OOSPORES. 
269 
A. SPHiEROPLEA annulina^ is at present the sole representative of the most simply 
organised of the Oosporeae. It consists, when fully developed, of cylindrical filaments 
divided by septa into very long cells, the green protoplasm enclosing rows of large 
vacuoles, and thus forming girdle-like rings. When in the vegetative state the cells 
are all alike ; it is only when the process of sexual reproduction is commencing that 
a difference makes its appearance, some of the cells forming nothing but antherozoids, 
the rest nothing but oospheres. The latter are produced in large numbers within 
each cell, the contents breaking up, after various previous changes, into several globular 
portions, each of which is characterised by a hyaline speck. The antherozoids are 
formed in extraordinarily large numbers by the breaking up of the entire contents of a 
cell which had previously assumed a yellowish brown colour. In both kinds of sexual 
cells a number of holes are formed by the absorption of portions of the wall; the 
antherozoids escape through these orifices, forcing themselves in quantities into the cells 
in which the oospheres lie. The antheridia and oogonia therefore resemble one another 
in external form, while the antherozoids and oospheres are very unlike; the latter 
are elongated and club-shaped, with two cilia at the pointed end. The oospore or 
fertilised oosphere clothes itself with a thick warty cell-wall; its contents become 
brick-red. Its further development commences after a resting stage; the red 
contents divide by successive bipartition into a large number of primordial cells 
which escape from the oospore, are provided with two cilia, swarm about, and 
germinate after a period of rest. The germinating cell, which is at first shortly 
fusiform, then grows in both directions into a capillary filament, so that the anterior 
and posterior ends are exactly alike, and there is no distinction between base and apex. 
After the filament has grown to a considerable size, transverse divisions take place and 
the filament is then composed of a number of equivalent cells. 
B. — CCELOBLAST^. 
In this section are included for the present all those Oosporese in which the thallus 
consists of a single tubular cell, without a nucleus ', more or less branching, and usually 
fixed to one spot. It is only when reproduction is commencing that branches of special 
form are separated by septa. The Coeloblastae are therefore not, accurately speaking, 
unicellular ; it is only the vegetative body that is so. In all cases which have been accu- 
rately observed a non-sexual reproduction takes place by means either of stylogonidia 
or of motile endogonidia. The oogonia and antheridia are usually terminal cells of short 
lateral branches, and are very different in form ; the former are more or less spherical, 
the latter tubular ; the two being mostly placed close beside one another. 
FORMS CONTAINING CHLOROPHYLL. 
I, Vaucheria^ consists of a single elongated cell, branched in various ways, some- 
times as much as 30 centimetres long, containing no nucleus, and developing on damp 
earth or in water. The fixed end is hyaline and branched in a wavy manner ; the free 
part contains within the thin cell-wall a layer of protoplasm rich in chlorophyll-granules 
and drops of oil, and enclosing the large sap-cavity. This part of the thallus forms one 
or more main filaments which branch behind their growing point ; only in F. tuberosa is 
^ Cohn, Ann. des Sei. Nat., 4** ser., 1856, p. 187. 
^ [According to Schmitz (Sitzber. d. niederrhein. Ges, in Bonn, 1879) a great number of nuclei 
are present in Vaucheria and its allies.] 
3 Pringsheim, Ueber Befruchtung und Keimung der Algen, 1855; Jahrbuch für wissen. Bot. 
Bd. II. p. 470. — Schenk, Würzburger Verhandl. Bd. VIII. p. 235. — Walz, Jahrbuch für wissen. 
Bot. Bd. V. p. 127. — Woronin, Bot, Zeit. 1869, nos. 9, 10. [Stahl, Bot. Zeit. 1879.] 
