82 ZYGOPHYCE.E. 



rent. Indeed, having sent specimens to several celebrated algologists, 

 they hesitated to admit it into Tyndaridea, until Mr. Hassall, who also 

 at first strongly doubted whether it belonged to the Conjugate, fortu- 

 nately gathered fertile specimens. Such we ourselves found shortly 

 afterwards, and we have since repeatedly met with them ; the appear- 

 ance of the plant in conjugation, however, is so altered that its identity 

 can only be determined by tracing it through all its changes. 



" In its usual state the sheath is very conspicuous, and the dense en- 

 dochrome so fills the cells that the plant looks like a Conferva, the con- 

 tinuity being interrupted merely at the dissepiments. When about to 

 conjugate the sheath has nearly or altogether disappeared, and the en- 

 dochrome is collected into two stellae, leaving the rest of the cell colour- 

 less." Ralfs. 



Hassall also found and examined the plant, and figured it with zygo- 

 spores in the cells of the filaments, whereas the Continental species, 

 since the figure by Kutzing, is always described as having the zygospore 

 in the canal of conjugation. There cannot, therefore, be the slightest 

 doubt that the species found by Hassall and Ralfs is quite distinct from 

 that known to Kutzing, Rabenhorst, and De Bary. Priority certainly is 

 in favour of Hassall's name, and it is the Continental species which must 

 give way, and yield up a name, acquired in error, to its rightful claimant. 

 Our figures are based on the sketches and drawings by Ralfs, with 

 whom we have been in communication on this question. It is absurd to 

 suppose that Ralfs and Hassall were both deceived, as well as Mr. 

 Jenner (an admirable observer), to whom the species was undoubtedly 

 known, and finally Mr. Salter in preparing the drawings from the 

 specimens for the " English Botany." Unfortunately we could find no 

 fruit in the specimens which we possess, collected by Ralfs forty years 

 ago, nor could we obtain specimens in conjugation from Cornwall during 

 the past spring. 



Plate XXXI. fig. 1. a, b, portions of sterile threads X 400 ; c, 

 fertile cells with zygospores X 400, after Ralfs ; d, conjugating cells X 

 400. 



Zygnema leiospermum. De Bary. Rabh. Algee Exs. No. 638. 



Sterile cells equal in length and breadth, or sometimes twice 

 as long. 



Zygospore globose or broadly oval, formed in one of two 

 conjugating cells ; membrane brown, even. 



Sporiferous cells a little swollen. 



SIZE. Cells -022 mm. (Ham. Zygospore '023-*03 mm. 



De Bary Conj. p. 77, 1. 1, f. 7-14. Eabh. Alg. iii. 249. Kirsch. 

 Alg. Schl. p. 125. 



In ditches filled after rain. 



The two British species with the membrane of the zygospore even, 

 in this section, are the present and the following, which will require 

 some care in the discrimination. The inflated cells, which enclose the 

 zygospores, in the present, is relied upon as one of the featnres which 

 distinguish it from the succeeding ^species, as well as the larger size of 

 the zygospores. 



Plate XXXI. Jig. 2. a, portion of fertile thread X 400; d, c, 

 fertile cells, with zygospores, after De Bary X 400 ; d, mature zygospore 

 X 400, after DeBary. 



