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A TEXTBOOK OF BOTANY 



[Ch. VI. 4 



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

 other like divisions, always by 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 did the fertilized 

 egg cell from which 

 the plant has de- 

 veloped; and fur- 

 thermore it seems 

 reasonably 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 parent 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 structure chromatin 

 matter, that is, heredity material, derived 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 Vallisneria 

 spiralis, a common water plant ; x|. (After 

 Kerner.) 



