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). AD, stages in the develop- 

 ment of the carpellate cone, and its carpotropic movements. E, very 

 young carpellate cone much enlarged; F, venttal, 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; /, longitudinal section of a mature cone; 6, ovule; /, 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) 



