Ser. CHLOROSPERMEA. Fam. Oscillatorica. 
Prats CCCXV. 
RIVULARIA PLICATA, Carm. 
Gen. Cuar. Frond globose or lobed, fleshy, firm, composed of continuous, 
radiating filaments, annulated within and springing from a spherical 
globule, and surrounded by, or set in, gelatine. Rivotarta (Hoth), 
—in allusion to the fluviatile habitat of some of the species. 
Rrvutaria plicata; fronds rather large, densely gregarious, gelatinous, 
compresso-plicate, often hollow and at length ruptured, dark green ; 
filaments wavy, associated in dichotomous series, tapering to a fine 
point. 
Rivuarta plicata, Carm. Harv. in Hook. Br. Fl. vol. ii. p. 392. Harv. Man. 
ed. 2. p. 222. 
LICHEN corrugatus, Dickson! (fide Borrer). 
Has. On the rocky sea-shore, about high-water mark, or in situations only 
occasionally overflowed by salt water. Appin, Capt. Carmichael. 
Ballintrae, Ayrshire, Mr. W. Thompson. Eyrmouth, Dr. Johnstone. 
Torbay, Mrs. Griffiths. Innischerig Island, Malbay ; and elsewhere, 
Geoar. Distr. 
Descr. Fronds densely crowded together, each patch generally occupying a 
surface of several square inches; variously lobed, and by mutual pressure 
distorted and compressed, so that the mass has a plaited or warted appear- 
ance. When young the fronds are solid and firmly gelatinous; as they 
advance in age they become hollow, and are at length often ruptured and 
variously torn. Filaments wavy and much attenuated, associated in dicho- 
tomous or subdichotomous series, each filament being joined to its fellow 
_ by a spherical, pellucid connecting cell, and the whole firmly set in the ge- 
latinous matrix of the frond. Rings evident and close. Colour a dark, 
lurid, or blackish green. Sudstance elastic, smooth, and somewhat lubricous. 
In drying, the plant shrinks considerably, and if subjected to pressure will 
adhere firmly to paper. 
? 
A well-marked species of Rivularia, easily recognized and not 
uncommon on several parts of our shores. It was first noticed 
by the late Captain Carmichael on the west coast of Scotland. 
Tike R. nitida, it becomes hollow in age, but may always be 
known from that species by its much darker and duller colour, 
smaller size, and the difference of habitat. The fronds are very 
irregular im shape, and alter considerably as they advance to 
