550 Fry . — Some Types of Endolithic Limestone Lichens. 
they are without the dense lining of very small hyphae. The spores, how- 
ever, are very different from spermatia (Plate XXI, Figs. 4, 5, 6, and 7, and 
Text-fig. 8). They are borne on the hyphae lining the cavities and generally 
occur in such masses that it is difficult to see their actual origin. Since the 
spores are so large, 5 /x or more, the size of the cavity itself is very much 
reduced. They (Plate XXI, Figs. 4, 5, 6, and 7) are at first colourless and 
apparently thin walled, but later become thick walled and dark brown. In 
the younger stages one is able to see large projections into the cell cavity 
(Plate XXI, Figs. 6 and 7). Apart from such projections as appear almost 
Text-fig. 7. Lichen ‘X’. Spermogonium ; o.c. = Text-flg. 8. Lichen ‘X’. Pycnidia with macro- 
inflated oil cells. Inset : Sp. - spermatium. spore. Inset : portion of wall bearing macrospores. 
m = macrospore. 
to divide a cell into two, the spores may be uniseptate (Plate XXI, Figs. 6 
and 7), though often they are simple (Plate XXI, Fig. 4) and without 
projections into the cavities. 
Tulasne( 7 ) has recorded the presence of both spermogonia and pycnidia 
on the lichen thallus. The pycnidiospores or stylospores were described as 
‘ larger bodies than spermatia, occasionally septate, and containing oil drops 
or guttulae. These spores are pyriform or ovoid in shape and are always 
borne at the tips of simple sporophores ’ (8). In the case of lichen ‘ X ’, 
also, the two kinds of spores are quite distinct. 
/. A. c. Placodium rupestre , var. calvum , forma incrustans , A. L. S. 
Thalli of Placodium rupestre , var. calvum , forma incrustans , are small, 
being about one square centimetre in area. Nevertheless, they are often 
