118 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 
