562 Fry. — Some Types of Endolithic Limestone Lichens . 
Fig. 8. Placodium rupestre , var. calvum, forma incrustans. Low power. Vertical section of 
thallus and apothecium (depth in limestone, 160 ix). 
Fig. 9. P. rupestre , var. calvum , form incrustans. Vertical section of part of thallus. 
Fig. 10. Lichen ‘Y ’. (Gonidia, Trentepohlia). Vertical section of thallus (depth in limestone, 
140-200 \x). 
Fig. 11. Lichen ‘ Y \ Gonidial cell from lower part of thallus. 
Fig. 12. Lichen ‘ Y \ Gonidial cell from lower part of thallus. 
Fig. 13. Lichen ‘Y’. Lichen spore germinating on surface of limestone and sending hyphae 
into the rock, which attack the gonidium. (Dotted area indicates limestone.) 
Fig. 14. Aspicilia calcarea. Vertical section of thallus (width of whole thallus, 3,000 \i). Depth 
in limestone, 2,800 fx. Width of epilithic thallus, 190-250 fx. a. ‘ Transition’ zone at top of lime- 
stone ; b. Endolithic gonidial group; c. Small group of inflated cells; e. Four gonidial groups in 
vertical connexion. 
Fig. 15. Aspicilia calcarea. A few enlarged hyphal cells from the ‘transition’ zone. 
Fig. 16. Aspicilia calcarea. Endolithic gonidial group enlarged. Gonidia surrounded by small 
inflated cells. 
Fig. 17. Aspicilia calcarea. Endolithic gonidial group enlarged. 
