123 



incrustation, are long, slender, simple or sparingly branched (usually 

 once or twice toward the upper end), bearing terminal more or less 

 globose apothecia, that is, it is the thallus instead of being spread 

 over the substratum about the stipe has spread over the stipe itself, 

 thus converting the originally mechanical structure into a physiologi- 

 cal one as well. 



Upon the examination of sections of the podetium it is found that 

 the assimilating tissue is the outermost and consists of a network of 

 hyphae in which the algae ( Cystococcus hamicold) are suspended ; 

 no cortical tissue proper is present. The algae are intimately asso- 

 ciated with ectotrophic as well as endotrophic haustoria. This gran- 

 ular alga-bearing tissue forms a thin layer over the podetium extend- 

 ing to the base of the apothecia ; it is only loosely attached to the 

 internal mechanical tissue so that it is readily abraded, espe cially in 

 the older specimens. 



The mechanical tissue consists of a comparatively thick cylinder 

 of closely adnate hyphae extending for the most part longitudinally. 

 The interior is occupied by a very loose network of hyphae. The 

 transition from the mechanical tissue proper to the central loose tissue 

 is sudden and not gradual as in Baeomyces. From the above it is 

 evident that we have here a typically radial structure built on the 

 plan of a hollow cylinder. 



The apothecia are of medium size, globose, the thecium lining 

 the greater part of the surface ; they appear as black terminal 

 somewhat irregular knobs, somewhat thicker than the podetium. In 

 structure they closely resemble those of Baeomyces ; the hypothecium 

 is black, and the epithecium and greater portion of the paraphyses 

 are blue-black. This coloration is a marked contrast to the other 

 groups of the family. The spores are oblong spindle-shaped, sim- 

 ple, colorless. 



Only a few species occur in the territory ; they are somewhat 

 northern in their range and occur upon rocks in rather moist places. 



PLATE ii. 



PlLOPHORON CEREOLUS (Ach.) Tuck. 



1. Plants natural size. 



2. Section of apothecium. 



a, thecium, b, dark hypothecium. 



c, beginning of colorless hyphae of the podetium. 



