106 



The Naturalist. 



I hope I have shown, then — though I fear in a very laboured 

 manner — that to brmg about fertilisation in these plants it is neces- 

 sary that the spermatozoid of one cell should reach the germinal 

 vesicle of another cell, however remote these cells may be. In monoi- 

 cous mosses the distance those spermatozoids would have to travel to 

 accomplish this, would be a relatively great one, but in dioicous 

 ' mosses still greater. Any one who has looked at mosses will have 

 noticed that they often grow in tangled tufts, several species often 

 occurring together. In such mingled masses I can conceive it to be 

 a not unlikely matter of frequent occurrence, for the antherozoid of 

 one species to pass to the archegonia of another and distinct species : 

 should these plants be nearly allied, fertilisation would probably 

 ensue, and such fertilisation might result in the development of 

 capsules bearing spores. These spores, on germinating, would 

 naturally give rise to a number of hybrids ; if the crossing was very 

 near, such hybrids might be set down as a variety of one or other 

 parent, and hence might occur not unfrequently, but fail to attract 

 notice. If more attention was given to this subject than it now seems 

 to have, I have no doubt that we should find that hybridity is a 

 matter of more frequent occurrence than we may now think. We have 

 satisfactory evidence that mosses do hybridise, Bayrhojffer having 

 recorded the finding of hybrids between Funaria hygrometrica and 

 Physcomitrium pyriforme, and between Physcomitrium fasciculare and 

 Funaria hygrometrica^ so that here even generic distinction was not a 

 bar to perfect fertilisation. 



If mosses are liable to hybridise, ferns, I think, are much more so ; 

 for although the archegonia and anthcridia are usually developed on 

 the same prothallus in these plants, they are only rarely ripe at the 

 same time, so that the archegonia of one prothallus must be fertilised 

 by the antherozoids of another prothallus. Hence we may consider 

 that as a rule ferns are dioicous, and that cross fertilization is more 

 frequent than self-fertilisation in these plants. The spores of these 

 plants, both in nature and in cultivation, naturally get sown in mixed 

 masses ; these, on germinating, would give origin to a mixed mass of 

 prothallia, and such a mixed growth would tend to bring about an 

 intercrossing of species. In nearly allied forms this intercrossing 

 would be fertile, and the progeny of such union would necessarily be 

 hybrids. But why are they not more frequently found ? Because 

 only the few among the many fertilised archegones develope into fern 

 plants, and even of those plants Avhich are developed few ever get 



