Lycophyta-8

SEM Photo of Huperzia Spore

Ventral view of Huperzia Gametophyte with SEM.

This genus is in the Lycophyta. The ridges are the result of the proximity of Spores during the Tetrad stage. It is called the triradiate ridge. Don't worry about this term. The Spores can remain viable for years in the Soil. This is an extremely important adaptation because it allows the spores to survive until conditions are favorable for the growth of the gametophytes. This has obvious adaptive significance compared to taxa which produce ephemeral spores which must germinate quickly or die.

SEM image of a collapsed Antheridium and Sperm (red) from Huperzia Gametophyte. The Sperm swim through an opening created by the cell that occupies the apex of the Antheridium.

Archegonia (Yellow) on the Gametophyte of Huperzia. Rhizoids are also present.

Lycopodium produces biflagellate Sperm

The ventral surface has produced Rhizoids. The Dorsal surface is papilose & will also form Rhizoids. Gametangia will be produced on the Dorsal side of the Gametophyte. The Meristem is located at the constriction between the two surfaces and functions over many years. This is a subterranean form. The subterranean gametophytes are pervaded by the hyphae of soil Fungi which provide sustanence for the gametophyte. This allows them to persist in the soil for many years. This has obvious adaptive significance because it prolongs the period in which fertilization can occur. However, they remain very small and only grow to a few centemeters in width.

Some lycopods produce Photosynthetic Gametophytes. These are very small and relatively undifferentiated. Some produce shoot-like projections. These also have endophytic Fungi. These can persist for months but not years. Experiments have shown that one species can produce both types. Consequently, photosynthetic gametophytes may be produced when conditions are suitable. Otherwise subterranean gametophytes might develop. This ability to switch-hit has obvious adaptive significance as the species can form gametophytes which are best suited to their immediate environment.