322 LICHENACEI, [UMBILICARIA. 
‘4. UMBILICARIA 
Hoff. 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, 2ne or 8ne, 
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 
prounds, this has been 
definitely separated by Fig. 53. 
Nylander on account of (npiticaria pustulata Hoffm.—a. Vertical section of 
the peculiar type of the ~ thatlus, x 200. . Vertical section of a othecium, 
apothecia. These are 430. ¢, Atheca and paraphysis, X350, d. Two 
in a certain way leca- spores, X5(0. e. Vertical sectin of thallus with a 
norine, but not truly so; — spermogone, x30. jf. Sterigmata and spermatia, 
for though they present x500. 
externally a thalline re- 
ceptacle composed of the cortical and medullary layers, they do not con- 
tain gonidia (vide Ny]. Flora, J. ¢.). As to the structure of the thallus, 
will be seen from fig. 53a 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; (38) 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. Ny]. 
Flora, /. 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 Meérat (Fl. Par. (1836) p, 202 pro parte). 
—Thallus papulose above, lacunoso-foveolate beneath, internally 
with the chondrohyphe wanting in the lower concave portion of 
the pustules. Apothecia with the spores solitary or 2nw, murali- 
divided, brown. 
