The thalloid plant body is found in

The correct option is Marchantia.

To understand why this is correct, let us break down the botanical concepts step-by-step:

1. What is a Thalloid Plant Body?
A thalloid plant body (or thallus) is a vegetative plant body that is not differentiated into true roots, stems, and leaves. It is relatively simple, dorsiventrally flattened, and prostrate (grows flat against the substrate).

2. Analyzing the Options:
Let us examine the classification and plant body structure of each option provided:
• Marchantia: It is a liverwort (a class of Bryophytes). The plant body of Marchantia is a flat, dorsiventral, dichotomously branched thallus. It lacks true leaves and stems, and is attached to the substratum by unicellular rhizoids. Thus, it possesses a thalloid plant body.
• Funaria: It is a moss (Bryophyta). Mosses like Funaria have a leaf-like (phylloid) and stem-like (cauloid) structure, making them more differentiated than liverworts.
• Sphagnum: Similar to Funaria, it is a moss with a differentiated, leafy gametophyte structure.
• Salvinia: It is a pteridophyte (vascular plant). It has a highly differentiated plant body with distinct leaves, stems, and root-like structures.

3. Conclusion:
Among the given options, only Marchantia has a simple, undifferentiated thalloid body, which aligns perfectly with the definition of a thalloid plant structure.