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ally higher or lower. The thallus seems to be somewhat more highly 

 developed in Haematomma, while the thalloid exciple is considerably 

 higher in its development in Lecanora. This, however, only applies 

 to the Haematommas and Lecanoras of the territory, some of the 

 European Lecanoras having well-developed foliose thalli and are, 

 therefore, undoubtedly much above the highest Haematommas. The 

 apothecial, as well as the spore characters, point to close rela- 

 tionship with Lecanora and Parmelia. 



The thallus is usually regarded as crustaceous. A more or 

 less well-developed upper cortical layer is present in most species ; 

 in the lower forms it is scarcely noticeable, consisting of agglutinate 

 hyphae intermingled with the remnants of dead algae. The algae 

 are quite large, considerably larger than the normal or the majority 

 of other lichen Cystococci. Endotrophic haustoria are quite numerous. 



The medullary layer is well developed, consisting of much 

 branched hyphae, terminating below in the numerous rhizoidal 

 threads. In H. ventosa the thallus is very thick, warty and areo- 

 late ; in the other species, it is comparatively thin. Soredia are nu- 

 merous in most species, but they do not occur in clusters, being rather 

 evenly scattered over the entire upper surface of the thallus. The 

 color of the thallus is grey, tinged with green, or sometimes yel- 

 lowish. 



The apothecia are medium to sometimes quite large, sessile, or 

 partially adnate to the upper surface of the thallus ; they are 

 usually disk-shaped, sometimes irregular in outline, or several disks 

 agglutinate {H. ventosa) ; the disk may be flattened, somewhat con- 

 cave or convex ; the thalloid exciple rarely extends beyond the 

 disk ; the outer layer of the thalloid exciple is semicortical, 

 consisting of short hyphal branches placed vertically to the surface 

 and parallel to each other ; this layer is considerably thicker than 

 the upper cortical layer of the thallus, with which it is continuous. 

 The excipular algae are few in number and occur only near the cor- 

 tical layer. The hypothecium is colorless and not cortical, nor is it 

 possible to distinguish more than one layer. The paraphyses are 

 quite slender, sometimes branching ; the epithecium and the upper 

 ends of the paraphyses are usually reddish brown in color. The 

 spores are long, acicular, pointed at one end, indistinctly 4-6-septate, 

 curved, undulate or spiral, colorless ; they are so characteristic that 

 it is almost impossible to confound them with any others ; they 

 resemble most nearly those of Bacidia. 



