468 Identification and Eradication of Weeds, [sept., 



this weed is that it serves as a host for insect pests, and 

 especially of the white rust, Cystopus candidus, which is so 

 harmful to cultivated crucifers, e.g., wallflowers, cabbages, 

 and related crops. 



Seeds. — The seeds are long-oval, flattish, up to J- T in. 

 (i mm.) long, and rusty-brown in colour, with a dull, punc- 

 tured surface (Fig. 3, a). They are found in clover and grass 

 seed samples. " When put in water it develops a large amount 

 of mucilage and a covering of rather long, but very fine, trans- 

 parent hairs." * 



Seedlings. — Seeds of Shepherd's Purse sown in May, 191 1, j 

 gave rise to well-grown seedlings in seven days. The first 

 stage seedling has a thread-like root, and a slender, smooth 

 hypocotyl, which is whitish below to very light green above. 

 The cotyledons are small, oval, smooth, green, opening until 

 horizontal, and narrowing into a rather short, broad petiole ; 

 in the very early stage they are only about y 1 ^ in. long (2*5 

 mm.), not including the petiole (Fig. 3, b and b'). 



In the second stage the cotyledons are perhaps J in. long j 

 (4 mm.). The first leaves are radical, simple, oval to "round- 

 oval," somewhat hairy above and beneath, and are stalked, 

 the stalk being sparsely hairy (Fig. 3, c). 



The seedling grows rapidly, and in the next stage (Fig. 3, d) 

 the leaves are larger, increasingly lobed and cut (pinnatifid), 

 sparsely hairy, and tufted, or growing in rosette form. The 

 root is a branched and fibrous taproot. 



Mature Plant. — The advanced seedling soon sends up a ! 

 branched stem, which may be 18 ins. in height, and bears 1 

 but few leaves, these being oblong or lanceolate, often I 

 toothed, and clasping the stem (Fig. 3, e). The flowers J 

 (Fig. 3, e') are white, about T V in. in diameter, and 

 occur on slender pedicels in long loose clusters (racemes); j 

 they give rise to somewhat triangular (almost obcordate | 

 flattened pods, resembling a shepherd's "sporran," whence j 

 the name of the plant. The pods easily distinguish it from 

 other cruciferous plants. About ten or a dozen seeds are con- 

 tained in each of the two cells of the pod, and a single plant j 

 may produce some 4,500 seeds (Maier-Bode). 



Prevention and Remedy. — The chief means of reducing j 



* Farm Weeds of Canada, Canad. Dept. Agric, 2nd ed., 1909, p. 84. 



