GYMNOSPERMS: WHITE PINE. 



303 



mature cones. In fact the wall of the ovule forms the outer coat 

 of the seed, as we will later see. 



617. Pollination. At the time when the pollen is mature the 

 female cones are still erect on the branches, and the scales, which 

 during the earlier stages of growth were closely pressed against 

 one another around the axis, are now 

 spread apart. As the clouds of pollen 

 burst from the clusters of the male cones, 

 some of it is wafted by the wind to the 

 female cones. It is here caught in the 

 open scales, and rolls down to their bases, 

 where some of it falls between these 

 forceps-like processes at the 

 lower end of the ovule. At 



Fig. 355- 



Branch of white pine showing young female cones at time of pollination on the ends of 

 the branches, and one-year-old cones below, near the time of fertilization. 



this time the ovule has exuded a drop of a sticky fluid in this 

 depression between the curved processes at its lower end. The 

 pollen sticks to this, and later, as this viscid substance dries up, 

 it pulls the pollen close up in the depression against the lower 



