species. It was there that, in the summer of 1829, I first be¬ 
came acquainted with the true Tunbridgense , and had at once the 
gratification of clearing up my doubts concerning the spurious 
kind, with which, as the common Hymenophyllum of North 
Wales, Cumberland, and Perthshire, I had long been imperfectly 
familiar, and also of unexpectedly adding another Pern to the 
‘ British Plora.’ “ It is,” continues Mr. Wilson (viz. H. Wilsoni ), 
“ more rigid than 11. Tunbridgense , and more coarsely reticulated. 
Frond oblong, on a shorter stalk; the pinnae obliquely attached, 
and often much recurved; the segments not so evidently toothed 
at the apex, and their nerve is continued to the apex. Involucre 
with very convex valves, so as to appear compressed in a con¬ 
trary direction to the convexity: its stalk much bent upwards.” 
To these characters must be added the entire apices of the valves 
of the involucre. 
In regard to the second point of discussion, whether it be 
identical with the H. unilaterale of Bourbon ; probably most of 
those who maintain that opinion have not had the opportunity 
of seeing authentic specimens of Bory’s unilaterale. I do not 
profess to have had this advantage myself. A specimen from 
Bourbon, so named, has been sent to me by Yon Martins; but 
that (see Sp. Pil. 1. p. 95) I believe to be much more certainly 
referable to II. Tunbridgense. I have therefore hesitated to con¬ 
sider II Wilsoni as certainly the same as II. unilaterale , knowing 
the latter only from Willdenow’s description. Let me add, too, 
that the highest authority on this extensive group of Perns, 
Dr. Van den Bosch, maintains, in his ‘ Synopsis llymenophyl- 
lacearum/ that II. Tunbridgense , unilaterale , and Wilsoni are three 
distinct species. And of one thing I am sure, that our know¬ 
ledge of the exotic species of Hymenopliyllum and Trichomanes is, 
at present, but in its infancy; we have much to study and much 
to correct of what has been written. 
Plate 44. Fertile plant of Hymenophyllum Wilsoni , Hook .,—natural size. 
Fig. 1. Pinna and sorus,— magnified. 3. Sorus ,—more magnified. 
