1 82 INTRODUCTION TO THE STUDY OF FUNGI 



the Lichens, it will be observed that here again the discoid 

 Fungi come almost in touch with another outside group, and 

 seem to pass almost insensibly into Lichens, destitute of a 

 visible thallus. Amongst the Sticteae there are such genera as 

 Xylographa — which some lichenologists still claim, but which 

 mycologists will not reject — in which the relations of Fungi 

 and Lichens are most intimate. In Platysticta as compared 

 with Platygrwpha, and some species of Stictis with Thelotrema, 

 the resemblance, if not affinity, is maintained. 



The classification adopted by Fries in this, as in all other 

 groups, was based primarily on external characters distinguish- 

 able by the aid of a common lens. Microscopical characters 

 had none, or but a subsidiary place. Although his success was 

 very great in appreciating affinities, considering the limits of 

 his investigations, yet much was left imperfect and undecided 

 when subsequent observers came to apply the microscope. It 

 was felt that, however great was the success when applied to 

 large objects, the system was not sufficient for small ones ; so 

 that, step by step, alterations and additions were proposed by 

 Fuckel, Karsten, and others, which culminated in the carpo- 

 logical system elaborated by Saccardo. Whether, as a whole, 

 this latter is too artificial to satisfy the aspirations of those 

 who believe in natural affinities, must be left to individual 

 judgment. The basis of classification being transferred from 

 external characters to internal fructification, there was a 

 manifest danger lest external characters should be wholly 

 ignored ; fortunately, however, this was not the case, so that 

 the result may be expressed as a combination of the two, 

 giving the pre-eminence to the carpological. 



The fructification of the discoid Fungi, as compacted in the 

 disc, consists of the asci and their contents and appendages— 

 that is to say, the asci and their contained sporidia, and the 

 paraphyses. The asci for the most part are cylindrical, or else 

 clavately cylindrical, seldom ovate or approaching to globose. 

 The sporidia, subject to considerable variation in form and 

 size, are to a greater extent simple and uncoloured than in any 

 other group of Ascomycetes ; in the larger species elliptical 

 or globose, in the smaller cylindrical or fusoid — the colour of 

 the sporidia and their septation being held as of generic value. 



