WOODS AND THEIR DESTRUCTIVE FUNGI 605 



or in painted poles, the decay does not appear above the ground-line 

 on the exterior until after the breaking away of the interior wood-cells. 

 In chestnut poles, the sap-wood being so much thinner, the cells break 

 away sooner than in the spruce. 



From the place of growth at the ground-line the mycelia pierce 

 the upright longitudinal cells more readily than they do those of the 

 medullary system, growing up and down, but faster in the latter direc- 

 tion, from the fact that the moisture is retained below the ground- 

 line in greater abundance than above. Accompanying the mycelia 

 is a growth of ferments, either of the Schizomycetes (bacteria) or the 

 SaccharomyceteS) depending somewhat upon the particular fungi and 

 the wood. These aid in carrying on the destruction by producing 

 fermentations, which extend down the wood-cells preceding the growth 

 of the mycelia. The illustration was prepared from a pole of which 

 , five feet in length of the base was in the ground, and decay had fol- 

 lowed down the cells four feet, while above-ground the decay only 

 followed up the cells a few inches ; the pole being unpainted allowed 

 the moisture to escape sufficiently to retard the upward growth. It 

 will be seen from Fig. 10 that a few inches below-ground the exterior 

 of the wood is not so quickly affected, and, comparatively speaking 

 remains sound until destroyed from the inside, though retaining the 

 moisture and facilitating the growth of the fungi. This illustrates 

 one of the important principles to be observed in the care and pres- 

 ervation of our timber in structures, for it will be seen that exterior 

 protection to unseasoned timber, or to that which is to be in a damp 

 situation, retains the moisture and hastens internal decay. 



In the case of painted posts above the ground the paint prevents 

 the escape of the moisture, the mycelia and fermentations grow farther 

 up the cells and the posts often break off on the inside above the earth, 

 while appearing sound outside, with a cone-shaped fracture. 



In Fig. 10 the decay was extending toward the center of the pole 

 very slowly, the fermentation not being communicated with as great 

 rapidity by the medullary cells, which are only one fifth to one third 

 as large as the upright cells. 



Fig. 11 shows the tangential section of the tamarack, which is 

 quite similar to that of the black spruce. The three largest bundles 

 of rays contain resin-ducts, while the cell-cavities of the rays can just 

 be seen ; also the sections of the lenticular markings on the walls ; 

 in Fig. 12, they show in position on the walls parallel to the medullary 

 rays ; the latter are the lines partly crossing the cut, and composed of 

 short contiguous cells, which are thick- walled and not easily penetrated 

 by the mycelia or destroyed by fermentations. An example of the slow 

 lateral extension of the decay is found in the white cedar, a transverse 

 section of which was shown in Fig. 2 (see August number). In grow- 

 ing trees of this wood some of the lower limbs often die, and, not 

 breaking off close to the body, the fungi grow before the wound heals 



