582 THE GENESIS OF NEW SPECIES. 



In the one as in the other we find those floral contrivances for bringing about cross- 

 fertilization in the first place and autogamy in the second, of which an account was 

 given in the first part of this volume; in the one case as in the other cross-fertiliza- 

 tion often takes place as a result of those contrivances, and both categories include 

 forms which are incapable of self-fertilization, and only develop fruits and fertile 

 seeds in consequence of geitonogamy or xenogamy. Seeing that it has been ascer- 

 tained also that, provided the pollen from other species is excluded, hybrids transmit 

 their form unchanged to their posterity, and that the substitution of brood-bodies 

 for fruits as a means of reproduction and the enhancement of the development of 

 those bodies in the event of there being no fruit, are phenomena common to species 

 also, we come to the conclusion that no line of demarcation between hybrids and 

 species exists in respect of the function of propagation. 



The consideration of all these facts led me years ago to raise the question 

 whether hybrids could originate species, 1 and to answer it in the affirmative. 

 Looked at from this point of view, the hybrids which have been and are being 

 produced in nature acquire a special significance, and it becomes important to form 

 a correct notion as to their existence, behaviour, and distribution in localities where 

 the life of plants is untrammelled and undisturbed. Only the vegetation of Europe 

 has been thoroughly studied in this connection, yet this alone affords a fund of 

 information, and we may take it for granted that what is true for Europe will 

 apply likewise to the other quarters of the globe. 



We shall be rather below than above the mark if we estimate at a thousand the 

 number of wild hybrids belonging to the Flora of Europe which have been brought 

 to light during the last forty years. Of these only a small proportion are of the 

 class of Cryptogams, but this circumstance is due to the fact that it is only lately 

 that Botanists have paid any attention to hybrid Cryptogams. Future researches 

 will no doubt establish the hybrid nature of many so-called "transitional forms". 

 Amongst Mosses in particular, several hybrids arising from species which grow in 

 ditches and marshy places (Hypnum aduncum, H. fluitans, H. lycopodioides, &c.) 

 have been discovered. A few hybrids of the genera Orthotrichum, Grimmia, 

 Physcomitrium, and Funaria have also been identified. Fern hybrids are known 

 in the genera Aspidium, Asplenium, Ceterach, Polypodium, and Scolopendrium. 

 Scolopendrium hybridum, which was observed in Istria, is especially remarkable 

 as being the result of a cross between two species possessing widely different forms 

 and included in different genera. The parent-species of this hybrid are, firstly, 

 Scolopendrium officinarum, which is glabrous and grows in clefts in damp, shady 

 rocks and walls; and, secondly, Ceterach officinarum, which has the under surfaces 

 of its fronds thickly covered with brown scales and flourishes in the crevices of dry 

 walls exposed to the sun. Amongst the Horse-tails we may mention Equisetum 

 inundatum, a rather common hybrid, which owes its existence to the crossing of 

 Equisetum arvense and E. limosum. 



In the division of the Coniferae no less than seven hybrids have been recently 



1 Oesterreich. botanische Zeitschrift xxi. p. 34 (1871). 



