1920] Setchell-Gardner : Chlorophyceae 281 



County, California. Since its first publication it has been observed 

 in a similar habitat near Friday Harbor, San Juan County, Wash- 

 ington. 



Setchell and Gardner, in Gardner, New Pac. Coast Mar. Alg. I, 

 1917, pp. 384, 385, pi. 33, f. 5-9, and pi. 32, f. 5. 



Gayella constricta differs from G. polyrhiza in having fewer 

 rhizoids and these usually much longer and multicellular. It differs 

 also in having deep constrictions in the mature filaments caused by 

 the failure of certain cells to divide vertically. It differs finally in 

 the much greater diameter of the upper portions of the filaments and 

 in their uncinate tips. 



Gayella constricta has been observed in cultures in the laboratory 

 for over eighteen months as well as the Prasiola (P. m£ridionalis) 

 found growing with it. In pure cultures no transformation from one 

 to the other was observed. New plants of Gayella which were con- 

 stantly arising retained the Gayella form. No plants of Gayella arose 

 in pure cultures of the Prasiola. It seems to us that these cultures 

 justify keeping the two genera separate as well as establishing the 

 independence of both Gayella constricta and Prasiola meridionalis. 



Order 6. ULOTKICHALES blackman and tansley 



Frond of branched or unbranched filaments, tj'pically of a single 

 series of cells; cells uninucleate with one or few parietal chromato- 

 phores with or without one or more pyrenoids; multiplication by 

 fragmentation, akinetes or aplanospores ; reproduction by zoospores 

 and by isogamous or oogamous gametes. 



Blackman and Tansley, Class. Green Algae, 1902, p. 137 ; West, 

 Algae, vol. 1, 1916, p. 281. Chaetophorales Wille, in Engler and 

 Prantl, Natiirl. Pflanzenfam., Nachtr. zum I Theil, 2 Abt., 1909, p. 3. 



The Ulotrichales form a fairly compact group of families having 

 the frond branched or simple, and composed of uninucleate cells. 

 The cells are usually in a single series. There are a few exceptional 

 genera, but these usually occur among the fresh water species which 

 constitute the greater portion of the group. 



Key to the Families 



1. Filaments simple, rarely branched 11. Ulotrichaceae (p. 282) 



1. Filaments branched, at times prostrate and concrescent 2 



2. Cells green, without haematochrome 12. Chaetophoraceae (p. 286) 



2. Cells normally yellow or red, with haematochrome 



13. Trentepohliaceae (p. 305) 



