THE SPRUCE FIR 



281 



\Vc will not follow the further development of the 

 embryo in Picea in detail. Its growth, with which 

 the cell-division keeps pace, goes on from June until 

 October, by which time the seed is ripe. The sus- 

 pensor at first serves to supply the young embryo 

 with food, but by the time the seed is ripe its func- 

 tion is at an end. The embryo then extends through 

 the whole length of the embryo - 

 sac, but is still enveloped in a 

 mantle of prothallus ; the middle 

 part of the prothallus has been 

 absorbed by the embryo for its own 

 nutrition. 



The structure of the embryo in 

 the ripe seed is shown in Fig. 115, 

 which represents it in longitudinal 

 section. 



The root is directed towards the 

 micropyle. The apex of the root is 

 protected by an enormously thick 

 root-cap. The root itself is still but 

 little developed, while the hypocotyl 

 occupies nearly half the length of 

 the embryo. The cotyledons are 

 numerous, generally numbering about eight. This is 

 not, however, a character common to Conifers generally, 

 for many of them, such as the Yew, have only two. 



The cone opens in the spring, and the winged seeds 

 are scattered by the wind, as already described. 



When the seed germinates, the root grows out 

 through the micropyle, and turns downward into the 



FIG. 116. Young 

 seedling of Picea. 

 d, cotyledons ; h, 

 liypocotyl ; r, roots. 

 Natural size. (After 

 Kcrner.) 



