1920] Setchell-Gardner : Chlorophyceae 279 



and l-S/x wide with broad, hyaline margins (up to ISp. thick) ; 

 akinetes scattered, large thick walled ; aplanospores probably 128-512 

 (4x4x8 or 8x8x8) from a single aplanosporangium. 



On exposed rocks or rocky islets above the high water mark but 

 exposed to the force of the waves. Washington (Friday Harbor and 

 Neah Bay) to central California (entrance to Tomales Bay). 



Setchell and Gardner, Phyc. Cont. I, 1920, p. 291, pi. 25, fig. 2. 



The specimens taken as the type of this species were collected by 

 one of us (Gardner, no. 3824) at Neah Bay, Washington. We are 

 also inclined to refer here specimens collected on "Minnesota Reef" 

 at Friday Harbor, Washington, and at the entrance to Tomales Bay, 

 California. In both of the last two localities, the species is associated 

 with Gayella constricta. Cultures, however, definitely indicate the 

 independence of the two plants of one another. 



Prasiola meridion-alis comes near to P. horealis Reed, but the 

 frond of the latter is areolate and with more or less distinct inter- 

 cellular lines. P. horealis, so far as found, is infested with a fungus 

 {Guignardia alaskana Reed) while none of the three collections of 

 P. meridionalis shows any trace of such a parasite. 



23. Gayella Rosen v. 



Frond filiform, simple or very slightly branched, at first of a single 

 series of cells, later dividing longitudinally into many series, but 

 always remaining filiform, not flat; cell structure as in Prasiola. 



Rosenvinge, Groenl. Havalg., 1893, p. 936. 



Gaj'ella may be a genus of doubtful autonomy, but the cylindrical 

 rather than flattened character of its fronds seems to mark it off 

 distinctly from Prasiola. The behavior of Gayella constricta in cul- 

 tures, in retaining its characters and never showing a Prasio7a-stage, 

 induces us to retain the genus. Our experience of both species of our 

 coast does not conflrm that of Borgesen (1902, p. 482 et seq.) and we, 

 therefore, feel unwilling to consider G. polyrhiza as a subspecies of 

 Prasiola crispa. Certainly our G. constricta shows no distinctly tran- 

 sitional forms to the Prasiola found associated with it. 



Key to the Species 



1. Up to 175m diam. above, frequently constricted 2. G. constricta (p. 280) 



1. Up to 70m diam. above, without constrictions 1. G. polyrhiza (p. 280) 



