FOES AND FRIENDS OF THE PLANT 223 



in a covered box of wood or pasteboard and the necks of 

 bottles fitted into these so that the body of the bottle projects 

 outside the box. If such worms as army or cut worms are 

 placed in the box, together with the leaves on which they feed, 

 they will, when they have finished feeding, crawl into these 

 bottles, attracted by the light, and there change into moths. 



OTHER ENEMIES 



Root galls caused by nematofles. Very small worms 

 called nematodes cause swellings on many roots. On 

 the grape roots these look like the swellings caused by 

 phylloxera, but they are somewhat larger and firmer. 

 No remedy is known, but it is possible that roots which 

 resist their attacks may yet be found. 



The dying out of many plants, such as violets, after 

 being grown a long time in the-same place, is often caused 

 by nematodes. The remedy is rotation of crops. For 

 example, if beets are badly attacked by nematodes, 

 grain should be grown for a year or two in place of 

 beets, so as to starve the nematodes out. (California 

 Experiment Station, Bulletin 192.) 



Slugs and snails. These may be trapped by putting 

 cabbage leaves on the ground with the hollow side down, 

 so as to leave a little space between the leaf and the 

 ground, in which the snails gather during the night. 

 By going out early in the morning, you can catch and 

 destroy them. Choice plants may be protected by an 

 upright strip of zinc sunk edgewise into the soil so as to 



