356 



GYMNOSPERMS 



its starch and subsequent foodstulTs, but its cell walls break down, 

 so that a cavity is formed behind the embryo. The tissues of the nu- 

 cellus also break down. While this breaking-down of tissues is going 





Fig. 340. — Reduction in the number of cotyledons: A-E, Cedrus lihani: A, ordinary 

 embryo, with no fusion of cotyledons; B and C, earlier and later stages in fusion; D, the 

 large cotyledon has probably arisen by fusion; E, reduction in number of cotyledons by 

 abortion of a cotyledon, the small cotyledon (third from the left) is disorganizing; 

 F, G, Piuiis banksiana: F, two cotyledons fusing; G, transverse section of the group of 

 cotyledons, indicating two groups; s, stem tip; X32. — .\fter Buchholz.'* 



on around the embryo, the cells at the periphery of the gametophyte 

 divide and grow actively, until the embryo completes its intrasemi- 

 nal development. 



