290 University of California FuhUcations in Botany [Vol. 7 



or 26/u, wide. The aplanospores form a simple series of tetrads onlj' 

 and show no disposition to proceed further. On account of these 

 differences it seems best to describe these plants as belonging to a 

 new species, Prasiola nevadensis. It is to be recorded and is of 

 decided significance in Ibis connection that the other one of us 

 (Gardner) has collected characteristic Prasiola mexicana in the same 

 stretch of the same stream, at the same season but in a different year. 

 It may be, therefore, that our new species may be found to be included 

 among the stages in the development of, or states of, P. mexicana. 

 It seems so distinct, however, that we venture to describe it as new 

 and specimens will be distributed in a fascicle of the Phycotheca 

 Boreali- Americana soon to be issued. 



Prasiola nevadensis comes much nearer to P. fluviatilis (Sonnuerf.) 

 Aresch. than to P. mexicana. It differs from P. fluviatilis so far as 

 we may determine from descriptions, figures and scanty specimens 

 available to us, in being broader and not tapering regularly from 

 above toward, the base. We do not know much about the structure of 

 P. fluviatilis, but suspect that the general character and arrangement 

 of cells may closely resemble those of our P. nevadensis. Our plant 

 may be closer to P. fluviatilis var. Hausmanni Grun., in that it is a 

 broader species than typical P. fluviatilis, but further comparison is 

 impossible. We append the following diagnosis: 



Prasiola nevadensis sp. nov. 



Plate 21, figures 11-18 



Thallis gregariis, angustis, 2-3 cm. longis, 0.5-1 cm. latis, oblongis 

 usque ad oblaneeolatis, e basibus latis oriundis, primo disco minuto, 

 aetate provecta, rhizoidibus e basi decumbente emissis affixis, dilute 

 viridibus, marginibus undulatis et crispatissimis ; membrana l-i~25/i. 

 crassa; eellulis in gregibus parvis e superficie visis quaternis, rotundis 

 aut augulatis, laxe positis et in areolas indistinctas segregatis, in 

 sectione transversal! rotundis usque ad valliformibus ; viis intersti- 

 tialibus distinctis nullis; aplanosporis in serie singula, quaternis. 



Tlialli gregarious, narrow, 2-3 cm. long, 0.5-1 cm. wide, oblong to 

 oblanceolate, from a broad base, attached at first by a small disk, later 

 by rhizoids from the basal portion, pale green, witli margins undulate 

 and very much crisped ; membrane 14-25/x thick ; cells in small groups 

 of tetrads as seen from the surface, rounded or angular, loosely ])]aced, 

 forming indistinct areoles, but without interstitial lines, cells in trans- 

 verse section rounded to elongated vertically; aplanospores (?) in a 

 single layer of tetrads. 



In rapid waters of Crane Creek, Foresta townsite, Mariposa 

 County, California, at 3500^000 feet altitude. Type no. 6507, 

 Setchell. 



