112 BOTANICAL GAZETTE' [February 



from seeds furnished by the Office of Foreign Seed and Plant 

 Introduction of the United States Department of Agriculture. 

 The seeds of the strain of B. chinensis which have been grown were 

 obtained from China by a Chinese student at Columbia University 

 for the gardener in charge of the greenhouses belonging to the 

 University, and the writer obtained seeds from the first lot of plants 

 there grown. From controlled cross-pollinations between plants 

 of the two species, seeds were obtained and plants of an Fj hybrid 

 progeny were grown. 



The greater number of plants have been grown in pots in a 

 greenhouse and brought into bloom during the winter and spring 

 before they could suffer from the heat of summer. When thus 

 grown, plants of the head varieties of B. pekinensis form a rather 

 loose headlike rosette, much smaller and less compact than when 

 grown under field culture, after which they shoot up into flower. 

 Plants of the Nanking variety of B. pekinensis and plants of B. 

 chinensis do not form a head even under the best of field culture; 

 a very loose rosette of leaves develops, and this grades up into the 

 leaves of the flowering stem. Pot grown plants of these species 

 closely resembled field grown plants except that they were smaller. 



A few plants of all strains have been grown to full maturity 

 in the garden, both as spring and autumn crops. Such plants were 

 larger than the pot grown plants and more flowers were produced, 

 but their behavior in respect to fertility and sterility was identical 

 with that of plants grown in the greenhouse. Special effort was 

 taken to make controlled self-pollinations throughout the entire 

 period of blooming. 1 Numerous plants have bloomed alone or in 

 isolation from other species of Brassica, both in the greenhouses and 

 in the field, and hand pollinations were made from one to four days 

 apart as long as the plants bloomed. The plants not grown in iso- 

 lation were "bagged." Flowering branches were inclosed in glassine 

 paper bags on or within a day or two following the opening of the 

 first flowers; the plants were visited at least twice a week (at first 



1 During the winter season of 1919-1920 the writer was greatly aided by the 

 voluntary assistance of Mrs. Mortimer J. Fox. Miss Hester M. Rusk has assisted 

 in the research and made many of the pollinations of the plants grown in 1920-1921. 

 Through this efficient assistance and cooperation the many pollinations necessary to 

 the research were accomplished. 



