THE PINE 



123 



We saw that the green leaf of the fern does two kinds of 

 work : it manufactures food and it bears spores. In the pine, 

 these two kinds of work are performed by two distinct kinds 

 of leaves the foliage leaves and the spore leaves. The 

 spores borne on the spore 

 leaves of the staminate cone 

 are very small, and so are 

 called microstores; therefore 

 the leaves of the staminate 

 cone are micros pore leaves. 

 The under surface of each 

 microspore leaf (Fig. 71. A) 

 is nearly covered by two 

 microstore sacs (or pollen 

 sacs) ; within these sacs a 

 great many microstores or 

 pollen grains are produced. 



148. The Carpellate Cone 

 (Fig. 72). This, like the 

 staminate cone, is a branch 

 to which many spore leaves 

 are attached ; since these 

 leaves bear large spores 

 (macr os pores) , they are called 

 macros pore leaves. 1 On the 



FIG. 72. Carpellate cones of the 

 pine : <z, a young cone ready for pol- 

 lination ; b, a cone one year older, the 

 which are nearly ready for 



macrospore leaves have spread apart, 

 allowing the seeds to drop out. 

 After Stevens. 



upper surface of each macro- fertilization; c, one still older, whose 

 spore leaf (Fig. 73, A} are 

 two small swellings ; these 

 are macrospore sacs or, as 



they are more commonly called, ovules. Each sac is sur- 

 rounded by an integument, excepting that at one end, where 

 the integument projects in the form of two horns, there is a 

 narrow opening through the integument called a micropyle. 



1 The organ that is here called a macrospore leaf is more complex than the micro- 

 spore leaf, and there is a question as to whether it is not really more than a leaf. 



