Step 1: Understanding marijuana.
Marijuana is a psychoactive drug containing tetrahydrocannabinol (THC).
Step 2: Source of THC.
THC is mainly concentrated in the glandular trichomes present on the inflorescence of the female {Cannabis sativa} plant.
Step 3: Eliminating other options.
Latex, roots, and leaves do not contain high concentrations of THC.
Step 4: Conclusion.
Hence, marijuana is obtained from the inflorescence of {Cannabis sativa}.