Howe : Phvcological studies 243 



of the Algae Exsicc. Am. Bor. of Farlow, Anderson and Eaton, 

 issued as Halimeda Tuna, out of seven sets examined, three are 

 Halimcda scabra, two are the smooth species, and two contain a 

 mixture of the two species. In no. i6y of the Phycotheca Boreali- 

 Americana of Collins, Holden and Setchell, distributed as Halimcda 

 Tuna, out of ten sets examined, eight are Halimcda scabra, one 

 is the smooth Halimcda, and one is a mixture of the two. The 

 plants from Jupiter Inlet distributed in Curtiss' Algae Floridanae 

 as Halimcda Tuna, also include the two distinct species. 



The only specimens that we have seen from Atlantic waters 

 approaching the American shores, which seem to agree thoroughly 

 well with the typical Halimcda Tuna, are from Bermuda. These 

 we have found also in a fertile condition. 



The sporangiophores of Halimcda scabra show a good deal of 

 variety in mode of branching, as will appear from the above diag- 

 nosis and from the accompanying figures. A comparison with 

 the sporangiophores of Halimcda Tuna as figured and described 

 by Derbes & Solier * and by Mrs. Gepp, f and as exhibited in the 

 Bermudian specimens alluded to above, does not seem to bring 

 out any very important or reliable differences. Possibly the spor- 

 angia in H. scabra are more regularly distichous. The regular 

 alternation of the sporangia in H. scabra is often interfered with by 

 the suppression of one or more sporangia or by the occurrence of 

 a cluster of two or three where we would normally expect only 

 one, but a real interruption of the distichous arrangement is rarely 

 found, while in H. Tuna such interruption is perhaps of more fre- 

 quent occurrence. It should be noted that in Halimcda scabra 

 the stalk of the well-matured sporangium shov/s in most cases a 

 distinct septum or plug, cutting off, more or less completely, the 

 contents of the sporangium from the sporangiophore. This is- 

 variable in position, but is commonly near the base of the stalk 

 and is often accompanied by a slight constriction. The plug, 

 which seems to consist of a callose mucilage rather than cellulose, 

 sometimes extends throughout the length of the stalk to the base 

 of the sporangium, in the narrower sense of the word. It is often 



*Suppl. Comptes Rendus hebdoin. Seances Acad. Sci. i : 46, 47. pi. //. f 

 18-22 : pi. 12. f. 1-5. 1856. 



fjourn. of Bot. 42: 193-197. //. j6i. Jl 1904. 



