172 Ulothricaceae 



lins) would seem, judging by the meager description, to be asso- 

 ciate with Conferva Loefgrenii Suecica Wittr., but examination 

 proves it to be very different from that variety as issued in Wittr. 

 & Nordst. Alg. Exsic. 518. 1883. In the character of the chro- 

 matophore and in other features, Mr. Collins' specimen seems to 

 be more closely allied to M. floccosa. 



4. Microspora Wittrockii (Wille) Lagerh. Ber. Deutsch. bot. 



Gesell. 5: 417. 1887; Flora, 72: 208. 1889. DeToni, Syll. 



Alg. 1 : 228. 1889. 



Conferva Wittrockii Wille, Ofers. Vet. Akad. Forhand. l88l 8 : 

 20.pl. p. f i-ii. 1 88 1. (?); Jahrb. wiss. Bot. 18: 461. pi. 17. 

 f. 35-42. 1887. 



Filaments forming long, silky skiens, light green in color ; cells 

 perfectly cylindrical, never constricted at the dissepiments, 19. 5— 

 20// in diameter, 1—2^ times as long; cell-wall thinner than in 

 M. amoe?ta and M. Loefgrenii, about 1.5 fi thick, not exhibiting its 

 lamellated structure in the vegetative state ; chromatophore thin, 

 often perforated or sieve -like in appearance, sometimes retreating 

 from one end of the cell so as to be thimble-shaped, the large nu- 

 cleus (5-6.5 jut in diameter) nearly always clearly showing through 

 {pi. 23, f. 5-7\ 



In a brook draining a swamp, Van Cortlandt Park, New 

 York, April, May (287, 348, 415). Meadow brook, Norwich, 

 Vermont, May, 1902 (675). 



This form, which has not before been reported in this country, 

 was observed and collected several times in the spring of 1900. 

 It was always growing without other accompanying species than 

 the small form Microspora stagnorum. During the spring of 1901, 

 all search for it in the same brook was fruitless, but M. Loefgrenii 

 was found in abundance, although during the preceding season the 

 nearest station of the latter species was in another stream half a 

 mile or more distant. This circumstance cast suspicion on the 

 distinctness of the form determined as M. Wittrockii. 



However, a very careful reexamination of various collections 

 preserved by different methods, has shown in the most convincing 

 manner that the specimens in question are not to be confused with 

 M. Loefgrenii or M. amoena. Our form is distinguished by its per- 

 fectly cylindrical cells, the thin walls of which do not show the 

 lamellated structure until after maceration, and by its thin chro- 



