522 DE LAUDER LINDSAY ON NEW LICHENICOLOUS MICRO-FUNGI. 



3. 1 to 3-septate, mostly 3-septate and brown; sometime colourless. 



Microthelia vesicularia; 1-3 septate. 



Umbilicarise; 1- sometimes 



2-septate. 

 Nepromiaria; colourless. 

 Easomycearia. 



Parasites on 



(«.) Physcia ciliaris. 



(&.) Lecidea lurida. 

 Parasites accompanying 



(a.) Lecidea ferruainea v. sinapisperma. 



(5.) Verrucaria Taylori. 



Any such classification, however, is obviously artificial and defective; for not 

 only in the same species, but in the same individual, the sporidia frequently vary 

 much in character — in size, form, colour, and structure. In particular, they are 

 frequently both simple and compound, colourless or coloured, of regular or 

 irregular outline — according to the stage of growth. The " character" selected as 

 the basis of classification must, therefore, be that which is presumed to prevail 

 in maturity, and in normal conditions of growth. But what is prevalent or 

 normal in one district or set of circumstances is not so in another, especially if 

 the district or circumstances in or under which one systematist works are very 

 diverse from those of others. There is, therefore, in such cases no precise or 

 permanent basis of classification ; whence it follows that the classification itself 

 must be faulty. These remarks apply to too many modern " classifications 11 of 

 lichens, based on the characters of the sporidia alone, or on any single " characters" 

 or combination thereof ! 



In the group of parasites hereinafter described under Microthelia, the Iodine- 

 reaction, which by fungologists is considered lichenoid, denoting the presence of 

 lichenine in the lichen-tissues, is generally absent. In the parasite accompany- 

 ing Verrucaria epidermidis v. analepta, however, the asci give a blue reaction with 

 iodine; in Microthelia Stictaria they become deep violet j in M. Umbilicarice the 

 asci and hymenial gelatine assume various shades of violet; while in M. 

 Nephromiaria the hymenial gelatine becomes violet. These exceptional reactions, 

 however, neither prove nor disprove in themselves that the parasites, in which 

 they occur, are lichens or fungi ; for, as I have elsewhere* sufficiently shown, this 

 so-called lichenoid reaction occurs in indubitable fungi ; while there are many 

 true lichens destitute of any colour-reaction— indicative of the presence of starch, 

 or its varieties or allies — with iodine. 



Iodine-reaction is a subject of so great (supposed) importance in relation to 

 the differential diagnosis between lichens and fungi : and as a "character" it 

 bears so intimately on the place in classification to be assigned to the group of 

 fungo-lichens, and to the members of the provisional genus Microthelia, as adopted 

 or established by me, that it requires here some additional consideration. As a 

 ground for regarding it as a diagnostic " character," it appears to me necessary, 



* Arthonia melaspermella, p. 283 ; " Otago Lich. and Fungi," p. 423 ; " Parasitic Micro- 

 lichens." 



