Characiece 199 



Genus Centrosphaera Borzi, 1883. The cells are globose or 

 shortly ellipsoid and generally occur aggregated in a more or 

 less diffuse stratum beneath colonies of various members of the 

 Oscillatoriacege. The cell- walls are thick and lamellose, and possess 

 a projecting lamellose button of cellulose. Reproduction takes 

 place by biciliated zoogonidia, which usually arise in large numbers 

 from the zoogonidangia. Gametes have not been observed. 



C. Facciolace Borzi 1 is known from the south of England. Diana, of vege- 

 tative cells 26 42 p ; zoogonidangia up to 80 p ; zoogonidia 2 3 p in breadth ; 

 fig. 79 B D. 



There is scarcely any distinction between Centrosphcera Borzi, Endosphaera 

 Klebs and Scotinosphosra Klebs 2 , the vegetative cells being almost alike in all 

 three. In Endosphcera the reproduction is by gametes, zoogonidia not having 

 been observed. In Scotinosphcera the only observed reproduction is by zoo- 

 gonidia, which arise according to Klebs in a most extraordinary manner. 



Genus Phyllobium Klebs, 1881. The plants of this genus are 

 endophytic coenocytes which occur in the leaves of certain marsh- 

 loving plants. They send out branching tubes through the inter- 

 cellular spaces of the host-plant after the manner of Phyllosiphon 

 amongst the SiphoneaB. These branched tubes may or may not be 

 septate, and projecting from the surface of the leaf are small, 

 bright-green swellings. The latter contain a number of radiating 

 chloroplasts, each with a pyrenoid. Biciliated macro- and micro- 

 gametes occur. 



P. dimorphum Klebs, which occurs in the leaves of Ajuga, Lysimachia, 

 etc., has not been observed from this country, but I have recently obtained 

 what may prove to be another species from N. Uist, Outer Hebrides, thickly 

 studding the leaves of damp Sphagnum, the whole tissue of the leaf being 

 permeated by the branched tubes of the Phyllobium. 



Family 4. CHARACIEJE. 



The plants of this family are unicellular and they generally 

 occur as epiphytes, either solitary or in clusters, on other larger 

 AlgaB. The vegetative cells are of very variable form, but in most 

 cases they are attenuated and slightly oblique. There is always a 

 distinct differentiation into base and apex. The base is often 

 drawn out into a stalk of variable length with a disc for purpose of 

 attachment, and the apex is generally acuminate. There is a 



1 Borzi, ' Studi Algologici I,' Messina, 1883. 



2 Klebs in Botan. Centralbl. 1881, xxxix, p. 1621. 



