546 Fry. — Some Types of Endolithic Limestone Lichens. 
the thallus on the surface, penetrating the cortical gonidial and rhizoidal 
regions of the neighbouring lichen. 
The perithecium. The whole perithecium, except for the lid or cap, 
is embedded in a deep pit in the rock. This pit usually reaches down to two 
and a half to three times the depth of the gonidial zone (PI. XXI, Fig. i, 
and Text-fig. 3). The fruiting body figured in the plate is not mature ; asci 
are present, but ascospores have not yet been formed. Paraphyses, as is 
usual in this species, have decomposed and formed mucilage, which is 
indicated near the base of the neck. Lining the neck are numerous 
periphyses. The lid already shows the position of the pore. Even at 
immature stages the fruiting body never completely fills the hollow. The 
origin of the perithecium is within the limestone, and at an early stage the 
Text-fig. 3. Verrucaria calciseda. Young apothecium Text-fig. 4. Lecidea immersa. Old apothe- 
(longitudinal section). Inf. = inflated hyphae ; Inf . — cial pit being recolonized by gonidia and hyphae. 
inflated hyphae forming lid ; x = disorganizing part of 
thallus and dissolving limestone in process of dissolution. 
black lid is found to be situated immediately over the developing peri- 
thecium, but completely inside the thallus (Text-fig. 3). In the earliest 
stages this lid is seen to be made up of thin-walled, inflated cells which at 
a later period turn black and become thick walled, and can scarcely be dis- 
tinguished (PI. XXI, Fig. 1). As the neck and perithecium develop, so the 
lid is pushed up through the limestone and the tissue above becomes dis- 
organized, ultimately breaking away from the thallus (Plate XXI, Fig. 1 b). 
At the base of the developing perithecium there is a plate of inflated 
hyphae, which also becomes thick walled and dark coloured later on 
(Text-fig. 3 and PI. XXI, Fig. 1). After the spores have been freed through 
the pore the wall shrinks and the old perithecium is washed or is blown 
out of the depression. This pit is not filled in with hyphae, as are cavities 
similarly left in aerial lichens, but the limestone lining the hollow is soon 
occupied by gonidial groups (Text-fig. 4). 
limestone 
