Philosophical Charactrr of Decandolle. 225 



experiments of a kind more or less exact, and having, by- 

 means of them, traced our route, rectify it by means of geo- 

 metrical formulfe, which serve as a check upon the errors of 

 manipulation ; so, after having thrown together all known 

 plants of the cruciform family into groups determined by the 

 sum of their affinities, he submits these groups to the rules of 

 theory, and finding the two methods to lead him to the same 

 result, is satisfied that he has made a near approximation to 

 truth. 



But the object of the classifier, is not only to arrange in the 

 most natural order the several genera belonging to the family 

 which he describes, but also to ascertain the relations of the 

 family itself taken collectively to other portions of the sys- 

 tem. 



From the earliest times at which botany was studied, the 

 importance of this inquiry has been felt, and the first attempts 

 made to effect this object consisted in disposing the several 

 objects in a linear series, according to the degrees of their 

 deviation from some one taken as a standard of comparison. 



The objection to this method was, that the same plant might 

 be nearly allied to one member of the series in certain respects, 

 and to one occupying a very different place in others ; and Lin- 

 naeus himself, being fully alive to the impossibility of con- 

 structing a linear arrangement which should harmonize with 

 nature, suggested the ingenious idea of representing the rela- 

 tion in which plants stand one towards each other, by a kind 

 of map, in which the classes should stand toward each othei', 

 as the quarters of the world do on an artificial globe, including 

 the families as separate countries, their genera as provinces, 

 their species as districts. As on the map, each district touches 

 many others, at distinct points, so likewise do the families in 

 the vegetable kingdom ; as the individuals in each district 

 agree in so many particulars with the inhabitants of the neigh- 

 bouring districts as to be scarcely recognisable from them, so 

 also do the species composing various allied genera.* 



* Giesccke, in his " Prelectiones in Ordines Naturales Plantaruni, Hani- 

 burgli 1792," has attempted to carry out tliis idea, iaa Chart; entitled Tabula 

 Genealogir-o-Oeographica Affinitatum Plantarum. 



