GAMETOPHYTE AXD SPOROPHYTE. 



343 



while the other chroniosonie of eacli pair goes to the opposite 

 pole. The chromosomes here unite to form the daughter nuclei. 



Kach of these nuclei now 

 divide as shown in figure 

 409 (whether the chromo- 

 somes in this second divi- 

 sion in tlie mother cell split 

 longitudinallv or divide 

 transverselv has not been 

 Fig. 40S. definitely settled 1, and four 



nifferent stages in the separation of divided nutdei are formed in the 



L'-snaped cnroniosoines at the nuclear plate. (Alter 



Mottier) In podophyllum. pollen mother cell. The 



protopjlasm about each one of these four nuclei now surrounds 

 itself with a wall and the spores are formed. 



The number of chromosomes usually the same in a given 

 species throughout one phase of the plant. — In those plants 

 which have been carefully studied, the number of chromosomes 

 in the dividing nucleus has been found to be fairly constant in a 

 given species, through all the divisions in that stage or phase 

 of the plant, especially in the embryonic, or young growing 

 parts. For example, in the 

 prothallium, or gameto 

 phyte, of certain ferns, as 

 osmunda, the nmnber of 

 chromosomes in the di\id 

 ing nucleus is always twelve 

 So in the de\elopment of 

 the pollen of liliuui from 

 the mother cells, and in the 

 divisions of the anthend 

 cell to form the generati\ e 

 cells or sperm cells, there 



Fig. 409. 

 Second di\"ision 



Fig. 410. 

 Chromosomes uniting 



are always twelve chromo- °^^^i7 "\ p^V .""n^''^" ^* P9ies to form the 



a.i>^ cj.. . c _, c e 1 1 of podophyllum, nuclei of the four spores. 



somes so far as has been ch™mosomes at poles. (After Mottier.) 



found. In the development of the egg of lilium from the 

 macrospore there are also twelve chromosomes. 



