n6 



species occurring in the territory (A. tigillare) ; in the western A. 

 tympanellum this organ is longer, but still much shorter than in Cali- 

 cium. In A. tig-illarc the stipe as well as the greater portion of the 

 apothecium is enclosed by the thallus, producing a conical projec- 

 tion around each apothecium ; the thallus is very distinct, crusta- 

 ceous, uniformly spreading and minutely areolate ; each areole bears 

 one, rarely two or three apothecia ; the apothecia are very numerous, 

 the disk is open and considerably flattened, especially in A. tympa- 

 nelliDii. The general characters of the anatomical structure of the 

 apothecium and stipe are the same as in Calcium. The sub-hy- 

 menial hyphae are dark colored ; the spores are two-celled and dark ; 

 the paraphyses are sparingly present and rarely branched ; the 

 spore-sacs soon dissolve, setting free the spores while they are yet 

 quite small and nearly colorless ; the basal portion of the spore-sacs 

 is narrowed and wholly colorless, forming a sharp contrast to the 

 dark hypothecial hyphae. 



The thallus differs but slightly from that of Calicium. No cor- 

 tical structure is present, and the lower hyphal layer as well as the 

 algal layer has increased in thickness indicating an increase in the 

 assimilative function. 



There is only one species reported from the territory, Acolium 

 tigillare. Its natural substratum seems to be old pine fence boards, 

 on which it occurs in large patches. From its position on fences in 

 comparatively open countries it is evident that it has the ability to 

 resist greater extremes of dryness than the majority of lichens. It 

 seems to occur quite generally 'throughout the territory. 



PLATE 8. 

 ACOLIUM TIGILLARE (Ach.) De Not. 



1. Plants natural size upon a fragment of old fence-board. 



2. Semi-diagramatic section of apothecium and thallus (magnified). 



3. Section of apothecium. 



a, mature spores lying above the thecium ; a, the bright colorless 

 zone of the thecium formed by the narrowed basal portions of the 

 spore-sacs; b, dark colored hypothecium. 



4. Vertical section of thallus. 



5. Spore-sac with immature spores and paraphyses. 



6. Immature spores. 



7. Mature spores. 



