120 FRESH-WATER ALG^J OF THE UNITED STATES. 



parasitic on filamentous algae ; cells in part furnished with a 

 short seta or spine on the apex or back ; cell contents 

 granular. 



Diameter of cells, 5-7 yw. 



Marshy inlet to Lake Harvey, Luzerne County, Pa. 



Plate CV, figs. 9, 10, a filament of Zygnema, with the forms 

 described. 



Genus 21, GONGKOSIRA, Kg. 



Filaments simple or dichotomously branched ; branches as 

 thick as the stem. Cells thick walled, with chlorophyl -green con- 

 tents. The lower cells usually form a rhizome. 

 Live in the water and in the air. 



GONGROSIRA SCLEROCOCCUS, Kg. 



Thallus small, composed of semi -orbicular discs about 

 1 mm in diameter, bright green, often numerously attached 

 to stones in shallow flowing waters, often confluent ; fila- 

 ments radiating, branched, cells somewhat globose, the 

 upper cells larger than the lower ones. Cells about 10 // 

 diameter. 



Beside this form there are others that have found a place 

 under this head ; we have a number beside those recorded 

 from Europe. Prof. Wille, of Sweden, wisely rejects this 

 genus as & pseudo-genus. The plants arranged under it be- 

 long to a class of undeveloped growths known as prothalli^ 

 or protonemae. Thus : 



G. Sderococcus, Kg., is an undeveloped form of Chraolepus. 

 G. dicliotoma, Kg., is a peculiar condition of Vaucheria. 

 G. ericetorum, Kg., is a>protonema, a prothallus of a moss. 

 G. DeBaryana, Bab., is a condition of Ckroolepus. 



Plate CVI, figs. 1, 5, 6, are forms of protonema ,; figs. 2, 3, 

 magnified filaments of G. Sclerococcus ; fig. 4, natural size 

 of thallus of the same, found on moist rocks, submerged 

 stones in shallow water, and on old wood ; figs. 7, 8, a 

 growth sometimes found in large patches on moist earth, or 

 moist rocks, has much of the appearance of Cladophora ; the. 

 diagonal divisions, or septae, of the larger stems separate 

 it. It is a prothallus of B-ryum, a moss 5 figs. 9, 10, from 

 the trunk of a tree in Florida, is probably a prothallus of a 

 fern. 



