374 SELECTING AND IMPROVING PLANTS IN CULTURE. 



of cabbages and turnips having been adulterated when at a distance of 

 upwards of a mile, in an open country and in the direction of the 

 prevailing winds. To guard against the eifects of bees and other 

 insects, the blossoms when selected and fecundated by art may be sur- 

 rounded by coarse gauze, or enclosed in a case of glass, till the blossom 

 begins to fade. To strengthen the embryo seeds, the plant may be 

 pruned in such a manner as to throw an extra share of sap into the 

 branch, stem, or pedicel on which the flower is situated. Thus, if 

 the fecundated flower form part of a spike, the upper part of the 

 spike may be cut off; a corymb or an umbel may be thinned out; 

 the suckers may be taken from a sucker-bearing plant, such as the 

 raspberry ; the runners from the strawberry ; the offsets from a bulb, 

 the tubers from a potato, and so forth. 



Fixing and rendering permanent the variety produced is effected in 

 general by one or other of the modes of propagation. Improved varieties 

 of fruit trees are generally perpetuated by grafting ; fruit shrubs, such 

 as the gooseberry, and flowering plants, such as the fuchsia, pelargo- 

 nium, &c., by cuttings ; perennials, by division, offsets, or suckers, &c. ; 

 improved annuals and biennials, and some perennials, are perpetuated 

 by seeds. Numerous means are adopted, such as those named above, 

 to keep the stock of improved varieties true or pure. There is one 

 practice common among cultivators, the rationale of which it is difficult 

 to explain. This is the transplantation of culinary biennials, such as 

 the turnip, carrot, parsnip, beet, cabbage, cauliflower, onion, and many 

 such plants, after they are full grown, previously to their being allowed 

 to send up their flower- stems. By this practice the variety is said to 

 be prevented from degenerating ; and if so, it may probably be on 

 account of the greater part of the nourishment to the seeds being 

 furnished by the store laid up in the plant, and but only a small 

 portion taken from the soil. It is certain that transplanted plants do 

 not produce nearly so much seed as they would have done if not trans- 

 planted ; and it is equally certain that in the case of the turnip, when 

 the bulb is of a moderate size, and even small rather than large, much 

 stronger flower- stems are sent up, and more seed produced, than when 

 it is large. The reason probably is that the roots below the unswelled 

 bulb are stronger, not having yet fulfilled their functions, and hence 

 are enabled to draw a larger proportion of nourishment from the soil. 



The production of double flowers is a subject not yet thoroughly 

 understood by physiologists. As double flowers are seldom found in a 

 wild state, they appear to be the result of culture, and yet there is 

 scarcely any well-authenticated instance of culture having produced 

 them. It is certain, however, that double flowers degenerate into single 

 ones when culture is withdrawn, and that extraordinary supplies of 

 nourishment and moisture, as in moist and warm seasons, seem to pro- 

 duce flowers more double than in dry seasons. It has also been said 

 that by concentrating the strength of the plant one season into two or 

 three seed-pods, instead of allowing it to expend itself through a greater 

 number, double flowers will be produced, and scarlet stocks so reduced 

 produced nearly all double flowers, while those kept to ripen all the seed 



