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05_Mnium_antheridium.gif
Mnium antheridium antheridium antheridium antheridium antheridium antheridium antheridium antheridium antheridium antheridium antheridium antheridium paraphyses paraphyses paraphyses paraphyses paraphyses paraphyses paraphyses

06_Mnium_archegonium.gif
Mnium archegonium paraphyses paraphyses archegonium archegonium archegonium archegonium archegonium paraphyses archegonium

07_Mnium_capsule.gif
Mnium capsule operculum columella spore chamber (sporangium) with spores spore chamber (sporangium) with spores

08_Mnium_protonema.gif
Mnium protenema moss protonema moss protonema moss protonema moss protonema moss protonema moss protonema moss protonema

 

Plants are placed into two simple kingdom subsections: nonvascular and vascular plants. The big distinction between the two groups is that vascular plants have vascular_tissues: tissues that conduct water and dissolved food in the plant body. The vascular tissues include xylem, which moves water and minerals upward through the plant and phloem, which moves dissolved food downward in the plant.

Nonvascular plants lack these tubes, and therefore must be small and thin so that each cell can acquire its needed materials via passive_transport from the plant's surface, or from other cells within the plant that are located near the surface.

Regardless of whether a plant is vascular or nonvascular, it has structures that (1) anchor it into the soil, (2) provide physical support for its photosynthetic structures, and (3) specialize in performing photosynthesis.

These micrographs provide a comparison of the antheridia of nonvascular Liverworts, such as Marchantia, with nonvascular mosses, such as Mnium. The antheridial_head is supported on a stalk and contains numerous antheridia. Paraphyses (sterile hairs) are non-reproductive support structures positioned among the antheridia. Sterile_jackets are asexual surface support tissue that surrounds each antheridium.

Photo Atlas micrographs 45D and 45E are the same longitudinal sections, just at different magnifications. Paraphyses (sterile hairs) provide physical support for the developing egg cells located within each archegonium. The egg chamber is supported by a stalk, and a long narrow neck extends from the top of the egg chamber to the upper surface of the archegonial_head. This provides an entrance point for sperm released from the male antheridia.  NOTE: a venter is a thickened bottom portion of a single archegonium.

The capsule is the asexual phase of the life cycle of Mnium. Refer to Photo Atlas page 46 (photograph 46A) and you can see clearly that this spore chamber mechanism results from fertilization of a egg. The seta of a capsule is the stalk that supports the capsule. The columella is a central support pillar that prevents collapse of the spore chambers. The operculum is a protective covering over the top of the spore chambers.

Antheridia produce sperm, archegonia produce eggs, fertilization occurs, a capsule grows from the fertilized egg, spores are released from the capsule, new protonema emerge, new antheridia and archegonia mature, and the cycle continues. This is alternation_of_generations!