LICHENS AND LICHEN. PARASITES

DODGE-LICHENS AND LICHEN PARASITEE' 240
non bene evolutum ; thecium 55-6OP altitudine ; paraphgses tennes, super ascos dichotome ramosae,
ccllulis terminalibns nigro-brunneis, ad 4 ,~ diamet ro ; asci clavati, incrassati, protoplastis truncatis,
late mamillatis, ca. 35 X 8 ~ ascosporae ; octonae, oblique monostichae vel distichae, obscure
brnnneae, biloculares, ellipsoideae, septo non constrictae, 10-12 X 5-6~.
Thallils ambiguous, cortex not differentiated, the outermost algal cells protected by one to a
few layers of medullary hyphae; algae cystococc~id, up to 1 2 in ~ diameter, mostly eolitary and
relatively few ; medulla of closely woven, hyaline, thick-walled hyphae about 4p in diameter, forming
a cushion under the apothecium. Below what seems to be the thallus proper of the Buellia,
apparently the thallus of the host has been stimulated to elongation of the medullary hyphae,
forming a thick reticulate laxer, about 6OP thick, without algal cells, covered by a thin cortex,
lor. thick, of disintegrating fastigiate h;7rp?lae, and a lower medullary layer of anastomosing subvertical
hyphae, thin-walled, about 6~ in diameter. Dark brown hyphae from the base of the
parathecium, about 5~ in diameter, singly or in loose strands, penetrate the medulla of the host
thallus.
Apothecia black, 0.3-0-4 mm. in diameter, sessile, flat or slightly convex, margin black, not
prominent ; parathecium 4OP thick below, thirning to 3OP at the sides, dark brown, of thin-walled
periclinal hyphae, closely septate below and appearing almost pseudoparenchymatous, slightly
illrolled above, but not extending above the thecium; hypothecium scarcely differentiated;
thecium 55-6OP thick; paraphyses slender, dichotomously branched above the asci ; terminal cells
spherical, dark brown, about 4~ in diameter, forming a dark brown epithecium about 8~ thick;
asci clavate, wall and tip thickened, protoplast truncate, broadly mamillate, becoming thin-walled,
about 35 X 8p, &pored; ascospores obliquely aonostichous to distichous, dark brown, bilocular,
ellipsoid ,or flattened on one side, mcxderatel~ thick-walled, not constricted at the septum,
10-12 X 5-6~.
The interpretation of this species is not clear. Very little material is available. On the rpck, -
a few pulvinate, very thin areoles, 0.1-0.2 mm. in diameter, *nearly covered with a single
apothecium each, are visible. On the thallus of Lecanora exmlans close to them, the thallus seems A
still further reduced to about 0.1 mm. in diameter and is mostly covered by the much larger
apothecium. The surface of the Lecanora exsu!ms in the vicinity of the Buellia apothecia, is
abnormally coarsely verrucose, verrucae about 0 ~ 15 mm. in diameter. Apparently we are dealing
{with a species with a very reduced thallus which can survive alone, but which is a facultative
j'
f parasite. In the free livin-g phase, the apothecia are mostly 0.1 mm., very rarely up to 0.2 mm.,
while in the parasitic phase, the apothecia are mostly 0.2 mm. with some reaching 0-4 mm. in
diameter. The almost complete disappearance of the algae in the vicinity of the brownish
parasitic hyphae, and that the dying algal cells are about 1 2 in ~ diameter, suggests a facultative
parasite rather than an obligate one. Hence we have preferred to describe this species in Bz~elliu
rather than in Karschia, a segregate from Bue!lia for the obligate parasites.
On the thallus of Lecanora Johnstoni is the same or perhaps another species of Buellia which
shows a similar transition. The algae under the Bztellia apothecia appear cystococcoid, usually
in tetrads or larger colonies, cells mostly 45,~ in diameter; parathecium and hypothecinm black
and carbonaceous ; thecinm only 25-3OP tall ; paraphyses dichotomously branched above the asci ;
epithecial gel fuliginous or darker; asci broadly clavate to almost ellipsoidal, 25 X 15~; ascospores
immature in the asci A few ascospores 8-10 X 6-7~, bilocular, brown, constricted at the septum
were seen floating in the preparation. I have been dnable to decide whether this Buellia is epiphytic
with algae of its own, or whether it is parasitic, 'stimulating the host alga to divide more fre-