630 



Yearbook^ of Agriculture 1949 



A last as long as they do on woods of 

 group 1 : 



Softwoods: 



Eastern white pine. 



Western white pine. 



Sugar pine. 



Group 3 Woods on which paints 

 of types A and B wear out more rap- 

 idly than they do on groups 1 or 2: 

 Hardwoods: 



Aspen. 



Basswood. 



Gottonwood. 



Magnolia. 



Yellow-poplar. 

 Softwoods: 



White fir. 



Eastern hemlock. 



Western hemlock. 



Lodgepole pine. 



Ponderosa pine. 



Eastern spruce. 



Engelmann spruce. 



Sitka spruce. 



Group 4 Woods on which paints of 

 types A and B wear out more rapidly 

 than they do on woods of group 3 : 



Hardwoods: 

 Beech. 

 Birch. 

 Blackgum. 

 Maple. 

 Redgum. 

 Tupelo gum. 

 Softwoods: 

 Douglas-fir. 

 Red pine. 



Southern yellow pine. 

 Tamarack. 

 Western larch. 



Group 5 Woods unsuitable for con- 

 ventional house painting because wood 

 filler is required before painting to fill 

 the large pores properly : 



All hardwoods with pores larger 

 than those in birch, as ash, chest- 

 nut, elm, hickory, oak, walnut. 



FREDERICK L. BROWNE has been in 

 charge of work on painting and fin- 

 ishing of wood at the Forest Products 

 Laboratory since 1922. He studied 

 chemistry at Cornell University and 

 the University of Wisconsin. 



FUNGI AND WOOD 



CARL HARTLEY 



Wood is subject to several kinds of 

 defects or blemishes that are caused by 

 fungi and bacteria. They are forms of 

 plant life. Many of them grow on the 

 contents of the cells of the wood but 

 do not attack the cell walls ; their only 

 important effect is on color. Only part 

 of the discolorations are due to organ- 

 isms and the causes of many of them 

 have yet to be determined. Most dis- 

 colorations of hardwoods are already 

 present before the tree is cut, but sap 

 stain or blue stain usually occurs after 

 the lumber is sawed. 



The discolorations of yellow-poplar, 

 the tuliptree, are particularly striking. 

 In this and several other important 

 species most of the discolorations have 

 been found to indicate no appreciable 

 weakening of the wood. Browned or 



bleached spots or streaks, however, 

 commonly indicate the presence of 

 decay fungi, which dissolve the cell 

 walls and thereby weaken or destroy 

 the structure. 



The decay fungi belong to a special 

 group, most of which have fleshy spore- 

 producing bodies toadstools, mush- 

 rooms, brackets. The gills or the pores 

 found on the under side of the fruit- 

 ing bodies of most of the species have 

 a large surface area. On these surfaces 

 are borne a myriad of microscopic 

 spores that are carried by wind to start 

 new infections. The Division of Forest 

 Pathology has about 300 species of 

 these fungi growing in pure culture. 



Wood attacked by fungi is lowered 

 in toughness or shock resistance and ( to 

 a less degree) in bending or crushing 



