Final answer:
A Marchantia thallus under the microscope appears as a flattened sheet of cells with multiple layers. The top layer has open pores, and the lower skin has fish-scale-like structures and rhizoids for attachment. The gametophyte produces antheridiophores and archegoniophores that extend above the thallus.
Step-by-step explanation:
Under the microscope, a Marchantia thallus appears as a flattened sheet of cells with multiple layers. The top layer has open pores for carbon dioxide entry, and below it is a layer of chlorophyll-containing cells. The thallus is differentiated into a top and bottom, and the lower skin has fish-scale-like structures and rhizoids for attachment to the substrate.
The gametophyte of Marchantia produces two types of vertically oriented structures: antheridiophores and archegoniophores. Antheridiophores have anthers that produce sperm, while archegoniophores have archegonia that produce eggs. These structures extend above the main body of the thallus, and the antheridia and archegonia are located on the upper and lower surfaces, respectively.