380 SCOTS PINE. 



harder and greatly thickened, especially at their outer 

 ends ; (4) the two ovules (now the seeds) on each scale 

 have grown larger. 



(d) In the third-year cone, note that (1) the scales 

 have become brown and woody ; (2) as the cone dries the 

 scales gape asunder starting at the top so as to expose 

 the ripe seeds, which are confined to the middle portion of 

 the cone, the uppermost and lowest scales being sterile ; 

 (3) the seeds, two on the upper side of each fertile scale, 

 each seed having a thin wing ; (4) the seeds are easily 

 detached from the scales and carried away by wind, leaving 

 the empty cone on the tree from which it usually falls 

 later in the autumn or winter of the third year. 



531. L.S. of Young Female Cone. In radial longi- 

 tudinal sections of the young current-year cone, note 



(1) The relatively thick axis, bearing scales of two 

 kinds (2) small bract scales or carpels each having in 

 its axil (3) a much larger and thicker placental or ovu- 

 liferous scale, which alone reaches the surface so as to be 

 visible from the outside of the young cone. (4) On the 

 upper surface of each placental scale, close to the axis, 

 there may be seen one of the two ovules which lie side by 

 side. 



Note that in a section cutting an ovule in the middle, 

 there are seen (1) the single integument several layers 

 thick, with (2) the rather wide micropyle facing the axis, 



(3) the central mass of parenchyma tissue, nucellus 

 (megasporangium), containing towards its lower end 



(4) the embryo-sac cell or megaspore, a large cell 

 usually surrounded by a sheath of nucellus cells with 

 dense contents. (5) If pollination has occurred, pollen- 

 grains may be seen at the top of the nucellus, within the 

 micropyle. 



Note that the placental scales of the young cone ready 

 for pollination are separated at their ends, to allow pollen 

 to reach the ovules ; after pollination, the scales grow 

 thicker and close up, not opening again until the seeds are 

 ripe and ready to be shed. 



