FREE BOOKS

Author's List




PREV.   NEXT  
|<   74   75   76   77   78   79   80   81   82   83   84   85   86   87   88   89   90   91   92   93   94   95   96   97   98  
99   100   101   102   103   104   105   106   107   108   109   110   111   112   113   114   115   116   117   118   119   120   121   122   123   >>   >|  
seeds is larger than in the first crop, and that the largest seeds are now somewhat larger and more numerous. Again sowing these, we obtain a further slight increase of size, and in a very few years we obtain a greatly improved race, which will always produce larger seeds than the unimproved race, even if cultivated without any special care. In this way all our fine sorts of vegetables, fruits, and flowers have been obtained, all our choice breeds of cattle or of poultry, our wonderful race-horses, and our endless varieties of dogs. It is a very common but mistaken idea that this improvement is due to crossing and feeding in the case of animals, and to improved cultivation in the case of plants. Crossing is occasionally used in order to obtain a combination of qualities found in two distinct breeds, and also because it is found to increase the constitutional vigour; but every breed possessing any exceptional quality is the result of the selection of variations occurring year after year and accumulated in the manner just described. Purity of breed, with repeated selection of the best varieties of that breed, is the foundation of all improvement in our domestic animals and cultivated plants. _Proofs of the Generality of Variation._ Another very common error is, that variation is the exception, and rather a rare exception, and that it occurs only in one direction at a time--that is, that only one or two of the numerous possible modes of variation occur at the same time. The experience of breeders and cultivators, however, proves that variation is the rule instead of the exception, and that it occurs, more or less, in almost every direction. This is shown by the fact that different species of plants and animals have required different _kinds_ of modification to adapt them to our use, and we have never failed to meet with variation _in that particular direction_, so as to enable us to accumulate it and so to produce ultimately a large amount of change in the required direction. Our gardens furnish us with numberless examples of this property of plants. In the cabbage and lettuce we have found variation in the size and mode of growth of the leaf, enabling us to produce by selection the almost innumerable varieties, some with solid heads of foliage quite unlike any plant in a state of nature, others with curiously wrinkled leaves like the savoy, others of a deep purple colour used for pickling. From the very same species
PREV.   NEXT  
|<   74   75   76   77   78   79   80   81   82   83   84   85   86   87   88   89   90   91   92   93   94   95   96   97   98  
99   100   101   102   103   104   105   106   107   108   109   110   111   112   113   114   115   116   117   118   119   120   121   122   123   >>   >|  



Top keywords:
variation
 

plants

 

direction

 

produce

 

selection

 
exception
 
animals
 

varieties

 
obtain
 

larger


common

 

breeds

 
occurs
 

numerous

 
required
 

improvement

 
species
 
increase
 

cultivated

 

improved


purple

 

colour

 

modification

 

proves

 

breeders

 

cultivators

 

experience

 

pickling

 

wrinkled

 

curiously


growth

 
property
 

cabbage

 

lettuce

 

enabling

 
innumerable
 

unlike

 
foliage
 

leaves

 
examples

enable
 

nature

 
failed
 
accumulate
 

ultimately

 

gardens

 
furnish
 

numberless

 
change
 

amount