296 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



Bryothamnion pacificum n. sp.^^^ 

 Plate 96, Fig. 1 



Plants bushy, to over 11 cm tall, the axis to about 2 mm diam., terete; 

 main branching alternate, generally distributed though somewhat denser 

 in the upper divisions, without dominant main axes, the intei^vals being 

 0.5-2.0 cm, in transverse section showing a distinct axial cell row, which 

 is rather large and thick walled, to 150 /a diam,, the 7 pericentral cells 

 larger and surrounded by one complete and one partial layer of outer 

 medulla; cortex of one layer of rather thick-walled cells, very irregular 

 in form and position, about 25-40 ix diam. in surface view ; patent determi- 

 nate branches distributed throughout the plant, little congested at the 

 main branch tips, spirally disposed, to about 1.5-2.0 mm in length, at the 

 base becoming corticated, sharply tapering to the summit, with about 4-10 

 alternately placed acute uncorticated branchlets which are simple or bear 

 1-4 subsidiary aculeate branchlets; undivided branchlets relatively stout, 

 to 40-90 /A diam., and to about 360 ju, long, abruptly tapering to the small 

 acute somewhat indurated tip cells; reproductive structures not seen. 



These plants considerably resemble B. triquetrum in habit, but are 

 much more slender in all parts. The determinate branches are exceedingly 

 like those of B. Seaforthii f. imbricata J. Ag., but are shorter and much 

 less closely imbricate, and the habit differs from the forms of that species. 

 In the absence of reproductive structures the allocation to this genus is 

 necessarily tentative, though the structural resemblances are very convinc- 

 ing. 



Mexico: Nayarit, dredged from 5.5-9.0 meters' depth at sta. 971 

 near I. Maria Magdalena, Las Tres Marias, no. 39-665 (TYPE), 9 

 May 1939. 



DIGENIA C. Agardh, 1822 



Plants erect, bushy, the branches cylindrical, alternately or dichot- 

 omously divided, firm, in the main divisions heavily corticated, bearing 

 densely placed short branchlets with 6 to 10 pericentral cells and one layer 

 of cellular cortication; tetrasporangia in the irregular, largely uncorti- 

 cated upper portion of fertile branchlets; spermatangia numerous near 

 the tips of male branchlets; cystocarps ovoid, on the middle or upper 

 parts of fertile branchlets. 



189 Bryothamnion pacificum n. sp. — Plantae fruticosae, plus quara 11 cm alti- 

 tudine, identidem, radiatim, alterneque ramosae, sine axe primario dominante; 

 ramis determinatis spiraliter dispositis, 1.5-2.0 mm long., infra corticatis, habenti- 

 bus 4-10 ramulos alternatos, acutos, ecorticatosque, infra 40-90 \i diam., ante divisi- 

 onem ad 360 \i long., cellulis cacuminis parvis acutisque. Planta typica in loco 

 dicto I. Maria Magdalena, Las Tres Marias, Mexico, legit W. R. Taylor no. 30- 

 665, 9 May 1939. 



