THE BRYOLOGIST. 



Vol. VI. 



July, 1903. 



No. 4. 



LICHENS-STICTA. 



By Carolyn W. Harris. 



Sticta is largely a tropical genus, but we have in our own country a 

 number of very interesting species ; a few are found in the gulf states which 

 are tropical. The name, meaning spotted, probably comes from the 

 cyphellse with which the underside of the thallus of most of the Stictas is cov- 

 ered, those in which cyphellse are not present are beset with light-colored 

 spots. As this is the only genus we have bearing cyphellse it is readily dis- 

 tinguished by them from the other foliaceous lichens which it somewhat 

 resembles. These cyphellse are circular breaks in the lower cortical layer, 

 and are analogous to the stomata or breathing pores of leaves. 



The thallus of Sticta is usually wide lobed, elongated, medium in thick- 

 ness and cartilaginous in texture ; it lies flat upon the substratum and is 

 usually loosely attached by rhizoids. The color is generally brown, light or 

 dark, tinged with bluish green in some species. Sometimes the upper sur- 

 face of the thallus presents a series of depressions, outlined by ridges. In 

 the majority of species the upper surface is smooth or slightly wrinkled. 

 The under part is always villous, the spongy nap varying in thickness, this 

 with the cyphell£e or naked pale dots give the specimens a peculiar appear- 

 ance. In several species the inner layer is a lemon or orange color which 

 shows through the breaks in the corticaHayer ; these species are usually cov- 

 ered with soredia of the same color. 



The apothecia are medium in size, varying in color from a bright to a 

 dark chestnut, the disk is often convex, the margin thin and lighter in color. 

 Stictas are found on shaded rocks, frequently growing with mosses, they 

 also grow on the trunks of dead or living trees. Where conditions are fav- 

 orable, some species attain a large size. A specimen of Sticta ainplissima 

 collected at Chilson Lake, Essex Co., N. Y,, measured nearly a foot in diam- 

 eter ; it is now in the Museum of the New York Botanical Garden. 



Sticta amplissima (Scop.) Mass. Plate IX. Fig. 3. Thallus large, 

 round, rather thin and brittle, when young it is smooth but grows somewhat 

 wrinkled when fully developed. It is a light greenish gray when fresh, 

 turning darker when pressed, often changing- to brown. The lobes are 

 elongated, somewhat appressed with wavy margins. The under surface is 

 light brown, growing darker toward the centre; it is covered with a fine nap 

 and scattered bunches of short rhizoids with which it is loosely attached to 

 the substratum. The apothecia are very numerous, especially toward the 

 centre, they are found in all stages of development on the same plant; when 

 young they are sessile and cup-shape, becoming flat, the disk is a bright' 

 shiny chestnut with an entire margin. 



The May Bryologist was issued May 5th, iqo3. 



