428 



PART IV. CLASSIFICATION. 



THE GAMETOPHTTE. As the G-ymnosperms are heterosporous, the 

 sexual generation is represented by a male and a female individual. 



The Male Individual is a prothallium developed from the micro- 

 spore as described on p. 405. It consists of two or more cells, one 

 of which grows out into a pollen-tube (see Fig. 240). 



Fro. 252. 4 Longitudinal section of the micropylar portion of the female prothailium of 

 Picea excelsa snowing two archegonia ( x 100) : c neck of archet*onium ; cl canal-cell. 

 If Surface-view of unopened neck of an archegonium ( x 250). C Pollen-tube penetrating 

 to the oosphere through the neck of the archegonium ( x 250). (After Sirasburger.) 



