ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 505 



Paris, including one new species, S. gallica, allied to aS^. sericea. 

 The following is his classification of the species : — 



Section I. Cell-wall recurved in the form of an annular fold at 

 each end of the cell. 

 § 1. A single spiral band, rarely two in a few cells. 



A. Middle layer of wall of zygospore smooth (7 sp.). 



B. Middle layer of wall of zygospore dotted (1 sp., 



(*S^. calospora.). 

 § 2. Two or more spiral bands (2 sp.). 

 Section II. Cell-wall not folded in at the ends of the cells. 

 § 1. A single spiral band. 



A. All three layers of wall of zygospore smooth 



(13 sp.). 



B. Middle layer of wall of zygospore dotted (2 sp.), 

 § 2. Two or more spiral bands. 



A. Zygospores ovoid (7 sp.). 



B. Zygospore lenticular or flattened (4 sp.). 



Sykidion, a new Genus of ITnicellular Algae.* — On a BMzodo- 

 nium gathered at Howth, Dr. E. P. Wright has observed fruit-like 

 structures which he has determined to be an epiphytal unicellular 

 alga allied to Hijdrocytium and Cliaracium, but constituting a new 

 species and genus, to which he gives the name Sykidion Di/eri, with 

 the following characters. 



The vegetative stage consists of a unicellular organism, with a 

 tough cell-wall, attached by its narrow basal portion to the filaments 

 of Bliizoclonium Casparyi ('?). It presents somewhat the shape of a 

 little fig. The cell-contents are of a bright grass-green colour. 

 When the cell attains its full dimensions, a second cellulose layer is 

 formed, and shortly afterwards the protoplasmic contents divide into 

 a number of separate masses, which escape by the rupture of the 

 apical portion of the two cell-walls in the form of biciliated green 

 zoospores. On their escape the walls of the mother-plants scarcely, 

 if at all, alter in shape, remaining persistent. These are then of pale 

 straw colour, and might be mistaken for the empty loricje of an 

 infusorian. The apical slit by which the zoospores escape distin- 

 guishes the genus from Hydrocytium and GTiaracium, in which the slit 

 is always lateral. 



Chroolepus aureum.t — This alga, besides growing freely on damp 

 rocks, occurs in conjunction with the lichen Graphis scripta on trees, 

 on Opegrapha saxatilis, on calcareous rocks, and on other members of 

 the group Graphidece. In a specimen found by Professor T. B. 

 Schnetzler in the free state on a mass of molasse rock at Lausanne, 

 the ramifying filaments bore globular sporanges on their sides. At 

 the sides and base, however, the hyphsB of fungi were observed in 

 contact with and penetrating through the walls of the algal cells, and 

 they formed a plexus among the ramifications of the alga. 



* Trans. R. Irish Acad., xxviii. (1881) pp. 27-30 (pi. ii. fig. 5). 

 t Bull. Soc. Vand. Sci. Nat., xvii. (1880) pp. 13-14. 



