20 Proceedings of the Royal Irish Academy. 



Holstein, distinguishes merely cortex, gonidial layer, and medullary tissue ; 

 he describes and figures the ruptures of the cortex of E. fraxinea, where the 

 medullary tissue comes to the surface, and names them "Atemporen," i.e. 

 breathing pores ; he further regards the attaching organs as the portion first 

 formed. 



In 1901, also, Bitter, 1 in his account of the variability of some foliose lichens, 

 describes E. obtusata Am. as having two opposed cortices, scattered groups of 

 gonidia, and a loose mesh of medullary tissue. He observes the effect of light 

 on the cortices as producing gaps in the cortical tissue on the under surface, 

 but rarely on the upper. He cites similar occurrences in E. ililacerata Hofl'm., 

 and in 11. minu&cula, a rare British species; he refers to gaps in E.fraxinea 

 as piercing the thallaa lie farther points out in reference to Lindau's account 

 of the sucker-like reproduction of Evernia prwiastri, that in the allied but 

 prostrate species B. furfv/raoea, the method is common. Brandt, 2 in 1906, 

 investigated the anatomy of many species of E"iinilina. He discusses previous 

 work, dismissing that of Speerschneider as primitive in method, and regarding 

 all failures to distinguish between cortex and mechanical tissue as regrettable 

 oversights, lie explains that his material is dried and treated with potash 

 to dissolve oat the usneic acid between 1 1 « « - hyphae, neutralized with acetic 

 a>id, and finally Btained with alcoholic solution of iodine. By these means 

 he finds pseudoparenchymatic tissue in the mechanical strands, consisting of 

 more or less isolated hyphae enclosed in dark walls — an appearance which 

 will be discussed later. He also regards the tissue of the basal disc as 

 secondary in origin, but does not give details of its structure nor of his 

 reasons for the view. His account of the varying proportions of cortical and 

 other tisanes present in the different species, in the light of Bitter's work on 

 the effect of external influences, may possibly he unnecessarily detailed; the 

 differences being phj>iological rather than specific. Zahlbruckner 3 also 

 follows Schwendener in distinguishing an inner cortex of mechanical tissue 

 in which the hyphae run more or less longitudinally, and a true cortex in 

 which they are more or less at right angles to the longitudinal axis; he 

 ! urds the inner cortex as frequently cut into supporting "pillars" by out- 

 growths of the medullary tissue towards the surface. 



Funfstuok,' in his general account of lichens, refers to the thickly-woven 



1 Pringaheim, 3<i. 1901. 



: Brandt, Th. I! zur anatoinischc Kenntnis der Flcchtcngattung Ilamalina 



II. Iwig i. i".. 1906). 



X ihlbruckner. En^'lur and PrnntIV Naturlichen Pllanzenfainilii n — Flechteo Tuil I, 

 p. 2S 



I .ufstuck. En •' • r ind Prantl'* Natiirlichcn PUaiizcnfamilieu— Flcchtcn Teil I, 

 p. 20. 



