2I 4 



rhizoids ; the color of the upper surface is usually dark brown tinged 

 with bluish-green ; frequently the margin is lined with yellowish so- 

 redia ; the lower surface is either lighter or darker than the upper. 



The upper cortical layer is well developed and of quite uniform 

 thickness ; the cells are rather small, the cell-walls are comparatively 

 thick ; the uppermost layers are colored a dark brown, evidently a 

 protection against excessive illumination ; the algae are Dactylococ- 

 cus infusionum and in their arrangement in the thallus strongly re- 

 mind one of Peltigera ; the medullary layer consists of the usual 

 network of hyphae ; it presents a yellowish appearance owing to a 

 deposit of yellow acid crystals upon the hyphae. It is this deposit 

 of acid crystals which gives the yellowish color to the soredia and 

 the cyphellae ; the lower cortical layer is much thinner than the upper 

 and bears numerous long, usually colored, rhizoids below ; the lower 

 portion of this layer is also colored ; this layer is also broken here 

 and there by the cyphellae, both forms of which are represented. 



Stictinas occur only sterile within the territory. The descriptions 

 of apothecia and spores are based upon the examination of South 

 American specimens. Even in southern specimens apothecia are 

 few ; they are rather small, disk-like, sessile upon the upper surface 

 of the thallus. It is worthy of note that the thalloid exciple is very 

 deficient for a lichen in which the thallus is evidently so highly 

 organized. In most of the older apothecia the algae have entirely 

 disappeared ; the excipular margin rarely extends above the surface 

 of the disk ; otherwise it presents the distinctive tissues of the thalloid 

 exciple ; that is cortical layer and medullary layer. In the younger 

 apothecia the algal layer or layers are present, however, only toward 

 the periphery. The hypothecium is not cortical, consisting of a 

 close, indistinct network of hyphae, usually of a brownish color ; the 

 paraphyses are of medium length, rather rigid, due to the thick cell- 

 walls, the upper ends are colored dark brown, as is also the epithe- 

 cium. Here and there the thecium bears pillars of a cortical struc- 

 ture, indicating perhaps a tendency to become thalloid in nature. 



Considerable confusion exists as to the nature of the spores. In 

 the majority of species examined the spores were spindle-shaped with 

 a tendency to become acicular, colorless, usually two-celled, though 

 some were four-celled, usually colorless, though coloration may at 

 times be marked (brown coloration of the exosporium in S. crocata]. 

 In most cases the spores have the appearance of being degenerate, 



