EXPLANATION OF THE [ILLUSTRATIONS 
Prare IV. Fie. 1. Transverse section of xylem of Laurelia 
aromatica Juss., showing enzymatically produced cavities in 
the secondary wall. Note the partial localization of action 
within the central layers. (After Bailey, I. W. and Mary 
Vestal: Journ, Arnold Arboretum 28, Plate 209: 19387.) 
~990, 
kia, 2. Transverse section of hard pine wood which was ex- 
posed to the sea and to the action of marine fungi. Enzy- 
matic attack on the cell wall is concentrated within the cen- 
tral layers. Compare with anaerobic degradation as shown 
in Plates I, Il and III. 500. 
Fic. 8. ‘Tangential section of xylem of U/mus crassifolia 
Nutt. showing normal wood structure. * 100. 
Kia, 4. Tangential section of xylem of Ulmus americana L. 
degraded by an unidentified brown rot fungus. The structu- 
ral residue closely resembles delignified residues of anaero- 
bically degraded wood as shown by comparison with Plate 
III, Figs. 1, 2 and 8. 100. 
Fra, 5, ‘Transverse section of xylem of U/mus americana LL. 
showing normal wood, with scattered gelatinous fibers. 
LOO. 
Fic. 6. Transverse section of xylem of Ulmus americana L. 
degraded by unidentified brown rot. Same specimen as 
shown in Fig. 4. The structural residue is lgnified cellulose 
as shown by lignin extraction, ~ 100, 
