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TEXTBOOK OF BOTANY 



a large tree, and that the youngest part. A root contains 

 the same tissues as does a stem or branch, although somewhat 

 differently arranged. 



147. The Staminate Cone. — The pine bears two kinds 

 of cones. It is not easy at first to think of these as corre- 

 sponding to the stami- 

 nate and pistillate 

 flowers of the cucum- 

 ber. But the cones 

 really are very primi- 

 tive flowers. The 

 two kinds of cones 

 differ in size, the 

 staminate cone beii^g 

 much smaller than 

 the carpellate. Both 

 are borne on the sama 

 tree. Staminate cones 

 (Fig. 70) grow in clusters ; carpellate cones grow singly. A 

 staminate cone has a large number of leaf -like or scale-like 

 parts, attached to a central stalk. As a matter of fact, the 

 central stalk of the cone is a branch, and the leaf -like struc- 

 tures that it bears are really leaves. These leaves are not 

 green and so cannot manufacture food, as foliage leaves do ; 

 their work is to produce spores, and so we call them spore leaves. 



Fig. 70. 



— A cluster o£ staminate cones of 

 the pine. After Stevens. 



A B C , _ 



Fig. 71. — A, a microspore lea£ of the pine as seen from below, showing 

 the pollen sacs. B, the same, seen from the side. C, a pollen grain; ii, the 

 generative cell ; b, the nucleus of the large vegetative cell ; c, the bladder- 

 like expansion of the outer wall of the pollen grain. 



