ASPLENIUM ACUTUM. 233 



brother-botanists will view this question in its proper hght. 

 Asplenium acutum is a species, admitted to be distinct, as I 

 beheve, by every continental author who is acquainted with it : 

 it was described as distinct forty-four years ago, and no com- 

 petent botanist has suggested a doubt of the propriety of the 

 decision at which Willdenow arrived : that eminent botanist, 

 and, long afterwards, Sadler also, compared it with its near 

 ally, Asplenium Adiantum-nigrum ; they went carefully into 

 the evidence of its being identical with that fern, weighed 

 fairly and deliberately all the pros and cons of the case, and 

 rejected as untenable the idea of uniting the two. The next 

 point is that I ascertain, beyond any reasonable doubt, that this 

 very Asplenium exists abundantly in the South-west of Ire- 

 land. Having satisfied myself on this second point, I proceed 

 to consider whether I shall reject a species clearly and unmis- 

 takably characterised by Willdenow, and unhesitatingly adopted 

 by fifty botanists far better than myself. The onus of proving 

 the plant a species does not rest with me ; but the onus of 

 uniting it with another species, if I attempt to do so, must rest 

 with me. I am unable to show that acutum is a form of Adi- 

 antum-nigrum, produced by latitude, temperature, soil, expo- 

 sure, shade, altitude, or other varied conditions, because in all 

 its localities Adiantum-nigrum also exists in its most normal 

 form, and, growing side by side with acutum, remains un- 

 changed. I am unable to show that acutum is a monstrous or 

 diseased plant, because it exhibits all the symmetry and uni- 

 formity of parts which indicate health, vigour, and normal con- 

 dition. I am unable to show that the difference is simply one 

 of amount of cutting or subdivision, because there is also a 

 difference of texture always observable. I am unable to show 

 that acutum returns to Adiantum-nigrum under cultivation ; 

 on the contrary, the result of a careful examination of the indi- 

 vidual plant which has been supposed to establish this fact is, 

 that the departure from the ordinary acutum is in one direction 

 only, namely, in size ; and as discrepancy in size is not urged 

 by any author as a diagnostic between the two nearly allied 

 species, it is not logical to adduce uniformity in size as cotmter 

 evidence, and a proof of their identity. Even on this subject 

 a few words may be appropriate : Mr. Watson and Mr. Cheshire 

 have found Adiantum-nigrum so large as entirely to remove 



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