494 Howe : Phycological studies 



from the margins of the segments (pl. 28, fig. 3) are mutually 

 coherent near the point of emergence and communicate with each 

 other there by pits or pores like the vegetative filaments of the 

 central strand at the nodes, but the sporangiophores from the 

 disc-surfaces originate as direct continuations of the peripheral 

 utricles or of the utricles of the subcortical layer and are without 

 fusions or adhesions of any kind (pl. 28, figs. 4-7). The sporangia 

 are obovoid or pyriform and are 0.20-0.38 mm. broad. The callose 

 or mucous plugs which we have described * as forming basal septa 

 of a certain sort for the sporangia of Halimeda scabra we have not 

 observed in Halivieda trideiis ; such are, however, of occasional 

 and irregular occurrence in the Porto Rican material of Halimeda 

 Tuna. 



B. On the American species of the Halimeda Tuna group 



At the time of describing the strongly marked species Halimeda 

 scabra,^ attention was directed to another species which likewise 

 had commonly been confused with Halimeda Tiina. Of this 

 " smooth plant of the Tiina-cJineata alliance," we remarked, " It 

 seems rather violent to identify it either with Halimeda Tuna or 

 with H. cuneata, and it is possible that further acquaintance with 

 it will show constant and reliable characters for distinguishing it 

 from both." At that time nearly all of our American material of 

 the Tuna group belonged to this " species inquirenda " and to H. 

 scabra and the only specimens we had seen from the American 

 side of the Atlantic which we could refer to H. Tuna were from 

 Bermuda. But since then we have collected what we believe to 

 be the true H. Tuna both in Porto Rico and in Jamaica and have 

 seen a specimen of it purporting to come from Key West, Florida, 

 so it now seems probable that both it and its ally are of general 

 distribution in the West Indian region. And the two " forms," 

 so far as we have seen them, are always absolutely and abundantly 

 distinct and in our opinion are as much entitled to be considered 

 specifically different from each other as are Halimeda Tina and 

 H. Opiintia or Halimeda Tuna and H. scabra. It soon became 

 evident that this ally of H. Tuna had already been recognized as 



*Bull. Torrey Club 32 : 243. 1905. 



t M. A. Howe, Bull. Torrey Club 32 : 241-244.//. //, 12. 1905. 



