Some pokemon fan art. What the title means is explained by this:
"Like its previous stage, Parasect is an insectoid creature. However, in this stage, the mushroom has completely overtaken the host's body. The insect has been drained of nutrients and is now under the control of the fully-grown tochukaso." From Bulbabedia.
Oh and also Parasect's Info in Pokemon FireRed:
"It scatters toxic spores from the mushroom cap. In China, the spores are used as herbal medicine."