 
to Calberla’s fluid (alcohol-water-glycerine) where they were left 
until needed. The dehydrated fragments were penetrated with 
bergamot oil and embedded in 52° paraffin. The sections were cut 
with the microtome as a rule to a thickness of 10/x. 
III.— The Female Prothallus. 
The concluding figure of the first part of this paper shewed a 
uni-nucleate embryo-sac capped by three disorganising sister spores 
(l.c. PI. iv., Fig. 32). In an ovule gathered on June 30th, a week 
1 H. O. Juel. “ Uebcr den Pollenschlauch von Cupressus,” 
Flora, 1904, p. 56. 
