Fig. 58.— Development of male gametophyte iu Aselepiae. A-B, A. Corwuti; C-E, A. 

 tuberosa. A, section of young microsporangium showing archesporial cells; B, 

 portion of the single layer of elongated, mother-cells; C\ later stage showing two 

 mother-cells, the lower one dividing and showing 10 chromosomes, the gametophyte 

 number; 7>, second division of mother-cell, by which the row of four microspores is 

 formed; F, microspore showing tube nucleus (t) and generative nucleus {g). A, 

 x 200 ; B-E, x 800.— After Frye .« 



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