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Mycologia 



rays, then the bordered pits. The lignified structures including 

 the ray tracheids and the vertical tracheids are then attacked 

 and eventually (at least in the spring wood) entirely destroyed. 

 Consequently it is believed that cellulose dissolving enzymes are 

 produced in quantity by the younger mycelium, although prob- 

 ably a lignin dissolving enzyme is not entirely absent. In later 

 stages of decay a lignin dissolving enzyme is produced in greater 

 quantities. 



State College, Pa. 



Explanation of Plates 

 Plate 12 



Fig. 1. Sporophores of Polyporus amorphus showing its effused-reflexed 

 habit and the concentrically zoned pileus. 



Fig. 2. Wood of pitch pine decayed by Polyporus amorphus. The 

 elongated cavities alternating with bands of the sounder summer wood are 

 quite conspicuous. 



Fig. 3. Rhizomorphs of Polyporus amorphus. 



Plate 13 



Fig. 1. Camera lucida drawing of a tangential section of pitch pine wood 

 rotted by Polyporus amorphus. The parenchyma cells of the medullary rays 

 have entirely disappeared. Ray tracheid cells still persist in the angles of 

 some of the rays. The branching of the hyphae at the rays is conspicuous. 



Fig. 2. Camera lucida drawing of a radial section of wood rotted by 

 Polyporus amorphus. Various stages in the destruction of the bordered pits 

 are seen at A-E. At F note remains of a medullary ray. 



Fig. 3. Drawing of a radial section of wood rotted by Polyporus 

 amorphus. Earlier stage of decay than figure 2. The parenchyma cells have 

 disappeared from between the ray tracheids (R. T.), leaving the cavity M. 

 The tracheids still show the characteristic denticulate wall of pitch pines. 

 P is a pit in the wall of a ray tracheid. H, a large hypha running through the 

 medullary ray. 



