FRESH -WATER ALGJS OP THE UNITED STATES. 179 



centre. The sperraatozoids, which are at this time already free in the water, are very 

 minute, longish, ellipsoidal or ovate masses, provided with two unequal cilia. These 

 commonly both arise together from one end of the body, and are directed in oppo- 

 site directions — one backwards, the other forwards. According to M. Walz, how- 

 ever, in V. sericea the cilia arise from the opposite ends. According to De Bary, 

 the spermatozoids of V. aversa, Hassall, contain reddish pigment-granules. M. 

 Walz states that he has twice seen the process of impregnation in V. sericea, Lyngb., 

 and describes it essentially as follows : After the bursting of the antheridium and 

 the formation of the opening in the oogonium, the spermatozoid clustered around the 

 little orifice in the latter, but were apparently debarred entrance by the presence of 

 a glutinous jelly. After a time, however, one, and then another, forced a passage 

 through this obstacle until finally a number gained access to the protoplasmic ball 

 within. Over this they swarmed, pushing it and retiring and butting against it 

 until some of them actually forced their way into it and were absorbed by it. Im- 

 pregnation being now completed, the oospore acquired a very sharp definite outline, 

 and secreted in a very short time a membrane around itself. The changes which 

 followed during its maturing consisted of the acquiring of a thick coat and the 

 replacing of the chlorophyl within by a reddish-brovra coloring matter. The ripened 

 resting spore of almost all the Vaiicheria is provided with three coats, of which the 

 middle is the thickest. The contents consist of protoplasm, reddish-brown pigment, 

 and numerous oU globules. 



Genus VAUCHERIA. 



Genus unicum, character idem ae familiae. 



The only genus of the family, haying the same characters. 



V. sessilis, (Vauch.) De Candqlle. 



V. laxe intricata, pallide et subsordide viridis ; thallo capillar!, paree ramose ; oogoniis 2-3 

 approximatis, rarins singulis, ovatis vel ovali-oblongis, plus minusve obliquis, rostratis; anthe- 

 ridio intermedio, ramuli modo brevi hamate, mode recto snbulato, subclavato, mode elongate 

 et incurvato, hand rare circinato sustentato; oosperis maturis fusco-punctatis, membrana 

 triplici involutis. (R.) 

 Syn. — V. sessilis, (Vauoh.) De Candolle. Rabenhoest, Flora Europ. Algar., Sect. III. p. 

 267. 

 F. csespitosa, (Vauch.) Agardh. Rabenhorst, loc. cit. 



Eab. Salem, North Carolina; Schweinitz. Common at West Point, New York; Waterville, 



Maine; Culpepper Co., Va. ; Bailey. 



Laxly intricate, pale and subsordid green ; thallus capillary, sparsely branched ; oogonia 2-3, 

 approximate, rarely single, ovate or oval-oblong, more or less oblique, rostrate; antheridia 

 intermediate, sustained upon branches partly shortly hamate, partly straight subulate, sub- 

 clavate, partly elongate and incurved, and not rarely circinnate ; oospores at maturity, fus- 

 cous-punctate, surrounded by a three-fold membrane. 



Remarh. — I think I found this species near Philadelphia in my earliest re- 

 searches, but cannot speak certainly, having preserved neither notes nor specimens. 



