Ii8 BOTANICAL GAZETTE [February 



This type of sterility, of course, is very common in all sorts of 

 flowering plants, and is clearly associated with old age and death 

 of the entire plants or of the individual flowering branches. In 

 these species of Brassica it is unusually conspicuous, and begins to 

 develop when growth has ceased and parts of the plant, especially 

 the basal leaves, are dying or even dead and falling from the plant. 

 Flowers that have aborted or developed poorly at the beginning 

 of the period of bloom, and those in which development is arrested, 

 are all functionless. Their failure to produce fruit is entirely 

 independent of any sort of fertilization. It is clearly due to 

 impotence. 



II. Proliferation 



In a few plants of several strains of both Brassica chinensis 

 and B. pekinensis, noticeable axial proliferations develop. The 

 axis anlage inclosed within the carpels of the pistil grows and 

 branches until it bursts open the pistil. The pedicel of the flower 

 enlarges; the proliferated branch may become several inches long 

 and bear as many as twenty-five flowers, many of which are able 

 to function in seed production. Proliferation may be regarded as 

 the sterilization of a pistil by vegetative growth of the tissue 

 beneath and within it. In the end it is the expression of a tendency 

 to vegetative vigor which culminates in the production of many 

 more pistils and stamens. 



Although proliferation is often irregular in its distribution, it is 

 most frequent during the earlier portion of the period of bloom. 

 Frequently it is most highly developed in the first flowers of plants 

 which show little or no flower abortion, but it often does appear 

 later. The last flowers of those which open normally as a rule are 

 free from proliferations. This abnormality is certainly to be 

 regarded as an expression of excess vegetative vigor, as a result of 

 which the axis about which flower parts are grouped resumes 

 active vegetative growth. The stamens in many of the flowers 

 whose axes proliferate seem to be normal, but the pistils are not 

 productive of fruit. 



Another type of excessive vegetative vigor is seen in the develop- 

 ment of green leaves at the base of each flower, giving a leafy 

 inflorescence. This has only been observed in a few plants, and 



