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LICHENS— THELOSCHISTES—PYXINE. 



By Carolyn W. Harris. 

 Following the classification of Prof. Tuckerman, who is still the author- 

 ity on North American Lichens, Theloschistes andPyxine complete the fam- 

 ily of Parmeliei which we have been studying in The Bryologist, with the 

 exception of one rather doubtful and little known genus, Speerschneidera, 

 represented by only one species S. euploca. 



Theloschistes is still included in the genus Physcia by many lichenists 

 in Europe. Several species are found growing with Physcia, and the con- 

 trast between the yellow thallus of the Theloschistes and the gray of the 

 Physcia is very effective. All the species of Theloschistes which are de- 

 scribed in this article, have a yellow or greenish-yellow thallus, which is 

 either foliaceous or fruticose. The underpart is always white, or light gray, 

 with clusters of darker rhizoids with which it is attached to the substratum. 



Placodiuin elegans is much like some species of Theloschistes, but the 

 thallus is crustaceous, and a much deeper orange ; the apothecia are also 

 smaller and darker; the underside, while pale, is much appressed or wrin- 

 kled and is free from rhizoids. 



In Theloschistes the apothecia are usually quite large, in several species 

 are very crowded. They are cup-shaped as in Parmelia and Physcia, but 

 the disk is flatter and the thalline rim is thinner. This genus is found on 

 living trees, old fences and on rocks. The yellow color of the thallus is said to 

 be due to the large amount of the gold-colored crystals of chrysophanic acid. 



Theloschistes chrysophthalmus (L.) Norm. 

 (Fig. I.) Thallus fruticose, yellow or yellowish- 

 gray, ascendant and tufted. The narrow, linear 

 branches terminated by fibrils. The underside 

 is a pale gray, appressed, with mats of rhizoids 

 toward the middle which serve as hold- fasts to 

 the substratum. This lichen, except in color, re- 

 Fig I Theloschistes sembles Rainalina calicaris var. fastigiata. 

 chrysophtalhmus. The apothecia are large, subterminal, the disk is 



^, bright orange color with an entire margin ; they are often so numerous 

 as to cover almost the entire thallus. Found on trees in the United States, 

 also in the South and West. 



Theloschistes chrysophthalmus 

 (L.) Norm., var. flavicans, Wallr. 

 (Fig. 2.) This beautiful lichen is in 

 color and general appearance much like 

 T. chrysophthalmus, but can be distin- 

 guished from it by its much divided 

 branches which are long and linear, giv- 

 ing it a more delicate appearance, some- 

 what resembling /'^/-^^^'^ ciliaris, except 

 Fig. 2. Theloschistes chrysoph- in color. The thallus is yellow, some- 

 thahmis YSiV. flavicans X2. times with a grayish tinge. The 



