Rev. W. A. Lcigliton on the British UmbilicarifC. 285 



Piggot. Birkdalc, Westmoreland ! Mr. IV. Rofjcrfson in herb. 

 Borrer. Dartmoor ! Mr. Borrer. Swiiihope Fell, Durham ! Mr. 

 It'. Mudd. Barmouth, N. A\'ales ! Rev. T. Habiiey. 



" Thallas peltate, consisting of a single leaf, attach(!d by a 

 thick, callous, central base, suborbicular or oblong, an inch or 

 two in diameter, flattish, but elevated towards the centre, so as 

 to have an irregularly convex appearance, undulated, and not 

 unfrequently erect or reflexed at the edges, rugged all over, and 

 torn, without any order, into various rounded lobes of most un- 

 certain size, which are most usually shallow, but occasionally 

 reach almost to the root, and slightly imbricated : it is also per- 

 forated, chiefly towards the edges, with numerous cavities of no 

 definite size or figure, giving to some specimens the appearance 

 of being fringed with beautiful lacework ; in other specimens the 

 perforations are found all over the thallus, and again in others 

 they are almost, if not altogether, wanting : upper surface dusky- 

 greenish-brown when moist, when dry deep brown, and fre- 

 quently almost black, always naked, in a young state even, and 

 marked with various undulating black indented lines, which, as 

 the plant becomes older, grow more numerous, and, frequently 

 anastomosing, divide the cuticle into irregular areola?, which 

 swell into pustular elevations : under surface, when wet, semi- 

 transparent, generally light greyish-brown, but sometimes of the 

 same colour as the upper one, turning darker, often blackish, 

 from drying; minutely granulated, so as to look like shagreen 

 when magnified, entire in young specimens, in old ones ragged 

 with irregular holes, which have elevated thickened lips, and do 

 not extend to the upper coat of the thallus; besides which, there 

 also grow out of the under surface, in all stages of its existence, 

 fibres of the same colour and substance as itself, aptly compared 

 in ' English i3otany ' to shavings, performing, according to Dil- 

 lenius and Sehrader, the office of roots : substance coriaceous, 

 variable in thickness, flexible when moist, rigid and brittle when 

 dry. Trica numerous, scattered all over the thallus, affixed by 

 th(;ir centres, sessile or slightly elevated, flat or variously convex, 

 varying in shape I'rom linear through every gradation to orbi- 

 cular ; sometimes svu'rounded by a nearly entire slightly elevated 

 margin, but more frequently wanting it, and consisting merely 

 of irregular clusters of twisted gyri"^'^ — Lick. Brit. 



The sporidia were not seen in the specimens of U. Muhlen- 

 bergii from Mrs. Merry in herb. Borrer ; but in specimens of 

 U. Muhlenbergii and its variety alpina in the same herbarium, 

 received from America from Mr. Edward Tuckerman, jun., they 

 were identical with those oi' erosa (see PI. X. figs, 9 & 10). 



* For the sijermagoiiia of this form sec Tulasnc, /. c. 



