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or hy disease caused by a meager diet of unhealthy and iniiutritious 

 food is set down at six hundred thousand during the two years of 

 the potato bhght. This disease was not so destructive in 1847 as in 

 1816 and by 1818 it Jiad virtually disappeared. Some one has said 

 that if Great Britain had expended one dollar foi: investigating the 

 diseases of potatoes where she has spent a thousand dollars for per- 

 fecting the engines of war, the terrible famine might have been 

 averted. We now think it a relatively easy matter to keep the 

 Might in check by thorough spraying witli Bordeaux mixture. 



How THE Potato Has Been Improved. 



All plants have their origin in pre-existing plants. While the 

 young plant is always similar to the one from which it was derived, 

 it is never exactly like it in every detail. This arises from the fact 

 that all of the conditions under which the parent plant and its off- 

 spring grow are never exactly alike. The variations or differences 

 in the plants are usually exceedingly small in a single generation, 

 but occasionally they are wide, in which case they are called 

 ''sports" and are usually difficult to perpetuate. If successive 

 generations of plants are reared under continuously improved con- 

 ditions, there will be a continuous and accumulating variation from 

 generation to generation, which in time may come to be so great as 

 to make it difficult to discover a marked similarity between the wild 

 and cultivated forms of the same plant. 



When conditions are undisturbed bv man there is found to be a 

 fierce struggle for existence, the hardiest or those best suited to the 

 conditions preponderate, and this without any reference to the 

 wants of mankind. The farmer steps in and selects those plants 

 which give promise of being most useful or most beautiful and then 

 decreases or eliminates the struggle for these selected plants, by 

 destroying the plants which are least desirable, by fertilizing and 

 tilling the soil, by conserving moisture and by improving the physi- 

 cal conditions of the land, thereby making it more comfortable for 

 the plants which he has chosen. The selected or " improved " plant, 

 by reason of being more comfortable and better nourished, tends to 

 vary in one or more directions from the wild and unimproved types. 



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