29 CHAETOPHORACEAE 
fluent forms. These large forms have probably been generally 
referred to Chaetophora tuberculosa, but extended observations in 
field and laboratory have convinced us that they are merely 
growth forms of C. elegans. 
The presence or absence of terminal setae should not be made 
a character for separation of varieties in this species, for plants 
which possess them early in their growth, lose them later. 
A suspicion was expressed by Wolle, that C. elegans, C. pisi- 
formis and C. tuberculosa might be stages in the growth of one 
plant, because he found it difficult at times to separate them. 
One is inclined to question whether Wolle understood the true 
character of the species, particularly C. pisiformis. The separa- 
tion of the species is not a matter of cell measurements, for these 
are subject to the greatest variation. Practically the only dis- 
tinction between C. elegans and C. pisiformis as described by 
Roth, that holds good generally, is in the much more open and 
loose branching of the former. The issues of the two species in 
American exsiccatae are badly confused. 
2. CHAETOPHORA PISIFORMIs (Roth) Agardh, Disp. Alg. Suec. 43. 
1812; Syst. Alg. 27. 1821. Grev. Scot. Crypt. Flor. 6: 
Synop. 40. ibid. 3: pl. 150. 1825 (as C. elegans). Kütz. Spec. 
Ale 532. 1849; Tab. Phyc. 3: pl. 78. f. 3. 1853. Harvey, 
Ner. Bor. Am. 3: 70. 1857. Rabenh. Flor. Eur. Alg. 3: 383. 
1868. (?) Cooke, Brit. E. W. Ale 193. pl. 78. f. 1. 1883. (?) 
Wolle, F. W: Alg. 116. al 703. f. 7-3, 12-15. 1887. Kirchn. 
Mik. Pflanz. 11. A. 2. f. 20. 1891. Saunders, Flora of Neb. 
pl. 13. f. 5. 1894. (?) 
Rivularia pisiformis Roth, Neue Beitr. Bot. 1: 272. 1802.* 
(Ann. of Bot. 1: 261. 1805.) 
. Colonies globose or tuberculose, 2-5 mm. in diameter, usually 
dark green, rarely confluent, the gelatinous substance dense and 
resistant ; filaments densely radiating from the center, strict, di- 
chotomously or less frequently trichotomously branched, branches 
erect or appressed throughout ; terminal branchlets slender, acute 
or sometimes setiferous; cells of main branches about 6-7 بر‎ 
(5.5-8 زم‎ in diameter, 3-6 times as long; terminal cells 4-6 مم‎ in 
diameter )۸ 38, f. 7). 
* Citation from Cat. Bot. 3: 338. 1806. 
