142 



FUNDAMENTALS OF CYTOLOGY 



with both nucleus and cytoplasm. In other species thej^ appear as 

 nuclei A\dth no cytoplasm distinct from that of the sac or pollen tube. 

 Often the sperm nuclei have a worm-like form. One of the gametes 



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Fig. 104. — Syngamy in Crepis capillaris. 1, upper part of embryo sac. Material just 

 discharged from pollen tube above egg contains two sperms in one mass and an irregular 

 body. Polar fusion nucleus below. 2, two sperms at tip of egg; one synergid visible. .3, 

 one sperm in contact with egg nucleus, the other moving toward the polar fusion nucleus; 

 72 minutes after pollination. 4, sperm spread out on surface of egg nucleus. 5, sperm 

 spread on surface of polar fusion nucleus. 6, sperm beginning to transform inside egg 

 nucleus. 7, 8, later stages in alteration of sperm in egg nucleus. 9, embryo sac about 32 

 hours after pollination. The embryo is developing with a diploid chromosome comple- 

 ment, and the endosperm with a triploid complement. {After H. Gerassimova.) 



applies itself to the egg and fuses with it. The nucleus can be followed 

 through all the stages leading to its union with the egg nucleus, but the 

 sperm's cytoplasm, even if it is recognizable before syngamy, has not 

 been definitely proved by direct observation to enter the egg. There is 



