MASTIGONEMA. 241 



Genus 82, MASTIGONEMA, ( Fisher) Kirch. 



Filaments short, free, without gelatinous sheath, branchless, 

 singly or sometimes in small mats. Heterocysts at the base of 

 the filaments ; spores unknown. 



All the forms under this genus are probably merely arrested, 

 or intermediate conditions of higher developments of plant-life, 

 as will appear in the following list of forms, under the names 

 of species. 



MASTIGONEMA ^ERUGINEUM, (Kg.) Kirch. 



Filaments straight, bent, or curved. Sheath thin and 

 close, extended into a slender flagelliform end. In vegeta- 

 tive state aeruginous, distinctly or indistinctly articulate ; 

 cell contents more or less granular. Heterocysts variable in 

 size and form, single or geminate, globose, oval, depressed 

 globose, pyriform, etc., usually yellow of lighter or darker 

 shade ; sizes indefinite ; with age the sheath widens and 

 sometimes becomes fibrillose. 



Plate CLXXIV, figs. 3-9, three distinct forms ; figs. 3-4, 

 having double heterocysts, a larger oval, connected with a 

 smaller globose cell ; figs. 5-7, pyriform heterocysts, both 

 forms with thin, close sheaths ; figs. 8, 9, spherical, single 

 heterocysts, wider sheath, becoming fibrillose. 



Plate CLXXI, figs. 8-10, three forms in a gelatinous coat- 

 ing on the sides of a pump trough, commencing to branch 

 after the manner of a Scytonema. 



Plate CLXXVI, figs. 2, 3, 4, another form, indicating the 

 same manner of branching as the last. 



Plate CLXXV, figs. 1-3, young stages, developed from 

 spores, and more advanced conditions ; fig. 4, a long filament 

 indicating a connection with Tolypothrix ; figs. 5$ 6, another 

 form, developing after a manner of its own. The young 

 filaments commencing growth in small clusters, like fig. 9 ; 

 these changing to horizontal positions, so that alternate cells 

 lie in opposite directions, ifig. 8) ; at first short, flagelli- 

 form, then elongating and becoming linear (fig. 6), and much 

 longer, having the appearance of Tolypothrix muscicola; fig. 

 7, is another specimen of the same ; the branching com- 

 mences at some distance from the basal heterocysts. Penn 

 sylvania. Figs. 9, 10, same mode of developing; Florida 

 specimens ; figs. 12-14, a larger form, from New Jersey ; 

 manner of arrangement the same ; figs. 15, 16, 17, more 

 scattered filaments showing a gradual increase in breadth 



