102 College of Forestry 
and proceeds toward the middle lamella. After the cell-wall 
is delignified down to the middle lamella, the reduction of 
the cellulose commences. With the destruction of the cellu- 
lose, nothing is left but a skeletonized framework of middle 
lamellee, which in turn break up and undergo complete reduc- 
tion. Within a pocket or unit area of decay, all stages of 
decomposition from incipient to final may be seen within 
the range of a few cells (Plate X XI, Fig. 2). 
THe Decay or Sucar Marie Woop. 
Structure of Normal Wood.— The wood of the sugar 
maple (Acer saccharum Marsh.) is heavy, hard, strong, and 
close-grained, but is not durable in the soil or otherwise 
exposed. The sapwood is creamy white while the heartwood 
is light brown tinged with red, there being no sharp demar- 
cation between them. In a transverse section of the wood, 
the pores are numerous, indistinct to the unaided eye, and 
uniformly distributed throughout the growth ring. The pith- 
rays, while not conspicuously broad, are very distinct without 
a lens. 
Microscopically the wood of sugar maple presents the 
usual features of the diffuse-porous type. The growth rings 
are distinct and regular in outline; their ride he however, 
is subject to considerable variation. The wood is seen to 
consist of (a) uniseriate and multiseriate pith-rays, (b) 
pitted vessels with spiral thickenings, (¢) scanty wood paren- 
chyma which is mostly paratracheal, and (d) wood prosen- 
chyma with simple pits. The pith-rays are composed of 
small, homogeneous, radially elongated cells bearing numer- 
ous simple pits. Part of the 1 rays are comparatively large 
— from five to seven cells wide — and many cells high. The 
intermediate rays are mostly uniseriate. The vessels are 
distributed unifor mly throughout the growth ring and dimin- 
ish gradually in size from the spring to the summerwood. 
The “vessel segments, which do not possess large lumina, are 
comparatively thin-walled, provided with simple perforations 
at the ends, and are characterized by spiral thickenings. The 
