THE MICROSCOPE. 



Vol. V. ANN ARBOR, NOVEMBER, 1885. No. 11. 



ORIGINAL COMMUNICATIONS. 



CAN THE SPECIES OF EXOGENOUS TREES BE DE- 

 TERMINED BY CELL-MARKINGS. 



PHILIP E. LAWRENCE AND CHAS. S. RADDIN, EVANSTON, ILL. 



IT is held by many botanists and microscopists, that the fam- 

 ilies, genera, and species of woods, may be determined by 

 the markings on the cell walls ; that each tree bears within 

 itself a signet, invisible to the naked eye, which stamps its 

 character. 



There being no standard of drawings or descriptions to 

 which microscopical investigations in this line could be referred, 

 a collection, numbering upwards of two hundred species, was 

 obtained from different parts of the United States, and drawings 

 made of the supposed characteristic structure, with results that 

 raise serious doubts as to the veracity of the theory, for not only 

 was there an absence of any family characteristic, — with the 

 exception, perhaps, of the coniferas, — but still less any generic 

 or specific, distinctive properties. Every tribe examined con- 

 tains some species, characteristic of, and in many cases impossi- 

 ble to distinguish from, specimens from other families. For ex- 

 ample, — the slippery elm, ulmus pulva, — the red oak, quercus 

 rubra, — and some of the pines are almost undistinguishable, as 

 not only do the cell markings bear the same relation to each 

 other and present a similar appearance, but measurement shows 

 no appreciable difference in size. 



Upon discovering that an eminent microscopist of Chicago 

 had carried on similar observations, obtaining similar results,we 

 now set about to break down the theory to which we had pre- 



