92 Vnivcrsity of California Publications in Botany [Vol. 8 



24. Nostoc \';iu('iier 



Thallus mucous, gelatinous or coriaceous, usually globose or oblong 

 at first, later either remaining so or assuming a variety of forms, solid 

 or cavernous, usually with more or less firm periderm, floating or 

 attached, composed of a mass of more or less densely intertwined and 

 contorted filaments, witii thin walls and thick mucous or gelatinous 

 confluent teguments ; trichomes usually torulose, cells cylindrical, sub- 

 globose or doliiform ; heterocysts terminal and intercalary, spherical 

 to oblong, seriate, beginning midway between the heterocysts and 

 developing centrifugally. 



Yaucher, Hist, des conferves, 1803, p. 203. 



The genus Nostoc was founded bj- Vaucher in 1803 (p. 203) as a 

 segregation from the old genus Tremella of Dillenius (1741, p. 41) 

 which by common consent has been restricted to a group of species 

 of basidiomycetous fungi. As founded by Vaucher, Nostoc is a very 

 distinct genus, only one of five species described being now referred 

 elsewhere and that is now referred to the lichen genus Collema whose 

 algal constituent is Nostoc. Nostoc is adopted for the name of the 

 genus by Bornet and Flahault (1888, p. 181), and this is the starting 

 point of our nomenclature in this group. The type may be taken as 

 Nostoc commune Vauch. and the species are practically^ entirely ter- 

 restrial or inhabitants of fresh water. The single species listed below 

 is clearly a migrant into a salt water pool, but is worthy of inclusion 

 because of its physiological significance. 



Nostoc Linckia (Roth) Bornet 



Thallus soft and gelatinous at maturity, of indefinite and irregular 

 form, aeruginous or brownish with age ; filaments abruptly contorted, 

 intricately and closely intertwined, sheaths distinct in young colonies 

 and on the surface of older ones, becoming confiuent in the interior 

 of the colonies, hyaline ; trichomes 3.5-4/^ diam., pale grayish green, 

 cells short, depressed-globose ; heterocysts d-Q/x diam., globose or sub- 

 globose ; spores seriate, developing centrifugally, subglobose, 6-7 /x 

 diam., 7-8/x long; spore membrane smooth, hyaline or slightly brown- 

 ish with age. 



Floating in long, slender masses, 7-20 mm. diam., and up to 25 cm. 

 long in a salt water pond, near the C. M. & St. Paul Railway station. 

 Port Townsend, Washington. July, 1917. 



