In all other cases, zoospores are uninucleate bodies.
Cell Division.With the exception of a few plants among the Thallophytes, which consist of a single multinucleate cell, Caulerpa, Vaucheria, &c., the division of the nucleus is followed by the division of the cell either at once, in uninucleate cells, or after a certain number of nuclear divisions, in multinucleate cells.
The discovery by Brebner of the specific identity of Haplospora globosa and Scaphospora speciosa marks an important step in the advance of our knowledge of the group. Three kinds of reproductive organs are known: first, sporangia, which each give rise to a single tetra-, or multi-nucleate non-motile, probably asexual spore; second, plurilocular sporangia, which are probably antheridia, generating antherozoids; and third, sporangia, which are probably oogonia, giving rise to single uninucleate non-motile oospheres.
In plants with multinucleate cells, such as Albugo, Peronospora and Vaucheria, it is usually a uninucleate cell differentiated by separation of the nuclei from a multinucleate cell, but in Albugo bliti it is multinucleate, and in Sphaero plea it may contain more than one nucleus.
The contents of the antheridium are not set free, but that organ penetrates the oogonium by means of a narrow outgrowth, the fertilizing tube, and a male nucleus then passes over into the single oosphere, which at first multinucleate becomes uninucleate before fertilization.