53 



THE THALLUS OF THE GENUS PARMELIA 



By John Shirley, D.Sc. 

 (With 6 plates auci 12 figures). 



[Keceived. 30th August, 1918. Keacl 9th September, 1918.] 



Introduction. 



In the ordinary works on Lichenology, the main 

 object of the author is to give siuch a. description of a 

 species as will enable a student to determine a plant by 

 himself, by exaiUiination of the thallus with a pocket lens, 

 and of the apothecia and spores by the aid of a microscope. 

 The spermagonia and spermatia may be briefly referred to, 

 but other matters are usually ignored. In this papei' 

 no reference will be made toi a, macroscopic study of the 

 thallus, or to the histology of the apothecium, its para- 

 physes or spores. For those who- require this information 

 any OT'dinary work on Lichenology will sufficiently meet 

 their requirements. 



In such works as Goebel's "Outlines of Classificatioax 

 and Special Morphology," Green's "Manual of Botany," 

 Vine & "Text-Book of Botany, ' etc., the same illustratioins 

 of thalline structures are repeated with wearisome regu- 

 larity, and with little addition to existing knowledge. 



In preparing the mlatteiiial for this paper, serial 

 sections of the following lichens were cut, stained, and 

 mounted for exa.mination : — Parmelia ttJiaced, Ach., P. 

 tinctorum, Despr., P. j)erlata, L., P. limhata, Laur., P. 

 lara, M.A., P. perforata, Ach., P. latissima, Fee, P. 

 placorhodioides, Nyl., P. mundata, Nyl., P. olivacea, L., 

 P. cetrata v. sorediifera, Wain., and P. aaxatilis v. signi- 

 fera, M.A. 



Twelve photo-micrographs illustrating these are s^ub- 

 mitted with this paper. It may be noted that Dr. Jean 

 Muller of Aargau regarded P. ^j/'acor7<of/?'oic/e.s and P. 

 mundata as varieties of P. physodes, and P. Jaxa as a 

 variety of P. conspersa, Ach. 



Of the material examined, the whole of the specimens 

 are Australian with the exception of P. cetrata v. sore- 

 diifera, Wain., which was chosen for special study of the- 



