Organs and Fertilization in Picea excels a. 355 
wall of the pollen-grain, and together with the generative cell 
moves down into the pollen-tube (Figs. 11, 12). Strasburger 
(’92) states that in Picea excelsa the generative cell divides 
in the pollen-grain, and of the resulting two cells the one in 
advance is smaller than the other 1 . Belajefif (’93) also ob- 
served in Picea excelsa that the generative cell divides into 
two before it leaves the pollen-grain, and only the naked 
nucleus of the stalk-cell enters the pollen-tube. Dixon (’94) 
made a similar observation in Pinus sylvestris. Miss Ferguson 
(’01 a), in her studies on the development of the pollen-tube 
in several species of Pinus , obtained very different results. 
She found that the generative cell enters the pollen-tube 
before it divides, and also demonstrated that the whole stalk- 
cell moves down into the pollen-tube. My observations in 
Picea agree with Miss Ferguson’s in both points. 
The generative cell, as it passes into the pollen-tube, is 
more or less elongated and increases much in size ; it has no 
definite cell-wall, and is somewhat irregular in shape (Fig. 12). 
The stalk-cell, which is attached to the generative cell at its 
lower side and more or less surrounded by the cytoplasm of 
the latter, seems to move down the pollen-tube more rapidly ; 
it passes by the generative cell, and soon afterwards is seen 
at the lower end of the latter (Figs. 13, 14). 
Shortly after this the generative cell divides. The process 
of the division has not been trace<Fvery carefully, but judging 
from several division-figures so far observed, I may say that 
in general it is very much like that of Pimis as studied by 
Miss Ferguson (’01 a). The mitotic figure, like Fig. 15, suggests 
that the spindle may very likely be unipolar in origin as in 
Pinus. The cell-plate is formed at the equator of the spindle, 
but persists only for a short time and finally disappears, as 
was already noticed by Miss Ferguson in Pinus (Figs. 16-20). 
Soon after the division the two sperm-nuclei are separated 
from each other by a considerable distance (Fig. 1 7). Gradually 
1 * Bei Picea vulgaris sieht man die grosse Antheridialzelle sich ebenfalls schon 
im Pollenkorn theilen. Die vordere generative Zelle ist auch bei Picea kleiner als 
die hintere’ (Strasburger, ’92, p. 25). 
