46 



FIRST GROUP.— THALLOPHYTES. 



of the observer into an open beak-like canal (Fig. 22, 5, z) through which the sperma- 

 tozoid enters and coalesces with the hyaline portion of the protoplasm of the oosphere, 

 the two protoplasmic bodies and the nuclei uniting with one another. In Oe. diplandrum 

 the large spermatozoids display amoeboid movements, and creep round about the 

 oogonium till they reach the canal, through which they then slowly make their way. 

 Immediately after fertilisation the oospore invests itself with a cell-wall which like the 

 cell-contents is eventually coloured brown ; but in Biilbochaete the contents of the 

 oospore are a beautiful red. The oospore remains enclosed in the oogonium, which 

 ^ separates from the adjoining cells in the 



filament and falls to the ground, where 

 the oospore passes through its period of 

 rest. When it awakes to new activity, 

 which may be within the vegetative period 

 in which it was formed, it does not itself 

 develope into a new plant, but its contents 

 issue forth from within the cell-wall 

 wrapped in a thin layer of jelly and divide 

 into four zoospores, which are set free by 

 the dissolution of the gelatinous envelope 

 and move actively about. After coming 

 to rest they grow each into a new plant. 



d. The Coleochaeteae' are distin- 

 guished from the Confervoideae which we 

 have been considering by the structure of 

 the oogonium, and by the peculiar forma- 

 tion of the fructification, which recalls that 

 of the Florideae. Entrance to the oosphere 

 is secured here, not as in Oedogonium and 

 Vaucheria by a short beak, but by a long 

 hair-like process from the oogonium, which 

 is open at the upper end. Fertilisation 

 takes place by means of spermatozoids 

 formed in special small branches or in 

 cells of the thallus which have undergone 

 division. The oospore becomes invested 

 by tubes which are branches from the 

 thallus, as in the cystocarp of many of the 

 Florideae, and then passes into the resting 

 stage. In the next vegetative period it 

 becomes by division of its contents a 

 parenchymatous body in which numerous 

 swarm-spores are formed, one in each 

 cell. 



The Coleochaeteae are small chlorophyll -green fresh-water Algae (1-2 mm. in breadth), 

 composed of branched rows of cells. They are found in stagnant or slowly-moving water 

 fixed to submerged parts of plants, such as species of Eqtnsettan, and form circular 

 closely attached disks or cushions ; their chlorophyll is attached to parietal plates or 

 isolated masses ; the genus Coleochaete (sheath-hair) derives its name from the cir- 

 cumstance that certain cells of the thallus form lateral colourless bristles which are 

 enclosed in narrow sheaths (Fig. 23, A, h). Comparison of the phenomena of growth 

 in the different species shows that there are two extreme cases, but these are connected 



Fig. 23. -•/ Coleochaete so!:i/a. an asexual plant (magn.' 250 

 times) K portion of a similar disk The letters a~g show the 

 successive dichotomies of the terminal cells. After Pringsheim. 



' Pringsheim, Beitr. 

 Bot. II. Bd.). 



z. Morphol. u. System, der Algen, III. die Coleochaeten (Jahrb. f. wiss. 



