1920] Setcheil-Gardner : Chlorophyceae 301 



the walls thicken more or less and the ''rhizoids" often thicken so 

 as to become entirely solid or, at least, throughout the greater portion. 

 The "sporangia" vary considerably in shape and size, even in speci- 

 mens inhabiting the same shell, and at times exhibit extraordinary 

 differences, but at other times closely follow a particular type. It 

 has been puzzling to us to interpret this variation. As a result of 

 considerable experience, however, we are inclined to lay more stress 

 on distinctions of form and size in the "sporangia" than has been 

 done by others. 



In connection with any attempt to examine carefully and critically 

 the various specimens of Gomantia as to their identity with, or dis- 

 tinctness from, the eight or more species already described, it has 

 become necessary to examine carefully the type of the species, viz., 

 Gomontia polijrhiza (Lager.) B. and F. We have two sources of 

 information as to the type species, viz., the original description and 

 figures of Lagerheim (1885) and the careful and detailed description 

 and figures of Bomet and Flahault (1888). For reasons which we 

 shall give below, we are inclined to suspect that the plant of Bornet 

 and Flahault is a different species from that of Lagerheim, and our 

 suspicion is so strong that we have felt it necessary (cf. Setchell and 

 Gardner, 1920, p. 298) to bestow upon it a new specific name, viz., 

 G. Bornetii S. and G. In carrying out the idea that the "sporangia" 

 furnish diagnostic characters, we have separated several species which 

 present difficulties, to be sure, in narrow diagnosis, but which seem 

 rather more satisfying than the attempt to lump all under the one 

 name. The explanation of the variability may possibly be that the 

 different texture of the various species of shells, or of different portions 

 of the same shell, affect the size and shape, but there does not seem 

 to be evidence forthcoming to support this idea. It seems possible that 

 two, or even more, species may be inhabitants of the same shells and 

 thus cause an intermingling of different types of "sporangia." In 

 our attempt to clear up the situation, we have assumed the possibili- 

 ties of distinct species, at times, intermingled. 



Key to the Species 



1. "Sporangia" with 2 to several rhizoids 2 



1. "Sporangia "usually with a single rhizoid 4. G. caudata (p. 304) 



2. "Sporangia" longer than broad (Codiolum-type)....l. G. polyrhiza (p. 302) 



2. "Sporangia" broader than long (Acarid-type) 3 



3. Rhizoids nearly simple, stout, blunt 2. G. Bornetii (p. 302) 



3. Rhizoids branched, slender, acute 3. G. habrorhiza (p. 304) 



