FRESII-W A TKK ALQ^E OF THE UNITED STATES. 173 



I have met with an American plant, which has some of these characters, and at the 

 same time other* "Inch have been supposed to belong to the genus Sjriroyyra. It 

 unites the method of reproduction of Siroyotiium and the arrangement of the 

 chlorophU liand of Xj'ii-<>>/i/r<i, standing as it were midway between them. It is 

 not midway, however, lint mneh nearer Sirogonium, for the passage from a very 

 loose spiral to a longitudinal hYxuous filament is a brief one, and although in some 

 cells of S. n ( rr> rsum the spiral makes a number of turns; in other long cells it 

 scarcely gets around once, in other words the chlorophyl band is nearly straight. 

 On the other hand, the reproduction is strictly that of & stricttim, at least in 

 all cases which have come under my notice. There is, therefore, but one of two 

 things to he done, either to unite Siroyotiium with Spirogyra, or else to give up 

 the arrangement of the chlorophyl as an essential character of the former genus. 

 The great variance, in the latter respect, in our American species, greatly weakens 

 the value of any such character, and I have, therefore, preferred tlie latter of the 



t\M) OOUJ 



v i < 1 1 ovtTMim, WOOD. 



S. articulis sterilibua diamctro 715 plo longioribus ; fnsciis epiralibns 1, rare 2, latis, grann- 

 laiis ; uiifrartilms 1-9; articulis fcrtilibus valdu tumidis, retrovereis ; conjugationc genuflexaet 

 sine tubo connexivo ; cytiudurmate nonnibil crasso, utroque fine proteuso vel rcplicato ; 

 eporis ellipticia. 



Diam. Art. stcril. T |J,," =.00146"; spor. lat T Uo" 7 i! ff "~.00133" .0016"; long, ^j" 

 = 0033". 



n. S. n-troversum, WOOD, Prodroraus, Proc. Am. Phil. Soc. 18C9, p. 139 

 Huh. In stagnis, prope Philadelphia. 



Sterile joints 7-15 times longer than broad; chlorophyl band 1, rarely 2, broad, granulate; 

 turns 1-9 ; fertile article very tumid, retroverted ; fertile cells scarcely swollen ; cell wall folded 

 in at the ends; chlorophyl band single; turns 6; spores oblong or elliptical, spore wall very 

 thick. 



Remarks. I have found this species growing in stagnant ditches in the Neck 

 helow the city. In fruit the cells are almost always very markedly bent backwards, 

 and have a broad pouch-like dilatation in front. The spores are elliptical, and, as 

 I have seen them, greenish and with a thin coat, but may not have been completely 

 matured. 



Fig. 1, pi. 16, represents this species. 



Genus MESOCARPUS, HASSALL. 



i ' lUilae mnssa chlorophyllosa initio diffusa, postea in fasciam longitndinalem, hand raro flexnosam 

 contracta; niirluum contralem et granum amylaceum unicam vcl duo involvens. Zygospora globosa 

 vel ovata, in tnbo connexivo inter cellulas binas plus minus genuflexas formata. 



Clilorophyl mass in the beginning diffused in the cell, afterwards contracted into an often flexuons 

 fascia, and involving a central nucleus and one or more starch granules. Zygospore globose or 

 ovate, formed in the connecting tube between two more or less bent cells. 



*, HASSAI.L. 



M. cellulis sterilibus diamctro 3-6 plo longioribus, fertilibus valdu cnrvatis ; zygosporis ovalibns. 

 Diam. Max. T f S 5 = .0011". 



