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 being 

 much smaller than 

 the carpellate. Both 

 are borne on the same 

 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 of staminate cones of 

 the pine. After Stevens. 



FIG. 71. A, a microspore leaf of the pine as seen from below, showing 

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

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

 like expansion of the outer wall of the pollen grain. 



