Many of the pitfalls were anticipated. A battle over psychedelic mushrooms was not. Last week, the Senate amended a decriminalization bill to include psilocybin, the hallucinogenic compound in so-called magic mushrooms, or “shrooms,” snarling the time-sensitive negotiations over a separate legalization bill. That bill creates a framework for the constitutional amendment legalizing marijuana, which takes effect Jan. 1. The mushroom amendment was tacked on just as social justice advocates were spotlighting what they saw as an overarching flaw in the legalization bill: a lack of guaranteed benefit to Black and Latino communities that have suffered most from criminal enforcement of marijuana laws.