130 



MORPHOLOGY 



Zukal 1 claims to have found breathing-pores in Cornicularia (Parmelid) 



tristis and in several other Parmeliae, notably 

 in Parmelia stygia. The thallus of the latter 

 species has minute holes or openings in the 

 upper cortex, but they are without any definite 

 form and may be only fortuitous. 



Zukal 1 published drawings of channels of 

 looser tissue between the exterior and the 

 pith in Oropogon Loxensis and in Usnea bar- 

 bata. He considered them to be of definite 

 service in aeration. The fronds of Ramalina 

 dilacerata by stretching develop a series of 

 elongate holes. Reinke 2 found openings in 

 Ramalina Eckloni which pierced to the centre 

 of the thallus, and Darbishire 3 has figured 

 a break in the frond of another species, R. 

 fraxinea (Fig. 75 A), which he has designated 

 as a breathing-pore. Finally Brandt 4 , in his 

 careful study of the anatomy of Ramalinae, 

 has described as breathing-pores certain open 

 areas usually of ellipsoid form in the compact 

 cortex of several species: in R, strepsilis 

 (Fig. 75 B) and R. Landroensis, and in the 



Fig. 75 A. Ramalina fraxinta Ach. 



A, surface view of frond, a, air- 

 pores; l>, young apothecia. x 12. 



B, transverse section of part of 

 frond, a, breathing-pore ;/, strength- 



! ening fibres, x 37 (after Brandt). 



British species, R. siliquosa and R. fraxinea. These openings are however 

 mostly rare and difficult to find or to distinguish from holes that may 

 be due to any accident in the life of the lichen. It is noteworthy that 



Fig. 75 B. Ramalina strepsilis Zahlbr. Transverse section 

 of part of frond showing distribution of: a, air-pores, and 

 /, strengthening fibres, x 37 (after Brandt). 



Rosendahl found no further examples of breathing-pores in the brown 

 Parmeliae that he examined in such detail. No other organs specially 

 adapted for aeration of the thallus have been discovered. 



b. OTHER OPENINGS IN THE THALLUS. Lobaria is the only genus of 

 Stictaceae in which neither cyphellae nor pseudocyphellae are formed ; but 

 in two species, L. scrobiculata and L. pulmonaria, the lower surface is marked 



1 Zukal 1895. 2 Reinke 1895, p. 183. 3 Darbishire 1901. 4 Brandt 1906. 



