215 



the septa being indistinct and variable as to number and size ; they 

 are indefinite in outline as well as in color. 



The Stictinus are distinctly southern in their range. They occur 

 upon rocks, trees and moss in shaded places. 



PLATE 75. 



STICTINA CROCATA (Nyl.). 



1 . Plant natural size ; a, apothecia ; b and c, soredia. 



2. Section of apothecium. 



3. Section of thalltis. 



4. Paraphyses and spore-sac. 



^. Spoi'es with indistinct septa. 

 6. Spores of S. fidiginosa. 



13. STICTA Schreb. Gen. 2: 768. 1791. 



The general structural characters of the Stictas are almost identi- 

 cal with those of the Stictinas. We shall therefore mention only those 

 characters which are different. 



The thallus as a rule is larger and more distinctly lobed ; the lobes 

 are broad, rarely becoming narrowed (S. nitida) ; the margin is en- 

 tire, or lined with orbicular patches of soredia which may also be scat- 

 tered over the upper surface of thallus, especially along the hyphal 

 ridges. The thallus is sometimes pustulate, similar to UmbiUcaria 

 pnstulata, only the pustules extend downward so that the upper sur- 

 face presents a series of depressions lined by the hyphal ridges (^S. 

 pulmonaria) ; these ridges are formed by hyphal bundles which fre 

 quently branch and again unite, forming a reticular mechanical tissue 

 to prevent the tearing and breaking of the thallus. In the majority 

 of species the upper surface of the thallus is smooth, the necessary 

 mechanical support being supplied by the cortical layers. The prevail- 

 ing color is grayish green, becoming brown on drying. The lower 

 surface is lined by a cortical layer bearing numerous rhizoids and 

 cyphellae. Large cephalodia occur on S. Orcgana. A species of 

 Mucor is quite frequently parasitic on some species, especially S. 

 glomnlifcra and S. ainp/issinut. The coloration in the upper and 

 lower cortical layers is as in Stictina ; the deposition of acid crystals 

 is much less than in that genus. 



The apothecia vary from small to medium and are much more 

 common than in Stictiua; in fact, their presence is the rule. In 

 16 



