ic6 THE CULTURE OF VEGETABLES 



root, which contains large proportions of potash, phosphorus, and sul- 

 phur, with smaller proportions of magnesia and lime, without which 

 the plant cannot prosper. A succession of heavy crops of Potatoes 

 on the same land may be said to take from the soil all its available 

 potash and phosphates, and this crop will not, like some others, take 

 soda instead of potash when the last-named alkali runs short. Here 

 then is a chemical reason for change of soil. Another reason is 

 found in the history of the species of fungi that prey on the Potato 

 when its growth is checked by heavy rains and a low temperature. 

 These leave their spores in the soil, like wolves hiding in ambush, to 

 destroy the next crop. They are powerless to attack any other crop ; 

 therefore a suitable rotation gives them time to die out and leave the 

 land clean as regards the peronospora and other parasites that destroy 

 our Potato crops. As for occasional change of seed, that rests on an 

 old experience, and should scarcely need enforcing. One word may 

 be said here by way of explanation, and it is this : the seed house 

 which aims to put a good article in the market adopts measures 

 altogether different to those followed by the majority of persons 

 who have not been trained to the business. It is a common 

 experience to find that those who save their own seed from year to 

 year have as a result a constantly declining strain, so that every year 

 the growth is weaker, less true, and less profitable. It is so all 

 through, but is especially the case with Potatoes. We do not say 

 that all who save their own seed act unwisely, for some are most 

 expert in the business. But we do say that seed saving is not 

 learned in a day, and many who think they save shillings when they 

 save seeds, actually lose pounds by burdening themselves with a bad 

 article. The art of roguing is but one part of the seed-saving 

 process. There is the proper storing, and the selecting and sorting 

 processes, to which eyes and hands must be trained, and there must 

 be no scruple about the sacrifice of false, ugly, immature or diseased 

 samples. The point we have in view is to advise the Potato grower 

 to be sure of his seed, and when a doubt arises as to the purity and 

 healthiness of the sample at command, it may be remembered that 

 the seed merchant practises methods of purgation that produce the 

 best seed possible, while by growing his seed in many different parts 

 of England, and on very diverse soils, he can furnish stocks which 

 make an admirable change of seed for any description of land. 



In certain districts of the north, it is not unusual to obtain two 

 crops of Potatoes in one season from the same plot of land. The 

 return is so profitable that it is surprising a similar proceeding is not 



