458 SPERMATOPHYTES (SEED PLANTS) 



and spread apart and the seeds fall out. Although the seeds are 

 protected between the scales, they are not enclosed as the seeds of 

 a Bean or an Apple are. They are on the outside of the structure 

 which bears them, whence the name Gymnosperms. 



The seeds are dispersed by the wind and usually do not germi- 

 nate until the next spring after dispersal. In germination the 

 axis (hypocotyl) of the sporophyte elongates, forming an arch 

 and drawing the cotyledons out of the ground, and at the same 

 time the tap-root at the lower end of the hypocotyl becomes 

 established in the soil. By the straightening of the hypocotyl 

 the green cotyledons are lifted into the air and sunlight, and the 

 sporophyte soon becomes independent of the seed. After a 

 number of years of growth, it begins to bear strobili, thus com- 

 pleting the life cycle of the Pine as shown in Figure 406. 



In summarizing it should be noted that the Pines have two 

 kinds of strobili, reduced gametophytes, pollination, and pollen 

 tubes, features which were pointed out as the notable ones of the 

 Cycads. But in contrast with the Cycads the Pines have more 

 massive sporophytes with leaves bearing no resemblance to those 

 of Ferns, and also the Pines have abandoned swimming sperms 

 and conduct the sperms to the eggs through pollen tubes. 



In pines the cones mature the second fall after pollination, but 

 in some genera of the pine family, as the Spruces illustrate, sexual 

 reproduction proceeds more rapidly, although similar in nature, 

 and the cones mature the fall following pollination. 



