124 Journal of Agricultural Research vol. xx, no. 2 



The plants in all stages of their growth were generally smooth, with 

 entire leaves. The young leaves, however, especially if grown in humid 

 atmosphere, were more or less hairy, mainly on the margins (PI. 11). 

 In older leaves hairs were observed only occasionally. It was noted 

 that isolated plants showed variations in the lobing, the leaves in some 

 instances being deeply notched (PI. 13). Experiments are being carried 

 on to determine the latitude and significance of these variations. The 

 appearance of some of these lobed leaves was very similar to that de- 

 scribed for Brassica napiformis Bailey (Sinapis juncea var. napiformis 

 Paill. and Bois), an observation which has much significance in view of 

 Bailey's statement (3) that — 



it is nearly related to pak-choi, and it may have sprung from the same species; but 

 it is clearly distinguished by its sharply toothed lvs. . . . 



In the early stages the cotyledons had the same general appearance 

 but were somewhat larger and thicker than those of the following mus- 

 tards, Brassica nigra (L.) Koch, Brassica juncea (L,.) Cosson, and Bras- 

 sica cernua Thunb. 1 They were about 1 cm. long and 1 cm. broad, 

 exclusive of the petiole, and are heart-shaped and smooth (PI. 11). The 

 first leaves were obovate, variously toothed, and somewhat crenate, 

 and were hairy, especially on the margin if the seedling had been grown 

 in very humid atmosphere. The leaves had a long petiole and a mid vein 

 extending at least one-third of the length of the blade (PI. 11). 



In the late rosette stage (PI. 14, 15) the leaves were arranged in a loose 

 cluster, the wings of the leaf extending along the greater portion of the 

 petiole, with the margin of the leaf more or less wavy and almost entire. 

 The time required for the development of the full-grown rosette stage 

 varies with the conditions for growth, being on the average about two 

 months when grown under normal conditions in the field and about 

 three months in the greenhouse. This period is materially shortened 

 when there are conditions decidedly unfavorable for growth, such as 

 insufficient nutriment, insufficient moisture, or too high temperature. 



The early flowering stage (PI. 16, 17) is characterized by a few erect 

 branches up to 1 foot in length. The early stem leaves are similar to 

 the rosette leaves, being almost entire, and obovate with long petioles. 

 The upper stem leaves are variously stem-clasping, entire, somewhat glau- 

 cous and somewhat lanceolate acuminate. Many of the leaves of the 

 secondary stems are not stem-clasping. The mature plant reaches a 

 height of about 2 or 2 l / 2 feet, branching, and often showing an enlarged 

 stem base (PI. 16, A). 



The flowers (PI. 17, B), which are somewhat larger than those of Bras- 

 sica nigra, B. juncea, and B. cernua, are in dense wide corymbs, \% inches 



1 Plants of Sinapis alba need not be considered in the comparison, since they are distinctly different from 

 the other forms and can readily be recognized by such characters as the abundance of typical hairs on the 

 entire young plant, as well as on the later plants, especially the pods, which themselves are readily distin- 

 guished by their typical shape. 



