FBB8H-WAT1B ALG.E OF T 11 E UNITED STATES. ;>3 



hut, when they arc, the joints arc shorter than broad. The endochrome is mostly 

 \< iy ^'iMiiulate ; sometimes, ln>\\r\cr, it is niucli more honiogvncnns. The sheaths 

 in the old filaments are rather tliick, and freqiu 'iitly partially empty; the exterior 

 i if such sheaths has often a roii^'h, ra^ed look. The larger cells are very few in 

 numher. They are elongated cylinders with concave ends. I have found this plant 

 in the Schuylkill Hiver, just above 1 airmount dam, in a younger state, and appa- 

 rently without heterocysts. The threads near their ends had their endochrome 

 distinctly articulate, like an oscillatoria, but elsewhere the protoplasm was continu- 

 ous. It often contains numerous large granules resembling minute starch grains, 

 which however fail to exhibit the reaction with iodine. 



l-'ig. ~. ". pi. 1, represents a portion of the filament slightly magnified; fig. 7, 6, a 

 heterocyst from the same specimen more magnified ; fig. 7, cam! <I, are drawings from 

 another specimen from the same locality, each magnified 800 diameters ; fig. 8, 

 pi. 1, represents the form alluded to in the text as having been found ill the 

 Schuylkill River just above the dam. 



FAMILY NOSTOCHACELE. 



Trirhomata simpliciix, c cellulis distinct!* composita, interUum vaginata, articuluta, in gclatina 

 immrrsa, ccllulis pcrdurantibus, ct intcrdum sporis porro instructa. 



Filaments simple, rmiipii.-cil .f di.-tinct cells, sometimes vaginate, imbedded in jelly; furnished 

 with lictcroeysts and sometimes with spores also. 



/,' murk*. The nostochacere are plants of simple construction, consisting of a 

 more or less firm jelly in which arc imbedded serpentine filaments, composed of 

 numerous cells. These cells are mostly more or less globose, especially in the true 

 no-toes, so that the filament has amoniliform aspect. They have not distinct walls, 

 or at least any that can be distinctly seen by ordinary powers of the microscope, 

 and arc sometimes closely connected, sometimes rather widely separated. No 

 nuclei are usually discernible ; I have, however, seen in some instances central 

 spots, which were possibly of that nature. The filaments themselves arc of various 

 length, almost always tortuous, sometimes widely separated, sometimes closely in- 

 terwoven. The gelatinous portions of the fronds are of various consistence some- 

 times semifluid, sometimes very firm, almost cartilaginous. 



The order is divisible into two families the Noatocs proper and the Sjtermosirccr. 



In the former, the outer portion of the frond is condensed and firm, forming a 

 sort of outer coat or epidermis, which is sometimes quite distinct, but in other 

 instances can scarcely be said to exist. 



In the filaments of a true nostoc are placed at irregular intervals cells, which 

 are mostly larger than the others, and have thick, distinct walls. These cells con- 

 tain very little or no chlorophyllous protoplasm. They arc often, but by no means 

 always, provided with numerous exceedingly attenuated, hair-like processes, or 

 quiescent cilia. These bodies were supposed by Kutzing to have some sexual 

 value, and received from him the name of Sjxrmatia. But, as their functions are 

 entirely unknown, the name of heterorysts, first applied by M. Allman, is prefera- 

 ble. They arc the " connecting cells" of Thwaites. No one has as yet demon- 



