276 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



purplish red, firmly membranous; segments 5-10 cm long, 4-10 mm 

 broad, tapering below, a little tapered and rounded at the tips, with a 

 midrib which becomes denuded below and forms the stalks; the margins 

 entire to crenulate or sparingly proliferous denticulate ; normal branching 

 marginal, the branches like the main axes, a little contracted at the base; 

 structurally showing a medulla of notably large cells reaching 90-175 /x 

 diam. which commonly form decussate rows, covered by a cortex of small 

 cells which are not in any obvious order ; growth from a prominent trans- 

 versely dividing apical cell; tetrasporangia on stipitate proliferous branch- 

 lets formed from the margins and from the midrib, at first circular, 1.5- 

 3.0 mm diam., later lanceolate, to 7 mm long or more, the sporangia in 

 patches on each side of the midrib, leaving a narrow sterile margin. 



The growing apex of this plant shows a notable transversely dividing 

 apical cell. All axis cells of the first and second orders appear to bear 

 branches, which on the former are equal and opposite, but on the latter 

 appear on the lower side only. Apical cells of the outermost of these 

 tertiary axes are elongate and prominent, and reach the margin, but the 

 tertiary axes nearer to the midline of the blade are shorter, have less 

 distinctive apical cells, and do not reach the margin. The aspect is some- 

 what intermediate between Kylin's (1924) fig. 6a and fig. 8. The blade 

 in section shows in the upper segments a single medullary layer of large 

 firm-walled cells occupying most of the thickness, covered by a very small- 

 celled cortex of one cell layer, or of two cells at the junction of neighbor- 

 ing medullaiy cells. The thickness varies from 125-155 [x in the upper 

 blades. Sections shov/ the midrib to consist of large thick-walled cells in 

 no particular order, unmixed with descending rhizoids, in the upper 

 blades with a cortex of one cell layer, but in the lower denuded stalk 

 portion covered by a thick cortex of small cells in anticlinal rows much as 

 Kylin (1924, p. 52, fig. 42e) shows for Yendonia crassifolia (Ruprecht) 

 Kylin. It is difHcult to know in which segregate genus to place these 

 plants, since the observed characters do not seem conclusive and cysto- 

 carpic plants are lacking. 



Ecuador: Archipielago de Colon, occasional in tufts on surf-beaten 

 rocks near Black Beach Anchorage, I. Santa Maria, no. 34-225 (tetra- 

 sporic, TYPE), 17 Jan. 1934. 



H YPOGLOSSUM Kiitzing, 1 843 



Thallus bushy, freely branched, the divisions foliaceous, narrow, deli- 

 cate, except for the midribs of one cell layer, with the branching from 

 the midribs; lateral veins and veinlets absent; apical cells of all orders 

 maintained at the thallus margin, and intercalary divisions absent ; tetra- 



