250' SCIENCE OF AGRICULTURE. Piat II. 



sixe, and color, which it afforded. In 1787, a degenerate sort of pea was growing in his garden, which had 

 not recovered its former vigor even when removed to a better soil. Being th us a good subject of experiment, 

 the male organs of a dozen of its immature blossoms were destroyed, and the female organs left entire. 

 "When the blossoms had attained their mature state, the pollen of a very large and luxuriant grey pea was 

 introduced into the one-half of them, but not into the^other. The pods of both grew equally ; but the seeds 

 of the half that were unimpregnated withered away without having augmented beyond the size to which 

 they had attained before the blossoms expanded. The seeds of the other half were augmented and 

 matured as in the ordinary process of impregnation ; and exhibited no perceptible difference from those 

 of other plants of the same variety ; perhaps because the external covering of the seed was furnished 

 entirely by the female. But when they were made to vegetate in the succeeding spring, the effect of 

 the experiment was obvious. The plants rose with great luxuriance, indicating in their stem, leaves, and 

 fruit, the influence of this artificial impregnation ; the seeds produced were of a dark grey. By im- 

 pregnating the flowers of this variety with the pollen of others, the color was again changed, and new 

 varieties obtained, superior in every respect to the original on which the experiment was first made, and 

 attaining in some cases, to a height of more than twelve feet. {PhU. Tram. 1789.) Knight thinks his 

 experiments on this subject affbrd examples of superfcetation, a phenomenon, the existence of which has 

 been admitted amongst animals, but of which the proof amongst vegetables is not yet quite satisfactory. 

 Of one species of superfcetation he has certainly produced examples ; that is, when, by impregnating a 

 white pea-blossom with the pollen both of a white and grey pea, white and grey seeds were obtained. 

 But ot the other species of superfcetation, in Vtrhich one seed is supposed to be the joint issue of two males, 

 the example is not quite satisfactory. Such a production is perhaps possible, and further experiments 

 may probably ascertain the facti but it seems to be a matter of mere curiosity, and not apparently con- 

 nected with any views of ytility. 



1600. The practicability qf improving the species, is rendered strikingly obvious by these experiments ; 

 and the ameliorating effect is the same, whether by the male or female ; as was ascertained by imjjreg- 

 nating the largest and most luxuriant plants with the pollen of the most diminutive and dwarfish, or 

 the contrary. By such means any number of varieties may be obtained, according to the will of the 

 experimenter, amongst which some will no doubt be suited to all soils and situations. Knight's ex- 

 periments of this kind were extended also to wheat j but not with equal success. For though some 

 very good varieties were obtained, yet they were found not to be permanent. But the success of his 

 experiments on the apple-tree were equal to his hopes. This was, indeed, his principal object, and no 

 means of obtaining a successful issue were left untried. 'J'he plants which were obtained in this case 

 were found to possess the good qualities of both of the varieties employed, uniting the greatest health 

 and luxuriance with the finest and best-flavored fruit. 



1601. Improved varieties of every fruit and esculent plant may be obtained by means of artificial impreg- 

 nation, or crossing, as they were obtained in the cases already stated. Whence Knight thinks, that this 

 promiscuous impregnation of species has been intended by nature to take place, ana that it does in fact 

 often take place, for the purpose of correcting such accidental varieties as arise from seed, and of con- 

 fining them within narrower limits. All which is thought to be countenanced from the consideration of 

 the variety of methods which nature employs to disperse the pollen, either by the elastic spring of the 

 anthers, the aid of the winds, or the instrumentality of insects. But although he admits the existence 

 of vegetable hybrids, that is, of varieties obtained from the intermixture of different species of the same 

 genus, yet he does not admit the existence of vegetable mules, that is, of varieties obtained from the 

 intermixture of the species of different genera ; in attempting to obtain which he could never succeed, 

 in spite of all his efforts. Hence he suspects that where such varieties have been supposed to take place, 

 the former must have been mistaken for the latter. It may be said, indeed, that if the case exists in the 

