A because a controlled experiment only tests one variable.
I think the deficiency of dedicated respiratory and circulatory systems in Planarians does not cause a problem because none of their cells are far removed from the gastrovascular cavity or from the external environment. Planarians are free-living flatworms and form the class Turbellarians in the Phylum Platyhelminthes. Flatworms have three tissue layers, that is the ectoderm, mesoderm, and endoderm.
Fungi, many birds, and a wide variety of insects all share the HABITAT of a tree in the forest.
Part of the NICHE of the fungi is to obtain energy from dead organic matter, such as dead wood.
Temperatures above 0°C and sufficient water in the environment help define the range of TOLERANCE for fungi.
