240 FRESH-WATER ALG^E OF THE UNITED STATES. 



The first condition is described as Zonotrichia minutula, 

 Wood. 



Fronds very small, blackish green, semi -globose, not dis- 

 tinctly zoned, rather soft, growing on mosses ; not impreg- 

 nated with lime ; internal filaments shortly articulate, very 

 distinctly fasciculately josew^o-ramose, etc. 



Second condition Zonotrichia parcezonata, Wood. 



Blackish green, irregularly semi-oval, to six lines long, 

 hard, slippery, not fragile, impregnated (partially) with 

 lime, internally distinctly radiate, sparsely and often obso- 

 letely zoned ; filaments moderately long, straightish, etc. 



The author remarks, " I found this plant growing 011 rocks 

 as glossy, blackish, very hard and slippery fronds or masses, 

 which varied in size from that of a very small shot to nearly 

 half an inch in length. The filaments (internal) are often 

 very evidently and frequently pseudo-r&mose." 



Certain specimens which I obtained, growing with the 

 others, instead of being blackish in color, are grayish, but 

 agree in all other respects with their fellows. The gray 

 color depends upon the deposit of lime salts, distributed in 

 quantity with the spray of the falls. It is probably this 

 condition which Prof. Bailey refers to as Rivularia calcaria. 

 This stage would make the third condition. 



A fourth condition is well calculated to deceive the novice 

 with age the trichome contracts, and the ends of the wide 

 sheaths become fibrillose. 



Syn. Besides the above three, may be added Schizosiphon crusi- 

 formiSj Naeg. ; Sch. cataracta ?, Naeg. ; Petronema fructicu- 

 losum, Thwaites ; Scytonema crustaceum, (Ag.) Cooke. 



Very abundant, particularly on the rocks subject to the 

 spray of water falls, Niagara, Genesee River falls, Adiron- 

 dack Mountains, etc. 



Plate CLXXII, figs. 4, 5, the gray crustiferous form, 

 natural size, often forms a thicker crust ; fig. 3, a section of 

 a glossy blackish frond, Zonotrichia parcezonata fig. 6, section 

 of a more advanced growth ; fig. 2, a single plant separated 

 and more highly enlarged ; fig. 7, more advanced stage, ends 

 of trichomes fibrillose. 



Plate CLXXVII, fig. 15, natural size of thalli, as some- 

 times found in clusters ; fig. 14, a section of one of them 

 showing the Zonotrichia form. 



