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greater the distance the sap will have to travel, and the greater will be 
the time required for its ascent and descent. In an exogenous tree, as 
the apple, a layer of wood has to be formed each year on the outside of 
that of the year preceding; sap-wood has also to be converted into 
heart-wood ; and as a tree can in one season, under given circumstances, 
only elaborate a given quantity of sap, it follows, the more that is re¬ 
quired for the formation and perfecting of wood, so much the less must 
remain for the extension of roots and branches, and the production of 
fruit. I have long had my eye on this subject, and I am convinced by 
practical observations, aside from theory, that the prevailing method of 
training up fruit trees to long stems has a tendency to check the vigor of 
a tree, and the production of fruit, and is altogether decidedly injurious 
and unprofitable. 
Having now reviewed the life of a plant from its first germination as 
a seed to the ultimate object of its existence, the reproductive perpetua- 
• tion of the species, I propose, in conclusion, to consider by what means 
improved varieties of useful plants may be obtained. This, I look upon 
as a question of the highest importance, hitherto strangely neglected by 
Societies established for the improvement of agriculture. This is the case 
in older countries where Agricultural Societies have long been in opera¬ 
tion. The chief encouragement hitherto has been bestowed on the breed¬ 
ers or improvers of animals, and great results have unquestionably 
followed. But, as the editor of the Agricultural Gazette observed, 
‘‘perfect farming will prevail when land shall have been made to yield 
profitably the maximum of produce ; and this is to be effected : 
1. By the proper cultivation of the soil. 
2. By a selection of the best plants. 
3. By a selection of the best animals, as a means of converting some 
of these plants into human food. 
These are the fields on one or other of which all agricultural improvers 
are at.work ; and this, we contend, is the order of their relative import¬ 
ance. An influence exerted in the first of them is felt through all the 
others ; one acting in the last is felt nowhere else.” 
Plants are capable of being progressively improved by the skill of mao, 
or, in other words, they can be made to assume, by improved culture 
and judicious selection through successive generations, various modified 
