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XX. — On a New Clover Disease. By P. Mouillefeet. 



[Translated from the 'Journal d' Agriculture Pratique,' 187i, pp. 667-G70, by 



W. Caekuthees.] 



The cultivator, after liavino: seen all his food plants in succession 

 attacked by various maladies produced by insects, vegetable para- 

 sites, or some conditions unsuited to their constitution, finds also 

 his plants grown for industrial uses suffering from destructive 

 plagues, and his fodder plants yielding gradually to diseases 

 more or less destructive. 



Plants are as a rule free from diseases in their natural state.* 

 Does, then, cultivation, by making them more luxuriant, render 

 them also more liable to be attacked by their enemies ? I have 

 no doubt that this is so. Indeed the stability of a wild plant can 

 be determined only after its struggle for life — that is, alter it has 

 overcome the various difficulties which beset it either from soil, 

 climate, parasites, or neighbouring plants striving for the pos- 

 session of the same ground : if it did not succeed then, like many 

 others, it would disappear in this struggle. The characteristics 

 whereby the plant has been able to conquer in this fight being 

 possessed by the surviving plants, it follows that, in the locality 

 where it naturally grows, it is in the most robust condition pos- 

 sible, and further that, wherever a plant does not enjoy con- 

 ditions identical with those of the locality whei'e its particular 

 characteristics were developed, it would be less robust and 'more 

 liable to the attacks of enemies, diseases, and competitors. Every 

 cultivator is well aware of this, and he therefore ascertains the 

 proper soil, exposure, and care needed by the plants he cultivates, 

 so as to prevent the loss of his crop, and secure all the advantages 

 he wishes. 



One cannot, unfortunately, always secure for a cultivated plant 

 conditions similar to those which it had in its natural state ; the 

 plant consequently either decays or produces modified varieties 

 suited to its altered condition. We have accordingly among cul- 

 tivated plants varieties suited to different soils and situations. 



On the other hand, the more highly a plant is cultivated, the 

 less it seems to rely on its own powers ; it is as if man's care for 

 it enervated the plant and made it unaware of the dangers that 

 surround it. Cultivated varieties are consequently liable to 

 many diseases. As far as plants have retained their natural 

 characteristics, they have not suffered ; but where the character- 

 istics produced by thousands of years of struggle for life have 



* This is too frequently assumed by writers, -without investigation. Wild plants 

 in their natural state are liable to the attacks of, and are often extensively 

 attacked by, parasitic fungi and insects. — Translator, 



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