NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 27 



diam., e cellulis 1.2-1.5 longioribus quam latae constantes, in 4 ordines ramosi, 

 ad ramos ultimos 10-15 p. diam. per longitudinem gradatim attenuati; ramifi- 

 catio e parte superiore cellularum successivarum alterna, saepius spiralis infra, 

 distichia supra, partibus mediis per 8-12 cellulas saepe sine ramis; cellulae 

 partium mediarum 4-6 plo longiores, supra 3-5 plo longiores quam latae, 

 rami ultimi e 4-8 cellulis constantes, extrema in parte obtusi, aliquantulum 

 adaxialiter curvati; glandicellulae nullae; sporangia asexualia semel divisa ad 

 bisporas formandas, bisporis adaxialibus, serialibus interdum duabus ex una 

 cellula formatis, sessilibus, ellipticis, 50 ji long., 30 /jl diam.; plantae sexuales 

 non visae. 



Thalli about 1 cm tall, consisting of a few branched axes attached 

 by multicellular rhizoids; erect axes non-percurrent, ecorticate, to 200 

 fj. in diameter at the base, of cells 1.2-1.5 diameters long, branched in 

 four orders, gradually attenuated throughout to the ultimate branches 

 10-15 [x in diameter; branching alternate from the top of successive 

 cells, tending to be spiral below, distichous above, the mid-parts often 

 barren of branches for 8-12 cells; cells in mid-parts 4-6 diameters long, 

 3-5 diameters long above; ultimate branches of 4-8 or more cells, 

 terminally blunt, somewhat adaxially curved; gland cells absent; asexual 

 sporangia once divided to form bispores, these adaxial, serial, some- 

 times 2 from a cell, sessile, elliptical, 50 /x long, 30 ii in diameter; sexual 

 material not seen. 



Type: Holotype is E. Y. Dawson 7190, March 18, 1949, in Herb. 

 A. Hancock Foundation. An isotype slide is in Herb. Beaudette 

 Foundation. 



Type locality: Dredged in 6-9 m., outer bay Puerto Escondido, 

 Gulf of California, Mexico. 



C. bisporum Gardner has been reported only from the type locality 

 in Puget Sound, Washington. This collection from a remote locality in 

 Mexico provides a strikingly disjunct distribution and has called for a 

 varietal distinction which is found largely in the longer ultimate 

 branchlets and smaller bisporangia. 



Callithamnion breviramosum Gard. 

 PL 8, fig. 3-4 



Gardner, 1927 b, p. 403, pi. 84. Callithamnion varispiralis Dawson, 1949, p. 

 16, fig. 29, 30, 54. 



Thalli epiphytic, 7-12 mm high, consisting of a tuft of principal 

 axes from a common fleshy, somewhat pulvinate base composed in part 

 of a mass of multicellular, branched rhizoids; erect axes 140-170 [x in 

 diameter in lower parts, the cells about as long as broad, becoming 

 distinctly corticated by closely appressed descending filaments from the 

 basal cells of lateral branches, later becoming obscured, in part, by 

 loose entangling rhizoids; main axes densely clothed with short, rigid 

 branchlets of mostly five orders arising spirally from each axial cell, 

 these of cells about 1.5 diameters long, somewhat assurgent, the ultimate 



