POLYPODIUM ANOMALUM. 361 



the scales are again contracted, subulate, and closely imbricated. So 

 deciduous are the scales sometimes, that we have a specimen with 

 scarcely a trace of one upon them. 



Many years ago this anomalous Fern attracted the attention of Dr. 

 Arnott and myself, in the Hookerian Herbarium, when the only speci- 

 mens we had received, were from Mrs. General Walker. Lately we 

 have been favoured with specimens in a letter from our friend Mr. 

 Thwaites, gathered by him in a mountain region in the same island, 

 accompanied by the remark that "the fructification appeared to be on 

 the superior^ and not, as usual among Eerns, on the under side of the 

 frond," This upper side is at once recognizable by the darker colour, 

 more glossy surface, slight convexity, and still more surely by the fur- 

 rowed rachis and more or less sunken veins. The plant is here figured 

 rather with a view of directing attention to the fact, than from a con- 

 viction of the specimens being otherwise than a lusus : nay, were it not 

 that even in the youngest state of the fructifications we find no trace 

 of indusium, I should be disposed to consider it an abnormal form of 

 Polystichum vestitum^ where, too, the indusium is often early deciduous. 

 It is true that, if viewed in the light of a monstrosity, the absence of 

 an indusium might be accounted for by the supposition that the upper 

 surface of the frond was destitute of that peculiar organization which 

 would give origin to the indusium. Such is not the fact however with 

 a specimen of Asplenium lately placed m Dr. Hooker's hands by N. B. 

 Ward, Esq. {Aspl. TricJiomanes, L.), gathered in Italy by E. W. Cooke, 

 Esq., E.A., which, besides the copious fructification on the under side 

 of the frond, exhibits one pinna bearing a solitary sorus on the disc of 

 the upper side, with its indusium as perfect as any on the under side. 

 Even on one specimen of our present plant I have detected, on two or 

 three of the pinnules only of an entire frond, a few son on the under 

 side, and in one or two instances corresponding with a young sorus on 



the upper side. 



I am aware that some acrostichoid Ferns {Folylotrya, for example) 

 are considered to have both paginae of the pinnules clothed with fruc- 

 tifications, and this is the normal character of the particular species, 

 and where the whole frond, changed in form, becomes fertile ; and the 

 Davallia immersa. Wall (Leucostegia, Pr,), has been described as bear- 

 ing the sori on the upper side, but this is in appearance only, for, as 

 Presl well explains it, " Frondis— pagina superiore pallidiore faciem 



VOL. VIII. 



3 A 



