. i75 



PLATE 48. 

 Alectoria sarmentosa Ach. 



1. Portion of thallus natural size. 



2. Section of apothecium. 



a, thecium ; b, c, d, three layers of the hypothecium ; d, algal and 

 medullary layer; f, protective layer. 



3. Transverse radial section of thallus. 



a, outer layer of longitudinal hyphae ; b, algal layer; c, medullary 

 tissue. 



4. Paraphysis and spore-sac. 



5. Spores. 



11. Bryopogon Link. Handb. 3:164. 1833. 



This group is very closely related to Alectoria in the structural 

 arrangements of the thallus. The essential differences are found 

 in the spore-characters. 



The thallus is in all cases typically friiticose and radial in struc- 

 ture ; the outer mechanical and protective layer resembles that of 

 Alectoria in structure, but differs in being considerably thinner and 

 in the meagre deposit of acid crystals. The cell-walls of the outer- 

 most hyphae become dark to black in color ; the algae are distrib- 

 uted as in Alectoria. The central medullary tissue of loosely inter- 

 woven hyphae is traversed by a few mechanical bundles consisting 

 of several agglutinate hyphae extending longitudinally ; these give 

 additional support to resist longitudinal (pulling) tensions, which 

 is highly essential, since the thalli in most species are very long and 

 slender. 



The thalli are also somewhat flattened at the points of branching ; 

 soredia are common in some species ; the prevailing color of the 

 thallus is black, the long slender forms closely resembling coarse 

 black hair ; branching is dichotomous and usually less frequent than 

 in Alectoria. 



The apothecia are very few and sessile upon the sides of the thal- 

 lus. The spore-sacs and paraphyses are quite short, the hypothe- 

 cium colorless and separable into two layers ; the disk is entire, 

 somewhat irregular in outline ; the epithecium is of a lighter color 

 than the thallus; the spores are very small, colorless, simple, eight in 

 each spore-sac. Owing to the fact that forms of Alectoria and Bry- 

 ofogon are very frequently sterile, one is apt to confuse the genera ; 



