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PHYCOLOGICAL SOCIETY OF AMERICA
Egregia menziesii LIFE HISTORY
Refer to this sketch while you read this page on reproduction and growth of the beautiful Egregria menziesii.
Redrawn from thesis by Margret E. Myers, 1928 (see reference below)
SPORES TO GAMETOPHYTES
Beginning with the mature,diploid sporophyte, this is the gorgeous plant we
all know and love. Intermixed with the normal blades are smaller, more
brittle sporophyll blades. These contain sporangia in clumps called
sori. The sporangia are the site of meiosis, and, when mature, release
haploid zoospores. This occurs sometime in the fall.
The motile zoospores are homosporous (those that grow into male and female plants look the same) and diflagellated. They are pointed at one end and rounded at the other. Within half an hour, the motion of the zoospores can cease, and they settle as spherical, un-flagellated spores.
It takes about fifteen days before there is a definite difference between the young male and female gametophytes, which remain microscopic. The mature male gametophyte usually has around 5-7 cells, each of which is smaller than the mature female gametophyte, which typically has 2-3 cells. The spore can remain alive for some time, with the gametophyte growing from it, but it usually disintegrates.
FERTILIZATION
When time for fruiting comes around (usually November), the vegetative cells
of the the female either fuse into one oogonium, or each one develops into
an individual oogonia. Either way, the oogonium is much larger than
the vegetative cells of the gametophyte. The oogonium forms a beak through
which it will discharge the egg.
The mature male gametophyte has "warty" looking, smaller cells on the sides of the vegetative cells, which are the antheridia.
When fertilization time arises, the eggs are discharged from the oogonia (one each), and clings to the tip of the beak, waiting for the sperm from the antheridia.
THE YOUNG SPOROPHYTE
Following germination, the very young sporophyte will consist of a short, thick
filament made of 6-8 cells. The apical cell is the first to devide
into the other direction, then the other cells until a cell plate is formed.
At the same time, rhizoids begin to grow from the cell closest to the oogonium (on which the sporophyte is growing). Rhizoids grow away from light. This small, young sporophyte grows into the grand macroalga that is the "feather boa."
Reference for this page:
Meyers, Margret E. "The Life History of the Brown Alga, Egregia
menziesii." University of California Publications
in Botany, v. 14. 1928.
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