208 FRESH-WATER ALG^ OF THE UNITED STATES. 



Syn. Conjugaia inflata, Vauch. ; Zygnema inflatum, Hass. ; Spiro- 

 gyra gastroides, Kg.; 8. ventricosa. Kg.; Rhynchonema 

 vesicatum. Kg. 



Rather common in smaller ponds. 



Plate CXXXII, figs. 6, 7, two filaments in fruit scalar! - 

 form and lateral copulation. 



SPIROGYRA SPREEIANA, Eab. 



Diameter of filaments, 18-21 /*. Cells 10-25 times longer 

 than wide, ends inlaid; spiral slender, loose, making l?.-4 

 turns; fructiferous cells inflated, 36-42 yw diameter; zygo- 

 spores 36 ^ diameter, 2-3 times longer than broad. 



Mountain pools, Pennsylvania. 

 Plate CXXXII, figs. 4, 5, two parts of fruiting filaments. 



SPIROGYRA QTJADRATA, (Hass.) Petit. 



Diameter of vegetative filaments, 24-30 ju ; cells 3-9 times 

 as long as broad ; ends inlaid ; spiral single, good size, 

 making 1 -5 turns; fertile cells much swollen, often some- 

 what quadrate, flattened in the middle, cylindrical ; one or 

 rarely two spirals. Zygospores elliptical or fusiform, diam- 

 eter 27-32 ^ ; 2-4 times longer than broad ; copulation most 

 frequently lateral. 



Syn. Zygnema quadrafum, Hass.; Rliynclionema quadratum, Kg.; 

 Spirogyra pulchella, Wood. 

 Frequent in stagnant waters; 



Plate CXXXII, figs. 8, 9, 10, a sterile filament; lateral 

 and scalar if or in copulation. 



Plate CXLII, figs. 7, 8, parts of two filaments having a 

 sort of rootlets, sometimes observed on plants in a strong 

 current of water, or .when partly out of the water on shores 

 of ponds ; they are developed, apparently, as a means to 

 sustain life in precarious situations. This feature is not 

 peculiar to plants of this genus only. Compare Plate CIX, 

 fig. 3, a Cladophom, and Plate CXYIII, figs. 29-33, a 

 U lothrix. 



SPIROGYRA WEBERI, Kg. 



Diameter of vegetative filaments, 18-28 // ; cells 6-15 

 times longer than broad ; ends inlaid ; spiral always single, 

 slender and lax, describing three and a half to six turns ; 

 fructiferous cells not inflated or but slightly dilated ; zygo- 

 spore oval, one and a half to two times longer than broad. 



Diameter, 26-30 //. ^ 



