[Vor. 4 
94 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
radius of the stem, (5) sap- and heart-wood, and (6) the dis- 
tance of the sample from the pith. 
Susceptibility to decay and comparative resistance to-Tün- 
gous attack vary with the different species of wood, and it 
was believed that in any one species various qualities of the 
wood may influence its durability. "Therefore, in the series of 
experiments reported below the three species of yellow pine 
were used, and a comparison of their relative resistance will 
be diseussed. However, before deseribing the experiments 
and their results it will be necessary to consider the results 
of previous workers who have contributed to our knowledge 
of the influence of the physical properties of wood upon its 
durability. 
НіѕтовісАІ, REVIEW 
Resin occurs widely distributed in the plant kingdom ава 
solid, semi-liquid, or dissolved in a resin solvent. It is шовҒ” 
abundant in coniferous wood, where it exists in the sap-wood 
dissolved in terpenes or turpentine oils, and in the heart-wood 
as an amorphous solid or semi-liquid mass according to the 
degree of seasoning and age of the heart-wood. Various types 
and compositions of resin are found in many other groups of 
plants. Harz (’68) showed by analyses that it is to be found 
in the mycelium and fruiting bodies of Polyporus officinalis 
Fries, and more recently Malencovie (’07) has reported it in 
the mycelium and sporophores of Lenzites saepiaria. Resin 
has been generally considered a hindrance to the attack of 
wood-destroying fungi. 
In discussing the inroads of the mycelium of Trametes Pini 
Fr. Hartig (778) says that the terpenes and oils of turpen. 
tines are driven out of the wood in advance of the fungus, and 
the resin which is soluble in the terpenes is carried forward 
until it becomes so concentrated as to form a barrier or re- 
sistant wall, as it were. This is especially true in the sap- 
wood where resin exists in certain species of wood diluted in 
the terpenes. In the heart-wood where the resin is in алпоге 
or less solid condition it is difficult to conceive that it may һе- 
driven out by the entrance of the mycelium, yet the pressure 
