THE PIXE 



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 t-n-o kinds of work are performed by two distinct kinds 

 of leaves — the foUage leaves and the spore leaves. The 

 spores borne on the spore 

 leaves of the staminate cone 

 are very small, and so are 

 called microspores; therefore 

 the leaves of the staminate 

 cone are inicrospore lea'ces. 

 The under surface of each 

 microspore leaf (Fig. 71. .4) 

 is nearly covered by two 

 microspore sacs (or pollen 

 sacs) ; within these sacs a 

 great many microspores or 

 pollen grains are produced. 



148. The Carpellate Cone 

 (Fig. 72). — This, Hke the 

 staminate cone, is a branch 

 to which many spore leaves 

 are attached; since these 

 leaves bear large spores Fig. 72. — CarpeUateconesof the 



(macrospores) , they are called pi°e : o> a young cone ready for pol- 



, ", /-. ,-1 lination ; b, a cone one j-ear older, the 



macrospore leaies} On the • v.- u 1 j c 



'^ eggs in which are nearly ready for 



upper Siuf ace of each macro- fertihzation ; c, one stffl older, whose 

 spore leaf (Fig. 73, A) are macrospore leaves have spread apart, 



two small sweUings; these SteT'sLjns. "^ '° ^"^ "'' 

 are macrospore sacs or, as 



thev 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 caUed a micropyle. 



• The organ that is here called a macrospore Uaf is more complex than the micro- 

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



