94 ZYGOPHYCE. 
rated by distinctions so minute and variable, that they cannot be main- 
tained as other than varieties, and Zygnema malleolum and Z. affine were 
at the time suspected of being varieties the one of the other. 
Plate XXXVII. fig. 1. Variety gracilis. a, sterile cells X 200; b, 
conjugating cells with zygospores X 200; e, fertile cells of Rhyncho- 
nema form with zygospores X 200; d, outline zygospores x 400. Fig. 2, 
variety flavescens. a, sterile cells X 200; b, c, conjugating cells with 
zygospores X 200; d, fertile cellsof Rhynchonema form with zygospores 
X 200 ; e, outline zygospores X 400. Fig. 8, variety parva. a, sterile 
cells x 200; 0, conjugating cells with zygospores X 200; e¢, outline 
zygospores X 400, 
Section 2. Cells replicate at the ends. 
A. Chlorophyll bands usually two or more. 
Spirogyra insignis. Hass. 
Sterile cells with the extremities replicate, 44 to 5 (rarely 6) 
times as long as broad, chlorophyll bands 2 to 3, lax, with 1 to 2 
turns of spiral, or nearly erect. 
Spores ovate-elliptic, twice as long as broad, membrane even. 
Sporiferous cells slightly swollen, 
Sizs. Sterile cells -03--085 mm. Zygospore :04-05 mm., 
2 to 3 times as long. 
Rabh. Alg. Eur. iii. 248. 
Zygnema insigne, Hass. Alg. 440, t. 1038, f. 1, 2. 
Zygnema Hassallii, Hass. Alg. 157, t. 86,f. 4,5. Jenner Fl. 
Tunb. Wells, 182. 
Spirogyra insignis, Kutz. Tab. v. t. 31, f. 4. Sur. Obs. 
t.1, f. a. 
Rhynchonema Hassallit, Kutz. Tab. v. t. 82, f. 7. 
Spirogyra Braunti, Rabh. Alg. Ex. No. 1810, 1395. 
Spirogyra Hantschii, Rabh. Alg. Ex. No. 1291. 
Spirogyra Theobaldit, Kutz. Tab. v. t. 31, f. 2. 
Spirogyra Hassallii, Petit Bull. Soc. Bot. Fr.; Spirogyra t. 2, 
f. 6-8. 
Rirynchonema gallicum, Ripart. in Petit Spirogyra. 
In streams. 
The number of British species in which the cells have replicate ends 
is much less than of those with truncate ends. We have only included 
two species with two or more chlorophyll bands, in one of which the 
membrane of the zygospore is smooth, and in the other punctate. Doubt- 
less neither of them are common. 
Plate XXXVIITI, fig. 1. a, d, sterile cells X 200 ; 3, conjugating cells 
with zygospores X 200; ¢,fertile cells of Rhynchonema form X 200; 
outline zygospore X 400. 
Spirogyra calospora. Cleve Mon. Zyg. p. 26, t. 8, f. 1-5. 
Sterile cells with the extremities replicate, 6 to 12 times as long 
as broad, chlorophyll bands 1 to 3, making 23 to 7 turns. 
Spores elongate, obtuse ovoid, 14 to 2 times as long as broad, 
membrane yellow, scrobiculate. 
Sporiferous cells scarcely turgid. 
