510 Howe: Phycological studies 



irregularly perforate, the margins entire or sinuate or here and 

 there irregularly dentate or lacerate, the surface nitent, the color 

 mostly a light greenish rose; medullary filaments sparingly lat- 

 erally or subdichotomously branched, 14-24^ in diameter, gradu- 

 ally enlarging distally (often becoming 27-40^ in older parts) and 

 each terminated by a subglobose capituliform cell, this 45-95M 

 in diameter and emitting radially or stellately 3-14 (usually 6 or 

 7) rather straight and rigid branches, these connecting with one 

 or two series of similar or more flattened radiately branched and 

 reticulately joined subcortical cells, succeeded by one or two series 

 of smaller subglobose or flattened anastomosing subcortical cells 

 and the monostromatic or occasionally distromatic cortex; the 

 cortical cells subglobose, obovoid, or more often flattened in the 

 plane of the surface, 5-1 3m in diameter, usually 3-6 from each 

 subjacent cell: other parts unknown. [Plate 34.] 



La Paz, Vives 2od. 



The three specimens on which the foregoing description is 

 based are evidently fragments and some of the details of the 

 diagnosis, especially as regards the size and form of the thallus, 

 may require modification when more material is available. The 

 specimens, also, appear to be sterile, but their structural characters 

 are such that we feel little hesitation in referring them to the 

 Hymenopsis section of Halymenia — the section that includes the 

 European and Mediterranean Halymenia latifolia Crouan and H. 

 nlvoidea Zanard., and possibly also the American H. floridana J. 

 Ag. Halymenia latifolia has a firmer, relatively narrower, less 

 nitent thallus of more definite regular form and a well-defined 

 cuneate stipe; it is not certain that the holdfast is present in any 

 of the Baja California fragments, but what appears to be a sub- 

 truncate or slightly cordate base in one of them suggests that the 

 plant is sessile. H. latifolia has radially branched cells in the 

 subcortex that sometimes resemble the smaller of the radiate or 

 stellate subcortical cells of H. actinophysa, but they are (in a Brest 

 specimen) only 25-30/i in diameter, have usually but 3-5 branches, 

 and are nearly always much flattened; if these radiate cells in H. 

 latifolia often in form suggest Asteroid or Ophiuroid "star-fishes," 

 the corresponding cells in H. actinophysa in a detached condition 

 may remind one of the pollen grains of certain Malvaceae or the 

 "morning-star" maces of the 15th century. 



The limits of Halymenia floridana J. Ag. are imperfectly under- 



