38 LINDSAY, ON ABROTHALLUS. 



II. On PaT7nelia consptrsa. 



1. Barmouthj North Wales (Leigliton) ; witli spermo- 

 gones. 



III. On Cetraria glauca. 



1. Barmoutli, North Wales (Leigh ton) ; with spermo- 

 gones. Korher also speaks of it as abundant on 

 C. glauca in Germany. 



In the earliest state in which I have observed them, the 

 deformations of the thallus of P. saxatilis, on which the 

 Abrothalli grow, occur as minute, simple, orbicular squa- 

 mules, smooth above, black-fibrillose below. If they are 

 studded over with the young apothecia of A. oxyspoms, they 

 greatly resemble the scale-like thalli of some Endocarpons. 

 They are very different in appearance from the laciniffi of 

 P. saxatilis, which are sinuate-lacinulate, and the lacinidse 

 divaricate- angulose with retuse extremities. They are epi- 

 thalline, seated upon the ordinary thallus of P. saxatilis, 

 from which they appear perfectly distinct. Hence such 

 squamules have the appearance of separate and parasitic 

 vegetations. Occasionally I have seen the Abrothalli grow- 

 ing on the normal lacinise of furfuraceous forms of P. saxa- 

 tilis, or on lacinise very slightly modified. In other cases, 

 the anamorphoses, in the structiu'c of their lacinise, closely 

 resemble the ordinary thallus of P. saxatilis. Occasionally 

 a few scattered apothecia of A. Smithli, with its pycnides, 

 occur on simple squamules ; but this is comparatively rare. 

 With age these squamules imdergo great modifications, and 

 it is generally at a somewhat later period of development 

 that they l^ecome the sites of the Abrothalli. The first 

 change consists in their becoming lobed and polyphyllous ; 

 in this condition they not unfrequently resemble the var. 

 complicatum of Endocarpon miniatum. A. oxysporus often 

 inhabits thalli of this kind. This condition is well marked 

 in specimens of A. oxyspo?'us from Glen Nevis. Sometimes 

 the lobes or squamules preserve a concavity of surface ; more 

 generally they acqviire a convexity from a tendency to evolu- 

 tion or curling out of their edges, which in some cases are 

 much thickened. The surface is occasionally much cor- 

 rugated or pitted, and scattered over with grayish soredia or 

 warts, which frequently crown the ridges of the plicae. I 

 have also seen the squamules pruinose like the thallus of 

 Pannelia pulverulenta. In some cases — as in A. oxysporus, 

 from Loch Coruisk, Skyc, and in yl. Sinithii, growing on the 



