from The Century Dictionary.
- noun In botany, an asexually produced spore of large size as compared with others belonging to the same species.
- noun In zoology, one of the spore-like elements, few in number, but of relatively large size, into which the bodies of many monads become subdivided. Also
from the GNU version of the Collaborative International Dictionary of English.
- noun (Bot.) One of the specially large spores of certain flowerless plants, as Selaginella, etc.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun One of the specially
large sporesof certain flowerless plants, as Selaginella, etc.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun larger of the two types of spore produced in heterosporous plants; develops in ovule into a female gametophyte
Sorry, no etymologies found.
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."
But the formation of the macrospore or embryo-sac is simpler than the corresponding process in cryptogams.
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.
_G_, section of a full-grown macrosporangium (ovule), × 25: i, ii, the two integuments. _sp. _ macrospore (embryo sac).
(Fig. 79, _A_, _E_), the embryo sac or macrospore.
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.
_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.
The nucellus is a cellular tissue enveloping one large cell, the embryo-sac or macrospore.
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.
The macrospore divides into two cells, a large lower one, and a smaller upper one.