CONIFERAE : THE SCOTS PINE 



313 



others, and the rest are absorbed. It has been calculated that in the Scots 

 Pine only about one per cent, of the potential embryos are matured. 



The maturing embryo, borne on the end of its elongating suspensor, 

 is thrust downwards into the substance of the endosperm. With 

 less regular segmentation than that in Angiosperms it matures into 

 the germ, which in the ripe Pine-Seed is cylindrical in form. It is 

 terminated by an apical cone, round which cotyledons, varying to 





K > ,f .^~ ,. v -; ;;. 



iiilii I:, C 



&k^&^'^' Wjj&$^& 



JlpPli-flP 



FIG. 255. 



Pinus Laricio, stages of embryology. A shows two tiers of four cells at base of 

 the archegonium. B shows three tiers, and the last division proceeding in the lowest 

 tier. C shows the tier of suspensors (s) elongating, and carrying forward the lowest 

 embryonic tier. (After Coulter and Chamberlain.) 



the number of fifteen, are arranged in a ring. The radicle is massive, 

 with the large root-cap characteristic of Gymnosperms. The female 

 prothallus persists as the nutritive endosperm; the nucellus is crushed 

 between the enlarging endosperm and the hardening seed-coat. The 

 seed is thus albuminous, which is the case for all Gymnosperms. Its 

 parts when mature correspond in nature and position to those of the 

 seed in Angiosperms (Fig. 256, I.). 



A period of rest is followed by germination of the seed. The 

 embryo, drawing upon the nutritive endosperm, enlarges, and the 

 radicle projects and grows down (Fig. 256, II.). The hypocotyl 

 elongates, and the seed is carried above ground. The tips of the 

 cotyledons remain within it till the store is exhausted, when it is cast 



