278 University of California Publications in Botany [Vol.8 



whose alf,'al portion was later referred to Prasiola tcssellata by Kuetz- 

 in<r (1849, p. 473). P. horealis differs from P. tessellata at least in 

 habit and in being less regularly areolate. Prasiola horealis also 

 resembles P. furfuracea (IMert.) Menegh. except in that its cells are 

 larger, the membrane thicker, and the areolae and intercellular lines 

 more distinct (cf. also Reed, loc. cit., p. 156). 



A similar composite to those of Prasiola horealis Reed witli 

 Giiignardia ahishana Reed and Prasiola tessellata Kuetz. with 

 Guignardia Prasiolae (Winter) Reed is the Dermatomeris georrjica 

 Reinsch (1890, p. 425, pi. 19, f. 1-6), which has not been, so far as 

 we are aware, examined carefully with regard t.o its two components. 



3. Prasiola delicata S. and G. 

 Plate 17, fig. 3; plate 19, fig. 8; plate 20, fig. 1 



Frond 1-1.5 mm. high, broad and shortly stipitate, expanding 

 directly and abruptly to broadly oblong or cordate, margins crisped 

 and inrolled, dark bluish green; membrane 17-20/a thick, cells not 

 grouped into distinct areolae and not separated by intercellular lines ; 

 akinetes not seen; aplanospores up to 512 from a single cell (8x8x8) 

 but often only 128 ; cells palisade-like and 10-12ja in vertical diameter, 

 in section twice or more as high as broad. 



Growing at or near the upper tide mark on rocky islets. Sitka, 

 Ala.ska. 



Setchell and Gardner, Phyc. Cont. I, 1920, p. 291, pi. 22, fig 3 ; 

 pi. 24, fig. 8 ; pi. 25, fig. 1. 



Prasiola delicata has a decidedly thinner membrane than any other 

 of our marine species, shows little areolation, and has a large number 

 of aplanospores formed within a single aplanosporangium. These 

 characters seem to indicate its just claim to be considered a distinct 

 species. It is known to us, as yet, from a single collection, although 

 in considerable quantity. 



4. Prasiola meridionalis S. and G. 



Plate 20, fig. 2 



Frond up to 7 mm. high, with short and broad stipe, soon expanded 



into a broad, cordate, rosulate or cucullate blade, dirty green; cells 



neither arranged in distinct areolae nor separated by intercellular 



lines; membrane 40-45/i, thick, section showing cells 14— 18/a high 



