THE ROCK BBAKES. 33 



each lobe, and they then form a series on each side the mid- 

 vein ; but sometimes more of the venules are fertile, and the 

 sori then range in short lines near the margin of the lobes. 



This Fern has so remarkably the aspect of the common 

 Lady Fern, that although common on the Scotch mountains, 

 it has been till very recently overlooked, the plants having 

 been supposed to Belong to that species. It would appear 

 to be plentiful on the higher parts of the mountainous dis- 

 tricts of the counties of Perth, Forfar, and Aberdeen, in 

 company with the Lady Fern in its lower range, but without 

 it at higher elevations. The fronds appear in May, and 

 perish early in autumn. 



The very distinct and remarkable variety called foxile 

 called by some Pseudathi/rium flexile, differs in its lax spread- 

 ing habit, narrow fronds, short deflexed pinnse, and fewer 

 pinnules. The plant as seen in cultivation produces stalk- 

 less or almost stalkless fronds, which often bear their sori 

 abundantly at the base, but scarcely if at all upwards. 

 These latter marks the sessile fronds, and basal sori dis- 

 appear in some instances both in the wild and cultivated 

 specimens. A very imperfect indusium has been observed 

 on some of the sori in the plant under culture, but occurs 

 on the least perfect sori. The sori, as also sometimes 

 happens in P. alpestre itself, is not in all cases punctiform, 

 but occasionally, though rarely, lateral on the veins. It was 

 first found in 1852, in Glen Prosen, by Mr. Backhouse and 

 Mr. Westcombe ; and the same botanists again found it 

 plentifully in the same district of the Clova Mountains, in 

 the summer of 1855. 



CHAPTER V. 



THE ROCK BRAKES. 



THE technical name of the family to which the Eock 

 Brakes belongs, is Allosorus. The family is known from all 

 other British Ferns by the coincidence of the following fea- 

 tures : It bears fronds of two kinds, one being leafy and 

 barren, i.e., without sori ; the other contracted, and bear- 

 ing sori, and hence called fertile ; then the edges of the 

 lobes of the fertile fronds are rolled under (which is what 

 gives them the contracted or narrowed appearar/ce), and 

 cover the sori in the stead of an indusium ; and moreover, 

 the sori when young form distinct circular clusters beneath 



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