OUBLIU NATUIUL HI8T0BT SOCIETT. 181 



justified on this account alone in uniting the two, and thus converting 

 species into genera ? Dr. Kinahan had spent much time and labour 

 some years since in investigating changes of form to which the frond in 

 ferns is liable, and the result of these investigations showed him that, 

 although in some cases these abnormal forms might be perpetuated under 

 cultivation for several generations, that this was alone attributable to 

 constant watching and culture, as there is always a tendency to revert 

 to the original form, and the plants almost invariably revert to it when 

 deprived of the advantages of their artificial training. Arguments drawn 

 from such examples must, therefore, be excluded when we come to plants 

 in a state of nature ; for among these latter, when modifications of cha- 

 racter, owing to peculiarity of habitat, occur, we find that, in the first 

 place, the varieties are local, not as in the case of the species now under 

 consideration, where the two forms are wide-spread, and frequenting 

 often the same districts; and next, when natural varieties are placed under 

 the same culture as plants of a normal type, they almost always return 

 to it. It is further to be remarked, that when either of the species under 

 consideration are found growing in extreme abnormal situations, the only 

 changes which take place (exclusive of extinction) are in the frond, the 

 involucres remaining the same. Hymenophyllum Tunhridgense growing 

 on the bare face of a grit rock, facing the north-east, at some hundreds 

 of feet of elevation, unsheltered either by trees or overhanging rocks, as 

 on Monounta Hill, near Feakle, county of Clare, though stunted in its 

 growth, preserves all its other characteristics equally with plants grow- 

 ing in the most favourable situations in Killamey; andSiTFihom, in its 

 Killamey and Tipperary situations, sheltered from the wind and sun, 

 becomes merely taller and more luxuriant, differing in no other respect, 

 save that of fruiting more sparingly, from plants carpeting the wind and 

 spray swept rocks of Valentia Island, 



Much had been said about the advantages of travel in enabling us to 

 form a correct judgment as to the unity or not of species ; but, on the 

 one hand, have all who contend for unity of those species possessed this 

 advantage? — and had any of them brought home specimens of the much- 

 quoted intermediate forms ? — and, on the other hand, had the supposed 

 advantages derived from travel been enjoyed only by those who argue 

 in favour of the union ? Had none of its opponents ever been equally 

 favoured, either in this respect or in the advantages to be derived from 

 examination of herbaria and living foreign species ? For his own part, 

 it appeared to him that Linneus's great axiom, " I own no master but 

 observation," was entirely overlooked, and in its place what logicians 

 call the "argumentum ad hominem" substituted. 



For himself, until better arguments were brought forward, he must 

 decline following blindly at the beck of any master in matters in which 

 every observer of common diligence can judge for himself; and, there- 

 fore, preferred ranging himself among those whose observation of the 

 pUmt in the field, and examination of it under culture, led them to be- 

 lieve in the distinctness of the species. It had been stated that because 



