35 6 Miyake . — On the Development of the Sextial 
the two nuclei approach each other, or rather the lower nucleus 
moves towards the upper one, until they come to lie in the 
uppermost part of the common cytoplasm (Figs. 18-21). The 
two nuclei are not equal in size, and the upper one seems to 
be always smaller. This inequality in size could be detected 
as far back as the formation of the daughter-nuclei (Fig. 16). 
Miss Ferguson (’01 a) made a similar observation in Pinns. She 
also demonstrated the fact that in Pinns two sperm-nuclei are 
surrounded by the common cytoplasmic mass ; two sperm- 
cells never being formed as was supposed to be the case by 
former investigators (Strasburger ’ 92 , Belajefif ’ 93 , Dixon ’ 94 , 
Coulter ’ 97 ). 
At this time the pollen-tube has reached nearly half way 
down towards the archegonium. After the formation of the 
sperm-nuclei the downward growth of the tube is comparatively 
rapid. The pollen-tube is somewhat sinuous in its course, 
but I have never observed it to branch, as is often the case 
in Pinus. 
The sperm-nuclei increase in size after they are formed, 
and present a densely granular appearance under a low power, 
although these granules seem to be somewhat reticularly 
arranged under a high power. The nuclei, when mature, often 
stain intensely, taking the violet in Flemming’s triple method. 
They seem to contain several nucleoli, but the latter are often 
obscured by the other densely staining structures (Figs. 19-22). 
Fig. 15 shows two mature sperm-nuclei near the tip of a pollen- 
tube which has reached the lower part of the nucellar cap 
almost approaching the neck of the archegonium. The stalk- 
cell with its characteristic nucleus is found at the lower end 
of the sperm-cytoplasm. 
The nucleus of the stalk-cell usually takes the violet stain 
in the triple method. It is very much like one of the nuclei 
of the nucellar cap both in its size and staining character 
throughout its entire history in the pollen-tube. Although 
Miss Ferguson for the first time clearly established the fact 
that the stalk-cell remains intact throughout its entire history 
in the pollen-tube, a careful examination of Strasburger, 
