Change of Seed. 323 



changed. But as wheat is not a native production of Bri- 

 tain, it has here a great tendency to degenerate, more espe- 

 cially in the northern districts ; and it degenerates rapidly y 

 if the seed be sown, year after year, in the neighbourhood 

 where it was produced. Nor is it sufficient that the seed 

 be procured from a different field; it ought also to be taken 

 from a different soil, and a different atmosphere ( 7a ). 



Besides preventing a degeneracy in the quality of the 

 grain, a judicious change of seed, has a tendency to effect an 

 earlier maturity in the crop; an object, in many cases, of the 

 greatest moment. It is well known, that a change of con- 

 stitution in plants, originating from the situation in which 

 they have been placed, is commonly transmitted to their off- 

 spring. Plants propagated from seed produced in a warm 

 sandy soil, will therefore grow quickly, in whatever soil the 

 seed is sown ; and plants from seed produced in a cold stiff 

 soil, are late of growing, even in a warm soil. Hence the 

 advantage of changing seed from a warm to a cold soil ; 

 for though seed from a warm soil, will not grow so fast in a 

 cold, as in a warm soil, it will, however, always grow more 

 quickly than seed from a cold soil ( 73 ). The quantity also will 

 be increased. From an experiment made by the celebrated 

 Lord Kames, it would appear, that the produce of changed 

 seed, exceeds that of old seed, at the rate of nearly twenty- ! 

 six per cent. ( 74 ). The farmer however, ought not to alter 

 his seed, while it gives him fair and reasonable satisfaction, 

 unless he has every reason to be convinced, that better can 

 be obtained by a change. 



It is proper to add, that in two cases it has been found 

 expedient, to change the seed from an inferior to a superior 

 climate. In Flanders, where great quantities of flax are 

 grown, the seed must be brought from the Baltic, other- 

 wise the crop will be deficient. In the case of potatoes also, 

 seed is imported from an inferior climate, as the most likely 

 means of preventing the disease called the curl. It has for- 

 tunately, however, been discovered, that by taking up pota- 

 toes for seed early or sowing them so late, that they cannot 

 reach maturity, the same object may be obtained. 



Besides changing seed, crossing different varieties has 

 been found of use. Mr Knight has not only raised new 

 varieties of apples, and of the garden pea, but has likewise 

 tried experiments with crossing wheat, which he has effected 

 by sowing the different kinds together. This was attended 

 with a most extraordinary result ; for when, in the year 

 1796, almost the whole crops of corn in the island were 



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