Porter — Organs of the Common Corticolous Ramalinae. 21 



strands of the Ramalinae as possessing only a slight capacity for water con- 

 duction. He further states the view generally held that rhizoids of corticolous 

 lichens never reach the living tissues. 



III. — Material and Methods Used. 



The species of Ramalina used in this investigation were the commoner 

 corticolous ones — R. calicaris, fraxinea, farinacca, fastigiata, {populina), and 

 pollinaria, i.e. the closely allied species of the section Euramalinae Stizbg. 

 and the sub-section C'ompressiuscidae Wainio, characterized lay the flattening 

 or bilaterality of the thallus segments. All the above species agree in being 

 more or less longitudinally striato-nerved, and possessing a filamentous 

 cortical layer (Crombie) ; the medulla gives no reaction on treatment with 

 potash. 



R. calicaris and fraxinea do not give rise to soredia, and the latter is 

 distinguished by its broader, flatter thallus, largely rugose receptacle of the 

 apothecia, and its curved spores. 



R. fastigiata is distinguished, especially from young states of R. fraxinea, 

 by its more caespitose habit and its numerous apothecia, which are 

 peltatosessile rather than distinctly stalked ; its spores are curved. 



R. farinacca is typically more or less covered with whitish, round or oval 

 soredia, especially towards the tips of the laciniae, the bases being frequently 

 smooth ; its apothecia are rare. 



R. pollinaria differs from R. farinacca in that the laciniae of the latter are 

 stiff; those of the former tend to be flaccid and inflated. Its soredia are 

 white, farinose, and scattered ; its apothecia are rare. 



The morphology of the above species was studied in the fresh condition, 

 abnormal and sub-specific forms being discarded. 



Comparisons were made with the collections in the Herbaria of the 

 University of Manchester and of University College, Cork, by kind 

 permission of the curators, Miss G. Wigglesworth and Miss B. E. Duke, and 

 at Bangor with the collection of Mr. Griffith, 1 to whom my thanks are due. 



The anatomical investigations were carried out as far as possible on the 

 fresh material, comparisons being made with the dried material, preserved 

 material and specimens treated with various reagents. 



Throughout the observations recorded potash was used with caution, as its 

 clarifying properties are neutralized to a great extent by its action on the 

 walls of the hyphae, and especially by the swelling it causes in the walls of 

 the periderm. 



1 Griffith, J. Flora of Anglesey and Carnarvonshire, Bangor. 



