196 Ferguson . — Development of the Pollen-tube and the 
stain cell-walls, by Bismarck brown. Iron-haematoxylin, 
followed by Flemming’s triple stain or by gentian-violet, 
and orange G, brought out the so-called kinoplasmic structures 
with great definiteness. 
During the course of these investigations more than three 
thousand ovules have been sectioned, stained, and studied. 
The present paper is concerned only with the development 
of the pollen-tube ; fertilization and associated phenomena 
will be considered in a second paper which is to appear 
subsequently. 
Historical. 
Comparatively few students have occupied themselves with 
the growth of the pollen-tube in the Abietineae, and no one, 
in so far as I have been able to determine, has described the 
cytological features attending the formation of the sperm- 
nuclei in this group. 
In 1862 Hofmeister described and figured the pollen-grain 
in the Abietineae as consisting of a cell-complex, noted the 
depression at the apex of the nucellus in Pinus at the time 
of pollination, and traced the pollen-tube into the corpusculum. 
He also figured the pit in the apex of the pollen-tube which, 
however, he said remained closed until after the formation 
of the proembryo, when it was ruptured by mechanical means. 
Hofmeister further observed what were doubtless the sperm- 
nuclei at the apex of the pollen-tube, but he did not under- 
stand their function and was unable to determine their later 
history. 
The works of Strasburger on this subject have been more 
numerous and complete than those of any other investigator. 
It is extremely interesting to note how his interpretations 
have kept pace with the improvements in methods of research. 
In 1869 he followed the pollen-tube into the corpusculum in 
Pinus and Picea and confirmed Hofmeister’s observation 
regarding the presence of a closed pit at the apex of the 
pollen-tube ; but he did not observe the nuclei in the pollen- 
tube, and remarked that inasmuch as the sexual organs touch 
