100 M. FOSLIE. [1905 



show about the same size and almost the same condition of things 

 as those of f. typica. They may, however, be now a little shorter, 

 now a little longer than usual in the said form, and the corners 

 are often more or less rounded. The conceptacles are also of the 

 same size as in f. typica, but they are of scarce occurrence. The 

 form is mostly sterile. 



As already observed by Mr. Rosanoff, this species occurs 

 on very heterogeneous substrata, particularly on a series of other 

 algee. It is often found abundant also on eelgrass (Zostera, Tha- 

 lassia, Cymodocea, Poseidonia or Enalis) except in cold boreal 

 areas, where it is replaced on Zostera by M . Lejolisii. The form 

 callithamnioides has been met with on Peyssonnelia and several 

 other algee, on chitine tubes of hydroids and on tubes of Serpula 

 among specimens of Cladophora prolifera and Corallina rubens 

 from the Adriatic. On the hydroids it was found partly associated 

 with Lithoph. macrocarpum (or L. pustulatum). One of these 

 species frequently accompanies M. farinosa in warm or warm- 

 boreal areas, but farther to the north, where M. farinosa does 

 not occur, it accompanies M. Lejolisii. Sometimes, however, both 

 the species last mentioned or even all the three species are found 

 growing gregariously on the same substratum, e. g. on the West 

 coast of Ireland and in the Mediterranean. Thus in the former 

 place M. farinosa f. borealis partly occurs associated with M. 

 Lejolisii and Lithoph. pustulatum on Gigartina mamillosa, and 

 the two species first mentioned are found gregariously on the leaf 

 of Laminaria saccharina. The form distributed by Mr. Holmes 

 in Alg. Brit. rar. exsicc. under the name of Melobesia myriocarpa 

 on the leaf of L. saccharina from Weymouth also embraces both 

 species, in conformity with a specimen communicated to me by 

 Mr. Batters. In more southern areas both species sometimes 

 grow gregariously also on Zostera. This is e. g. the case with 

 the alga from Ancona distributed by Mr. Caldesi, admitted in 

 Erbar. Crittog. Ital. no. 127 (1127) and in Rabenhorst Algen Eu- 

 ropas No. 1676 under the name of Melobesia verrucata. At any 

 rate it includes partly both M. farinosa and M. Lejolisii. Among 

 algas worth noting on which the typical form of the species in 



