72 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



Thalli saxicolous, 15-28 cm. high in the intertidal zone, to 125 cm. 

 high in the infratidal, consisting of several to many erect, long-stipitate 

 fronds arising from a holdfast of entangled stolons, brownish to purplish- 

 red in color; fronds compressed throughout except in lower parts of 

 stipe, 1.5-2.0 (or to 3) mm. wide in broadest main parts, repeatedly and 

 distichously branched, the branches mostly opposite, but in part alternate; 

 young branches at first standing almost at right angles at the base, geni- 

 culate, the outer end almost parallel with the branch from which it 

 arises, later all branches straightening and standing at about a 45° angle; 

 thallus in transection showing an abundance of rhizoidal filaments in the 

 subcortical region and a very few scattered among the medullary cells; 

 fructiferous ramuli short, blunt and repeatedly branched ; cystocarps 

 usually single and below the center of the ramule, the outer ends of 

 which are commonly branched ; antheridia superficial, borne in elong- 

 ated sori occupying the middle of the flattened surfaces on either side 

 of terminal parts of branchlets ; tetrasporangia borne in sori on the outer 

 ends of expanded ramuli with cordate apices. 



Type: Holotype is a collection by Gardner on sheet 294572 in the 

 Herbarium of the University of California, Berkeley. 



Type locality: Near Ensenada, Baja California, Mexico. 



Mexican distribution: Pacific Baja Calif. — This plant finds its 

 region of maximum development in the infratidal, rocky, coastal areas 

 bathed by cold upwelling water. In such areas, as for example along 

 Punta Banda and at Punta Santo Tomas, this plant becomes excep- 

 tionally abundant and luxuriant, some individuals reaching more than 

 a meter in length and consisting of hundreds of erect fronds. It ap- 

 pears to occur all along the Pacific peninsular coast, but is confined 

 primarily to those areas where moderate to strong upwelling occurs. In 

 the intertidal zone it extends at least as far as Punta Entrada, Isia Mag- 

 dalena where plants up to 27 cm. high have been taken in March and in 

 May. It has recently been collected at Islas San Benito and at Punta San 

 Eugenio, but in the Bahia Vizcaino area where temperatures are pro- 

 hibitively high, it is absent, or at best occurs only occasionally as a de- 

 pauperate individual. 



Gelidium purpurascens Gardner 

 Plate 5, fig. 1 



Gardner, 1927a, p. 275, pi. 38, 39. Gelidiuin pulchrum Gardner, as 

 interpreted by Dawson, 1945b, p. 60, as to Cabo Colnett specimen. 



