PLATE XL— VAUCHERIA and (EDOGONIUM. 



Vancheria. 



Vaucheria, named in honour of the Swiss botanist Vaucher, occurs usuallv on damp soils as a green film, but may readily be 

 obtained from the surface earth of flower-pots kept in green-houses. It is a long filamentous green Alga, consisting of a single tubular 

 cell which branches, and also forms root-like structures. 



Fig. 1. Take a small portion of the green film, tease it out in a drop of water, and examine under microscope. 

 Filament showing the granular protoplasm lining interior of tube. 



Multiplication — 



Fig. 2. End of branches forming Zoogonidia. 



These are formed during night, by the protoplasm, towards the end of a tube, collecting itself into an oval mass 

 and becoming separate from the rest by a partition. The end of the tube gives way, allowing this oval mass to 

 escape into the surrounding moisture, where it revolves and progresses by means of delicate cilia with which the 

 whole surface is covered. The cilia, however, soon disappear, and the motionless mass then sinks to the bottom. 



Fig. Za, b, c. Germinating Zoogonidium. 



It gives rise to filaments at two or even three points, which branch and grow to the size of the parent 

 Delicate transparent branches are also formed (as in c) which serve to fix the plant to solid bodies, and thus 

 partly serve the purpose of rootlets. 



Reproduction — 



Figs. 4 and 5. Male and Female Organs — Antheridia and Oogonia. 



Both organs arise as branches, sometimes as in Fig. 4, or as in Fig. 5, where a branch ends in a hooked 

 Antheridium, with an Oogonium on each side below it 



The contents of the Antheridium break up into minute particles of protoplasm, each furnished with two cilia 

 and motile — called Antherozoids. 



The Oogonium forms a single body in its interior— the Oosphere— which is a portion of the protoplasm 

 marked off from the rest by a partition. It is relatively large and motionless, and the antherozoids find access to 

 it through a rupture in the cell-wall, thus converting it into an Oospore. 



Fig. 6. Germinating Oospore. 



The Oospore is surrounded by a three-layered membrane and, after resting for a few months, the contents pro- 

 trude to form a branching tube. 

 Life History. — Vaucheria either multiplies by Zoogonidia, or reproduces itself by means of Antherozoids and Oospheres. The 

 naked protoplasm of the Antherozoids blends with the naked protoplasm of the Oosphere, and the result is a body capable 

 of germination— an Oospore. This surrounds itself with a membrane, becomes detached along with the Oogonium, and is 

 finally set free by the dissolution of the Oogonium. After a period of rest it germinates and gives rise to the original 

 branched structure. 



(Edogonium. 



(After Juniiv/i.) 



(Edogonium (Gr. oideo, to swell; gone, seed) derives its name from the fact that the joints of the filament swell out to form the 

 female organs. It may be looked for in waters where Conferva and such organisms are found, and occurs as patches of green filaments, 

 composed of cells attached end to end. 



Fig. 7. Young Filament, consisting of a row of cells. % 



The green-coloured protoplasm is arranged in stars and stripes, and each cell has a distinct nucleus. 



Multiplication — 



Fig. 8. Zoogonidia produced in the cells. 



The protoplasmic contents of each cell form a single rounded mass — the Zoogonidium, which escapes by a fissure 

 in the wall, and revolves and progresses by means of the band of cilia. 



Fig. 9. Germination of Zoogonidium 



The zoogonidium loses its cilia and settles down, producing from the colourless ciliated end a root-like struc- 

 ture for fixing the plant, while the opposite end divides and forms a row of cells. 



Reproduction — 



Fig. 10. Male Filament 



The contents of certain cells become orange-yellow and produce the Antherozoids, which resemble the Zoo- 

 gonidia in form and motion, differing mainly in the colour. In some cases, however, zoogonidia are formed 

 in the cells, which become rudimentary plants, and the sole object of these Dwarf-males, as they are called, is to 

 produce Antherozoids. They attach themselves to the Oogonium, as in Fig. 12, and the upper portion separates 

 like a lid to allow the antherozoids to escape. 



Figs. 11 and 12. Female Filaments. _ 



The joints here and there are swollen, forming the Oogonia, which contain the Oospheres. The ripe Oosphere 

 consists of a coloured and a small colourless portion, which protrudes through a small opening. 



Fig. 13. Process of Fertilisation. 



An Antherozoid blends with an Oosphere, and the result is an Oospore. 



Fig. 14. Ripe Oospore. 



It becomes surrounded with a membrane, and assumes an orange-red colour. The swelling of the Oospore 

 finally ruptures the Oogonium, and the oospore escapes as a naked mass of protoplasm. 



Figs. 15, 16, and 17. Germinating Oospores. ,.,,.., 



The germinating Oospore does not grow in the usual way, but surrounds itself with a new membrane, and the 

 contents divide into four portions generally. The Zoospores thus formed are set free by the dissolution of the mem- 

 brane, and produce a young plant, as in Fig. 17. 

 Life History. — (Edogonium multiplies by Zoogonidia, or is reproduced by Antherozoids and Oospheres. An Antherozoid, produced 

 either directly from the joint of a filament or through the intermediate agency of Dwarf-males, blends with the Oosphere and 

 produces an orange-red Oospore. This Oospore does not directly produce the plant, but divides into usually four Zoospores, 

 like the zoogonidia, except in the matter of colour, and each germinates and grows into a filament, as in Fig. 17. 



