MISSOURI BOTANICAL GARDEN. 



been applied to a form of decay in the cypress in which the 

 wood is destroyed in local pockets. As this is a distinct 

 form of wood destruction I would apply the term " pecky" 

 to all forms of destruction where pockets or holes are 

 formed as in the cypress. One would therefore call the 

 affected Libocedrus wood " pecky cedar." 



STRUCTURE OF DISEASED WOOD. 



The normal wood of Libocedrus differs but little from that 

 of Taxodium distichum. Penhallow * places the two genera 

 side by side. The diseased wood is decidedly different 

 from the healthy wood. It has the appearance of a brown 

 charcoal, breaks with a dull fracture and when pressed 

 crumbles into a fine powder. In the mortar an impalpable 

 dust is formed. In this respect it is very different from 

 much-rotted cypress wood. In the latter the chemical 

 transformation is far from uniform. Diseased Libocedrus 

 wood is changed throughout ; both the spring and the sum- 

 mer wood are changed, and very rapidly at that, i. e., 

 there are no intervening steps as in Taxodium. A section 

 made through the edge of a diseased pocket shows that at 

 a certain point the cells are brown (PI. 4, fig. 2). It 

 will be noted that the color of fig. 2 is the normal color of 

 the wood. Hand in hand with this coloration goes a shrink- 

 age of the middle lamella, so that the walls of the tracheids 

 become much thinner. They have lost all tenacity. If a 

 piece of charred wood is boiled in water for a few moments 

 it can be pressed into any shape like a piece of dough. 

 Sections on a slide can be pushed about so that the cells 

 assume a rhomboidal shape, i. e., the whole acts like a net- 

 work of fine flexible wire. This is to some extent visible in 

 PL 4, fig. 2, where a number of the walls are much bent, 

 and do not have the rigid appearance of the healthy wood 



* Penhallow, D. P. Generic characters of N. A. Taxaceae & Coni- 

 ferae. (Trans. Roy. Soc. Canada ii. 2 : 51. 1896.) 

 48 



