Division of the Generative Nucleus in Pines . 21 1 
case here, for the nucleoli, after the condensation has arisen 
and the spindle-threads have attained considerable length, are 
morphologically the same as they were before the Inception 
of the spindle. Nemec (’99, 1) remarks that in the higher 
plants where the centrosome is not present, the entire nucleus 
may exercise the function of the centrosome. The idea of 
the diffused centrosome in the cells of the higher plants was 
suggested by Guignard (’97), and again hinted at by Le 
Dantec (’99). If we may accept Gulgnard’s suggestion, 
then the kinetic centre of the cell in the higher plants Is 
no longer Indicated by the presence of a definite organ, the 
centrosome, but the power of this organ has become dis- 
sipated throughout the entire cell. When that phase of 
cell-activity which has to do with spindle-formation comes 
into play, the points at which it is centred would naturally 
be indicated by a greater accumulation of the microsomes, and 
thus an aster of more or less definiteness would be formed, 
as when the individualized centrosome is present. In the 
division under consideration, the position of the generative 
nucleus is such that the energy active in spindle-formation 
must perforce be centred at some point below it. Such a 
centring of activity would naturally result in an attraction- 
sphere of unusual prominence ; and there would be no 
occasion for its division since the spindle is unipolar in origin. 
The endosperm has become a solid mass of tissue at the 
time when the generative nucleus divides. The details of Its 
development will not be given here, more than to say that 
It resembles in many points the growth of the prothallium in 
Taxus baccata as described by Jager (’99). The archegonia 
are still comparatively small and quite vacuolate and the 
central cell has not yet divided (Fig. 4 ). 
Growth of the Sperm-Nuclei and later history 
of the Pollen-Tube. 
After the mitotic figure has entirely disappeared, the sperm- 
nuclei are separated by a considerable distance ; and the form 
which the cytoplasm surrounding them assumes seems to 
p 2 
