PIN US AUSTRIACA, OR P. LARICIO. 143 



In the pines the sporophylls are likewise gathered into 

 cones, but the two kinds of cones are unlike, due to 

 the difference in the sporophylls that compose them. 

 The megasporangia (ovules) are produced upon the 

 megasporophylls (carpels) and the microsporangia (pollen- 

 sacs) upon microsporophylls (stamens). The mega- 

 sporangium does not open and therefore the megaspore 

 is never shed, but germinates, as often in Selaginella, 

 within the tissues of the sporangium (ovule). There it 

 produces a female gametophyte which remains enclosed 

 within it, because it does not grow large enough to rupture 

 the spore-wall, yet the gametophyte bears distinct arche- 

 gonia. Since these archegonia are not exposed, the 

 male gametes cannot gain entrance to them by swimming 

 in water as heretofore, even were such a medium present. 



The microspore (pollen-grain) may begin its germina- 

 tion before it leaves the sporangium or afterward. Since 

 these pollen-grains are carried in quantity by the wind, 

 one or more of them may be deposited on the nucellus 

 of the ovule. From the inner wall of those favorably 

 deposited there develops a tube that grows parasitically 

 through the sporangium and spore- wall to an archegonium 

 on the female gametophyte. The male cells, which may 

 have been formed before or after the tube began to grow, 

 migrate to the end of the tube which passes to the neck 

 of the archegonium. At this time the end of the tube 

 opens and allows the male cells to escape. One male 

 cell unites with the egg, thus producing the oospore. 1 



1 It is noteworthy that in several other Gymnosperms ciliated sperms 

 have been found. Such structures suggest the existence formerly of a 

 watery medium enabling them to pass by swimming from the male 

 gametophyte to the egg. 



