X INTRODUCTION. 



practice of dividinf? the Vegetable Kingdom into three great branches 

 {embrnnc/icments), founded on the presence or absence, and the number 

 of cotyledons, and shall successively examine Dicottledons, Mono- 

 roTYLKDONS, and Acotyledons. Seeing that we begin the study of 

 DicoTYi.EDONS with the orders called Poli/carpiccs — i.e., those in 

 wliii.-li the carpels of the flower, and later on of the fruit, are free 

 from each other, and recall as nearly as possible by their arrange- 

 ment on the floral axis that of the leaves on the stem — the reader 

 will at once perceive the importance we assign to the female repro- 

 ductive organ in classification. But as even from the very beginning 

 he will here and there find types which are exceptional in that their 

 carpels are united to a variable extent, while most authors have still 

 put them in the same natural group, he will also understand that 

 we cannot admit either "absolute characters" or "immutable sub- 

 ordination," the foundations of what is at present called the natural 

 system. "We have said enough to indicate what principles we 

 shall follow in the classification of the Vegetable Kingdom, 



BoTAXic Gardens of the Society of Medici>'e of Paeis, 

 FEBHrABT, 1869. 



TO THE ENGLISH READER. 



I WISH to take this opportunity of expressing my thanks to the 

 authorities of the Linna^an Society and of the Cambridge University 

 Library for their courtesy to me ; also to my brother, Mr. Numa 

 Edward Hartog, for his kind assistance in the wearisome task of 

 revising the proofs, which has materially increased whatever value 

 this translation may possess. 



M. M. H. 



Trixity College, Cambridge, 

 Makcii, 1871. 



