Green’s Dictionary of Slang

1. marijuana.

1972		Dahlskog Dict. Contemp. and Colloq. Usage.
2001		ONDCP Street Terms 12: Jane — Marijuana.

2. cocaine [note cocaine is a ‘feminine’ drug, cf. girl n.² ].

1997

Simon & Burns Corner (1998) 62: They called it ‘girl’ or ‘Jane’ or ‘Missy’ in feminine contrasts to ‘boy’ or ‘John’ or ‘Mister’ for king heroin.