LANDMARKS OF BOTANICAL HISTORY GREENE lOI 



the wood of palm and umbellifer, we realize the expression of the 

 popular notion of wood as being that which the bark of any tree 

 encloses, without regard to density or ponderability. His language 

 here nevertheless evinces plainly his having taken full cognizance 

 of the fundamental difference between the wood of palms and 

 that of all exogenous trees. To pith he attributes flesh and sap 

 only. Bark is composed of all three of these elementals in most 

 cases, as in the oak, poplar, and pear tree, though in some, the 

 grape-vine, for example, of nerve and sap only — that is to say, 

 without flesh, or what we call parenchyma. 



The structural elements of the leaves of exogens he apprehended 

 as substantially identical with those of the bark. The stalklet, 

 and therewith the fibrous framework of the blade, are of that which 

 he designates as nerve, or sinew. ^ Next to this he names the 

 epidermis, and after that, what he callsthe flesh, known to us as the 

 mesophyll. In the leaves of palms and reedy or grassy plants he finds 

 no flesh at all, and thinks these are composed of fibre and epidermis 

 only. The edible fruits of trees and shrubs are composed mostly 

 of flesh, with little or no fibrous tissue; while, on the other hand, 

 some pericarps consist of a rind or skin only. He has so clearly 

 distinguished these two or three elementals of the plant fabric 

 that he is able to trace and point them out in every plant organ 

 from root to fruit. 



Phytography. In descriptive botany there are two different 

 methods by which it is undertaken to convey by means of language 

 the image, so to speak, of some tree or other growth which the 

 describer has seen, and the reader is supposed not to have seen. 

 That two distinct methods in phyi:ography exist is something of 

 which I have seen no mention either with any botanical author, 

 or with any historian of botany; but a suggestion of them has been 

 made very recently, with also a good account of Theophrastus' 

 phytographic method, in an excellent treatise on some parts of 

 Theophrastan botany by Dr. Hugo Bretzl. Let me for con- 

 venience designate the methods as the natural and the artificial. 

 They may, however, quite as fitly be named the comparative and 

 the positive methods of plant description. Of the two, one is very 

 ancient, the other strictly modern; and the artificial or positive is 

 doubtless the more perfectly adapted to its purpose, though only 

 for such writers and such readers as are competent to use it; for 

 it requires the mastery, on the part of both, of a very extensive 

 vocabulary of special terms; in reality, the learning of a new 



» Hist., Book i, ch. 17, 



