macrospore

IPA: mækroʊspɔr

One of the specially large spores of certain flowerless plants, as Selaginella, etc.

Examples of "macrospore" in Sentences

(Fig. 79, _A_, _E_), the embryo sac or macrospore.
The macrospore divides into two cells, a large lower one, and a smaller upper one.
The nucellus is a cellular tissue enveloping one large cell, the embryo-sac or macrospore.
But the formation of the macrospore or embryo-sac is simpler than the corresponding process in cryptogams.
_G_, section of a full-grown macrosporangium (ovule), × 25: i, ii, the two integuments. _sp. _ macrospore (embryo sac).
The single macrospore (_sp. _) is very large and does not lie free in the cavity of the sporangium, but is in close contact with its wall.
The germination of the macrospore consists in the repeated division of its nucleus to form two groups of four, one group at each end of the embryo-sac.
In the full-grown ovule the macrospore, which in the seed plants is generally known as the "embryo sac," is completely filled with the prothallium or "endosperm."
_Casuarina_ and others, instead of a single macrospore a more or less extensive sporogenous tissue is formed, but only one cell proceeds to the formation of a functional female cell.
When we compare the embryo sac (macrospore) of the angiosperms with that of the gymnosperms a great difference is noticed, there being much more difference than between the latter and the higher pteridophytes.