

118 MISSOURI BOTANICAL GARDEN. 



ilar ones obtained from the roughened areas. To all 

 intents and purposes, the sections from the two different 

 regions were perfectly alike. There was no sign of fungus 



attack in 



e o 



til 



thicknes 



is sy 



the rough areas. In seeking for an explanation of the pecu- 



most 



glassy areas surrounded the healed-over portions of old 

 branches, or they were at any rate near such regions. 

 Where these areas were isolated they were generally near 

 some check. In all cases, the sap wood had the glassy 

 appearance. 



All of the specimens examined were cut during the 

 months of February and March, in other words at a time 

 when the temperature in the Maine forests is 32° Fahren- 

 heit, or generally very much lower. The following ex- 

 planation was finally adopted as explaining the peculiar 

 glassy appearance. It is very probable that during the 



present 



them 



then filled with solid ice. When the trees were cut down 

 by means of a saw, the teeth of the saw tore the fibres of 

 the spring wood, giving the appearance of roughened 

 areas, usually seen when a soft wood like the balsam fil- 

 ls cut with a saw. Wherever these wood cells were filled 

 with ice, however, the latter acted as a reinforcing material, 

 and when the saw cut through the fibre, enclosed on all 

 sides by the solid ice, the fibres were not torn as is usually 

 the case. The result was that when the sawing operation 

 was complete, those areas which were filled with solid ice 

 presented a smooth appearance. The ice, in other words, 

 acted very much in the way any imbedding material like 

 collodion, paraffin, etc., acts in sustaining weak cell-walls 

 during the operation of cutting sections with a knife. 

 In order to test this theory, sections were made with a 



