

f 



120 



MISSOURI BOTANICAL GARDEN. 



^ The result of these experiments seems to prove conclu- 

 sively that the smooth appearance of certain of the areas 

 is probably due to the reinforcing action of the ice which 



filled the wood cells. Th 



distribution of the 



to them, becomes readily intelligible when one re- 





glass} 

 close 



members that the lowering of temperature is more likely 

 to take place along such channels as are in communication 

 with the outer portions of the tree trunk. Many of the 

 branches are frequently in direct communication with the 

 outside air. In cooling, the first part of the tree "in which 

 the water would probably freeze is the part immediately 

 under the bark, that is the sap wood. This, as has been 

 stated, has a uniform glassy appearance in all the speci- 



The lowering of temperature would then gradually 

 proceed inward. It would take place most rapidly along 



as the older branches. The presence 

 of liquid water in any of the cells is another factor to be 

 considered. As a rule, the heart wood of a tree like the 



» 



mens 



such 



bal 



sam 



h 



most of it being held by the cell walls. It is very well 

 conceivable that there should be more water, first of all, in 



branch 



Iso- 



lated spots like the one shown in the upper right-hand 

 corner of the upper figure of plate 20 may be explained by 

 the fact that certain portions of the wood, for reasons not 

 yet clear, frequently " 



mass 



Where such quantities of water occur, 

 it would be possible to get smooth spots of the character 

 referred to. 



From a practical lumbering standpoint, the glassy fir 



in no way defective. Further 



should be 



regarded 



studies concerning this appearance are in progress and will 

 probably throw more light on the conducting capacity fo 

 heat of various portions of a tree trunk. 







