1914] COULTER— REPRODUCTION IN PLANTS 351 



it has developed a well nourished body, cells in the apical region 

 become checked in vegetative activity, the substances character- 

 istic of gametes appear again, and eggs are produced. 



We still face the fact that there are cell fusions, even pairing 

 and fusing cells, which show the presence of the mutually attractive 

 substances characteristic of gametes, but which do not represent 

 the sex act. All such cases may be explained as evidences of 

 declining vigor of the protoplast concerned, but if pairing and 

 fusing are not peculiar to gametes, although universally displayed 

 by them, what is the esssential feature of gametes, or, in other words, 



of the sex act ? 



made 



are pairing cells whose fusion results in the production of a new 



means 



individual. This 



attractive substances formed in connection with declining metab- 

 olism, gametes possess nuclei so constructed that when the two 

 fuse, a new individual is produced. This does not mean that 

 neither gamete can produce a new individual alone, for partheno- 

 genesis would contradict this. It means ordinarily that a new 

 individual can be produced only after the nuclei have fused. In 

 other words, the essential feature of sexuality must lie in the 

 peculiar structure of the nuclei of the sexual cells. Whether this 

 peculiar structure is chemical or physical, or both, must be a matter 

 of opinion based on no direct evidence. Nor can it be true that 

 gametes are peculiar in containing the factors of heredity, for these 



must 



all the cell generations 



leading to the gametes. Gametes furnish the opportunity for 

 heredity to express itself, but so do spores, and so does vegetative 



m 



gametes 



do they develop this peculiarity ? 



seems 



make it clear that this gametic peculiarity, whatever it may 



in 



plants this division occurs generally in connection with 



Among 



in 



connection with gamete-formation. In case the reduction division 



connection with snore-formation 



the sperm. In any event, 



