554 Fry. — Some Types of Endolithic Times tone Lichens. 
these have been found in the freshly decalcified material without sectioning. 
They measured at least 12 /x in diameter and arose from hyphae similar in 
every respect to the ordinary Aspicilia calcar ea type. The simple chain 
of inflations resembled very closely those described for lichen ‘ X and 
since they have not been seen in sections of Aspicilia one feels very doubtful 
whether they belong to that form. 
The wider rhizoids are unevenly distributed and their origin from the 
hyphae of the crustaceous part of the thallus seems a little obscure. This, 
together with the fact that they are usually brownish or yellow, makes one 
doubt their relation to A. calcarea , although they are present in most of the 
sections of A. calcarea in the limestone immediately below the epilithic 
thallus. Bachmann’s description of the yellow hyphae found by him below 
the thallus of this species agrees with those of the present investigation. 
The rhizoids penetrate the limestone to a depth of 2,800 /z, making the 
width of the whole thallus over 3,000 [ x. 
Occasionally algal cells are found in the £ transition ’ zone, but apart 
from these and the gonidial region of the epilithic thallus, there is the 
extraordinary development of gonidial groups in the limestone, where they 
may penetrate to a depth of 280 /x (PL XXI, Fig. 14). If they occur near the 
surface of the limestone, they are spun round by hyphae which are directly 
connected with the ‘ transition ’ zone : if lower down in the rock, they are 
encircled by thin-walled rhizoids. In some cases cells with dense contents 
surround the gonidia ; in other cases slightly inflated hyphae with little or 
no deeply staining contents (PL XXI, Fig. 16), and sometimes a mixture of 
the three, may take part in encircling the algal cells (PL XXI, Fig. 17). 
Generally these groups occur as isolated rounded masses in the rock, and in 
this respect remind one of the Placodiwn type of endolithic thallus described. 
Occasionally these groups are connected vertically with each other 
(PL XXI, P'ig. 14), but very rarely is there any lateral communication 
between them. 
Yet another peculiarity obtains in the upper limestone layers below 
the crustaceous part of A. calcarea thallus. Certain thin rhizoidal hyphae, 
arising in the £ transition ' zone in the usual way, penetrate the limestone and 
immediately branch very freely and form numerous inflated cells in the same 
way as that indicated for the hyphae of the 4 transition * zone in PL XXI, 
Fig. 15. This branching of the hyphae and swelling of the cells goes on 
until huge clusters of spherical hyphae are formed. Bachmann (loc. cit.) has 
described the formation of these masses as follows : £ On one of the hyphae 
there arise, close together, numerous short branches. These go on growing 
parallel to each other and at right angles to the main hypha, projecting 
from it in all directions. A dilation of each of the cells of the entire 
branching system, not excluding those of the main hypha, goes on at the 
same time, until the spherical shape is attained. As a result of these 
