Question

the part of Funaria which helps in fixation of the plant is

Answer 1

Usually in plants, fixation in carried out roots which in turn helps in absorption of all the nutrients, minerals, and water from soil. 

But as Funaria is a type of Moss, it does not have roots to carry out this function. These function in Funaria is carried out by "Rhizoids".

These are unicellular and unbranched structure, which are either smooth or tuberculate. Rhizoids perform/carry out their mineral/nutrient absorption function by Osmosis through their own cell wall and use capillary action for water absorption. 

Hope this gives some additional details which you can refer for fixation. 

Answer 2

Funaria is genus of moss with approximately 210 species belonging to it. The most common species is Funaria hygrometrica, which is called 'cord moss' because of its twisted seta which is hygroscopic, i.e. absorbs moisture from the atmosphere, and untwists itself when moist. Funaria is a name derived from Latin, like for a lot of plants and animals. 'Funis' is the Latin word of origin, meaning a rope. In funaria, root-like rhizoids are present. These rhizoids from a mesh which helps it to cling to surfaces.

So, my answer would be 'rhizoids'.