THE SCHOOL GABDEN. 297 



spiny bracts. Seeds furnished with feathery pappus are 

 wind-distributed. On production of seeds the plant dies 

 down. 



The Creeping Thistle is a perennial which spreads from 

 a branching root below ground as well as by means of 

 seeds carried by the wind. It is a troublesome weed, diffi- 

 cult to eradicate. Stem erect, flower heads light purple, 

 numerous, of two kinds on separate plants, male globular, 

 female ovoid. Leaves narrow, pinnatifid. Order: Corn- 



Charlock (Brassica sinapis). This is one of the com- 

 monest weeds in cornfields. It is an annual with rough 

 stem of 1 to 2 feet, usually branched. Upper leaves rough, 

 toothed or lyrate, sessile ; the lower stalked, ovate or lobed. 

 Flowers pale yellow, -J-f in. diam. Sepals 4, narrow, 

 spreading ; petals 4 ; stamens 4 long and 2 short. The fruit 

 a siliqua from 1 to 2 inches long, with three faint veins on 

 the valves, and with cylindrical straight beak. Order : 

 Cruciferae. 



Charlock germinates early in spring, and besides being 

 a prolific and troublesome weed, is indirectly the frequent 

 cause of loss to agriculturists in harbouring the fungus 

 causing " finger and toe " disease in turnips. By main- 

 taining this parasite in the years intervening between the 

 turnip crops, it renders the disease difficult to eradicate. 



Charlock further serves in the spring to maintain the 

 turnip beetle (" turnip fly," " flea- bee tie ") before the 

 turnips are sown. This is a critical time for this beetle, 

 which on awakening to activity in the spring flies to the 

 charlock and related plants where it feeds. These small 

 beetles, on the turnip -seed leaves appearing above ground, 

 forsake the charlock for them, and when numerous they 

 may eat these up before the ordinary foliage leaves have 

 time to appear. If such happens the turnip plant is 

 killed (Fig. 159). 



Besides the foregoing weeds pupils should be set to 

 identify others which are common in their neighbourhood, 



