Journal 



OP THE 



NEW-YORK MICROSCOPICAL SOCIETY. 



Vol. I. APRIL, 1885. No. 4. 



THE CELL-STRUCTURE OF PINUS STROBUS. 



BY P. H. DUDLEY, C. E. 



{Read March bth, 1885.) 



Fi/ius Strobus, or White Pine, is one of our most valuable 

 coniferous trees. Its wood from different localities presents 

 variations in structure, hardness, density, and strength ; and, as 

 observers are not fully agreed as to all of its features, any de- 

 scription of its structure can only be considered as a contribu- 

 tion to the mass of facts yet to be collected to give us the infor- 

 mation desired. 



Under the microscope, transverse sections and radial longitu- 

 dinal sections from the duramen usually show two classes of 

 tracheides, one of thin and the other of thick walls. Tracheides 

 of the former class occupy the inner portion of the annular ring, 

 and contain a part of the resin canals : those of the latter class 

 are in the outer portion of the ring. The cells of the outer three 

 to five rows are more flattened than the others ; and their tan- 

 gential surfaces contain the lenticular cavities, which are smaller 

 than those of the thin-walled cells ; and the openings in their 

 domes seem oblong. Openings of the same description in the 

 thin-walled tracheides are round or elliptical. 



On the periphery of the annular ring are found the occasional 

 cells, which, when young, contain starch. 



Recent examinations of the conifers show a greater differen- 

 tiation of the tissues than was formerly supposed to exist. The 

 larger the proportion of the thick-walled to the thin-walled 

 tracheides, the greater, within certain limits, is the density, hard- 

 ness, and strength of the wood. I have here two pieces of select- 

 ed clear lumber, the best the market affords, and you will be 

 surprised to see the difference in their appearance. In one block, 

 — marked A^ — the annular rings number eighteen or nineteen 

 per inch, each of which has from thirty-five to forty rows of 



