Fig. 160. MELOBESIA LICHENOIDES. 



Colour. Pale-lilac, or rather mauve. 



Substance. Hard; stony; solid; but thin and extremely brittle. 



Character of Frond. A lichen-like expansion, composed of thin, circular, leafy plates, 

 one above another; attached to rocks by a central base. The foliations gener- 

 ally free at the margins; often overlapping each other {imbricated). 



3Ieasurement. From 1 to 5 inches across. 



Fructification. Only one kind known. Clustered strings of spores in large, conical, 

 prominent capsules; sessile on the frond. 



Habitat. Cornwall and west of Ireland. On rocks and in tide-pools near low-water. 

 Not uncommon. 



Fig. 161. HILDENBRANTIA RUBRA. 



Colour. Bright, or sometimes dull red. 

 Substance. Gristly-membranaceous. 



Character of Frond. A thin, skin-like film, forming a circular or irregular red patch; 

 adhering by its under surface to the rock. 



Measurement. Indefinite. From 1 to 6 inches, or thereabouts, in extent. 



Fructification. Only one kind known. Tetraspores in round cavities, sunk in the 

 frond. 



Habitat. Our coasts generally. On smooth stones and pebbles between tide-marks. 

 Common. 



So thin that it looks merely like a red stain on the stone. When in fruit 

 its surface is pitted with small disc-like depressions, underneath which lie the 

 spore-cavities {conceptacles) . The figure of the cavities gives more the appear- 

 ance of raised capsules; but concavities are difficult to represent. 



Fig. 162. HAPALIDIUM PHYLLACTIDIUM. 



Colour. White. 



Substance. Thin; limy; brittle. 



Character of Frond. Minute dot-like patches, which, under the microscope, prove to 

 be composed of one or several thin fan-shaped, watery fronds. 



Measurement. The dots from to J of an inch across. 



Fructification. Unknown. 



Habitat. Malahide, Dublin, and elsewhere. Parasitic on Chnjsymenia clavellosa and 

 other small algse. 



A very remarkable little plant, and said to be common; but, if so, it wants 

 looking for. It was, until lately, known as Lithocystis Allmanni. (See Harvey's 

 Manual of Br. Mar. Algm, 2d edition, p. Ill : 1849.) It is now (1862), by many, 

 believed to be the young of a Melohcsia. 



70 



