National Museum of Natural Science

When parasite A (Formosan alder mistletoe) invades host B (Formosan alder), it forms haustoria with which it penetrates the trunk. When the seeds of this mistletoe germinate, the radicle extends out like a sucker, attaching to the trunk of the host and invading the host’s tissue, absorbing needed moisture and nutrients. Externally, all that can be seen is swelling of the trunk at the site of the invading haustorium, as it plunders the host like an extraneous branch, stationary and quiet.

A. Formosan alder mistletoe (Viscum alniformosanae Hayata) and B. Formosan alder (Alnus formosana (Burkill) Makino)