164 ULOTHRICACEAE 
more, physiologically it behaves like other species of Stichococeus, 
in that its cell-walls do not become gelatinous like those of U/o- 
thrix when kept in stagnant cultures. In describing the species 
under this genus, Klercker identified it with hesitation with Kütz- 
ing’s Ulothrix subtilis, but in our judgment the figure furnished by 
Kützing makes the identification as certain as in the case of most 
of our species of that date. 
Of the eight or more varietal forms that have accumulated 
about Ulothrix subtilis from the time of Rabenhorst down to Hans- 
girg, at least three (viz., variabilis, stagnorum and fenerrima) 
belong to other genera than S#chococcus ; it is doubtful whether 
some of the rest can be placed in close relation with this species 
as here interpreted, even if they are to be brought into the genus. 
The form illustrated by Kützing (Tab. Phyc. 2: 31. ۸۰ 97. f. 4. 
1852) under the name Ulothrix rupicola Bailey, but apparently 
never described, appears both from the figure and from an authen- 
tic specimen furnished by Mr. Collins, to be simply Stichococcus 
subtilis. 
5. SricHOCOCCUS FLACCIDUS (Kütz.) Gay, Rech. sur Alg. Vert. 
79. pl. 17. f. 101-106. 1891. Klercker, Flora, 82: 104. 
1896. De Wild. Flor. Alg. Belg. 94. f. 42. 1896. 
Ulothrix flaccida Kütz. Spec. Alg. 349. 1849; Tab. Phyc. 2: 
pl. 95. f. 2. 1852. Rabenh. Flor. Eur. Alg. 3: 367. 1868. 
Wolle, P. W. Ale. 197: 128. f. 27, 20. 1887. De Wild. 
Bull. Soc. Bot. Belg. 277: 79-81. 1888. 
` Hormidium flaccidum Braun ; Rabenh. Als Eur. 2480. 1876. 
Klebs, Fortpflanz. Einig. Ale 341—345. pl. 2. f. 27-24. 1896. 
Hormiscia flaccida Lagerh. Flora, 71: 62. 1888. Hansg. 
Flora, 71: 265. 5. ~. 1888. DeToni, Syll. Ale 1: 161. 2. f. 
1889. 
Hormococcus flaccidus a flaccida [sic] Chodat, Beitr. Krypt. 
Flor. Schweiz, 1°: 269. 1902. 
Filaments rather short, forming floccose masses or interwoven 
strata: cells generally somewhat tumid, 6-9.5 4 (6-14 14, Gay) in 
diameter, 1/—2 times as long: cell-wall thicker than in S. subtilis ; 
chromatophore broad, containing a large pyrenoid. 
Reproduction by zoóspores, as well as by the vegetative mode, 
frequent )۵ 2r, f. 14-17). 
