lengthening at the same time, undergoes first of all a transverse division followed h] 

 numerous other divisions. The mass of tissue thus formed puts out from the part or 

 which it rests a root-like hyaline organ of attachment, while the thick free end forms th( 

 growing apex (Fig. i6i, IF). The development of a fertile thallus from the oospon 

 has not yet been observed ; and the whole cycle of forms of the Fucace^ has there 

 fore not yet been certainly determined ^. 



The CEdogoniese - include at present only the two genera CEdogonium and Bulbo 

 chaete, a few species of which are common in stagnant fresh water, fixed by an organ o 

 attachment at the lower end to solid bodies, mostly the submerged parts of other plants 

 The thallus consists of unbranched (CEdogonium) or branched (Bulboch^te) rows o 

 cells, which multiply by intercalary growth, while the terminal cells readily elongab 

 into hyaline bristles. The longitudinal growth of the cylindrical cells is caused by th( 

 formation of an annular cushion of cellulose inside the cell, close beneath its uppe: 

 septum ; the cell-wall ruptures at this place circularly ; the ring of cellulose thei 

 stretches, and a broad transverse zone is thus intercalated in the wall of the cell. Th( 

 process is constantly repeated immediately beneath the older very short upper piec( 

 of the cell, so that these pieces, forming small projections, give to the upper enc 

 of the cell the appearance of consisting of caps placed one over another, while th( 

 lower end of the cells appears to be enclosed in a long sheath (the lower old piec( 

 of cell-wall). This lower part of an elongated cell is always separated by a septum fron 

 the upper cap-bearing piece (Fig. 17, p. 22). In Bulbochaete the growth of all th( 

 shoots, even of the first which proceed from the spores, as far as it is connected witl 

 cell-multiplication, is limited to the division of their basal cell ; so that the cells of eacl 

 shoot must be considered at the same time as basar cells of the lateral shoot whicl 

 stands upon them. The cells contain chlorophyll-grains and nuclei in a parietal layei 

 of protoplasm. The Reproduction of the CEdogonieae takes place by asexual swarm^ 

 spores and by oospores produced sexually. Both are formed, like the spermatozoids 

 in the cells of the filaments. An alternation of generations takes place in the fol- 

 lowing manner. From the oospores which have remained at rest for a considerabk 

 period several (usually four) swarm-spores are immediately formed, which produce 

 asexual, /. e. swarm-spore-forming plants, from which again similar ones proceed, unti 

 the series of them is closed by a sexual generation (with formation of oospores) ; bul 

 the sexual plants produce swarm-spores as well. The sexual plants are either monoeciouj 

 or dioecious ; in many species the female plant produces peculiar swarm-spores (Andro- 

 spores), out of which proceed very small male plants (dwarf males). Several generative 

 cycles or only one may be completed in a vegetative period. The Swarm-spore \i 

 formed in an ordinary cell of the filament (sometimes even in the first cell, Fig. 162, E) b) 

 the contraction of its whole protoplasmic substance ; it becomes free from the mother- 

 cell, the cell-wall splitting by a transverse slit into two very unequal halves (as in the 

 division of the cells) (Fig. 162, A, B, E). It is at first still surrounded by a hyaline mem- 

 brane, which however it also breaks through. The swarm-spore is encircled at its hyaline 

 end — the anterior end during the swarming — by a crest of numerous cilia. This end 

 lies laterally in the mother-cell, and, after the movement ends, becomes the lower 

 attached end which grows out into a rhizoid. The dir-ection of growth of the new 

 plant is thus at right angles to that of the mother-cell. The Spermatozoids are very 

 similar in form to the swarm-spores, but much smaller (Fig. 163, D, 2); their motion, 

 due to a crest of cilia, is also similar. The mother--cells of the spermatozoids 

 are cells of the filament, but shorter and not so rich in chlorophyll as the vegetative 



1 [Thuret divided the olive-coloured sea-weeds (Melanosporea?) into two groups, of which the 

 Phceosporece (Laminaria, &c.) are distinguished by possessing zoospores, the Fucaceoe being desti- 

 tute of them. — Ed.] 



2 Pringsheim, Morphologic der CEdogonieen in Jahrb. fiir wissen. Bot. vol. I. [Ann. des Sci. 

 Nat. 1856, vol. V. p. 251.— Carter, Ann. and Mag. Nat. Hist. 1858, vol. I. pp. 29-39.] 



