232 AI.G.E CHLOROSPERMEzE. [Cvdiuin. 



green, parallelly joined; articulations with numerous arching 

 spires. Harv. in Hook. Br. Fl. v. ii. p. 362. C. nitida, 

 Dillw. t. 4. / c. (bad.) 

 In ditches, &c. 



2. Z. deciminum, Ag. Two-spired Zygnema. Filaments 

 dark-green, parallelly joined ; spires double, cruciate. Harv. 

 in Hook. Br. Fl. v. ii. p. 362. Conf. jugalis, Dilhv. t. 5. and 

 C. nitida, t. 4. f. A. B. 



In ditches, &c. Spires double, crossing each other, like a continual 

 multiplication of the Roman numeral X, whence the specific name. 



3. Z. guininum, Ag. One-spired Zygnema. Filaments pale 

 yellow-green, parallelly joined ; spires simple. Harv. in Hook. 

 Br. Fl. v. ii. p. 362. "Conf. spiralis, Dillw. t. 3. 



In ditches, &c. very common. This is marked with a spiral line, re- 

 sembling a multiplication of the numeral V. If the length of the 

 joints, and the diameter of the filaments, be considered specific cha- 

 racters in this genus, it would be easy (as some authors have done) to 

 multiply the species to any extent. Their characters are eminently 

 variable ; indeed, in a single specimen, all gradations are often to be 

 found. 



TRIBE XVIII. SIPHONED. 



Plants found in the sea, in fresh water, or on damp ground, of 

 a membranaceous or horny hyaline substance ; filled with a green 

 granular matter. Frond tubular, filamentous ; the filaments 

 free, or collected into spongy difform fronds, which are either 

 crustaceous, globular, cylindrical, or flat. Fructification : vesi- 

 cles ( conioscystce ) external, often stalked, containing a granular 

 mass. 



67. CODIUM. Stackh. Codium. 



Frond spongy, dark green (crustaceous. globular, cylindrical, 

 or flat), composed of an interwoven mass of tubular, conti- 

 nuous filaments. Fructification: opaque vesicles, attached 

 to the filaments near the surface of the frond. Name ; Kodiov 

 the skin of an animal; from the soft nature of the frond. 



1. C. tomentosum, Stackh. Tomentose Codium. Frond cy- 

 lindrical, dichotomous. Hook. Br. Fl. v. ii. p. 318. Fucus 

 tomentosus, Turn. t. 135. E. Bot. t. 712. 



On rocks in the sea, frequent. 6 1*2 inches long, much branched. 

 Since the publication of the British Flora, my friend, Mrs. Griffiths, 

 has been so fortunate as to add another species of this interesting 

 genus to our native list. This is C. adhcerens, Ag. Syst. p. 178, 

 which forms spreading crustaceous masses of indefinite form or size. 

 Her specimens were gathered at Torquay. 



