You're thinking of ergot, a disease that attacks rye grain. It contains an alkaloid called ergotamine.
From wikipedia:

"Ergot contains no lysergic acid diethylamide (LSD) but instead contains ergotamine, which is used to synthesize lysergic acid, an analog of and precursor for synthesis of LSD. Moreover, ergot sclerotia naturally contain some amounts of lysergic acid."

Good luck trying to get high off that though.. You're sure to see some shit, but you may not make it to tell anyone about it...