88 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Section 3. PLACODIUM (Hiller) T. Fries. 
Thallus peltately affixed. 
Disk reddish buff........................20085 ee eeeeeeeee 21. DL. rubina. 
Disk black. 
Thallus greenish yellow.............-...-.. Leceeeeeee 2la. L. rubina opaca, 
Thallus white............2..-.-22...2.-0222-2 2020202 0e 22. L. marginalis. 
Thallus not peltately affixed. 
Closely affixed to substratum. 
Sulphur-colored, furfuraceous............-..--..------ 23. L. pinguis. 
Greenish yellow to darkening ..................22.... 20. L. saxicola. 
Thallus not closely affixed, dull greenish brown, the periph- 
eral lobes white-margined.............-...--.------- 24. L. melanaspis 
alphoplaca. 
1. Lecanora calcarea (L.) Nyl. 
Thallus crustaceous, white, mealy, rimose-areolate, determinate or subdeterminate; 
hypothallus pale, KHO—, Ca(ClO),—; medulla not stained with iodine; apothecia 
immersed, almost punctiform but becoming larger; disk concave, dark but appear- 
ing white from a dense pruina, round or angular; epithecium sordid grayish yellow, 
subgranulose; thecium 216 » high, colorless; paraphyses subcoherent, moderately 
coarse, finely granular, septate, the septa quite close, especially in upper part (visible 
after KHO); hypothallus colorless; asci ventricose; spores 6 to 8, arranged in one or 
two files, ovoid and subglobular, 16 to 28 » long, 15 to 20 » thick; hymenial gelatine 
stained indigo blue with iodine, turning brownish reddish. 
The thallus is often grayish in color, but reactions and measurements are the same. 
On calcareous and other rocks. Mountains of Ventura County (Matilija Canyon), 
frequent in the Santa Monica Range. The thallus varies and the following forms 
occur: 
The forma hoffmanni Sommerf., with the thallus of contiguous or discrete verruci- 
form squamules, flattish at the circumference and rising crateriform toward the middle 
of the squamule, gray, sordid greenish gray, also pale testaceous, the disk not seldom 
black, naked—is found in the Santa Cruz Mountains, Herre, and at Daggett, Mohave 
Desert, Parish. The forma monstrosa Cromb. occurs occasionally on sandstone in the 
Santa Monica Mountains—the verruce white, mealy, discrete and scattered, convex 
with small, immersed, pruinose concave disk, without spores. 
2. Lecanora cinerea (L.) Sommeri. 
Thallus crustaceous, thick, whitish to light gray, rimose-areolate, the areoles angular, 
flat or slightly concave, smoothish, KHO+ yellow then rusty red, the medulla un- 
changed with iodine; apothecia immersed, small to minute, from 0.5 to 2 mm. wide; 
disk at first flat, sometimes finally slightly convex, dull black, the larger moderately 
umbilicated and sometimes with a thin grayish bloom, bounded by a persistent thal- 
line margin; epithecium forming a thin dark line, subcontinuous; thecium colorless, 
about 180 « high; paraphyses loose, coherent at the tips, septate, as seen after KHO; 
hypothecium pallid, a fourth of the height of the thecium; asci ventricose, 6 to 8- 
spored, the spores ovoid, with granular contents, 24 to 28 » long, 16 to 20 » thick; 
spermatia straight, acicular, 24 to 32 » long; sterigma simple, straight; hymenial 
gelatine with iodine blue, turning greenish blue. 
On granite, Mount Wilson at 1,700 meters; San Antonio Canyon at 1,500 meters; in 
the San Bernardino Mountains, Parish. 
3. Lecanora gibbosa (Ach.) Nyl. 
Thallus thick, gray, rimose-areolate, the areole rugulose, warty, KHO—, Ca 
(ClO),—; hypothallus pallid; apothecia primarily immersed-sessile; disk flat, 
black, naked, round or by crowding of apothecia irregular, now and then becoming 
convex, surrounded by a slightly elevated thalline margin; epithecium subcontin- 
