170 FRESH-WATER ALG^ OF THE UNITED STATES. 



X>iam.— 0.0025". 



Syn.—S. nitida, (Dillwyn) Link. Rabenhoest, Flora Europ. Algarum, Sect. III. p. 245. 



Edb. — Prope Philadelphia. 



Occurring in lubricous turfy masses, of a deep green color ; sterile joints after division about 

 as long as broad, before division 2-3 times longer ; fertile joints similar to the others, not 

 tumid ; spiral filaments 4, moderately broad, turns 1-2 ; zygospores elliptic. 



Eemarks. — This species appears to be somewhat rare, at least I have found it 

 but once, and then only in small quantity. Rabenhorst states that there are occa- 

 sionally only three spirals, and his maximum diameter is 0.0031"; he also speaks 

 of the fertile joints as "vix tumidis." 



Sp. diluta, Wood. 



Sp. articnlis sterilibus diametro subsequalibus ad duplo longioribns, fructiferis baud tumidis; 

 fasciis spiralibus 5, angustissimis, laxis, valde nodosis ; anfractibus plerumque ^, interdum 

 I ; zygosporis sparsis, late ellipticis vel ovatis aut globosis ; cytiodermate modice tenue, in 

 utroque fine nee proteuso nee replicato. 



Biam.— Artie, steril. ^Ig/ = .003". 



Syn. — S. diluta, Wood, Prodromus, Proc. Am. Philos. Soc. 1869, p. 139.' 



Sab. — In stagnis, prope Philadelphia. 



Sterile joints about as long as broad to twice longer, fertile cells not swollen ; chlorophyl bands 

 5, exceedingly narrow, lax, strongly nodose ; turns mostly ^, sometimes 1 ; zygospores few, 

 broadly elliptical, ovate or globose ; cell wall moderately thin, not infolded at the ends. 



Remarks. — I have found this species several successive seasons growing in the 

 ditches in the Neck, below the city, especially in the neighborhood of the large 

 stone bam, built by the great millionaire, and still known as " Girard's Bam." 

 The spirals are very narrow and slender, and are moderately close to one another. 

 They are chiefly made up of a number of chlorophyl nodules, the connecting thread 

 between which is often very faint. In all the fruiting specimens, as I have seen 

 them, the spores have been very few in number, most of the cells of the fertile 

 filaments appearing to have aborted, so that they are simply empty. In most cases 

 only about every third or fourth cell contained a spore. 



Fig. 2, nl. 15, represents this species. 



Sp. setiformis, (Roth) Ktz. 



Sp. saturate viridis, lubrica ; articulis sterilibus diametro paullum brevioribus ad 1| plo lon- 

 gioribns ; articulis fructiferis hand inflatis ; fasciis 3-8, latis, dentatis, interdum nonnihil 

 remotis, sed SKpe arete et dense conjunctis, nodosis ; zygosporis globosis vel late ovalibus. 



Diam.— .0035". 



Syn.—S. setiformis, (Roth) Kutzing. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 246. 



Hab. — In stagnis, prope Philadelphia. 



Deep green, slippery ; sterile joints a little shorter to one and a-half times longer than broad ; 

 fertile joints not inflated; spiral filaments 3-8, broad, dentate, sometimes somewhat remote, 

 sometimes closely and densely conjoined, nodose ; zygospores globose or broadly oval. 



^e?nar^s.— None of the descriptions which I have seen of this species state the 

 number of the spiral filaments, but the other characters of the American form so 

 agree with those of the European plant that it is probable that this one does also. 

 The plant is not uncommon in the Neck, fruiting in the spring. 



