REMEDIAL MEASURES. 163 



be killed while still adhering to the outside of 

 the seeds, tubers, etc., before germination. 

 " Finger and Toe " due to Plasmodiophora has 

 been successfully dealt with by the application 

 of lime, but we do not know whether the 

 effect is owing to indirect actions in the soil, to 

 direct actions on the plasmodia, or to the in- 

 creased production of root-hairs induced by 

 liming. 



Phylloxera has been treated by plunging into 

 the soil near the roots small blocks of some 

 slowly-soluble medium, such as gelatine, impreg- 

 nated with carbon-bisulphide, the volatile fumes of 

 which kill the insect, and even more drastic 

 remedies have been tried along similar lines. In 

 America orchard trees infested with insects or 

 fungi have been covered one by one with light 

 tents, and the vapours of prussic acid, burning 

 sulphur, and other poisons allowed to act inside 

 the tent. In all such cases it must be remembered 

 that uncontrolled ignorance of the properties of 

 poisons on the part of the operator may lead to 

 disaster, and the same applies to the much easier 

 treatment of greenhouses, and cases where poisoned 

 food is laid about for insects or vermin. 



Attempts, not altogether unsuccessful on the 

 small scale, have also been made to introduce epi- 

 demic diseases among rats, mice, and locusts and 

 other insects, by inoculating some of them with para- 

 sitic bacteria or fungi {Empusa, Isaria, etc.), and 

 then allowing them to run loose in the hope that 

 they will communicate the disease to their fellows. 



