394 DR. LINDSAY ON WEST-GREENLAND LICHENS. 
0024" long and :0009” broad ; muriform, consisting of a close aggregation of irregular 
cellules. Colour very deep brown. Apothecia flat. 
(3.) Sporidia irregularly oblong, pyriform or ellipsoid, with about 7 transverse septa, 
having longitudinal central subdivisions; deep olive or bottle-green ; :0012” long and 
:00045” broad. In the older, muriform condition, there is sometimes a central constric- 
tion of epispore, the sporidia showing at this point a great tendency to split. Halt- 
sporidia, split in this way, occur, intermixed with fully formed ones. In the old, muri- 
form state, the colour is so dark that the contained or constituent cellules are undistin- 
guishable. The younger sporidia exhibit no longitudinal subdivision, or only through 
one of the central or polar loculi. The contained cellules in the muriform state are 
sometimes few and discrete (sometimes only two or three in a row) as in Urceolaria 
scruposa. In other cases they are usually more minute, numerous, and crowded. 
(4.) Sporidia linear-oblong, 0009" to :0012” long and :00045” broad. At first exhibit- 
ing only about 7 to 10 transverse septa, which, by division longitudinally, gradually 
become muriform, the colour in the early stages being deep olive, in the older brown. 
(5.) On the thallus of different Lecidec (e.g. on forms of L. parasema), I found spo- 
ridia apparently referable to Z. petrea; old, very dark brown, and very irregular in out- 
line resembling those of U. scruposa; about -0009" long and :00045” broad. I have 
occasionally, in like manner, met with stray individual or single sporidia of very different 
genera or species on the thallus of many lichens, mostly crustaceous*. In all the Green- 
land forms of the variable petrea, the hymenial gelatine and the asci give a very deep 
beautiful Prussian-blue colour with iodine. gran 
In Scherer’s Exs. No. 177 (= L. confervoides, DC., f. concreta, Sch.), the sporidia 
are colourless, 9-locular, becoming muriform ; pyriform : :0010" to -0012" long and 
‘0005 broad. In its colourless sporidia this form of petræa resembles L. grenlandica. 
4. L. atro-alba, Ach.—Jakobshayn; Egedesminde; Atanakerdluk. In various forms, 
differing in their thallus, apothecia, and sporidia. The thalline areolæ are sometimes 
discrete and pulviniform, convex or even subspherical; or the young peripheral ones 
alone are so. "Though whitish or grey in the dry state, they become green when 
moistened. Sometimes the thallus is rather tartareous, thick, verrucose, without distinct 
areolæ, buff or cream-coloured. In other cases the areole are very black, glossy, 
convex, confluent, and deformed. "This condition is sometimes common in large patches, 
e.g. on granite about Egedesminde. Occasionally the areolæ are flattish and thin. 
The apothecia are sometimes flat, especially when young, with thin exeiple, which is 
sometimes wavy. In age they occasionally become convex and subspherical (the disk 
concealing the exciple), and variously deformed. They differ considerably also in size, 
being largish or small. Sometimes they are compound; or several young ones cover the 
surface of a decayed or degenerate old one, producing various irregularities of surface 
and outline. Frequently also, in age, the disk becomes convex and rough on the surface, 
with irregularity of outline. The asci are small generally, about :0015" long and 
700045" broad; 8-spored. The sporidia are never large, as described by Th. Fries 
(L. Arct. p. 230), but vary in size from about :00045" to 00060” long and :00022” to 
: * Vide Cladonia gracilis, and Lecidea parasema, No. 3. 
