624 Howe: STRUCTURAL DIMORPHISM IN GALAXAURA 
actual cultures should be made under control conditions as has 
been done by Hoyt* and by Lewist to demonstrate the alternation 
of generations in certain other tetraspore-producing algae. This 
could be done only in tropical or subtropical waters, would 
probably require months for its accomplishment, and is not likely 
to be achieved in the immediate future. Meanwhile, however, 
it seems to the writer that the proof is conclusive that the sug- 
gested correlation exists, that the ‘‘Spissae’”’ and ‘‘Cameratae’’ 
characters, first accurately pointed out by Kjellman, do not offer 
a proper basis for subgeneric groupings of species as supposed by 
him, but merely distinguish the gametophytic and sporophytic 
phases in the life-cycle of a single species. 
It is well known that differences of habit occur between sexual 
and tetrasporic plants of certain red algae, as, for example, in 
species of Griffithsia, but such differences seem to be due largely 
to the presence of the reproductive organs themselves or to 
differences in the form of the cells that are rather directly con- 
cerned with their production. So far as is known to the writer 
of these notes, there has been no previous record of a case in 
which there has been alleged to exist any such constant and 
pronounced dimorphism in the purely vegetative microscopic 
structure of the sexual and tetrasporic plants in the Rhodophyceae 
as is here attributed to Galaxaura obtusata—differences that do 
not express themselves in general habit, but afford an easy means 
of distinguishing a tetrasporic from a sexual plant, even though 
apparently sterile. 
NEw York BOTANICAL GARDEN, 
Bronx Park, NEw York City 
* Hoyt, W. D. Seubugs of generations and sexuality in Dictyota ‘dicholoma. 
Bot. Gaz. 49: 55-57. 1910. 
Tt Lewis, I. F. get of generations in certain Florideae. Bot. Gaz. 
53: 236-242, ror2. 
