130 CHORDARIACEJi;.— Ralfsia. iv. 



y. RALFSIA. Berk 



Frond coriaceo-crustaceous, fixed by its inferior surface, orbicular, concentrically 

 zoned, composed of densely packed, vertical, simple filaments, agglutinated 

 together into a crust. Fructification, depressed warts, scattered over the upper 

 surface, containing obovate spores, attached at the bases of vertical filaments or 

 paraneviata. 



The plants included in this group resemble the crustaceous lichens in outward 

 characters, and, like them, spread over the face of rocks in varying patches. In the 

 character of the fructification there is an approach to Dictyotacecs, but the genus is 

 retained in Chordariacece on account of the structure of the frond, and a supposed 

 affinity with Leathesia. 



1. Ralfsia expansa, J. Ag. ; frond orbicularly expanded into a crust, lobed at 

 the margin, flattish (?) in the middle, here and there raised in tubercles. /. Ag. 

 Sp. Alg. 1, p. 63. 



On Madrepores in the Gulf of Mexico. Vera Cruz, Liehman. 



I have not seen this plant, and am uncertain whether I have correctly translated 

 Prof J. Agardh's specific character, which is as follows : — " Fronde orbiculariter 

 expansa in crustam margine lobatam, medio subcontinuam hie illic in pustulas 

 elevatam." 



2. Ralfsia deusta, Ag., (not Berk.) ; frond concentrically lobed, the lobes sub- 

 reniform, imbricated, longitudinally striate, concentrically zoned. /. Ag. Sp. Alg., 

 1, p. 63. Fucus fungularis, Fl. Dan. t. 420. 



Hab. On the shores of Greenland, Vahl. Unalaschka, Tilesius. 



Frond orbicular, 1 — 2 inches in diameter, adhering to the rocks, constituted of 

 numerous lobes, one imbricating on the other. Colour chestnut brown. 



I am not acquainted with this plant. 



