Porter — Or (fans of the Common Cor ticolous Ramalinac. 19 



medullary layer as arachnoid, becoming sometimes very lax, and the cortical 

 layer as composed either of indistinct cells or of longitudinal conglutinate 

 filaments ; that is, he does not distinguish cortex and mechanical strengthening 

 tissue. 



Lindau, 1 1895, follows Schwendener closely as to anatomy and mode of 

 attachment, but whilst condemning the general use of the term hypothallus, 

 expands the idea. He regards it as a structure of secondary origin, the 

 hyphae of which are able to penetrate between the periderm cells, forcing 

 apart the cell layers, but unable to bore through the walls. 



The occurrence of definite cavities and cell remnants connected with the 

 basal disc is attributed to the chemical action of atmospheric agents, and he 

 suggests that the hyphae are able to assimilate the decomposition products 

 of the cellulose, which are thus rendered available as nourishment for the 

 whole organism. He figures and explains the basal disc in Evemia prunastri 

 as clearly cut off from the thallus itself by a narrow zone of brown-coloured 

 hyphae, which is to be regarded as the outermost layer of the lichen thallus. 

 This hyphal cylinder is open below, and the medulla of the lichen is directly 

 connected with the hyphae of the basal disc. On this appearance he bases 

 his view that the disc is secondary in origin, and supports it by the fact that 

 broken-off, isolated parts of the periderm, which are surrounded by hyphal 

 masses, move gradually outwards. 



He shows, too, in Evemia that sucker-like outgrowths arise. A branch 

 of the thallus may attach itself to the' bark of the twig on which the plant 

 grows, or to that of a neighbouring one. If the connexion with the mother 

 plant is accidentally torn, an independent individual arises, the origin of 

 which is not obvious later. He refers elsewhere to the thickly-packed, alga- 

 containing lobes of the cortex occurring in connexion with the thallus itself, 

 but dismisses them as non-typical in structure, mere occasional forms of 

 attachment, having no further meaning. 



Keinke- includes in his account of the comparative morphology of lichens 

 a review of the Ramalinac. He refers to Schwendener's work on the anatomy 

 of this genus, but disregards the mechanical tissue, indicating merely the 

 presence of a thickly-woven cortex, a loose medulla, and a gonidial layer 

 between them. Darbishire, 3 in his account of the Ramalinac of Schleswig- 



1 Liudau, G. " Licheuologische Uiitersuchungen, I,. Uber Wachstum und Anheft- 

 ungsweise der Rindenflechten." Dresden, 1895. 



2 J. Jteinke. " Abhandlungen uber Flecliten" IV (Pringsheim's Jahrbiieher f. w. 

 Botanik 28, 1895). 



3 0. V. Darbishire. " Einer Abhandlung uber die Naturgeschichte der Einheimischen 

 Flecliten," with R. v. Fischer Beuzon's Die Flecliten Schleswig-Holsteiu Kiel, 1901. 



[C2] 



