498 SOILS. 



DIFFERENCES IN THE FORM AND DEVELOPMENT OF TREES. 1 



It will be noted that in the above table, as well as in the dis- 

 cussion preceding it, identical species of trees are ascribed to 

 vegetative areas of widely different productive capacity. Per- 

 haps the most striking example is that the cretaceous prairies 

 and the adjoining flatwoods belt, standing respectively highest 

 and lowest in the scale of productiveness, are yet bearing 

 specifically identical tree-growth, to-wit, the post oak (Quercus 

 minor) and the black-jack oak (Q. marylandica) . While to 

 the field botanist 2 there can be no question as to the absolute 

 specific identity of the two trees as growing on the respective 

 areas, yet the mode of development of both is so different in 

 the two cases, that, as before remarked they are popularly sup- 

 posed to be different " kinds." 



Forms of the Post Oak. The post oak of the prairie lands is 

 a tree 50 to 70 feet high, with a stout, excurrent, rather conical 

 trunk, often somewhat curved to one side above, and densely 

 clothed from within 12 or 15 feet of the ground with com- 

 paratively short, sturdy branches set squarely to the trunk, 

 much crooked (geniculate), often reflexed downward; alto- 

 gether forming a dense head, beneath whose thick foliage, a 

 bird or squirrel is quite secure from the hunter's aim. In the 

 flatwoods, on the contrary, the post oak has a thin, rather short 

 trunk, divided up at 15 or 20 feet height into long, rod-like 

 branches, spreading broom-fashion, and scantily clothed with 



1 It is a matter of regret to the writer that owing to the long distance intervening 

 and the difficulty of securing competent and sympathetic observers for such work, 

 it has not been possible for him to secure photographs of the tree-forms here dis- 

 cussed. At the time his own observations were made, photography was prac- 

 tically unavailable as yet, and the figures given are therefore based upon sketches 

 made at the time, and partly upon recollection. They represent types rather than 

 definite individuals, which were however described when fresh in mind, in the 

 Report on the Agriculture and Geology of Mississippi, 1860, pages 254 et seq. 



2 It has been already, and doubtless will be again and increasingly, attempted to 

 make distinct " species " of these widely different forms of trees. But this is 

 simply begging the question. Mere external diagnostic marks will not avail here ; 

 it would have to be shown that the seed of these different forms do not produce 

 the other forms under changed conditions. Until this has been done, the number- 

 less transition forms which he that runs may observe in the field, throw upon the 

 species-makers the onus of proof of differences of specific value if it be possible 

 to define such value. 



