
OF FILAMENTOUS, FRUTICULOSE, AND FOLIACEOUS LICHENS. 259 
GENUS IV. SquamartA, DC. 
This genus is closely allied to the following one—Placodium ; but there are 
some prominent differences in regard to the character of the spermogones,—par- 
ticularly in regard to the spermatia and sterigmata. In reference to its spermo- 
gones, Placodium stands much nearer Physcia than Squamaria does. The sper- 
mogones of Sguamaria are mostly immersed, and are marked by an inconspicuous 
punctiform ostiole, which is frequently of the same colour as the thallus. The 
ostiole is sometimes black, bluish, or brownish—generally minute and round— 
occasionally stellate-fissured. Seldom are the spermogones tubercles or papillz ; 
seldom are they conspicuous or large. In S. aleurites, they are punctiform; in S. 
gelida, they are perched on pale thalline papille. They are usually scattered about 
the periphery of the thallus—sometimes distributed chiefly about its centre. Some- 
times, in S. chrysoleuca, they are studded on the apices of isidioid growths of the 
thallus; and in S. concolor, they are scattered over the apothecia. The greatest 
diameter of the body of the spermogone varies from 7th to th; in S. saxicola it is 
goth. The cavity is usually simple ; in S. crassa it is divided into sinuous compart- 
ments, as in Physcia ciliaris. The spermatia are, as a general rule, long, filiform, 
and curved or twisted, among the most beautiful and largest that occur in lichens. 
Their length varies from sth to jooth, many being about ;,th long; their breadth 
varies from 35;nth to santh, and is frequently inappreciable. InS. alewrites, Ihave 
found short rod-shaped spermatia, about zath long; this, however, is the only in- 
stance in which I have ever met with them other than filiform and curved. In this 
species, too, the sterigmata are of an exceptional character, being articulated, 
consisting of a few linear, delicate cells, and resembling those of many Parmelie. 
They are usually simple, linear, elongated, branching or not at the base, and re- 
sembling those of Lecanora subfusca. The spermatia, sterigmata, and spermogones 
of Sqguamaria are much more closely allied to those of Zecanora than to those 
of Physcia—quite the reverse being the case in regard to Placodium. The length 
of the sterigmata varies from ;,th to xath; their breadth from ;5;th to eunthe 
Species 1. S. crassa, DC., 
Which occurs equally in Africa and Europe. Its spermogones in French speci- 
mens, according to Tutasne—for I have not myself met with them—are minute 
tubercles scattered over the thallus, generally of a pale-brown colour, sometimes 
flesh-coloured, occasionally violet. The apex is more frequently marked by a 
fissured ostiole than by a round imperceptible pore. In the old state, the ostiole 
expands so as to assume a discoid character, its borders being very irregular and 
lacerate. The greatest or transverse diameter of the spermogone varies from 
ath to yth. Its body is wholly or nearly immersed in the thallus ; it is sometimes 
girt by the gonidic layer of the thallus; at other times it is plunged immediately 
