293 



In order to determiue, if possible, what peculiarity of structure pro- 

 duced such variations in the wood, since the wood itself is formed en- 

 tirely of similar elements, and there is not the chance for variations in 

 structure that appear in the dicotyledonous wood, certain species of the 

 pines were examined microscopically, by means of sections and by macera- 

 tion of the wood, by the latter method separating the elements. Thirteen 

 species were examined. The wood varied In age from seven years in 

 Pinus glabra to over fifty years in Pinus elliottii. In order to compare 



Pine Tracheides. X 145. 



the elements in the different species, and also the spring and summer wood 

 of the same species, camera lucida drawings were made of the tracheides. 

 These were then measured, so as to determine the actual length, width, 

 and the thickness of the walls of the spring and the summer woods. 



The tables give the results of the measurements, the characteristics of 

 the woods as obtained from sections studied with the microscope, and also 

 the properties of the wood in bulk. 



