150 FRESH-WATER ALG^B OF THE UNITED STATES. 



Syn. V. ornithocephala, var. avers. Kg. 



Plate CXXVII, figs. 5-8, sections of filaments with oogo- 

 iiia and antheridia, as found on thalli recognized as properly 

 belonging to this species, although differing from the Euro- 

 pean form, in the more erect and regular oogonia and the 

 less inclining antheridia. 



Find this species intermingled with aquatic plants near 

 river banks. Compare note, V. sericea, Lyngb. 



VAUCHERIA SERICEA, Lyngb. 



Aquatic or terrestrial, occurring in turfy mats, of a 

 yellowish, dirty, or bright-green color ; filaments thin, 

 densely intricate, laxly or vaguely branched ; often ascend- 

 ing and erect together with the branches ; oogonia sessile or 

 very shortly pedicellate, 1-6 seriate, unilateral, obliquely 

 irregularly oval, their lateral mouths produced into a ros- 

 tellum or beak ; antheridia sessile upon the filament 

 (thallus) near the oogonia ; somewhat cylindrical, subclavate, 

 deflexed, especially in age ; spermatozoids (according to 

 DeBary) oblong and furnished with a single cilium at each 

 end. 



Diameter of filaments, 50-75 ^. 



Dr. Wood, in his Contribution, page 181, remarks, "I can 

 see no constant differences between V. sericea, Lyngb., and 

 V. aversa, Hass. The extreme forms differ somewhat, but 

 both are very common about Philadelphia, and everywhere 

 grade into one another. The plant grows in springs and 

 actively running water abundantly in this neighborhood; 

 also on very wet ground, especially on that which is habitu- 

 ally overflowed, such as the face of dams, neighborhood of 

 springs, etc." Evidently the Doctor had but one species, 

 V. sericea, in different stages of growth. The plant I figure 

 for V. aversa is clearly not the same ; distinct in habitat, in 

 form of oospores and in the more erect antheridia. 



Syn. V. ornithocephala, Ag. ; V. polysperma, Hass. 



Plate CXXVII, figs. 12, 13, apart of a filament thickly 

 set with oogonia ; from a specimen from Iowa. The plant is 

 common, but not always so abundant in fruit. 



VAUCHERIA DILLWYNII, Ag. 



Terrestrial, broadly expanded, forming a rather thin 

 stratum, of bright or dark green color. Oogonia globose, 

 or ellipsoid, rostrate, sessile, usually single, sometimes 

 twin, enclosed in delicately punctate membranes. Mature 



