512 University of California Puhlications in Botany [Vol. 8 



broad, with 6-8 uniseriate loculi; zoosporangia pyriform or ovoid, 

 35-60ju, long, 16-22/A broad. 



Growing on other algae and on rocks in the littoral belt. Ranging 

 from Bering Sea, Alaska, to southern California. 



Areschoiig, Phyc. Scand. I, 1846, p. 154 (Repr.) ; Saunders, Alg. 

 Ilarriman Exp., 1901, p. 423 ; Setchell and Gardner, Alg. N.W. Amer., 

 1903, pp. 249, 250; Collins, Holden and Setchell, Phyc. Bor.-Amer. 

 (Exsicc), no. 829; Tilden, Amer. Alg. (Exsicc), no. 243 (?). Tre- 

 meUa difformis Linnaeus Fl. Suec. (ed. two), 1755, p. 429. 



Regarding the dimensions of Leathesia difformis as a whole or 

 especially of its parts the literature is practically silent. Areschoug 

 (loc. cit.) states "Thallus nunc semine Cannabidis vix major, nunc 

 2-5 uncias diametro aequans, ' ' but gives no definite statements regard- 

 ing the size of the various parts. Farlow (1881, p. 82) gives as the 

 diameter of the frond "from half an inch to two inches." De-Toni 

 (1895, p. 422) states sporangia "35 x 17." It seems to us quite prob- 

 able that this name has been used freely to include a number of species 

 somewhat similar in general appearance, but in reality distinct. We 

 feel that much more work should be done on our Pacific coast material 

 before the limits of the species can definitely be determined. 



Gardner no. 3462 was collected at Tomales Bay, California, in 

 August and shows mature zoosporangia and gametangia on the same 

 individual. The gametangia have 6-8 loculi. Gardner no. 4501 was 

 collected at Pacific Grove, California, in December, and has only game- 

 tangia. These have 9-13 loculi. It may be that we are dealing with 

 two entities, but for the present we are grouping them under L. dif- 

 formis. Plants from both of these numbers are figured on plate 43. 



The dimensions given in our diagnosis above are more or less a 

 composite but represent a fair average of the size of the structures 

 found in the plants which we have included in the species. We have 

 examined material of this species in our herbarium from Kylin, col- 

 lected at Strangahnfund and at Varberg, Sweden, which may be 

 considered to be topotypes of L. difformis. The material from both 

 of these localities is bearing fruit and apparently mature. The fol- 

 lowing measurements of their parts will indicate the relation in this 

 respect to our Pacific coast material. Paraphyses, composed of 3-4 

 cells, 38-44/x long in plants with gametangia, up to 15fx long in plants 

 with zoosporangia, terminal cells 14-18/x in diameter. Gametangia 

 composed of 4—6 uniseriate loculi, 20-25;li long, 5-6/x in diameter. 

 Zoosporangia are 30-50;a long, 15-22fi in diameter. 



