154 DK. J. STIKTOX OX TILE LICHENS 



Epipasta characterizes well the appearance of this tribe gene- 

 rally, and may accordingly stand as the specific distinction of one 

 of them. 



All this appears trivial enough and even out of place in such a 

 subject as the present ; but it should be remembered that the dis- 

 cussion has been forced on me by way of defence. 



Lecidea thgrsodes, Strn. — Mr. Crombie has given the dimen- 

 sions of an immature spore. Being more favourably situated, 

 I selected the best of the three or four apothecia detected. 

 Perhaps I have overstated the thickness a very little ; but cer- 

 tainly Mr. Crombie has understated it. The dimensions of the 

 spores may be stated as "06--085 X '003-0035 millim. 



I find also that while the perithecium is complete in a young 

 state, it is wanting, or very nearly so, at the base in a mature 

 apotheeium, whence my description, viz. "hypotbecium incolor," 

 is much nearer the truth. "What has been already stated accounts 

 for the darker thallus as described by me. 



Opegrapha undulata, Strn.,= 0. dialeuca, Cromb. — In this the 

 margins are truly undulated in nearly every instance, while the 

 spores are not determinately 7-septate, as stated by Mr. Crombie. 

 In fact it very seldom happens that pluriseptate spores are de- 

 terminately septate. By the way, it is rather curious that the 

 same exception may be taken to Mr. Crombie's distinction dia- 

 leuca that he advances against epipasta, as there are several Ope- 

 graplice dialeucous. 



I have again examined what has been termed Eamalina her- 

 mudiana, and I cannot reconcile myself to its identification with 



JR. complanata as Mr. Crombie does. I find the rufo-ferrugi- 

 nous reaction by K on the thallus is confined to the soredioid 

 points on which it is immediate, while this reaction is developed 

 much more slowly over the general thallus, and only shows through 

 this by the medulla being so affected. 



In Lecanora chlaronella, NyL (No. 13, Bermud.),Dr. Nylander 

 founds the distinction from L. chlarot erodes, NyL, in the fact 

 that the former lias an after vinoso-fulvescent reaction by means 

 of iodine on the hymenial gelatine, while the latter has no such 

 secondary reaction. My experience already tells me that this is 

 a very unstable foundation. A solution of iodine very little 

 stronger than usual will develop this secondary reaction in a 

 pretty large proportion of such cases when a feebler one will not ; 

 and it should be remembered that it is very difficult, if not im- 



