FOUND BY THE ARCTIC VOYAGERS. 48 
form a distinct section in the genus leading to Cystotricha, which they 
much resemble in habit, though it does not appear that they em 
longitudinally. 
Hendersonia fibriseda; peritheciis subglobosis minutis tenerrimis atro- 
cæruleis; sporis elongatis flexuosis utrinque obtusis. 
Has. On Birch planks. King's Cliff. Dec. 1851. 
Perithecia punctiform, subglobose, seated on definite white spots, fol- 
lowing the direction of the fibres. Very delicate pale blackish-blue, es- 
pecially at the edge, which consists of interwoven fibres. Sporophores 
short, obtuse; spores 44, of an inch long, ,.2,, broad, containing ob- 
scurely defined nuclei. 
This is a Hendersonia according to M. Desmazi?res' view of the genus, 
agreeing in structure with such species as H. Typhacearum. The 
white spots on which it occurs are more decayed than ordinary bleached 
surfaces. 
Sporidesmium Lepraria; maculis effusis aterrimis ; sporis irregulari- 
bus basi nulla distincta suffultis. Lepraria nigra, Eng. Bot.! t. 2409. 
Extremely common on planks of wood exposed to the weather, on 
which it forms broad black persistent patches. Sometimes however it 
occurs in distinct black specks, which wear the appearance of little ob- 
long perithecia of various species so common in such situations. The 
spores are extremely irregular, of no definite shape, and without any 
distinct base. 
The Arctic specimens differ only in their darker colour, and slightly 
smaller cells. This may be called var. nigerrima. I am indebted to 
Mr. Borrer for authentic specimens of Lepraria nigra, Eng. Bot., from 
whom also I have Spiloma microscopicum, Eng. Bot., which appears to 
be a mere variety of the same species. 
In S. polymorphum, Corda, there is a distinct istisi geliau 
and in S. antiquum the spores are erect and elongated; S. melanopum. 
has the same habit, but there is a distinct cellular base to the spores. 
Spheria (Platystome) ibritecta, n. s.; sparsa obtecta; peritheciis 
depressis; ostiolo obsoleto vel qu vario ; ques curvulis 
quinqueseptatis. 
Has. On bleached fibres of Larch slate King’s Cliff. Dec. 1851. 
Scattered, minute, black, often slightly elongated, depressed; osti- 
olum sometimes quite obsolete, but. frequently present, and varying 
from punctiform to linear. Asci clavate, varying greatly in length, 
