SCYTONEMA. 257 



plified, and also, that the two forms described by Wood, viz.: 

 /Sc. cortex, and Sc. Ravenelii, are really one and the same 

 species. 



The cells, or joints of the filaments which separate in the 

 older plants, commonly falling over, and slipping out of the 

 sheaths, are in fact sporangia, the spore-bearers ; they give 

 rise to microspores; these develop into macrospores and 

 finally produce the young plants. 



Plate CLXXXVII, figs. 18-21, four samples of larger 

 forms of branching filaments f figs. 22, 23, two brokeii-off 

 ends ; the internal trichome separating, and single cells, laid 

 over, sliding out of the sheath ; fig. 24, two cells enlarging, 

 maturing macrogonidia which are scattered by the breaking 

 of the membrane; they continue to enlarge (figs. 25, 26), 

 the cellules in the cysts at first without order, then arranged 

 in moniliform series (fig. 27), JVo^oc-like. Here commence 

 two processes the macrogonidia develop young forms, in 

 shape not unlike small chestnut-worms, (figs. 28, 29), and the 

 Nostoc process (figs. 30-33), both of which give rise to young 

 plants such as figs. 34-37. All of these forms (figs. 18-37) 

 with various modifications are constantly associated. 



Forma Ravenelii, Wood, may be retained as a form. It is 

 represented 



Plate CLXXXVI, figs. 1-4, matured plants, and figs. 5, 6, 

 young plants. 



Forma saxicola, Green. Another form, found on moist rocks, 

 but so much in character with Sc. cortex, it can not be 

 separated except by habitat, therefore the name is re- 

 tained as another form. The color is usually of a darker 

 reddish brown, not so much of an olive-green or aeru- 

 ginous as Sc. cortex. 



Diameter of filaments, 17-18 yw. 



Plate CLXXXVI, figs. 7, 8, 9, three parts of filaments, 

 showing the manner of branching, the position and form of 

 heterocysts. 



Forma corrugata, Wolle, (1879), another distinct form, bright 

 aeruginous color, coated with a colorless gelatin, which 

 in drying contracts irregularly, thereby causing the fila- 

 ments to appear crenated or corrugated., 



Diameter of filaments, 17-26 ^. 



The filaments are short; they occur in clusters on the bark 

 of trees in South Carolina and Florida. 



