Pl.cell.aph. 1.HYDROPHYT.. 5. Rivularia. 285 
Stones and posts in the sea, also on fuci. 
Tufts 1 or 2-tenths of an inch in diameter, mostly single. 
2. Rivularia natans. _ Floating rivulet-moss. 
Fresh-water ; tufts globular, hollow; threads stiff, not 
branched, attenuated; sporzdia nearly globular. 
Tremella utriculata, Huds. Fl. Angl. 564. 
Tremella natans, Hedwig Theor. gen. 2, 218. 
Rivularia angulosa, Roth Cat. 3, 340. 
Ulva pruniformis, Eng. Bot. 968, not of Linnzus. 
Boggy ditches and ponds. 
Tufts of various sizes, brownish or greenish; threads 
very stiff, attenuated; sheath thin, transparent at the base 
of the threads. 
3. Rivularia dura. Hard rivulet-moss. 
Fresh-water ; tufts globular, solid, hard, green; threads 
not branched, straight, agglutinated together at bottom, 
free above, awlshape; rings inconspicuous. 
Tremella globulosa, Roth Fl. Germ, 3, 551. 
Tremella verrucosa, Roth Fl. Germ, 3, 554. 
Rivularia dura, Roth Cat. 3, 338. 
On aquatic plants; annual; summer. 
Tufts the size of a large pin’s head. 
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4. Rivularia nitida. Shining rivulel-moss. 
Fresh-water ; tufts hemispherical, solid, hard, shining, 
black-green; ¢hreads very close, equal, very slender, light 
green. 
Rivalaria calcarea, Engl. Bot. 1799. 
Rivularia nitida, Agardh Disp. ed. |}, 44. 
Inundated places and sides of rivers. 
Tufts about a quarter of an inch in diameter, often 
uniting and forming an uneven bed. 
VI. 6. SCYTONEMA. Agardh. _ Leather-thread. 
Threads nearly leatherlike, free, not gelatinous, simple 
or branched, orange-colour in dark and blackish tufts.— 
Inundated places; appearing like lichens, and being per- 
haps the young state of some of their families. 
a. Branches given out at right angles. 
L. Scytonema myochrous. Mouseskin leather-thread. 
_ Threads olive yellow, very closely entangled into a 
blackish brown mat; branches in pairs, simple, facing one 
way; sporidia ringlike. 
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