14 THE DECAY OF TIES IN STORAGE 



Lensites trabca is widely distributed over the United States, and 

 is almost always found on hardwoods, of which it attacks a con- 

 siderable number, among which oaks, gums, cottonwoods and willows 

 deserve particular mention. 



POLYSTICTUS VERSICOLOR 

 (Plate I, Fig. 2; Plate IV, Figs. 7-9) 



This is perhaps the most common fungus one meets with on hard- 

 wood timber. The fruit-bodies are thin, shelving and densely clustered 

 one above the other. They are tough, leathery and flexible when moist, 

 but more or less rigid when dry. The upper surface is beautifully 

 banded concentrically with various shades of brown, blue or buff from 

 which character the fungus takes it name, and is densely covered with 

 short hairs, and hence velvety to the touch. The under surface is 

 white with small, shallow pores scarcely visible to the unaided eye. 

 This fungus attacks almost all species of hardwood timber and is very 

 vigorous in its action, producing a white rot. 



POLYSTICTUS ABIETINUS 

 (Plate VIII, Fig. 1) 



This is a thin, flexible fungus usually growing in loose clusters. 

 The fruit-bodies on structural timber rarely extend out more than an 

 inch, usually less. They are white and hairy on the upper surface and 

 usually violet on the lower when young, becoming brownish in age. 

 The pores in this species break up at an early stage of growth into 

 flattened, irregular teeth, but there almost always remain shallow pores 

 at the margin. 



The fungus is widely distributed over the entire United States, 

 and is limited to conifers, where it produces principally a sap-rot. 



POLYSTICTUS PARGAMENUS 

 (Plate VIII, Fig. 3) 



This fungus is found abundantly on hardwoods over practically 

 the entire country. Its closest relative is Polystictus abictinus, which, 

 however, grows only on conifers. The fruiting-bodies are shelving, 

 clustered and thin. They are somewhat larger and coarser than 

 Polystictus abictinus, but rarely project out on structural timber more 

 than iy 2 to 2 inches. In young specimens the upper surface is velvety 

 and whitish to creamy or buff; in older specimens it frequently becomes 

 concentrically banded and gray behind, losing much of its velvety cover- 

 ing. The under surface in young specimens is violet, which changes to 

 brown in older specimens. The pores readily split into irregular flat 

 teeth as the plant ages. 



In hardwoods having a well differentiated heart it produces mainly 

 a sap-rot, but in other species the heart may be decayed as well. 



