462 Identification and Eradication of Weeds, [sept., 



Peter has shown * that they may thus retain their germinative 

 capacity for forty years. On the other hand, we find it stated f 

 that "The seeds are longer-lived than most others of the Mus- 

 tard family. Recent research work showed that they do not 

 retain their vitality beyond fifteen years." It is probable that the 

 vitality is chiefly dependent on the natural conditions to which 

 the seeds are subjected, the period being much longer in some 

 instances than in others. In dealing with charlock and wild 

 radish, Pitt wrote, over 100 years ago, that "as they are very 

 quick of growth, and perfect their seeds expeditiously, it is 

 not uncommon for these plants to shed their seeds at the rate 

 of several bushels per acre, and, as it is well known that the 

 seeds will vegetate after laying many years in the ground, 

 it is no wonder they should produce a plentiful crop." J The 

 seeds are frequently brought to the surface by an extra deep 

 ploughing, and while charlock disappears when land is laid 

 down to grass, it is almost certain to spring up when old grass 

 land is ploughed. Owing to this inherent vitality of the seed, 

 the weed is the more difficult to deal with. 



The charlock pod is 1-2 ins. long, with a straight deciduous 

 beak; it is on a slender pedicel, is two-valved, and, when ripe, 

 opens longitudinally, to permit the seeds to fall out [cf. 

 Raphanus Raphanistrum, p. 465, in which the pod breaks into 

 jointed pieces] . The seeds of charlock cannot, unfortunately, 

 be easily distinguished from those of the turnip, which are of 

 about the same size, but not quite so dark in colour, while 

 their surface is rather rougher in texture, and they have not 

 the same pungent taste : adulteration with dead charlock 

 seeds was formerly common. 



Seedlings. — An examination of the first seedling stage 

 (Fig. 1, b) shows that the root is fibrous and slender, and the 

 hypocotyl stout, white, smooth, and shiny. As in most other 

 Brassicas, the cotyledons are heart-shaped ; one is larger than 

 the other, and the notch or sinus at the top is rather deep and 

 broadly V-shaped. The cotyledons are dark green above, 

 sometimes with a rather reddish tinge beneath, especially in 



* Deut. Landw. Presse, July 24th, 1909, p. 636. 



t Farm Weeds of Canada, Canad. Dep. Agric, 2nd ed. , 1909, p. 93. 



% William Pitt : " On the Subject of Weeding ; or The Improvements to be 

 Effected in Agriculture by the Extirpation of Weeds." — Communications to the 

 Board of Agriculture, Vol. v, 1806, p. 248. 



