GYMNOSPERMS 



433 



then very much smaller than those which contain ripe 

 seeds, spread their scales apart enough to admit some of 

 the drifting pollen. This pollen slides down the scales 



Fig. 224. — A, pollen-bearing (sUmiiiate) pine cone cut through lengthwise and 

 showing the relation of the pollen sacs {microsporangia) to the scales {microspore- 

 phylls). B and C, two views of a single sporophyll. D, enlarged cross section 

 of a single sporophyll, showing young pollen grains {microspores) inclosed within 

 the microsporangia. E, a single mature pollen grain containing what is now the 

 male gametophyte. 



until it lies at their inner ends, where they join the stem 

 part of the cone. This brings the pollen very near to the 

 ovules, those small oval bodies which are borne on the sur- 

 face of the scale, near its base. (See Figure 225.) These 

 bodies, as you have noted, are the megasporangia. It is 

 inside of these megasporangia that the ihegaspores are 

 produced, but by the time the pollen arrives, themegaspores 



