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II. 



ON THE ATTACHMENT ORGANS OF THE COMMON 

 CORTICOLOUS RAMALINAE. 



By LILIAN PORTER, M.Sc, 



From the Honan Biological Institute, Univeesity College, Cork. 



Communicated by Sir Bertram Windle, F.R.S. 



Plates II-IV. 



Read June 11. Published September 7, 1917. 



I. — Aim of Research. 



The aim of the present investigation was, in the first instance, the 

 examination of the so-called " rhizoids " of the corticolous members of the 

 genus Ramalina. It is obvious that these organs are not comparable 

 with the rhizoids of, for example, the Parmeliae, and that the work hitherto 

 published on the subject does not explain all the phenomena connected with 

 the development and spread of these plants. This involved a certain amount 

 of research in the general anatomy of the species under consideration, 

 especially as the investigator is met at the outset by fundamental disagreement 

 or misunderstanding among the leading authorities on the subject. 



In the course of the work a secondary aim, though one of more practical 

 importance, obtruded itself, namely, an estimation of the amount of damage 

 done by these lichens to their hosts. This amount is generally stated to be 

 negligible, and, in the case of timber trees, probably is so. Evidence 

 accumulated, however, to show that penetration of the host plant by lichen 

 elements is not limited to the dead tissues of the cortex, and demanded more 

 complete examination. 



II. — History. 



The earliest detailed work on the anatomy of species of Ramalina is that 

 of D.J. Speerschneider. 1 It explains the characters which distinguish the 



'Speerschneider. " Mikroskopisch-Anatoinische Untersuchung fiber Ramalina c«li- 

 earis Ft. und dereu Varietiiten fraxinea, fastigiata, canaliculate und faiinaeea" (Bot. 

 Zeitung, 1855, p. 345). 



R.I. A. PROC., VOL. 1XXIV, SECT. li. [C~\ 



