Linncean Society. 311 



arising from disease, which is shown by the sudden termination 

 of the costae and by the partial decay of the other segments. The 

 distinctions derived from the fructification, given in the English 

 Flora, are altogether fallacious, being dependent on age. It is clear, 

 therefore, Mr. Don concludes, that the Aspidium dumetorum must 

 be erased from the list of species. 



Aspidium rigidum. This species has recently been introduced 

 into the British Flora on the authority of a plant gathered on Ingle- 

 borough by the Rev. W. T. Bree, and by him communicated to Dr. 

 Hooker, by whom it has been published in the Supplement to En- 

 glish Botany, and in the second edition of his British Flora. Mr. 

 Don has not seen an authentic sample of the English plant ; but the 

 figure in the first of the works just named, which is unfortunately 

 taken from a cultivated plant, does not well accord with foreign 

 specimens of rigidum, and a sample in Mr. Forster's herbarium, 

 stated to have been taken from a plant received from Mr. Bree, 

 proves to be nothing but a dwarf state of Nephrodium Filix Mas. 



Asplenium Filix Jbemina. Of the two very marked varieties of this 

 plant, that which has the segments of the more delicate texture, and 

 the entire frond of a pale green, varies much in size according to soil 

 and situation : in damp shady places it becomes the jilixfcemina of 

 English Botany, and in more open exposed situations the irriguum, 

 but neither of these states, Mr. Don observes, is entitled to be re- 

 garded as a distinct form. 



Cystea dentata. This plant appears to be peculiar to the Scottish 

 Alps, on which it was discovered by Dickson and the late Mr. Don; 

 for the author, after an attentive comparison of specimens from va- 

 rious stations, both in the Smithian Herbarium and in that of Mr. 

 Forster, is satisfied that the Welsh plant is not in reality different 

 from Jragilis, from which dentata was first distinguished by Dickson. 

 The Scottish plant is distinguished by its broader, rounded pinnae, 

 with short, blunt teeth, rather crenate than serrated, with the costae 

 more conspicuous and flexuose. The angustata, Mr. Don fears, 

 must also be reckoned a variety ofjiagilis, as he can find no essen- 

 tial mark whereby to separate it. 



Cystea regia. Dr. Hooker regards this and the alpina as identical, 

 but to Mr. Don these plants appear to be essentially different; regia 

 being distinguished from alpina by its more compact frond, by its 

 shorter, broader, and cuneiform segments, and by the still more 

 important characters of its more copious sori, and of its narrow 

 and tapering indusium. It is hoped that some fortunate botanist 

 will discover a British station for this plant, for the original one at 

 Low Layton no longer exists, and the Welsh specimens belong to 

 fragdis. The alpina is accurately represented by Schkuhr, Jacquin, 

 Seguier and several other authors; but of the present species there 

 is no authentic figure, except that in English Botany. 



The real structure of this genus, Mr. Don remark.*, has been mis- 

 understood by most botanists. The Cystece are in fact Asplenia with 

 abbreviated sori, the insertion and structure of the indusium being 

 precisely similar in both genera. 



