156 University of California Pxhli rations. [botany 



Prasiola differs from Hooker's Prasiola tesselhda iu the shape 

 and color of the fronds and in the arrangements of the tetrads 

 and areoles. There is not that distinct tessellate arrangement of 

 the tetrads, but the areoles are polygonal or imperfectly quadrate. 



This Alaskan Prasiola, as seen from the surface, resembles 

 none of the authentic specimens available for comparison, except 

 Prasiola furfuracea (Mert.) Menegh, collected in Sweden by 

 Nordstedt. The cells of this specimen are smaller and the cells 

 and tetrads and hyaline spaces are not so distinct. The cross 

 sections resemble one another, lint P. furfuracea is thinner than 

 the Alaskan specimen. The frond of P. furfuracea is 20-23 /^ 

 thick, and the cells 10-13 /* vertical diameter and 4-C i^ 

 horizontally. The fronds of the Alaskan Prasiola are 16-45 /a 

 thick and cells 11-14 /^ vertically and 4-9 /^ horizontally. 

 Another specimen of Prasiola furfuracea, collected bj'H. Heiden 

 at Mecklenburg, (lermany, and published in Phykotheka Uni- 

 versalis Fasc. IX No. 438, is quite different from both the 

 Nordstedt specimen and our Alaskan Prasiola. In Heiden 's 

 specimen the tetrad areas are arranged between lines radiating 

 from the base of the frond, but near the outer edge the 

 areas are like those in Norstedt's specimen. The cells and the 

 plants are very much smaller, while the fronds are stipitate 

 instead of sessile as in Nordstedt' s specimen. If both these speci- 

 mens are correctly determined this species must vary greatlj"; 

 yet even then it could scarcely be considered the same species as 

 the Alaskan Prasiola. There is even a wider difference between 

 our Prasiola and P. crispa (Lightf.) Ag., both iu the surface 

 view and in the cross section. The cells of P. crispa are larger, 

 coarser, and stand out more prominently on the surface, while 

 the areas are rather rectangular and very distinctly separated by 

 a hyaline space. The fronds are very thin and flabby and are 

 very broadly reniform with rufQed edges. 



Our Prasiola does not agree with any Prasiola described in 

 De Toni's Sylloge Algarum, so is probalily a new species. It 

 seems wise then to give this Prasiola a provisional specific name 

 until more is known about this genus and the species have been 

 carefully revised after a thorough study. In the meantime we 

 suggest the name P. boreaUs as a good name, indicating its 



