SPEEMATOPHYTES: GYMNOSPEEMS 



181 



which shut off the archegonia it carries the male cells 

 along, and so they are brought to the archegonia (Fig. 150). 



Fig. 150. Tip of pollen tube of pine, 

 showing the two male cells {A, B), 

 two nuclei (C) which accompany 

 them, and the numerous food 

 granules (Z>) : the tip of the tube 

 is just about to enter the neck of 

 the archegonium.— Caldavell. 



Fig. 151. Pollen tube passing through the 

 neck of an archegonium of spruce (Picea), 

 and containing near its tip the two male 

 nuclei, w^hich are to be discharged into the 

 egg whose cytoplasm the tube is just en- 

 tering.— After Strasburger. 



101. Fertilization. — Before fertilization can take place 

 the pollen-grains (microspores) must be brought as near as 

 possible to the female gametophyte with its archegonia. 

 The spores are formed in very great abundance, are dry 

 and powdery, and are scattered far and wide by the wind. 

 In the pines and their allies the pollen-grains are winged 

 (Fig. 116, />>), so that they are well organized for wind dis- 

 tribution. This transfer of pollen is called pollination, and 

 those plants that use the wind as an agent of transfer are 

 said to be anemophilous, or ^^wind-loving." 



The pollen must reach the ovule, and to insure this it 



must fall like rain. To aid in catching the falling pollen 



the scale-like carpels of the cone spread apart, the pollen 



grains slide down their sloping surfaces and collect in a 



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