February, 19 19, The Irish Naturalist, ^3 



ASPLENIUM ADIANTUM-NIGRUM VAR. ACUTUM. 



BY R. LLOYD PRAEGER. 



(plate 2). 



In October, 1917, Mr. C. M. Fleury wrote me that he had 

 found Asplenium Adiantum-nigrum var. acutum near 

 Glendalough, and sent fronds which at first I accepted as 

 that form. On looking up my herbarium, I found that I 

 had collected the same plant in the same station in 1904, 

 but that after examination I had decided that it was not 

 the true acutum. This fern possesses a special interest 

 because it has been claimed by some of the leading pteri- 

 dologists as a distinct species, and also because, unlike most 

 of the innumerable variants found among the ferns, it has 

 a well-marked geographical range, that range being exactly 

 what among plants of the British Isles we call " Lusitanian " 

 — i.e., Ireland (particularly the south-west), Spain and the 

 Mediterranean region, and the Atlantic Islands. These 

 facts, together with the uncertainty which I felt as to the 

 identity of the Wicklow plant, led me to look into the litera- 

 ture of the plant and to examine available specimens, with 

 the results which are summarized below. 



The plant is sufficiently well defined in the original des- 

 cription^ : — " Asplenium acutum. A. frondibus triplicato- 

 pinnatis, pinnis oblongo-lanceolatis longissime acuminatis, 

 pinnulis pinnatifido-incisis, laciniis apice acute subbidentatis, 

 sori demum confiuentibus. W. Asplenium acutum. Bory 

 in Litt. . . . Habitat in rupibus Teneriffae, inque Hispania. 

 . . . Duplomajusprsecedenteet extototriplicato-pinnatum. 

 Apex pinnarum longissime acuminatus." 



The " preceding species " to which reference is made is 

 A. Adiantum-nigrum — " Frons plerumque bipinnata quan- 

 doque interne tri- et superne bipinnata. A sequente tamen 

 satis diversum : pinnis nunquam caudatis, id est longissime 

 acuminatis, pinnulis non acuminato dentatis, et fronde 

 nunquam ex toto triplicato pinnata " (I.e.). 



^ WiLLDENOW : Linnaeus' " Species Plantarum " (ed. 4), 5, 347 

 1810. 



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