38 BOTANY 



nuclei.| This is the act of fertilisation when the two 

 nuclei melt into one another and become as one, though 

 the distinct chromosomes retain their individuality. 

 The stimulus which results starts the active produc- 

 tion of new cells by the repeated division of the original 

 fertilised egg cell, and ultimately tissues differentiate. 

 But as the number of those rods (chromosomes) in the 

 dividing nucleus is fixed, it would appear that the intro- 

 duction of the male nucleus should perpetually double 

 the number, and thus disturb the regular specific 

 character. This would take place were it not for what 

 is called the reduction division, which occurs in both 

 the sexes in the generation of cells immediately pre- 

 ceding the actual male and female nucleus. By this 

 means there is but half the normal vegetative number 

 in the two fusing cells, the egg cell and the male cell, 

 and so when they fuse the number of chromosomes is 

 doubled and thus brought back to the number normal 

 in vegetative cells for the particular species. 



There are innumerable interesting details connected 

 with the reproductive cells, and indeed the work of 

 cytologists is principally with such problems. The 

 extreme delicacy of manipulation and the accuracy 

 of observation which are required make the study pre- 

 eminently one for specialists, and also account for the 

 diversity of opinion which now prevails regarding many 

 fundamental questions. As each new individual of a 

 new generation arises from the divisions of the fused 

 egg and male cell, it is certain that its characters, which 

 are largely inherited, must have been transmitted in 

 the minute structure of those two cells. The male 

 cell is generally much smaller than the female, even 

 though that is itself microscopic, and as the male enters 

 the female it is said to lose all its outer protoplasm 



