SEED-BEARING PLANTS 
419 
reproduction. The central axis bears lateral scales (Figs. 
309 and 310), but the homology of these scales is difficult 
to determine, and is still a matter of debate. There are 
FIG. 309. Scotch pine (Pinus sylvestris). A-D, stages in the develop- 
ment of the carpellate cone, and its carpotropic movements. E, very 
young carpellate cone much enlarged; F, ventral, G, dorsal views of a 
scale from E; i, ovuliferous scale; 2, ovule (in longitudinal section); 3, 
pollen chamber and micropyle leading to the apex of the nucellus (mega- 
sporangium); 4, integument of the ovule; G, i, tip of ovuliferous scale; 
5, bract; 4, integument; H, longitudinal section at right angles to the 
surface of the ovuliferous scale (diagrammatic); 6, megaspore; 7, pollen- 
chamber; 7, longitudinal section of a mature cone; 6, ovule; J, scale 
from a mature cone; 6, seed; w, wing of seed; K, dissection of mature seed; 
h, hard seed coat; c, dry membraneous remains of the nucellus, here folded 
back to show the endosperm and embryo; e, embryo; p, remains of 
nucellus; L, embryo; c, cotyledons; e, hypocotyl; r, root-end. 
good reasons for considering that they are not simple spor- 
ophylls, but are of a more complex character. 
Each scale comprises a bract and an ovuliferous (ovule- 
bearing) scale (Fig. 309). It is probable (but not certain) 
