8i 



HISTORY OF THE VEGETABLE KINGDOM. 



pre-existing in the ovary, where, furnished u-ith 

 its proper integuments, it waits the fecundating 

 influence of the pollen, which is necessary to its 

 complete development ; so that it requires in fact 

 the exertion of two distinct energies to bring it 

 to perfection, the vital principle, and the sem- 

 inal ; the former generating and organizing the 

 different parts of which the egg consists in com- 

 mon with the other parts of the plant ; and the 

 latter communicating to the egg thus formed a 

 distinct vegetable life. 



Theory of the animalctdes. But the theory of 

 the ovarists is not without its difficulties ; for as 

 the embryo is never found to make its appear- 

 ance till after fecundation, it has been thought 

 that it must necessarily pre-exist in the pollen 

 of the anther ; from which it is conveyed to the 

 ovary through the medium of the style, and 

 afterwards matured. This theory was founded 

 upon that of Lcuwenhoeck, with regard to animal 

 generation ; which supposes the pre-existence of 

 animalcules in the seminal principle of the male; 

 the animalcules being conveyed in coittt to the 

 ovary of the female, where alone they are cap- 

 ihle of development.* Hence it has been de- 

 nominated the theory of the animalculists, and 

 transferred to the case of vegetables by Morland, 

 Needham, Gleichen, and others, who regard the 

 pollen as being a congeries of seminal plants, one 

 of which at least must be conveyed to the ovary 

 entire before it can become prolific. 



But if the embryo pre-exists in the pollen, 

 may it not be detected by inspection before im- 

 pregnation takes place ? Spallanzani examined 

 the pollen in its ripe and perfect state with great 

 care, and under glasses of the highest magnify- 

 ing powers, but could distinguish nothing ex- 

 hibiting the appearance of an embryo. It may 

 be said, however, that the embryo must still be 

 supposed to pre-exist in the pollen, though not 

 visible, as Spallanzani has said of its pre-exis- 

 tence in the ovary ; and that its invisibility is 

 no proof of its non-existence. The animalculists 

 have no doubt a right to offer this reply ; but as 

 the embryo is not visible whether in the ovary or 

 pollen, till after fecundation has taken place, no 

 conclusion can be drawn on either side from the 

 circumstance of its invisibility. 



But admitting that the invisibility of the 

 embryo is no proof of its non-existence in the 

 pollen, the total want of a passage, in most 

 styles, fit to conduct the particles of pollen en- 

 tire, exposes this theory to the most serious ob- 

 jections, if it does not rather render the alleged 

 mode of impregnation altogether impracticable. 

 And if a passage of sufficient width were found 

 to exist even in all styles, still the probabilities 

 "of the two cases are in favour of the ovarist. 

 For if the embryo is to pre-exist at all, is it not 



*rhil. TraB3.No. 145, p. 74. 



more likely that it should pre-exist in the ovary, 

 where it is to be brought to maturity, than that 

 it should first be generated in one organ or plant, 

 and then transferred to another to be developed? 

 Is it not also most extraordinary that the em- 

 bryo should so invariably assume the same posi- 

 tion in the same species of seed, if it is merely 

 conducted to the ovary from a diflFerent organ or 

 ])lant, and introduced as it were at random? 

 And is not the doctrine of the ovarist counten- 

 anced from the analogy of the process for which 

 he contends to that of the generation of the ani- 

 mal egn, which is produced complete in all its 

 integral and distinct parts even without the co- 

 operation of the male, though still destitute of 

 the principle of fertility ? And finally, is it not 

 further countenanced from the fact of the ap- 

 parent and numerical perfection of parts often 

 observable in the fruit of insulated female plants, 

 in which the embryo is not always wanting, but 

 only not fecundated ? For which reasons the 

 theory of the ovarist seems to be much more 

 consonant to truth than that of the animal- 

 culist. 



Theory of the Epigenisists. But the diffi- 

 culties inseparable from both theories, together 

 with the phenomenon of hybrid productions, 

 have given rise also to a third ; this is the theory 

 of the epigenisists, who maintain that the em- 

 bryo pre-exists neither in the ovary nor pollen, 

 but is generated by the union of the fecundat- 

 ing principles of the male and female organs ; 

 the former being the fluid issuing from the pol- 

 len when it explodes ; and the latter, the fluid 

 that exudes from the surface of the stigma when 

 mature. As applicable to the case of plants, 

 this theory has been stoutly defended by Koel- 

 reuter, who adduces in support of it a variety of 

 experiments instituted with a view to ascertain 

 the fact by means of impregnating the ovary of 

 one species with poUeu taken from another, in 

 which cases the plant obtained from the seed 

 uniformly exhibited a combination of the charac- 

 ters of both species. The following is a most 

 prominent example, being the result of liis ex- 

 periments on nicotiana rustica and paniculata ; 

 the former having egg-shaped leaves, with a 

 short and yellow corolla approaching to green ; 

 and the latter having roundish or cordated leaves, 

 with a green corolla approaching to yellow, and 

 a stem longer by one half. A flower of the for- 

 mer species was accordingly deprived of all its 

 stamens, and fecundated with pollen from a plant 

 of the same species. The plant raised from the 

 seed thus obtained was an hybrid, exhibiting in 

 all its pai'ts an intermediate character betwixt 

 the two species from which it sprang. The 

 stamens of this hybrid, as well as of all others 

 he ever raised, were imperfect ; but when its 

 pistils were impregnated with pollen from the 

 paniculata as before, the new hybrid obtained 



