Dry rot species of fungi cause brown rot decay, preferentially removing cellulose and hemicellulose from the timber leaving a brittle matrix of modified lignin. The term "dry rot" is somewhat misleading, as both species of fungi "Serpula lacrymans" and "Meruliporia incrassata" require an elevated moisture content to initiate an attack on timber (28–30%). Once established, the fungi can remain active in timber with a moisture content of more than 20%. At relative humidities below 86 percent, growth of "Serpula lacrymans" is inhibited, but it can stay dormant at relative humidities down to 76 percent. These relative humidities correspond to equilibrium moisture contents
Serpula vigorous pumping movements of the abdomen and also by the activity of the ciliary tracts. The well-developed longitudinal muscles of the body wall of serpulids lack a special blood supply. The body surface in the larger serpulids, like "Serpula", has a rich blood supply, and the water in contact with this surface is constantly renewed. It seems probable that the outer body surface of serpulids serves as a respiratory membrane, supplying oxygen to the underlying muscles by diffusion. The biochemistry of the blood of "Serpula" is especially unusual in that the blood contains not only hemoglobin, but also chlorocruorin. While