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



very greatly in length in the various filaments, but is almost always shorter than 

 the cell containing it. Just beyond the spore is a series of distinct, variously 

 shaped cells, about seven in number, which are, as I have seen them, empty. In 

 the outer portions of the frond occur what I believe to be young filaments. These 

 are distinguished by their rapidly decreasing in diameter towards their distal end, 

 by their being distinctly articulated, by their basal cell not being distinctly sepa- 

 rated as in the older filaments, and by their sheaths being more ample. 



These various filaments composing the fronds do not arise from any one place, 

 but commence at very different distances from the centre, and pursue a more or 

 less straight course to the circumference of the frond, from which they often project. 



Fig. 9, pi. 2, represents a section of the frond moderately magnified ; fig. 9 b, is 

 a drawing of the basal part of a filament magnified 800 diameters. 



Genus ZONOTRICHA. 



Thalli pulvinato-hemisphaerici, scepe confluentes, calce praegnantes, plus minus indurati, basi plani 

 affixa, set ate provecta plerumque excavati, intus zonati; zonis concentricis, variegatis; trichomata 

 pseudoramosa, gracilia, inaequalia, apice hyalina et plus minus longe cnspidata vel in pihim producta. 

 Vaginae firmae, homogeneas vel longitudinaliter plicato-fibrillosse, apice Integra vel dilatatae et in 

 fibrillas solutte. Sporse ignotse. 



Thalli pulvinately hemispherical, often confluent, impregnated with lime, and more or less indu- 

 rated, fixed by the flattened base, in advanced age mostly excavated, zoned within ; zones concentric 

 variegated ; filaments pseudoramose, slender, unequal, their apices hyaline and more or less cuspid- 

 ate or prolonged into a hair ; sheaths firm, homogeneous, or longitudinally plicately fibrillose, their 

 apices entire or dilated and dissolved in fibrillae. Spores unknown. 



Z. inollis, WOOD (sp. nov.) 



Z. interdum subhsemispherica sed gregaria et in stratum nonnihil mammillosum confluens, 

 submollis, cinerea vel griseo-carnea, parcezonata ; trichomatibus longissimis, angustis, 

 flexuosis; vaginis arctis, decoloratis, non fibrosis, firmis ; trichomatibus internis articulatis, 

 saepe interruptis; articulis disjunctis, diametro a3qualibus ad 4 plo longioribus ; cellulis 

 perdurantibus singulis globosis. 



Diam. Trich. c. v. T5 TT " = .00017". Sine vag T5 J" = .000084". 

 Hob. In saxis irroratis, " Cave of the Winds," Niagara, Wood. 



Z. sometimes subsemispherical but gregarious and confluent into a somewhat mammillate, rather 

 soft stratum, ashy or grayish flesh-colored, sparsely distinctly zoned ; filaments very long, 

 narrow, flexuous ; sheaths close, colorless, not fibrillose, firm ; internal filament articulated, 

 often interrupted ; joints separated, equal to 4 times longer than the diameter ; heterocysts 

 single globose. 



Remarks. Every American tourist is familiar with that most wonderful spot, the 

 so-called " Cave of the Winds," at Niagara. It is simply a place where it is possible 

 to go underneath a portion of the great cataract, and then round upon the rocky 

 debris outside of it. Growing upon these rocks, eternally wet and glistening with 

 foam and spray, I found this and the following species. The present form was 

 much the most abundant, making a slippery, grayish, or grayish flesh-colored coat- 

 ing to many of the rocks, dotted here and there with the rigid, blackish fronds of 



