114 



BOTANICAL GAZETTE 



[FEBRUARY 



flowers. On such plants the lateral branches which come into 

 bloom at the time when the main branch is producing normal 



flowers as a rule have normal 

 flowers from the first (figs. 1-3). 

 This coordination between 

 flowers opening simultaneously 

 on different branches as to kind 

 of development is very marked. 

 At first view, this abortion of 

 flowers appears to resemble the 

 blasting of flowers which fre- 

 quently occurs in all sorts of 

 plants as the direct effect of un- 

 favorable environmental influ- 

 ences, but here the phenomenon 

 is due primarily to internal 

 conditions. As grown in the 

 various cultures, the plants 

 came into bloom at various 

 times, some were producing 

 mid-bloom and potent flowers, 

 while other plants by them and 

 just coming into bloom showed 

 flower abortion. The abortion, 

 therefore, is essentially self- 

 induced. 



Flower abortion of the first 

 flowers is the rule among plants 

 of the varieties of B. pekinensis 

 which form leafy heads and 

 which are grown in the field 

 under conditions which favor 

 the development of heads. In 

 such plants, if left to bloom, 

 the flowering branches are at 

 first inclosed within the head. 

 At the time when the flowering branches first come to the light, 



Fig. 1. — Typical case of flower abor- 

 tion in plant of Brassica pekinensis; about 

 forty of first flowers on main axis abor- 

 ted; there are five such flowers on upper- 

 most lateral and none on second lateral, 

 showing correlation in morphological 

 character according to time of blooming. 



