L925] Setchett-Gardner: Melanophyceae 511 



and differs in no fundamental characters from Leathesia, In the 

 larger species of Leathesia the whole under portion sooner or later 

 disintegrates, leaving only the marginal cells for attaching the plant. 

 Until more can be learned of the lifeddstory of and extent of variation 

 in these genera, it seems to us best to combine them and place them 

 all under the oldest name, Leathesia. 



Key to the Species 



1. Fronds diminutive, up to 1.25 mm. diam 1. L. nana (p. 511) 



1. Fronds variable in size, up to 8 cm. diam 2 



2. Paraphyses terminating in a spherical or subspherical cell 



3. L. amplissima (p. 513) 



2. Paraphyses clavate, gradually and uniformly enlarging upward 



2. L. difformis (p. 511) 



1. Leathesia nana S. and G. 



Plate 43, fig. 67 



Thallus solid, spherical, 500-800/x (up to 1.3 mm.) diam.; color 

 dark brown ; cells in the center subspherical, 40-55/* diam. ; paraphyses 

 30-40/* long, composed of 3-4 cells, terminal cell enlarged, sub- 

 spherical, 10-11/* diam. ; hairs 300-400/* long, 4-5/* diam., scattered, 

 not in fascicles ; gametangia with 4-5/* loculi, uniseriate, 3.5-4.5/* 

 diam. ; zoosporangia unknown. 



Growing on the leaves of Phyllospadix near the outer ends. 

 Monterey, California. 



Setchell and Gardner, Phyc. Cont. VII, 1924, p. 3. 



The host upon which this species of Leathesia was found has a 

 wide distribution along the west coast of the United States and careful 

 observation may show that this little known epiphyte is coexistent 

 with its host. In structure it is not far unlike the Corynephora marina 

 of Kuetzing (1843, p. 331 and 1858, pi. 3, fig. I) but is of smaller 

 dimensions and has much smaller interior cells. 



2. Leathesia difformis (L.) Aresch. 



Plate 40, fig. 52 and plate 43, figs. (55, 66 



Fronds gregarious, very variable in size, up to 6 cm. diam., 

 spherical and solid when young, becoming hollow and more or less 

 lobed at maturity, hairs in small scattered groups; cortical filaments 

 clavate. 5-6 cells long, with eidarged, subspherical to spherical terminal 

 cells ; color olive brown ; gametangia cylindrical, 34-45/* long, 4-6/* 



