EXPLANATION OF PLATES. 



Plate I. — A slab of red cedar, showing the first stage of decay induced by Polypo- 

 rus juniperinus. The white spot shows the cellulose fibers (x |) . 



Plate II. — A piece of the trunk of red cedar split open to show large hole caused 

 by Poly poms juniperinus. The white masses are cellulose fibers, the flocculent gray 

 masses in the hole are disintegrated wood fibers, while above and below the ends of 

 branches are seen (x i). 



Plate III. — Cross section of a red cedar trunk, showing five holes caused by Poly- 

 porus jimiperin us. Two of these are early stages and show the white lining of cellulose 

 fibers. The cracks in the block were made when the trunk was split (x ^) . 



Plate IV. — Polyporus juniperinus growing on Juniperus virginiana, showing how 

 the pileus forms around a dead branch (x I). 



Plate V. — Upper figure, radial view of a block of red cedar, shows the early stages 

 of decay (pecky cedar) due to Polyporus carneus; lower figure shows end view of 

 several pockets uniting to form a larger area. The change from sound wood to 

 brown wood is very abrupt. 



Plate VI. — A cedar log showing large pocket, filled with brown wood, formed by 

 Polyporus carneus (x \) . 



Plate VII. — Fig. 1, tangential view of wood from a large cavity caused by Polyporus 

 juniperinus, showing how the medullary rays are first absorbed. The small holes in the 

 cell walls show where hyphfe have bored through (x — ). Fig. 2, tangential view of 

 walls from same wood at a later stage. The torus is shown at t. The primary lamella 

 and part of the secondary lamellae have been dissolved. In two bordered pits the 

 torus is still in position. Fig. S, another wall, taken from sprmg wood, the stage of 

 decomposition being the same as in fig. 2. Fig. 4, radial view of several tracheids 

 from the same wood as shown in fig. 3: o, bordered pits, showing the initial stage of 

 decay, the central opening widening; h, c, and d, tracheids in various stages of disso- 

 lution. The dotted lines indicate the margins of thin membranes of the tertiary 

 lamella. Fig. 5, a single wood cell as it appears when changed to cellulose, from a 

 cavity such as shown in PI. II. Fig. 6, a stage in wood destruction later than that 

 shown in figs. 2 and 3 of this plate. The dotted lines indicate the deeper margins of 

 the holes. Fig. 7, a piece of badly decomposed wood lying free in a large cavity 

 (PL II), the bordered pits having been entirely destroyed. Fig. 8, sporophore of 

 Polyporus carneus Nees: a, lateral view; b, top view. The triangular shape shows 

 how it has adapted itself to the shape of the hole in the cedar trunk. Figs. 9 and 

 10, sporophores growing in holes within the trunk. Fig. 11, spores of Polyporus 

 juniperinus n. sp. 



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