Genera of Fresh Water Algce. 207 



forms which have enlarged after being ejected from the former. 

 These are singular in shape, and the process of development of 

 the young forms of the mother plant is also unusual. They 

 frequently germinate in the cysts {c c). There is likewise 

 something distinct in the perfected plant {d d). It is probably 

 a new species of Sirosiphon] but the specimens being few, I 

 have not ventured to describe it. 



Fig. 3 is a species of Scytone>/ia, near Sc. Castelli, Massl. In 

 its life history and general character it is not unlike Sc. CorieXy 

 Wd. and Sc. triincicola, Rab. I found it growing in extended, 

 bluish-green strata, on shelves, on flower pots, and on walls in 

 a greenhouse in Harrisburgh, Pa. Omitting the Ghvocapsa 

 forms, the process of development is similar to that of Sirosi- 

 phon. I represent a few filaments {a a). The articulations are 

 thin disks, two or four to a diameter; these separate, fall over 

 and slide out of a broken end of the old plant {bbb)\ from 

 these the microspores are evolved {c) and scattered; these en- 

 large by growth (^), and develop from one stage to another as 

 figured {efghikl)\ the latter (/) are Gicvothece iotvas. Clus- 

 ters of these are frequent without any filaments, but sometimes, 

 by turning a mass over and over again, the young plants (I vi) 

 are seen intermingled with the cysts [Ghvot/iece), and directly 

 traceable from them. 



Fig. 4 illustrates the early life of Scytonema triincicola, Rab. 

 from a specimen found on an old pine board, by H. W. Ravenel, 

 in S. Carolina. The microgonidia {a a) from an old filament, 

 advance in size {bcde)', the younger are microcystis forms, the 

 older are sporangia {ef), and emit small cells {g)\ these develop 

 new cysts continually until favorable circumstances, moisture 

 and warmth, cause them to cluster and to develop the young 

 of the mother plant {h/i/i). 



Fig. 5 shows the early development of forms of Ulothrix, as 

 U.flaccida K., U. niteiis, Mengh., and others. I add this as an ex- 

 ample of rapid and extensive multiplication of gonidia or spores, 

 before showing signs of fertility. There are green coatings low 

 down on shaded fences, and on damp places on rocks, on trunks 

 of trees, and sometimes on the ground. These may be seen at 

 all seasons of the year. If examined in the spring, or summer 

 months, they will usually be found to consist of masses of sim- 

 ple spherical cells {a a), rarely with signs of division; they are 

 generally filled with very minute granules. These constitute. 



