PLATE XIII. 



Fig. 127. The macrospore-mother-cell in synapsis. X Sio. Pinus austriaca. 

 June 6, 1898. 



128. The same in recovery from synapsis showing continuous skein. 

 X 810. Pinus austriaca. 



129-133. Stages leading to the organization of the chromosomes in the 

 first or heterotypical division of the macrospore-mother-cell. X 810. 

 Fig. 132, Pinus Strobus, the others, P. rigida. Fig. 131 illustrates an 

 instance in the unusually early disappearance of the nuclear membrane. 



134-137. Stages in the establishment of the spindle in the first division of 

 the macrospore-mother-cell. The reduced or one half number of 

 chromosomes appear in this mitosis. The spindle arises as a multi- 

 polar diarch. X Sio. Fig. 137, Pinus rigida, the others, P. Strobus. 



13S. Late telophase in the first division. A cell-wall is laid down and defi- 

 nite resting nuclei are formed. X 810. Pinus Strobus. June 13, 1S99. 



139-140. The close of the heterotypical division. Resting nuclei are 

 formed but the upper resting nucleus in each case shows signs of 

 disintegration and doubtless would not have divided. X 810. Fig. 

 139, Pinus austriaca, fig. 140, P. rigida. 



141. The two daughter-cells formed by the first division of the macrospore- 

 mother-cell. Both would doubtless have divided again. X 810. 

 Pinus austriaca. 



142. The second or homotypic division of the macrospore-mother-cell. 

 The spindles are oblique and arise as multipolar diarchs. The ciiro- 

 mosomes have the same form as those which arose on the first division 

 of the macrospore-mother-cell. X810. Pinus austriaca. 



(180) 



