Ch. XIII] 



THE CONIFERS 



521 



cells and two sperm cells, which later pass into the growing 

 pollen tube. The ovulate flowers, on either the same or a 

 different plant, are the familiar cones, formed of spirally- 

 arranged, ovuliferous scales specialized in construction. 

 Each scale is double, with a subtending and an axillary 



Fig. 366. — The life cycle of a Pine, chiefly Pinus rigida. 



Left, branches with clusters of staminate flowers, and cones, the latter 

 of the season, and one year old ; X $. Next, above, young cone in longi- 

 tudinal section, showing the double scales and ovules, X 3 ; scale from above, 

 showing the two ovules, X 15 ; staminate cone in longitudinal section, show- 

 ing stamens, X 2. Lower line, ovule in section, somewhat diagrammatic, 

 showing embryo sac and archegonia, with germinating pollen tubes, X 120 ; 

 pollen grain, and germinating pollen, X 100 ; ripe seed in section, showing 

 embryo, X 2, and seed with wing, X h- Finally, young seedling. (In part 

 after Strasburger, but chiefly from nature.) 



part, the latter bearing the two megasporangia or ovules, 

 which lie near its base with the micropyles downward and the 

 integuments flaring open. There is doubt, by the way, as 

 to the morphology of these inner scales, and two principal 

 views have been advocated with evidence in favor of each. 

 The outer scale may be the sporophyll, and the inner a 



