SELECTING AND IMPROVING PLANTS IN CULTURE. 405 



climates ; if the one were planted on the banks of the Rhine, and the other 

 on those of the Nile, each would adapt its habits to the climate in which it 

 were placed ; and if both were subsequently brought in early spring into a 

 climate similar to that of Italy, the plant which had adapted its habits to a 

 cold climate would instantly vegetate, whilst the other would remain per- 

 fectly torpid. Precisely the same thing occurs in the hothouses of this 

 country, where a plant accustomed to the temperature of the open air will 

 vegetate strongly in December, whilst another plant of the same species, and 

 sprung from a cutting of the same original stock, but habituated to the 

 temperature of a stove, remains apparently lifeless. It appears, therefore, 

 that the powers of vegetable life in plants habituated to cold climates are 

 more easily brought into action than in those of hot climates ; or, in other 

 words, that the plants of cold climates are most excitable : and as every 

 quality in plants becomes hereditary, when the cause which first gave exist- 

 ence to those qualities continues to operate, it follows that their seedling 

 offspring have a constant tendency to adapt their habits to any climate in 

 which art or accident places them." (Knight's Horticultural Papers, p. 172.) 



8C3. Selection. An individual wild plant being thus improved, the next 

 step is to sow its seeds under the most favourable circumstances of soil and 

 situation, and from the plants so produced to select such, or perhaps only one, 

 or even a part of one, which possesses in the highest degree the qualities we are 

 in search of. This plant being carefully cultivated, its seeds are to be sown, 

 and a selection made from the plants produced as before. In this manner 

 one generation after another may be sown and selections made till the desired 

 properties are obtained. In the case of annual plants the object may be 

 attained in a few years, but in the case of trees, and especially fruit-trees, a 

 number of years are requisite. Mr. Knight, who has had more experience 

 in raising new fruits by selection from seedlings than perhaps any person 

 ever had before his time, has the following instructive observations: 

 " When young trees have sprung from the seed, a certain period must elapse 

 before they become capable of bearing fruit, and this period, I believe, can- 

 not be shortened by any means. Pruning and transplanting are both 

 injurious ; and no change in the character or merits of the future fruit can 

 be effected, during this period, either by manure or culture. The young 

 plants should be suffered to extend their branches in every direction in 

 which they do not injuriously interfere with each other ; and the soil should 

 just be sufficiently rich to promote a moderate degree of growth, without 

 stimulating the plant to preternatural exertion, which always induces 

 disease. The periods which different kinds of fruit-trees require to attain 

 the age of puberty are very varied. The pear requires from twelve to 

 eighteen years ; the apple, from five to twelve or thirteen ; the plum and 

 cherry, four or five years ; the vine, three or four ; and the raspberry, two 

 years. The strawberry, if its seeds be sown early, affords an abundant crop 

 in the succeeding year." (Physiological Papers, $c. p. 178.) 



864. Selecting from accidental variations, or as they are technically termed, 

 sports. Among a great number of seedlings raised in gardens, or of plants 

 in a wild state, some entire plants, or parts of plants, will exhibit differences 

 in form or colour from the normal form and colour of the species. Among 

 these peculiarities may be noticed double flowers, flowers of a colour different 

 from those of the species, variegated leaves, leaves deeply cut where the 

 normal form is entire, as in the fern-leaved beech ; and even the entire plant 



