Analysis of similarity (ANOSIM) was conducted to determine if a difference in the number of perichaetia, perigonia, sporophytes and gametangia
existed for each species across the chronosequence.
in mature thallus are rays containing cysts.
Stimulation of the discharge of gametangia
from a brown alga by a change from light to darkness.
The development and structure of the gametophytes show some similar characteristics between the sister group Acrostichum and Ceratopteris: 1) Spore germination is of the Vittaria-type; 2) Prothallial developments is of the Ceratopteris-type; 3) Young prothalli are markedly lopsided; 4) Gametangia
are the common leptosporangiate type.
Gametophyte colonization only began when gametangia
were differentiated (Fig.
2), that is, each individual had two kinds of plant bodies, alike except that one, the diploid sporophyte, bore sporangia, while the other, the haploid gametophyte, bore gametangia
. Zimmermann thus adheres to the homologous theory of alternation of generations (for further discussion of this vs.
G, number of gametophytes; G c/g, number of gametophytes with gametangia
(antheridia and archegonia); G s/g, number of gametophytes without gametangia
; E, number of sporophytes; EA, number of apogamic sporophytes.
Also, the multicellular sex organs of Chara and Nitella are suggestive of land-plant gametangia
These gametophytes have shape and size similar to the female prothalli, but male and female gametangia
are originated together in the midrib area.
Because so many meiotic events occur in the microsporangium and because each sporangium contains only microspores or megaspores, recombination would be possible among gametangia
produced by the same plant.
The number of gametophytes includes neuter gametophytes, gametophytes with gametangia
and gametophytes with the first sporophyte leaves.