242 The Microscope. 



viously sought to add confirmation. To this end, woods of like 

 species were collected from different states and parts of the 

 states, with the belief that should the cell-markings of a certain 

 tree differ with the locality, or according to the conditions under 

 which it grew, it would satisfactorily prove, at least to our own 

 minds, that no such determination is possible. The result more 

 than realized these expectations. 



The second collection made, comprised species of the pines, 

 oaks, maples, elms, etc., from Florida, California, Indiana, Wis- 

 consin, and Illinois, and not only do the results of the examin- 

 ation widely differ, but species of the same genus, in many 

 cases, bear no relation to each other ; the same species differ ac- 

 cording to the conditions of the soil in which they grow, although, 

 often times, separated by a distance of less than a mile, and, as 

 has previously been pointed out, frequently assume coniferous 

 characteristics. 



To those who are not acquainted with the microscopical 

 structure of woods, be it known that a radial and longitudinal 

 section of any wood, presents markings on the cell walls, which 

 are the subject of this paper. These markings, whether discs 

 or simple dots, are thin places in the wall of the cell, and, with 

 age, often become real perforations. They are directly opposite 

 and correspond with the same thin places of the contiguous cell, 

 and are undoubtedly designed for maintaining a ready convey- 

 ance of the sap from cell to cell ; but, that in every species 

 these cell- markings exactly correspond in size, shape and ar- 

 rangement, making the determination of the species, under the 

 microscope, Infallible, or even possible, we cannot believe. 



In the case of a slide before us, of the Pin us Strobus, or 

 white pine, there are the characteristic discs of the order, which 

 vary greatly in size and arrangement. On another slide we have 

 a section of Quercus rubra, or red oak, showing similar mark- 

 ings, and somewhat confounding the statement made by a noted 

 botanist, that the smallest fragment taken from a pine tree will 

 at once discover the order. 



We have two other slides of these same species, but growing 

 under different conditions ; the one growing in sandy soil and 

 the other in rich alluvial soil. These do not show similar mark- 

 ings as do the other slides. 



