189 



D. pusillum is rather difficult to find because of its minuteness. 

 It seems to be southern in its range and rather rare, occurring upon 

 limestone. 



PLATE 59. 



Dermatocarpox pusillum (Hedw.) 



1. Natural size. 



2. Four apothecium-bearing areoles of the thallus, magnified. 



3. Section of the apothecium. 



4. Section of the thallus. 



a, upper cortical layer ; b, algal layer ; c, medullary tissue ; d, dark 

 colored lower limiting layer ; e, rhizoidal hyphae. 



5. Paraphyses and spore-sac. 



6. Spores with adhering algae (thecial algae). 



7. Algae of the thallus. 



8. Thecial algae. 



9. Endocarpon Hedwig, Stirp. Crypt. 2: 56. 1789. 



All the characters of this genus indicate its close relationship to 

 Verrucaria. It seems still more closely related to De?-matocarpon , 

 with the exception of the spore-characters, which are widely differ- 

 ent, as already indicated ; the high development of the thallus in this 

 genus determines the relatively high position of the family to which it 

 belongs ; yet it may be questioned whether the Verrucariaceae should 

 be placed higher than the Parmeliaceae. According to Reinke they 

 take even a higher position than is here accorded them. 



The representatives of the genus are distinguished from the spe- 

 cies of Verrucaria by the presence of. a foliose thallus. In the 

 lower Endocarpons (E. hepaticuni) the thallus-lobes are quite small 

 and closely adherent to the substratum, reminding one much of the 

 thallus of Dermatocarpon -pusillum ; in the intermediate forms {E. 

 jluviatile) the thallus-lobes are much larger and more or less ascend- 

 ing, while in the highest forms (E. ininiatuni), the lobes are very 

 large and attached by an umbilicus, in fact closely resembling 

 the thallus of some Umbilicaria or Gyrophora ; in consistency 

 the thallus is rigid, being comparatively thick ; its color is quite 

 variable ; grey and brown seem to be the predominating colors ; 

 the lower surface being usually darker than the upper ; the 

 dark lower surface of E. miniatum usually bears numerous wart- 

 like elevations which upon examination prove to be the apothe- 



