PoRTKE — Organs of the Common Corticolous Ramalinae. 23 



The grouping of the apices of the hyphae into lobes or bundles should 

 be noted, as it is apparently continued for a short distance into the general 

 cortex. 



Fig. 2 is a cross section taken near the base of a bushy specimen of 

 R. farinacca just above the surface of the periderm of Oak. The white 

 patches (c) are pillars and convolutions of cortical tissue, i.e. longitudinal 

 hyphae. The dark internal portions consist of loosely-woven medullary 

 tissue, edged here and there with a few gonidia. Externally and between the 

 lobes are masses and layers of varying character, in places distinctly soredial 

 or even gonidial, but as a rule indefinable. The figure resembles Brandt's 

 figures of R. Cumowii. 1 Whether each hyphal mass is continuous with one 

 lacinia would be hard to decide, but they are frequently separate and con- 

 tinuous for some distance into the periderm. 



Fig. 3 represents a portion of the transverse section of the thallus of 

 R. farinacea, showing the more or less horizontal direction of the apices (a) ; 

 the cut ends of the vertical hyphae, interspersed with other hyphae running 

 in various directions ; and, internally, the gonidial and medullary tissues. 



2. Attachment of the lichen, and anatomy of the hypothallus. 



In fig. 4 we have the longitudinal section of R. farinacca on Hawthorn. 

 This is very similar to the figures given by Lindau representing the attach- 

 ment of strap and fruticulose lichens to their hosts. We have here the 

 apparently sudden end of the portion of the thallus above the periderm (p), 

 whereas the hypothallus or basal disc consists of hyphae or hyphal masses 

 scattered among the periderm layers. Here, too, may be seen the wedge-like, 

 disintegrating action of these hyphae on the cork cells. 



Figs. 5, 6, 7, and 8 represent the paths of hyphae between the cells and 

 across the gaps in the periderm tissue. 5, 6, and 7 arc portions of R. fari- 

 nacca on Hawthorn, 8 is from a transverse section of R. calicaris on 

 Sycamore, showing the spread of hyphae outwards from the basal disc. 



In all these sections 4-8 the attaching hyphae appear inconsiderable in 

 bulk and power compared with the thallus to be supported, and with the size 

 of the gaps in the periderm. In some cases the latter discrepancy is due to 

 the growth of the periderm after penetration by the hyphae. But in all 

 these sections the two points of interest are the bridging of gaps by single 

 hyphae and the close adherence of the hyphae elsewhere to the walls of the 

 periderm cells, such cells frequently presenting a crushed or collapsed 

 appearance. 



1 Brandt, loc. cit., p. 152, and Plate VI, Gga. 1 and 2. 



