286 



GYMNOSPERMS 



spore mother-cell stage (fig. 290). This was easily determined by 

 comparing late autumn, mid-winter, and early spring conditions. 

 In Juniperus virginiana, in the same locality, the mother cells divide. 



Fio. 2?>q.— P'niiis Ininksiana: young staminatc cone with sporangia in early sporog- 

 enous stages at the liottom; at the top, archesporial cells have not yet appeared; near 

 Chicago (September lo, lo^O; X4S. 



the exine and inline of the microspores are developed, and the pollen 

 is nearly ready for shedding when winter arrives; but in Juniperus 

 communis, growing close to the other species, the winter is passed in 

 the mother-cell stage. 



