Whether a spore results from the sexual union of two similar gametes (zygospore) or from the fertilization of an egg-cell by the protoplasm of a male organ (oospore); or is developed asexually as a motile (zoospore) or a quiescent body cut off from a hypha (conidium) or developed along its course (oidium or chlamydospore), or in its protoplasm (endospore), are matters of importance which have their uses in the classification and terminology of spores, though in many respects they are largely of academic interest.
Myrioblepharis, with a peculiar multiciliate zoospore like that of Vaucheria, is provisionally placed in the same group. Monoblepharis was first described by Cornu in 1871, but from that time until 1895 when Roland Thaxter described several species from America the genus was completely lost sight of.
Pythium is of interest as illustrating the dependence of zoospore-formation on conditions and the indeterminate nature of conidia.
The zoospore is usually a pyriform mass of naked protoplasm, the beaked end of which where the cilia arise is devoid of colouring matter.
The movement of the zoospore is effected by the lashing of the cilia and is in the direction of the beak, while the zoospore slowly rotates on its long axis at the same time.
The so-called zoospore of Vaucheria is a coenocyte covered over with paired cilia corresponding in position to nuclei lying below.
It is held that in Coleochaete a parenchyma results from the division of the oospore, from each cell of which a zoospore arises.
Zoospore of Pandorina.
Derbesia sp., zoospore with ing.
Oedogonium sp., zoospore K1.
One is shown more highly magnified (400 diameters) at F; the contained protoplasm breaks up into a definite number of parts as at G, forming eight minute mobile bodies called "zoospores," each zoospore being furnished with two extremely attentuated vibrating hairs termed "cilia," as shown at H.
In Coleochaete this seems to be preceded by the formation of a minute parenchymatous mass, in each cell of which a zoospore is produced.