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TEXTBOOK OF BOTANY 



pendent upon the food that comes through the female gametophyte 

 and the nucellus. Pine embryos multiply vegetatively during their early 

 stages of development horn, the zygote; a young pine ovule may con- 

 tain four or more embryos (Fig. 327), but usually only one of them is 



Fig. 327. The formation of the embryo of a pine from the fertihzed egg (A) 

 to the development of four rudimentary embryos. Only one of the embryos may 

 survive in the mature seed. After Buchholz. Courtesy of the World Book Co. 



fully developed in the mature seed. It is usually about a year from 

 fertilization to the fullv formed embrvo. 



The seed. Two years have thus elapsed since pollination. In the mean- 

 time the integument has grown and become the seed coat, the nucellus 

 has been reduced to a membranous layer, and the female gametophyte 

 ("endosperm") has continued to grow (Fig. 328). The embryo consists 



FEMALE GAMETOPHYTE 

 EGG IN ARCHEGONIUM 

 POLLEN TUBE 

 EMBRYO 



WING 



EMBRYO 



FEMALE GAMETOPHYTE 

 (ENDOSPERM) 



Fig. 328. Diagrammatic representation of the forerunners of the various parts 



of a pine seed. 



