50 EKYTHEA. 



liberis vel inferne vagina comrauni plus minus longe inclusis; 

 vai^iii.i crassa gelatiiiosa rugos;i. Trichoinatihiis 18-30// crassis, 

 griseo-violascentibus; articulis 9-12// longis (in parte liormogouigeua 

 3.U tantum longis)." 



Nostoc amplissimura sp. nov. The specimens upon which tho 

 new species, here proposed, rests, were collected near Pasadena, 

 California, by Prof. A. J. McClatchie, in the spring of 1896, It 

 wrows in streams, attached to stones, and reaches a considerable size. 

 The thallus is at first spherical, becomes very early hollow and 

 lobulated, expanding until it becomes an irregular, verrucose, 

 brownish yellow sack, measuring as much as 60 centimeters by 30 

 centimeters. This species is therefore the largest species belonging 

 to the Cyanophycese. The wall of the sack is of varying thickness, 

 from 2 to 10 mm., and composed of one to several layers of jelly in 

 which the trichomes are imbedded. The structure of the wall is 

 not altogether simple, it seems to contain small, flattened cavities. 

 These cavities remind one of the figure of Nostoc iparmelioides by 

 Gomont (cf. Bull. Soc, bot. de France, 43, pi. 10, fig. 7, 1896), 

 but in that species the cavity is the only cavity of the jjlant, while 

 in ours there is, besides these smaller cavities, the huge main cavity. 

 The wall, too, contains abundant small lumps of li nie. The filaments 

 are very numerous in the jelly and arranged somewhat variously. 

 Near the surface, both upper and lower, they are much contorted, 

 while in the middle, they take more nearly a horizontal and parallel 

 course. The trichomes of the outer filaments are provided with 

 conspicuous, wide, browm sheaths, those of the lower often have 

 distinct colorless sheaths, while tliose of central portions seldom 

 show any indication whatever of sheaths. The trichomes, them- 

 selves, are always more or less torulose and the cells vary from 

 depressed spherical to short cylindrical and measure 2-3yu in diam- 

 eter and 3.5-5yU in length. The heterocysts are somewhat larger 

 than the cells of the trichorae and measure, usually, about Api in 

 diameter. The spores begin to form in the outer layer, as a rule, 

 and are from 5 to G/j-. long and from 3 to 4// thick. Tlie spore- 

 forming cells elongate perpendicularly to the length of the fila- 

 ment, as is shown in figure 2 of Plate III. The spores are 



