36 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



going species in every way. It is perhaps the most widely-distributed 

 pest of arable land in this country, and is by many considered the 

 worst weed of the farm (fig. 5). Seeds are produced in abundance and 

 possess great vitality. Growth is very rapid, and, as every farmer 

 knows too well, the fields yellow only too quickly when the pest is not 

 properly combated. On the farm spraying with a solution of copper 

 sulphate when the seedings are not over three inches in height kills 

 the weeds, but surface cultivation and thorough tillage and hoeing of 

 root crops are also necessary. In the garden regular hoeing will keep 

 it down. 



The cotyledons (fig. 6) are heart-shaped, smooth, and dark green, and 

 finally attain 2-5th inch in diameter (they grow somewhat after the first 

 true leaves appear). The petioles of the cotyledons also grow, being 

 at first short, and later about 4-5th inch long. 



Fig. 6. — Seedlings of Charlock (Sinapis arvensis L.). 

 a, cotyledon stage ; 6, first-leaf stage ; c, advanced stage. 



The first true leaves are about twice as long as broad, dark green 

 in colour, rather harsh and rough, while in shape they are spathulate 

 with irregular margins. (In turnips the first true leaves are smooth, 

 lighter green, and nearly equal in length and breadth, or irregularly 

 roundish.) 



As the plant grows the root becomes well-developed and fibrous, 

 with a stout central rootstock. The leaves grow larger, and are ovate 

 or lyrate and toothed ; the whole plant is rough, with hairy stem, and 

 when crushed in the hand stains a dirty green. The cruciform yellow 

 flowers give rise to longish two-valved pods. 



Shepherd's Purse is another annual cruciferous weed, the flowers 

 being small and white, and giving rise to nearly heart-shaped, laterally 

 compressed pods (fig. 7). This weed is frequently very troublesome in 



