ROOT CROPS. 217 



asserts, that cutting off the blossoms also increases the yield. 

 He puts the additional yield up to the high figure of one ton to 

 the acre. The early formation of the tubers is said to delay 

 the blooming; while the blooming and the ripening of seed 

 delay tiie growth of the tubers. Hence the practice of com- 

 pelling some early kinds to produce blossoms and seeds 

 contrary to their habits, namely to remove the tubers from the 

 hill as they are being formed. By this means all the energies 

 of the plant are concentrated upon the stem and the organs of 

 fructification, and blossoms and seeds are produced. 



The time of planting, the quantity of seed, the kind of soil, 

 the amount and quality of manure, the method of culture and 

 preservation, are all worthy of special notice ; but the limits 

 assigned to this essay forbid us to enter upon them. 



4. Diseases. — All other disorders to which potatoes are 

 liable, are overlooked in the presence of the modern rot. A 

 disorder so wide spread and so destructive has, of course, ai- 

 tracted the attention of practical and scientific men in many 

 countries; and all the resources of learning and skill have been 

 applied to the investigation of its causes, and its remedies, hith- 

 erto, with small success. At least they have only shown, not 

 what the cause is, but what it is not. The universality of the 

 evil proves that it could not have been occasioned by blight, 

 insects, climate or soils ; for it is not to be supposed that these 

 were everywhere, and, at the same time, cooperating to one 

 end. Besides, these causes existed long ago, and did not pro- 

 duce the results we now witness. As to insects and fungi, they 

 may be regarded rather as effects, than as causes of the dis- 

 ease. A true theory must account for all phenomena, and a 

 true remedy reach all similar cases. In both points recent 

 researches have signally failed ; and from various quarters we 

 learn that investigations are abandoned in despair of attaining 

 a satisfactory solution of the difficulty. 



I am not disposed to increase the number of unsuccessful 

 physicians ; but shall only suggest a few thoughts respecting 

 the proximate causes or aggravations of the disorder. I sup- 

 pose they are nearest to the right, who consider the continued 

 propagation of the plant without renewal from it original 

 climate and soil, and its over-stimulation hj strong manure, as, 

 28* 



