from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An asexually produced reproductive cell, such as a zeospore, found in certain algae.
- n. An algal cell filled with chlorophyll, formed in the thallus of a lichen.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A photosynthetic algal cell in the thallus of a lichen; a similar asexual reproductive cell in some algae
from the GNU version of the Collaborative International Dictionary of English
- n. A special groove or furrow at one or both angles of the mouth of many Anthozoa.
- n. A component cell of the yellowish green layer in certain lichens.
from The Century Dictionary and Cyclopedia
- n. In algol., a reproductive body produced asexually, as a tetraspore or zoöspore.
- n. In bryology, a cell filled with granules.
- n. One of the green or chlorophyl-bearing elements of lichens, usually occurring in the thalli in a distinct layer, but sometimes not definitely arranged.
These contents are now gradually forming themselves into the spore or "gonidium," as
"gonidium" (d), which, when ripe, is thrown off from the sterigma.
Eminent English authorities have advanced the theory that the ciliated gonidium of _Vaucheria_ is in reality a densely crowded aggregation of biciliated zoospores, similar to those found in many other confervoid algæ.
The motile force is imparted to the gonidium by dense rows of waving cilia with which it is completely surrounded.
It is also to be noted as a significant fact, that the cellulose wall was _intact_ at the apex, instead of showing the opening through which in ordinary cases the gonidium escapes.
At the same instant, the inclosed gonidium (for it is now seen to be fully formed) acquires a rotary motion, at first slow, but gradually increasing until it has gained considerable velocity.
The old cell wall seems to offer considerable resistance to the escape of the gonidium, for the latter, which displays remarkable elasticity, is pinched nearly in two while forcing its way through, assuming an hour glass shape when about half out.
It would seem to be a reasonable inference, I think, based upon the theory above stated, that in this case the newly formed gonidium, unable to escape from its prison by reason of the abnormal strength of the cell wall, became after a while resolved into its component zoospores.
After the gonidium comes gradually to a rest its cilia soon disappear, it becomes perfectly globular in shape, the inclosed granules distribute themselves evenly throughout its interior, and after a few hours it germinates by throwing out one, two, or sometimes three tubular prolongations, which become precisely like the parent filament (Fig 2).
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