44 



FIRST GROUP. THALLOPHYTES. 



c. The OEDOGONIEAE 1 include at present only the two genera Oedogonium and Bulbo- 

 chaete. The species, which are numerous in Oedogonium, abound in fresh waters, and are 

 fastened by an organ of attachment at their lower end to firm bodies, chiefly submerged 

 plants. The thallus consists of unbranched filaments in Oedogonium^ of branched ones 

 in Bulbochaete, and the cells increase in length by intercalary growth : in Btilbochaete the 

 terminal cells are prolonged into hyaline bristles. Increase in length of the cylindrical 

 cells commences with the formation of an annular cushion of cellulose on the inner side of 

 the cell close beneath its upper transverse wall (Fig. 20, w]. The cell-wall parts at 

 this spot by an annular spirt, and the ring of cellulose stretches, and thus a broad trans- 

 verse zone is intercalated into the wall of the cell (Fig. 20, B, /); this process is re- 

 peated always close beneath the older, short upper portion of the cell in such a manner 



FIG. 21. Oedogonium, development of the 

 swarm- spores (zoogonidia), (rnagn. 350 times). 

 A, B swarm -spores being formed from older 

 filaments. C free swarm-spore in motion. D 

 commencement of germination. K a swarm- 

 spore formed from the entire contents of a 

 young plant the product of a germinating 

 swarm-spore. After Pringsheim. 



FIG. 22. A Oedogonhon ciliatum, middle portion of a sexual filament 

 (magn. 250 times) with an antheridium m at the upper end, two oogonia 

 with oospores of, and the dwarf male m. B oogonium of Oedogonium 

 ciliatum at the moment of fertilisation, o the oosphere, z the sper- 

 matozoid making its way in, m the dwarf male. C ripe oospore of the 

 same plant. D piece of the male-filament of Oed. gemelliparum, z sperma- 

 tozoids. E branch of a young plant of Bulbochaete intermedia after the 

 winter's rest, with one oogonium above still containing the spore and one 

 which has just discharged it. Fthe four zoogonidia produced from an oospore. 

 G zoogonidia of an oospore come to rest After Pringsheim. 



that the new pieces form small projections at the upper end of the cell (Fig. 20, A, c), and 

 give it the appearance of being made up of caps set one over another ; the lower end of 



1 Pringsheim, Morphologic der Oedogonieen in Jahrb. f. wiss. Bot. Bd. I. De Bary, Ueber die 

 Algengattungen Oedogonium u. Bulbochaete, 1854. Juranyi, Beitr. zur Morphol. d. Oedogonieen 

 (Pringsheim's Jahrb. Bd. IX). 