 animal kingdom, why not in the vegetable kingdom ? to which it is, perhaps, difficult to give a satisfactory- 

 reply. But from the narrow limits within which this intercourse is in all cases circumscribed, it scarcely 

 seems to have been the intention of nature that it should succeed even among animals. Salisbury is of a 

 different opinion, and considers {Hart. Trans, i. 364.) that new species may be created both by bees and 

 the agency of man ; and the recent experiments of Herbert, Sweet, and others, seem to confirm this 

 opinion. Sweet's experience leads him to conclude that the plants of all orders strictly natural may be 

 reciprocally impregnated with success, and he has already, in the nursery-gardens of Messrs, Colville, 

 produced many new geraniae and rhoderaceas. 



1602. A singular or anomalous ^ect of crossing, or extraneous impregnation, is the change sometimes un- 

 dergone by the seed or fruit which is produced by the blossom impregnated. These effects are not uniform 

 results, but they are of frequent occurrence, and have attracted notice from a very early period. John Tur- 

 ner observes (Hort.Trans. v. 63.) that Theophrastus and Pliny (Theophrast. Hist.Plant. I. ii. c.4.; riiniiHist. 

 Nat. 1. xvii. c. 25.) seem to allude to it, and that the notion was entertained by Bradley, who, in his 

 New Improvements in Planting and Gardening, after giving directions for fertilising the female flowers 

 of the hazel with the pollen of the male, says, " By this knowledge we may alter the property and tasto 

 of any fruit, by impregnating the one with the farina of another of the same class, as, for example, a 

 codlin with a pearmain, which will occasion the codlin so impregnated to last a longer lime ^than usual, 

 and be of a sharper taste; or if the winter fruit should be fecundated with the dust of the summer kinds, 

 they will decay before their usual time ; and it is from this accidental coupling of the farina of one kind with 

 the other, that in an orchard, where there is a variety of apples, even the fruit gathered from the same tree 

 differs in its flavor and times of ripening ; and, moreover, the seeds of those apples so generated, being 

 changed by that means from their natural qualities, will produce different kinds of fruit, if they are sown. 

 Turner, after quoting several instances, and, among others, one from the Philosophical Transactions 

 *' concerning the effect which the farina of the blossoms of different sorts of apples had on the fruit of 

 a neighboring tree," states upwards of six cases of hybridised apples, that had come within his own 

 observation, and concludes with the remark, that if there does exist in fruits such a liability to change, 

 it will at once be evident to the intelligent cultivator how much care is requisite in growing melons, 

 cucumbers, &c. to secure their, true characters, even without reference to saving seed for a future crop. 

 In the same volume of the //orffcM^^wra/ Transactions (p. 234.), an account is given of different-colored 

 peas being produced in the same pod by crossing the parent blossom. All these facts seem to contradict 

 the generally received opinion, that crossing only affects the next generation ; here it appears to affect 

 the embryo offspring ; and a gardener who had no keeping apples in his orchard, might communicate that 

 quality in part to his^summer fruit by borrowing the use of a neighbour's blossoms from a late variety. It 

 is probable, however, that such counter-impregnations do not take place readily ; otherwise the produce 

 of a common orchard would be an ever- varying round of monstrosities. 



Sect. VIII. Changes consequent uj)on Impregnation. 



1603. The peculiar changes consequent upon imj^regnation, whether in the flowers or 

 fruit, may be considered as external and internal. 



1604. External changes. At the period of the impregnation of the ovary the flower has attained to its 

 ultimate state of perfection, and displayed its utmost beauty of coloring and richness of perfume. But as 

 it is now no longer wanted, so it is no longer provided for in the economy of vegetation. Its period of 

 decline has commenced ; as is indicated, first by the decay of the stamens, then of the petals, and then of 

 the calyx, which wither and shrink up, and finally detach themselves from the fruit altogether, except in 

 fome particular casce in which one or other of them becomes permanent and falls only with the fruit. Th 



