9 
lias been found useful. This may be described as a 
horizontal drum revolving at high speed between two 
carrying wheels, the drum being furnished with rows of 
combs protruded and withdrawn by machinery, by which 
the weeds entangled amongst the teeth are pulled up or 
the flowering heads torn off. Commonly, however, weed¬ 
ing under careful superintendence, so that the work may 
be thoroughly done, seems the main cure. 
Where a stubble is foul with Charlock and other weeds 
it is a very good plan, as a means of prevention, to run 
the chain harrows over it, or brush it, and so shed the 
ripe seeds. These will sprout at once, and the young 
weeds from them will be destroyed by after cultivation ; 
whereas, if they are left to ripen and shed gradually, 
these seeds are ploughed in too deeply to germinate at 
the time, and in the next ploughing they will be thrown 
near the surface, and will then sprout, and give us a 
growth of weeds along with the growth of the crop. 
The presence of shelter in the winter, and of plants 
suitable for food to the wintered Flea-beetles and their 
Maggots in the spring, seem to be the conditions to 
which we owe attack in ordinary seasons; and when, as 
in 1879 and part of 1880, we have such long continuance 
of wet weather as makes it impossible to clean or culti¬ 
vate the land properly, attack may be looked for as likely 
to occur in excessive amount. 
The long rains were followed by an unusually large 
appearance of Charlock in various places from the North 
of Scotland to the South of England, and when the dry 
hot weather of May, 1881, occurred, which was precisely 
suited to propagation and spread of the Fly, it burst 
forth like a plague upon us. 
Weather influences bear strongly on the amount of 
injury caused by Fly attack. 
It is most hurtful in hot dry weather accompanied by 
bright sunshine, because the Fly is then in its fullest 
vigour, propagates most freely, and also flies well, and 
consequently spreads far, whilst the young Turnips in 
such circumstances fail quickly under attack, but when 
