FRESn-WATER ALG.E OF THE UNITED STATES. 27 



nostocs has been shown, but only reason to study also their relations with the vari- 

 ous collema. 



In regard to the Sperm osirea', there is as yet no direct proof whatever connect- 

 ing them with lichens. It is very possible that they are not so closely related to 

 the true nostocs as is generally believed, so that the probabilities of their being 

 lichens are at present £o remote, that for the systematist to refuse to take note of 

 their distinct forms, seems to me most unwarrantable. 



Subfamily NOSTOCE.E. 



Thallus peridcrmate plus minus distineto instructus, sporis destitutus. 



Tballus provided with a more or less distinct integument, and destitute of spores. ' 



Genus NOSTOC, Vaucher, (1803.) 



Thallus gelatinosus, varie coloratus, aut globosus yel subglobosus aut foliaceo-mcmbranaceus et 

 irregulariter expansus, sffipe bullatus. Trichomata plus minus monilifovmia. Cellulaj perdurantes 

 exacte sphsericse vel rare oblougse. 



Thallus gelatinous, variously colored, either globose or subglobose, or foliaceously membranous 

 and indefinitely e.xpanded, often a bulla. Filaments more or less mouiliforme. Heterocjsts exactly 

 spherical or rarely oblong. 



a. niallus globo!<us vel subglobosus, vel disciformis. 

 Tfiallus globose, subglobose or discoid. 



I¥. Anstinii, Wood, (sp. nov.) 



N. subglobosum, parvuni, plerumque niagnitudine ovorum piscium, rare ad 2", fuscescente, 

 vel nigrcscente, interduni durum intordum submolle, superficie saepo corrugata ; tricho- 

 matibus varie curvatis, dense intricatis vel distantibus et laxissime intrieatis, viridibus, 

 fuscescentibus, subplumbeis vel luteo-brunneis, in thallis minoribus ssepe distincte vaginalis, 

 in thallis majoribus hand vel indistiucte vaginalis ; articulis maturis globosis, stepe didvrais, 

 crasse granulatis; cellulis perdiirantibus artieulorum diamctro ferpialibus vel paulo majoribus, 

 globosis, interjectis vel terminalibus, plerumque sparsis. 



Diam.—CcW. Teg , t/jj/— t^|,jo" = .0020"— 00033"; cell. i>erduraut, .00033". 



Hab. — in rupibus irroratis, New Jersey. (Austin.) 



Subglobose, small, mostly the size of fish-eggs, Init reaching the diameter of nearly two lines 

 fuscous or blackish, sometimes very hard, sometimes much softer; surface often corrugated* 

 filaments variously curved, densely intricate or distantly and loosely interwoven, greenish, 

 fuscous, subplumbeis or j-ellowish-brown, in the smaller fronds often distinct!}' vagiuate, in 

 the larger indistinctly or not all vaginate; mature joints globose; often didymous, coarsely 

 granulate; hetorocysts equal to the diameter of the other joints or a little larger, globose 

 interspersed or terminal. 



Remarlcs. — The fronds of this distinct species vary greatly in appearance; the 

 larger of them are often almost colorless, and, when viewed with the microscope, 

 are seen to be composed of a transparent colorless jelly, with remarkably large 

 filaments scattered through it. These filaments are generally without sheaths, 

 though occasionally a sheath can be faintly traced. The smaller fronds are much 

 firmer than the larger and are more decidedly colored. Some of them are entirely 

 opaque, looking simply black when viewed by transmitted light under the micro- 

 scope. In these the filaments are densely crowded together, often misshapen and 



