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1. The outermost layer of the wall of certain spores.
2. An asexual spore developed externally by budding, as from a sporophore.


(Botany) the outer layer of the spores of some algae and fungi
ˌexoˈsporous adj


(ˈɛk səˌspɔr, -ˌspoʊr)

the outer coat of a spore.
ex`o•spor′ous, adj.
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References in periodicals archive ?
Mature spores have a dense exospore coat, a pale endospore, and single rows of 8-11 polar tubule coils (Figure 2, panels B, C).
Perispore is microrugulate with rugulae homogenously distributed; it is adhered to exospore in young spores but tends to detach; detaching usually begins at the laesure zone in mature spores.
Micromorphology of outer exospore coatings in Selaginella megaspore.
4 urn in length and were characterized by an outer electron-dense exospore and a thick electron-lucent endospore.
The outer exospore is then covered by the perispore.
These changes are: #20, quadriseriate branching of axes/leaves absent [right arrow] throughout; #28, stele with radiating arms of xylem absent [right arrow] as rounded lobes; #41, radial axis/rachis trace round-elliptical [right arrow] lobed; #46, position of protoxylem in rachis/axis toward no face [right arrow] toward several faces; and #88, exospore surface nearly smooth or plain [right arrow] obviously sculptured.