306 



COLLEGE BOTANY 



grains) develop into very small three-celled Gaanetophytes, are 

 carried by the wind, some of them passing through the micropyle, 

 where they come in contact with the macrosporangiiim. They 

 develop tubes which grow through the nucellus, finally reaching 

 the archegonia. During this time the generative cell enters the 

 pollen tube and thence into the pollen chamber, divides into two 

 cells, the stalk cell and the body cell. This body cell gives rise 



FIG. 152. (o) Cluster of stamimue cones; (6) pollen grain; (c) pistillate cone; (d) scale from 

 pistillate cone snowing two ovules. 



to two ciliate sperm cells which swim in the fluid of the chamber 

 and finally reach the egg cell of the archegonium. In comparison 

 with the ferns, it will be noted that the number of sperms is 

 few and that they never escape from the tube. The result of 

 fertilization is the formation of a seed. 



The Finales includes the pine, larch, spruce, fir, cypress, 

 arhpr vitae, cedars and junipers. They are characterized by cone 

 fruits and are frequently referred to as " conifers." However, 

 in some of the species the cones are modified into berry-like 

 fruits, such as are formed in the junipers. There are about 40 



