Cross sectional shape of the top of the bud tells their distribution.
Vallate: has a shallow 'V' at the top, so has a 'V' distribution at the back of the tongue.
Fungiform: top is round so it is towards the round end of the tongue.
Note vallate is also sometimes called circumvallate
In brief about Papillae
The majority of taste buds on the tongue sit on raised protrusions of the tongue surface called papillae. There are four types of papillae present in the human tongue:
Fungiform papillae - as the name suggests, these are slightly mushroom-shaped if looked at in longitudinal section. These are present mostly at the apex (tip) of the tongue, as well as at the sides. Innervated by facial nerve.