Final answer:
Ectotrophic mycorrhizae do not invade plant cells, whereas endomycorrhizae do invade their host plant's cells.
Step-by-step explanation:
Ectotrophic mycorrhizae are associated with plant roots, but do not invade plant cells. Instead, the fungal hyphae form a dense sheath around the roots called a mantle.
The hyphae extend into the root and envelope the outer layers of the root cells in a network of hyphae called a Hartig net.
On the other hand, endomycorrhizae (also known as arbuscular mycorrhizae) do invade their host plant's cells. The fungal hyphae penetrate the cell walls of the plant root cells, but not the cell membranes.