500 Howe: Phycological studies 



both unmixed with vegetative cells; carpospores 8; spermatia 64; 

 thallus disintegrating and deliquescing when dried specimens are 

 soaked out with fresh water. 



Scinaia latifrons sp. nov. 



Thallus gelatinous-membranaceous, thin, complanate, 10-16 

 cm. long, 4-7 times dichotomous, not constricted, the segments 

 5-12 mm. broad (when dry), axils rather acute and branches some- 

 what patent, costa obsolete, apices obtuse or shortly and bluntly 

 apiculate: cystocarps 0.17-0.32 mm. in diameter, marginal, mostly 

 confined to areas 1-2 mm. broad measured from the margin; 

 carpospores irregularly ovoid or oblong, io-22/x long. [Plate 28 

 and text figure 1 .] 



La Paz, Vives 6, 11a (type), and 20c. 



The material submitted consists of eight specimens, all of which 

 are amply distinct from S. jurcellata undulata, with which it grows 

 associated, differing in the much broader thinner flattened mem- 

 branous thallus and the marginal cystocarps. Though having a 

 pronounced " Halymenioid " habit, the plants have the peculiar 

 and characteristic vegetative structure and cystocarps of Scinaia. 

 If aberrant in any particular it is in the absence of any costa or 

 well-defined axile strand that can be clearly recognized even in a 

 cross section, contrasting in this respect with S. jurcellata undulata, 

 with which it is associated and in which a compact axile strand is 

 very manifest in cross section at least. The thallus of 5. latifrons, 

 even when sections of the dried material have been treated with 

 potassium hydrate, shows a thickness of only 80-135/i, but it is 

 probable that fresh or liquid-preserved specimens would have a 

 greater thickness. The thallus appears to be the thickest towards 

 the margins, whether the margins bear cystocarps or not. A cross 

 section of the stipe shows a compact medullary mass of filaments 

 with a special axile strand only slightly indicated. The hyaline 

 peripheral cells of the thallus have a height of 27-36/x, averaging 

 considerably higher than in the associated S. jurcellata undulata. 

 The color of dried specimens of Scinaia latijrons is a light brownish 

 rose, while that of 5. jurcellata undulata is a dingy or purplish 

 brown. 



Among the described species, varieties, and forms of Scinaia, 

 S. latijrons is apparently most nearly allied to S. jurcellata forma 



