98 University of California Piihlications in Botany [Vol.8 



Agardh, Syst. Alg., 1824, p. 71 ; Boruet and Flahault, Rev. I, 1886, 

 p. 356; Setchell and Gardner, Alg. N.W. Amer., 1903, p. 197; Collins, 

 Holdeu and Setchell, Phye. Bor.-Anier. (Exsicc), no. 957; Bornet and 

 Thuret, Notes Algol. II, 1880, pp. 39, 161. Ceraminm pulvinatum 

 Mertens, in Jiirgens, Alg. Aquat. Decas IV, 1817, no. 5. 



This is a very distinct species in typical form because of its 

 peculiar syuiplocoid habit. Even when this habit is obscure the 

 filament and trichouie are fairly tj'pical. Our coast lacks its favorite 

 habitat of piles and logs exposed to fairly pure and fairly warm salt 

 water. 



6. Calothrix parasitica (Chauv.) Thur. 



Filaments aggregated among the cortical threads of Nenialion, 

 blue-green, 0.5 mm. high, 9-lOju, diam. (rarely 12-15jU, diam.), slightly 

 thickened in the middle, bulbous and curved at the base, up to 24/a 

 thick; sheath thin, hyaline, often dilated at the apex; trichomes 7-8/* 

 diam., cells short, prolonged into a very long, flexuous, hyaline thread 

 above; heterocysts basal; several hormogonia in a sheath, 4—5 times 

 as long as the diameter; color intense blue-green. 



Growing in the fronds of Nemalion lubricum. Probably co-existent 

 with the host along the Pacific Coast. 



Thuret, Essai, 1875, p. 381 {nomen nudum) ; Bornet and Thuret, 

 Notes Algol, II, 1880, p. 157, pi. 37, figs. 7-10 ; Bornet and Flahault, 

 Rev. I, 1886, p. 357. Rivularia parasitica Chauvin, Rech. sur 1 'organ 

 la fructification, 1842, p. 41. 



The same species grows in the fronds of Nemalion multifldum on 

 the Atlantic coasts of the United States and Europe. It seems to have 

 no deleterious effect upon either species of Nemalion, and while it 

 seems always to be associated with that genus, it has never been proven 

 to be really parasitic upon it in the sense of obtaining nourishment. 



There is some variation in the specimens found in Nemalion on 

 both the Pacific Coast of North America and the Atlantic coasts of 

 North America and Europe. The base is often swollen but not really 

 bulbous. The sheath is sometimes strict and hyaline, but also often 

 •ample, brownish, and ocreate above. The trichomes are at times toru- 

 lose, and again they show nothing of the sort. The heterocysts vary 

 in different collections from one to four. These may be differences of 

 age or of luxuriance of development, but also there may be more than 

 one species confused under this name. 



