No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 97 



Melobesia confervicola Maze et Schr. Alg. Guadel. (1870—77)? Murray, 

 Cat. Mar. Alg. West. Ind. (1888—89), p. 21? 



Melobesia pustulata Ardiss. Phyc. Medit. I (1883), p. 446, partim, Erbar. 

 Crittog. Ital. no. 856! 



Though this species is fairly well circumscribed by the descrip- 

 tion made by Mr. Rosanoff 1. o, still it has been somewhat 

 differently perceived. Thus, according to authentic specimens, M. 

 farinosa Aresch. Obs. Phyc. 3. p. 4 represents a typical M. Le- 

 jolisii. He expresses, however, 1. c. some doubt as to the identity 

 with the true H. farinosa. Besides, strange to say, Mr. Rosanoff, 

 under M. membranacea 1. c. p. 66, refers to Le Jo lis, Liste Alg. 

 Cherb. p. 150. In the latter is referred to Alg. mar. Cherb. no. 

 194. But the alga here distributed is a well developed, typical 

 M. farinosa growing on Cystosira discors. It also seems as if 

 several authors have partly referred forms of M. Lejolisii to M. 

 farinosa, but I find no reason here to enter more fully upon it. 

 The said two species are easily confounded when the specimens 

 are feebly developed, stunted, or coalescing on a small substratum, 

 or growing together with other species so as to check the deve- 

 lopment mutually. In such specimens there is frequently no distinct 

 line to be drawn either as to the cells or as to the conceptacles. 

 Sometimes the heterocysts are not traceable in M. farinosa, parti- 

 cularly when the conceptacles are somewhat crowded, and if at 

 the same time the cells are smaller or the conceptacles lower than 

 usual, the species can not be determined with certainty. On the 

 other hand, M. Lejolisii may show characters recalling M. fari- 

 nosa, and peculiarly f. limitata of the former species and f. horealis 

 of the latter species may often be hardly distinguishable. 



As representing a typical M. farinosa — or as good as a 

 typically developed one — I take the form mentioned above, di- 

 stributed by M. Le Jolis under the name of M. membranacea, 

 though apart from the shape and the extent of the frond, which 

 are conditioned by the shape of the substratum. As a matter of 

 fact the frond is more regularly developed on broader or more 

 foliaceous host plants than the Cystosira discors in question. The 

 cells of the said form are partly squarish, partly and more fre- 



