We don't have synonyms for endogen yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are endogean and indogen.
(n) :
(botany) A plant which increases in size by internal growth and elongation at the summit, having the wood in the form of bundles or threads, irregularly distributed throughout the whole diameter, not forming annual layers, and with no distinct pith.
(n) :
(botany) A plant which increases in size by internal growth and elongation at the summit, having the wood in the form of bundles or threads, irregularly distributed throughout the whole diameter, not forming annual layers, and with no distinct pith.