Serpula (fungus) are formed. The strand mycelium of "Serpula", which can be up to 8 mm thick, are invasive and can spread over non-nutritive surfaces to find new food sources, even spreading through pores in stone, brickwork, and cement. After its initial growth period, the fungus can produce the water it needs and can continue growth into dry timber, eventually degrading it to powder—hence the term "dry rot". "S. lacrymans" is the most serious cause of building timber decay in the UK and northern Europe. The "Dictionary of the Fungi" (10th edition, 2008), suggests that the genus contains two species. , the
Mycelial cord uninfected parts. The cords of some wood-rotting fungi (like "Serpula lacrymans") may be capable of penetrating masonry. The mechanism of the cord formation is not yet precisely understood. Mathematical models suggest that some fields or gradients of signalling chemicals, parallel to the cord axis, may be involved. Rhizomorphs can grow up to in length and in diameter. Mycelial cord Mycelial cords are linear aggregations of parallel-oriented hyphae. The mature cords are composed of wide, empty vessel hyphae surrounded by narrower sheathing hyphae. Cords may look similar to plant roots, and also frequently have similar functions; hence they are also called