Clue
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Neps do not form a tap root if that is what you are asking. Like a carrot or a ceph. It is a fibrous root (a complex system of smaller root structures). Like grass.
Incorrect, actually. Neps from Indochina often have long, Ceph like roots. Kampotiana, smilesii, some mirabilis, and mirabilis var. globosa from Trang, among others, have long, thick rootstocks.
The majority of Neps do, however, have relatively small, black fibres for roots.