180 



POPULAR HISTORY OF LICHENS. 



5. Umbiltcaria erosa (erodo, to eat into, or perforate) is 

 distinguished by the reticulate-cribrose character of the 

 thallus, which is bronze-coloured, — below ochroleucous or 

 brow r nish and papillose. Apothecia innate, then appressed, 

 otherwise resembling those of preceding species. Spermo- 

 gones frequently abundant, but not easily seen, from having 

 the same colour as the thallus ; they are small, prominent, 

 obtuse tubercles, w T ith an imperceptible pore or ostiole ; their 

 structure and contents resemble those of U. vellea. 



This is somewhat rarer than the preceding species, but 

 occurs in similar localities. 



6. Umbilicaria polyrrhizos a root) is chiefly dis- 

 tinguished by the fibrillose-pannose character of the black 

 under-surface of thallus, and by the apothecia being de- 

 pressed, tumid, devoid of a margin, and marked by lirellse 

 radiating from the centre to the circumference. 



Its habitat is similar to that of preceding species ; it is 

 not uncommon in the Highlands, and on the border-hills. 

 All the Umbilicarias when moistened are of a more or less 

 deep green or olive-green colour, becoming greyish, bronze- 

 coloured, or blackish in the herbarium. With the marked 

 difference in colour between the natural and dried state, 

 every botanist is familiar who has collected these leathery 



