DISEASES OF CULTIVATED PLANTS 351 
In addition to the exposure of the internal woody cylinder to 
these decays, we have sap-rots due to various species of fungi which 
belong on the border line between the parasitic and saprophytic sorts: 
Among them are species of Fomes, Polyporus, Lenzites, etc. Any 
wound of the sapwood even though 
it does not reach to the dark heart- 
wood, exposes to the danger of this 
infection, and with infection, to all 
the consequences of sapwood decay 
and premature death of the tree.- 
These decays and those of heart- 
wood are inline with those of the 
rots of structural timbers, but we 
are at this time interested only in 
their effects on the parts of the 
living plants. 
TIMBER ROTS AND TIMBER 
PRESERVATION 
The decay of dead logs, wood- 
en frameworks, or other structural 
timbers is caused by the attacks of 
.saprophytic fungi belonging to the 
gill and pore fungi mentioned under 
wounds; these are of the great class 
of basidium bearing fungi, to which 
the fleshy forms, everywhere more 
or less abundant, belong. The 
most of them are included in the 
“‘mushrooms,’ which there is a Fig. 25. Another wound parasite (a 
strong impulse now to study and frets oir The fungus ond 
illustrate by photogra phs. ‘These tree (an oak), and as shown by the fungus 
timbers are dead and are subjected [uting tates, is efadully, rorresing 
to invasion by timber infecting the photograph was taken, (After Free- 
species wherever the conditionsas  _™"" 
toair and moisture are suchas to favor their development. Dry 
timbers are not subject to such attack because lacking the requisite 
moisture for the organism. Floors and other timbers of houses 
adjacent to the earth or to unheated cellars are often attacked by 
rot-causing species. The timbers of trestles, railway ties and the 
bases of fence, telephone and telegraph posts, where inserted into 
the earth or in contact withit, are kept sufficiently moist to invite 
attacks of this sort. 
