Introduction. 9 



1759. To such of these small groups of related forms as had 

 not been already named both Linnaeus and Jussieu gave names, 

 which they took not from certain marks, but from the name 

 of a genus in each group. But this mode of naming plainly 

 expresses the idea which from that time forward prevailed in 

 systematic botany, that there is a common type lying at the 

 foundation of each natural group, from which all its forms 

 though specifically distinct can be derived, as the forms of a 

 crystal may all be derived from one fundamental form, an 

 idea which was also expressed by Pyrame de Candolle in 1819. 



But botanists could not rest content with merely naming 

 natural groups ; it was necessary to translate the indistinct 

 feeling, which had suggested the groups of Linnaeus and 

 Bernard de Jussieu, into the language of science by assigning 

 clearly recognised marks ; and this was from this time forward 

 the task of systematists from Antoine Laurent de Jussieu and 

 de Candolle to Endlicher and Lindley. But it cannot be 

 denied, that later systematists repeatedly committed the fault 

 of splitting up natural groups of affinity by artificial divisions 

 and of bringing together the unlike, as Cesalpino and the 

 botanists of the iyth century had done before them, though 

 continued practice was always leading to a more perfect 

 exhibition of natural affinities. 



But while natural relationship was thus becoming more and 

 more the guiding idea in the minds of systematists, and the 

 experience of centuries was enforcing the lesson, that prede- 

 termined grounds of classification could not do justice to natural 

 affinities, the fact of affinity became itself more unintelligible and 

 mysterious. It seemed impossible to give a clear and precise 

 definition of the conception, the exhibition of which was felt 

 to be the proper, object of all efforts to discover the natural 

 system, and which continued to be known by the name of 

 affinity. A sense of this mystery is expressed in the sentence 

 of Linnaeus : ' It is not the cl aracter (the marks used to 

 characterise the genus) which makes the genus, but the genus 



