why are tryptamine fumarates more stable?

[ungelesene_bettlek]

why are tryptamine fumarates actually more stable than the corresponding hydrochloride salts?

 

[sekio]

I would wager because the fumarates form more regular crystals that stay anhydrous (don't sequester water from the air). - that is, the HCl salts don't form crystals that stay nice for very long.