HOWE AND HOYT: MARINE ALGAE FROM BEAUFORT, N. C. II9 



conditions of a single polymorphous species. However, such 

 experiments would be difficult to carry out and what they might 

 prove is at the present time purely conjectural. The facts remain 

 that our plant, taken as a whole, differs in several particulars 

 from any one of the three plants named, and that, apart from the 

 priority of Acrochaetium Hoytii and the apparent identity of the 

 hosts of A. Hoytii and A. affine, there seems to be no compelling 

 reason for the association of our plant with any one of the three 

 names mentioned rather than with any other of the three. Under 

 these circumstances it seems justifiable to give our plant a new 

 specific name, which, like most new specific names, is a tentative 

 one at best. 



From Acrochaetium Hoytii, A. affine differs in its larger size 

 (1.0-3.5 mm. vs. 0.3-1.3 mm. tall), in its sparing and irregular 

 ramification with branches mostly long and flexuous {A. Hoytii 

 commonly has numerous short, mostly 1-5-celled branches and 

 branchlets, sometimes springing from nearly every cell of the 

 main axes, often once or twice compounded in a similar fashion 

 and arranged in a corymbose-secund manner), in the usually 

 greater diameter of the primary filaments (6-14^1 vs. 5-7 m)> 

 in the relatively longer more cylindric cells (mostly 3-9 vs. 2-4 

 diameters long), in the usually more imbedded primary basal 

 cell, in the occasional formation of secondary basal cells, which 

 now and then are so numerous as to constitute a small basal disc, 

 in the larger (18-27 ^u X 10-18 ^u vs. ii-15/x X 5-6 /x) and in- 

 frequent sporangia, and in the relatively abundant cystocarps. 

 The cystocarps of A. Hoytii were not observed by Mr. Collins. 

 We have seen a very few cystocarps in A. Hoytii, but have not 

 seen antheridia or procarps. The sporangia of A. Hoytii were 

 described as on one-celled pedicels, but we find them often sessile 

 also. 



From Acrochaetium unipes, which we know only from Dr. 

 BjzJrgesen's description and figures, A. affine would appear to differ 

 in having in mature conditions, except in rare cases, 2-4 erect 

 primary filaments. These are commonly subdichotomous or 

 subtrichotomous close to the base, so that at first sight the effect 

 of having 4-12 primary filaments is produced, while A. unipes 

 has a single erect primary filament with apparently only lateral 

 branching. No secondary basal cells are attributed to A. unipes. 



