Ltveb Rot in North Wai 



L920-21. 



159 



L. trunadula. Colonies of the snail inhabiting land of different 

 types were watched. For instance, in Anglesey, strong and 

 widespread colonies on limestone, sandy, and I n avy marshy 

 soils were under observation; while in the other counties colonies 

 on various grades of soil were similarly studied. As had be Q 

 previously noted* the resistance of the snail to drought is en- 



IncKe6 



10 







































































































* 







I 





W- 





















4 





\ ' v 



\' * 

 \ * 

























-n <— 



' \ k 



' \ * 









/ 



/ 





h 



























/ 



/ 



— v._ .. 







t 











f 





\ i 







\ 



\ 



\ 



\ i 



1 



1 



! 











s 









\ i 

 * 













X *19*0 » G 1921 



FIG. 1.— Monthly Rainfall for 1920 and 1021 at Penrhyn Gardens, Bangor. 



tirely dependent upon the environment. In many instances 

 the snails were present in numbers on grass land that was wet, 

 but not actually under water, and such spots dried out rapidly. 

 In such situations survival depended upon three factors (a) the 

 amount and type of vegetative covering present, (b) soil charac- 

 ters, (c) whether the soil was level, or had cracked or been 

 trodden (" poached ") much by stock. If the land was bare 

 and level, death speedily took place, but as the protection 

 afforded was increased by long and dense vegetation or by -ha<ic 



* Parasitology, op. cit., pp. 251-2 and p. 2f)7. 



