INTRODUCTION TO CRYPTOGAMIC BOTANY. 413 



occurs in the Himalayan and Abyssinian Alps. Nephroma is 

 found in the north and south temperate zones, with splendid en- 

 demic species in each hemisphere. Solorina occurs in Europe, 

 Abyssinia, and the Himalayas. Frioderma, Fee, with which un- 

 fortunately we are unacquainted, has been found only in Bour- 

 bon. We are not aware that a single species of this sub-tribe has 

 been gathered in tropical America, but it can hardly be absent 

 altogether. Some of the British species recur in the south tem- 

 perate zone. 



b. EuPARMELiACEl, Berk 

 Apothecia at first closed ; thallus horizontal. 

 452. In the second group, or Parmeliacei proper, we have 

 the more typical species, in which the disc is at first closed 

 and surrounded after expansion by a border arising from the 

 thallus. The thallus is always horizontal, furnished with a hy- 

 pothallus, and expands from the centre towards the circum- 

 ference, or, in other words, is centrifugal. The genus Sticta has 

 the habit of the Peltigeri, presenting highly foliaceous species, 

 often of considerable size and of great beauty ; sometimes 

 elegantly tomentose. Indeed, amongst the horizontal Lichens, 

 none can exceed in richness of colour, and elegance of form 

 and outline, many of the exotic species; nor are our own defi- 

 cient in beauty. Sticta pulnionaria is a fine species when 

 growing in favourable positions, and spreads over a large com- 

 pass, and is remarkable for its pitted frond. There is a pecu- 

 liarity about the species of this genus, by which they are at 

 once disting-uishable. The under side is clothed with delicate, 

 velvety down, amidst which are scattered round white spots, 

 which penetrate to the medullary stratum. These have been 

 called cyiDhell^, but there is no great use in giving them a dis- 

 tinctive name. In some species the texture is subcartilaginous, 

 but this is not true of all. One or two species are extremely 

 foetid when moist. Sticta glomulifera is remarkable for the 

 CoUema-like tufts, which are scattered over the upper surface. 

 They consist of shrubby, sub-gelatinous, dark-green tufts, 

 consisting of closely jDacked branched threads. The patches of 

 this plant are sometimes three feet across. Parmelia contains 

 some species which may vie with Sticta. P. perforata is 



