154 FRESH-WATER ALG^ OF THE UNITED STATES. 



VAUCHERIA TUBEROSA, A.Br. 



Flagella subterranean, apices swollen, tuber-like. Fila- 

 ments dichotonious, three or four, or more times divided ; 

 branches regularly constricted at the base of the divisions 

 and often intermediately ; lateral stolons not infrequent, 

 repeatedly constricted, bead-like, much enlarged at the ends. 

 Neither oogonia nor antheridia have been observed. 



Have three distinct varieties of this strikingly peculiar 

 plant. The type, Plate CXXX, was dredged in Lake 

 Michigan by Prof. S. A. Forbes, four miles from Chicago, 

 from a depth of six fathoms. It accords well with plants 

 collected in Swiss lakes. 



Var. INTERMEDIA, Wolle. 



Plate CXXIX, figs. 9-11. This form has not, as far as 

 observed, the tuberose swellings of the type, but has the 

 distinct manner of branching and the constrictions at the 

 bases of the psewdo-branchlets. It is bright green. The 

 former is duller green, tinted with red at the constrictions ; 

 the swollen ends very dark, or bluish green. 



Was found in marshes in Georgia by Capt. J. D. Smith. 



Var. MINOR, Wolle. 



Plate CXXIX, figs. 12-14, another form with only about 

 half the diameter of var. intermedia, light green color ; parts 

 between the constrictions proportionately much longer and 

 the dichotomous branching not so regular. 



From small pools on the banks of the Susquehanna, 

 Harris burg, Pa. 



Family XLBOTEYDIACE^E. 



Small unicellular plants, green, globose; on the surface of 

 moist earth, with a system of colorless radicles, much divided, 

 descending from the base of the cell into the earth. 



Propagation takes place by means of sexual zoospores ; these 

 copulate and produce zygospores, which quickly develop and 

 produce vegetative plants ; the cell contents of these finally di 1 

 vide into an indefinite number of resting spores. These ejected, 

 in turn germinate and again produce sexual microzoospores. 



Asexual multiplication takes place also, by means of macro- 

 spores. 



