284 



A TEXTBOOK OP BOTANY 



[Cn. VI, 4 



«fefe>^ V. ,H, 



original male and female set (Fig. 195). Then follow 

 other like divisions, always b}' the same method, though 

 presently proceeding more actively in some places than 

 others, — with the result that first an embryo, then a seed- 

 ling, and finally an 

 adult plant is pro- 

 duced. When, now, 

 the cells of the adult 

 are examined, their 

 nuclei are found 

 each to contain ex- 

 actly the same num- 

 ber of chromosomes 

 as chd the fertilized 

 egg cell from which 

 the plant has de- 

 veloped ; and fur- 

 thermore it seems 

 reasonalily certain 

 that these chromo- 

 somes of the adult 

 are the exact indi- 

 ■vidual descendants 

 of those in the fer- 

 tilized egg cell, and 

 therefore of those 

 contributed by the 

 original ]iarent male 

 and female cells. 

 This phase of our 

 subject appears clearly in a later diagram (Fig. 219). Thus 

 the adult would have in every cell of its strut'ture chromatin 

 matter, that is, heredity material, deri\-(Hi from both of its 

 parents. This arrangement helps us to understand how 

 an individual can resemble either father or mother in any 

 feature of its structure. 



Fig. 196. — The pollination of Vnllisncria 

 spiralis, a common water plant ; X -j. (After 

 Kerner.) 



