SECT. I 



MORPHOLOGY 



95 



tion of the chromosomes of the gemini takes place in the reduction 

 division. 



The nuclei of normal sexual cells are naturally haploid. A 

 reduction division must have taken place in their formation at some 

 earlier developmental stage of the organism. 



Sporogenesis. — The suggestion has been made to call the cell in 

 which the reduction division occurs the gonotokont (^^). Since a 

 second division (the homotypic, p. 86) follows immediately on the 

 reduction division, we find that a division into four is a chai-acteristic 

 feature of the process of meiosis (p. 8G). The cells resulting from 

 this division into four may form a row but usually lie side by side. 



Fig. 102.— In A a-J the process of meiosis in a spore mother cell is diagramatically represented. 

 In B a and b spore-formation by successive cell divisions in one plane, and in c and 

 d by simultaneous tetrahedial cell-formation. 



This happens especially when the gonotokont has a spherical shape, 

 as is the case, as a rule, not only in plants but in animals. An example 

 of this is seen in the spore mother cells, which would more accurately 

 be termed spore grandmother cells, of the higher plants; these separate 

 from connection with the surrounding tissues of the plant. In them, 

 after the first division of the nucleus (reduction division) a cell division 

 follows. In the two daughter cells the homotypic divisions of the 

 nuclei follow in the same plane, or in planes at right angles to one 

 another ; the orientation of the grand-daughter cells depends upon 

 this. In other cases the reduction division is not accompanied by a 

 cell division but the two daughter nuclei divide and the resultant 

 nuclei become tetrahedrally placed. Then cell walls form simul- 

 taneously between them, dividing the spore mother cell into four 



