Gardener’s Chronicle, p. 791. June 29, 1895
A THEORY OF MULTIPLE PARENTAGE IN FERNS
Charles T. Druery, F.L.S.
The very remarkable results of mixed sowings of Fern spores of different varieties, shown by Mr. E J. Lowe at the Conference and subsequent Fern Exhibitions held under the auspices of the Royal Horticultural Society, and detailed in his recently-published volume on Fern Growing, point so decidedly to the possibility of a single archegonium being fertilised by antherozoids of diverse origin, that the theory of the archegonium being only susceptible of monogamic fertilisation is, to say the least of it, rudely assailed. In deference, presumably, to this belief held by most biologists, Mr. Lowe advances the suggestion, that several archegonia on one and the same prothallus may be independently fertilised each by a single antherozoid derived from another prothallus of a different variety; that the varied influences thus introduced may be assimilated generally by the prothallus; and that eventually, when one of the fertilised ova survives in the struggle for existence (due to the fact that one prothallus is ordinarily only able to mature one plant), this survivor is enabled to display the combined characters of all the varieties with which the prothallus has been impregnated. In other words, the germinules of the suppressed ova find their way to the developed one, carrying with them, of course, all their varietal potencies. That the influence of the male is not always confined to the fertilised ovum and its resulting form of organic life, finds practical evidence in the care which breeders of cattle, horses, and other animals, find it needful to take in the selection of thoroughbred sires, it being a well-known fact that one inferior cross is always liable to show its effects in subsequent independent ones, and since during the period of gestation the circulation of mother and offspring is necessarily one, the maternal system must equally necessarily be pervaded by the paternal influence, as well as the system of the offspring. Now, the appearance in any degree of the characters of sire No. 1 in the progeny of sire No. 2 only differs from Mr. Lowe's theory in the matter of time, a factor in his favour, since with Ferns the multiple paternal influences are at work almost, or quite, simultaneously. Graft hybrids show, though in a less degree, a similar power of assimilation; and, considering that the sap-circulation between scion and stock-roots is single and common, the wonder seems to be, not that the varietal effects of the scion are now and again—but only rarely—made evident, but that this is not invariably the case,
From these remarks it will be seen that I am not prepared to challenge in any way the theory which Mr. Lowe advances, and which indeed may account for the observed phenomena in some instances. I venture, however, to submit, for the consideration of biologists, a theory which, to my mind, recommends itself as a simpler solution of the matter. The antherozoids, as is well known, are emitted in enormous numbers under congenial conditions of humidity. At the time of their emission, and for some little while afterwards, they are endowed with locomotory powers by means of cilia, and by virtue of this capacity reach the archegonia, and fertilise them. The archegonia, however, besides being usually clustered together at one spot, are comparatively few in number, and assuming the adequacy of one antherozoid to fertilise each single ovum the archegonium contains, it is clear that an enormous percentage of these fertilising cells fail to fulfil their proper destiny. These in time lose their powers of motion, and have been observed to dissolve shortly afterwards. This being so, my theory is simply this, granting that by means of insects, flooding or other agencies, the antherozoids of several varieties may become mingled together in the droplet of water which forms the medium of locomotion and fertilisation of the prothallus, it seems to me quite feasible that the moment of dissolution of form may not be coincident with that of actual loss of vitality of the contained germinules, and hence, given the presence of an unfertilised archegonium in the same drop of water, pervaded with the combined free germinules of various antherozoids, fertilisation might result therefrom, without actual contact with any individual antherozoid, and the resulting offspring show multiple characters in endless grades, precisely as do Mr. Lowe's specimens. The cases cited by Mr. Lowe of mixed sowings yielding crossed offspring only, without a single true parental form appearing, demands indubitably some such easily-imparted influence, since the antherozoids have, by their mere propinquity, the best chance of fertilising the adjacent archegonia of same prothallus, and hence a certain proportion of true plants should be expected if actual contact of foreign antherozoids were a sine quá non. Under the theory suggested, a single flooding at the right time might impregnate every archegonium in the pan with different proportional varietal potencies, and just such a mixed lot would be the outcome as is obtained.