98 



ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



elago de Colon, rare as dredged at sta. 145 off I. Isabela, no. 34-98, 12 

 Jan. 1934. Guayas, obtained by diving near the cable station, Salinas, 

 Schmitt no. 18A-33, 21 Jan. 1933. 



PADINA Adanson, 1763^1 

 Plants in erect clumps, rarely prostrate, several blades ultimately 

 arising from the same stupose base ; blades flat or somewhat plicate, fan 

 shaped to reniform, frequently becoming split into narrow segments which 

 are sessile or the lower part somewhat attenuate; blades generally thm 

 and pale brown or straw colored, sometimes darker brown, concentrically 

 zonate, in some cases lightly calcified on one or both surfaces; growing 

 margin inrolled, the growth from a marginal row of initial cells, pro- 

 ducing two or more cell layers, when of two layers the lower, and when 

 of three or more layers the inner ones with longer cells than the upper 

 or cortical layers; blades showing concentric rows of hairs, at least on the 

 morphologically upper surface, sometimes on both, and the reproductive 

 organs usually formed in bands with a prescribed arrangement with 

 respect to the hair zones. 



KEY TO SPECIES 

 1. Thin-bladed species; cortical cells predominantly 20 ju, and more 

 in width, intermittently equal to or half as long as the subcortical 

 cells ; apical rolled margin two layered in the outer part . . 2 



1. Thick-bladed species; cortical cells predominantly 12-20 /t wide, 

 half to a seventh as long as the subcortical cells; apical margin 

 3-6 layered in the outer part 3 



2. Plants about 16 cm tall, 14 cm broad, membranous above, cori- 

 aceous below, the frond split into cuneate, flabellate segments, the 

 lower surface lightly or not at all calcified ; stipe branched, about 

 6 cm tall, 1.5 mm thick at the base, 0.5 mm at the top; cortical 

 cells 20-25 /x, wide, lower cortical cells at first 30-100 ju, long; 

 region adjoining rolled margin two layered, about 50 ju, thick; 

 basal region of the blade 9-12 layered, 200-250 /x thick P. caulescens 



2. Plants 2-4 cm tall, 2-6 cm broad, membranous, with the frond 

 split into rounded, flabellate, crispate lobes, the lower surface con- 

 spicuously calcified ; stipe simple or branched, to 1 cm long, 0.5- 

 1.0 mm thick; cortical cells 25-40 /x wide; lower cortical cells at 

 first 45-75 ju, long, later 25-50 /x; region adjoining the margin 

 two cell layers and 30-40 /x thick ; basal region of the blade 6-8 

 layered and 130-200 /x thick P. crispata 



'1 The identifications in the genus Padina, and the key used to distinguish the 

 species, have been revised by Dr. F. Thivy. 



