77 



stalked, solitary, axillary, ovate, inflated ; the valves entire. Main 

 rachis very slightly winged. 



Hymenophyllum unilaterale, Willdenow. Moore. Newman. Hy- 

 menophyllum Wilsoni, Hooker. E. B. Supp. 2686. Hooker 

 and Arnott. Babington. 



Found in similar situations to the preceding, which it frequently 

 accompanies. Its distribution is more extended, especially in Scot- 

 land, where its extreme limit is Unst, the most northern of the 

 Shetland Islands. In general appearance this is not very much 

 unlike H. Tunbridgense, with which it was for a long time con- 

 founded; but the fronds are far less delicate in texture, and com- 

 paratively rigid. The principal characters of distinction are found 

 in the fructification, which, occupying a similar position, is stalked 

 instead of sessile ; the involucre proportionally longer and ovate 

 instead of rounded, with very turgid convex valves, meeting by 

 their edges, not compressed toward the apex, and never at all ser- 

 rated. The tendency of the pinnae to assume a recurved position 

 is not a character to be depended upon, but the darker green hue 

 and less compact growth will generally enable the observant eye to 

 distinguish the present at a glance from H. Tunbridgense, a plant of 

 more elegant habit. The involucres are generally curved forward. 



The treatment required for cultivation is the same as that already 

 noticed for its congener, and will succeed with the exotic species 

 of this curious family, all of which are well deserving the attention 

 of the amateur cultivator. 



Genus 16. OSMUNDA. 



GEN. CHAR. Fructification naked, clustered on contracted rachi- 

 form portions of the frond, forming a (generally) terminal 

 panicle. Thecse stalked, subglobose, reticulated, two-valved, 

 opening vertically. 



The name is from the Saxon, Osmund, c domestic peace/ but the 

 origin of its application is unknown, though several romantic 

 legends are connected with it. 



The ferns of this genus differ greatly from those of all the pre- 

 ceding, not only in the peculiar disposition of the fructifying masses, 

 which occupy, upon the veins or branches of the rachis, the place 

 of the leafy tissue on the upper part of the fertile fronds, but 

 likewise in the structure of the thecae; these are exannulate, or 

 without that prominent articulated continuation of the supporting 

 stalk, by the ultimate extension of which those of ordinary ferns 

 are torn open to discharge the spores ; their tissue is opaque, very 

 regularly reticulated, and the bivalvular dehiscence takes place 



