258 FRESH-WATER A LGJE OF THE UNITED STATES. 



Plate CLXXXVIII, figs. 5-9, a few representative short 

 filaments. Probably the same form as seen by Wood and 

 named by him Siroslplion scytonematoides. 



Forma brunea, Wolle, (1879). This form is dark brown and is 

 covered with what appear to be subspherical resinous 

 cells. Probably an older condition of the last (cormgata), 

 age making the change of color, and causing the gela- 

 tin to assume a resinous appearance. Size and habitat 

 the same as the last. 



SCYTONEMA INTERTEXTUM, (Kg.) Bab. 



Forms an interwoven tomentose stratum, dark brown, or 

 olivaceous: Ends of trichomes and pseudo-bT&ncfaes more 

 or less erect. Internal filaments light or dull aeruginous, 

 distinctly articulate, before division equal or longer or 

 shorter than the diameter ; sheath varies with the age of the 

 plants ; at first thin and close. Heterocysts most frequently 

 at the base of the branchlets, single or twin, oblong or sub- 

 globose, light brownish yellow. 



Diameter of filaments averages about 20 yw, including 

 sheath ; without sheath, 12-16 yu. 



Syn. Symphyosiphon interteodum, Kg. 



On old wood, Florida. 



This form appears closely related to the preceding 8c. 

 cortex. The only points of separation are, that the filaments 

 are somewhat thicker, the sheath firmer, and the cells fre- 

 quently inclined, producing dark interruptions in the in- 

 ternal trichome. 



Plate CLXXXVI, figs. 10-14, peculiarity of the species 

 in five parts of filaments ; figs. 15, 17, microgonidia devel- 

 oped from the joints of the filaments, enlarged, producing 

 first macrogonidia and then cysts of much greater dimen- 

 sions, and finally JVbsfoc-forms ; figs. 17, 18, the youngest con 

 dition of filamentous forms. Compare Plate CLXXXVII, 

 figs. 24-37. 



SCYTONEMA CINEREUM, Menegh. 



At first pulvinate, cinereous, green, then confluent, form- 

 ing a more or less tomentose pulverulent stratum, becoming 

 pale blue when dry, now and then violet or purplish; tri- 

 chomes very fragile, elongated, flexuose and curved, loosely 

 interwoven. Sparingly branching, indistinctly articulate, 

 internally dingy, aeruginous green, joints shorter than 



