322 



4. UMBILICARIA 

 Hoffin.Pl.Lich.(1795) 

 p. 109 pro parte ; Nyl. 

 Flora, 1875, p. 303. 

 Thallus efribrillose 

 beneath. Apothecia 

 lecanoroid, with thal- 

 line receptacle, con- 

 taining no gonidia ; 

 hypothecium brown- 

 ish-black; spores soli- 

 tary, 2nae or 8nae, 

 brown or colourless, 

 murali-locular or sim- 

 ple ; hymenial gela- 

 tine bluish and then 

 wine-red with iodine. 

 Spermogones some- 

 what prominent; sper- 

 matia short, cylin- 

 drical. 



Formerly distinguish- 

 ed from the following 

 genus by different au- 

 thors on insufficient 

 grounds, this has boen 

 definitely separated by 



LICHETfA.CEr. 



[tJMBILICA-RIA. 



Fig. 53. 



Ny lander On account of UnMKcaria pm t u lata Hoffm.-a. Vertical section of 

 the peculiar type ot the th;illus, x200. b. Vertical section of apothecium, 

 apothecia. These are x3 o. e . A theca and paraphysis, X 3.50. d. Two 

 in a certain way Lea- spores, x5(0. e. Vertical sectin of thallus with a 

 norine, but not truly so ; spermogone, X30. /. Sterigmata and sperniatia, 

 for though they present x 500. 

 externally a thalline re- 

 ceptacle composed of the cortical and medullary layers, they do not con- 

 tain gonidia (vide Nyl. Flora, I. c.~). As to the structure of the thallus, 



will be seen from fig. 53 a that this consists of four layers. These 

 are (1) an epithalline layer more or less developed or evanescent 

 (whence the presence or absence of pruina on the upper surface) ; (2) a 

 corticali-gonidial layer, the gonidia occupying the lower half of the more 

 darkly delineated portion ; (3) a white medullary layer ; and (4) a cor- 

 tical layer on the under surface, of which the upper portion is chondroid 

 (sometimes partly wanting) and the lower (blackish) cellular (cfr. Nyl. 

 Flora, 1. c.\ The spermogones have the spermatia in all the species*of 

 nearly the same size, viz. 0,004 mm. long, 0,001 mm. thick. 



The genus is divided into two subgenera, founded upon differences in 

 the cortical texture. 



Subgen. 1. LASALLIA Merat (Fl. Par. (1836) p. 202 pro parte). 

 Thallus papulose above, lacunoso-foveolate beneath, interm;lly 

 with the chondrohyphae wanting in the lower concave portion of 

 the pustules. Apothecia with the spores solitary or 2nae, rnurali- 

 divided, brown. 



