121 



wesentliclien nnd unwesentlichen Merkmalen. Es hat sich jedoch 

 herausgestellt, daB selbst sehr wesentliche Merkmale bei den dutch 

 sie charakterisierten Gruppen nicht immer konstant auftreten; es 

 hat sich ferner herausgestellt, daB viele Merkmale in der einen 

 Pf lanzengrtippe wesentlich, in der anderen tinwesentlich sind, so 

 z. B. Art der Konidienbildung, Bliitenfarbe, Sekretzellen, Sekretgiinge, Milchsaftsch- 

 Istuche, Zahl der Kotyledonen, Nebenblatter, Blattstellung, Venvachsung, von Blumen- 

 blsttern nsw. 



In the above passage, lie tells us that there are " wesentliche " and " uu- 

 wesentliche " characteristics. Now let us consider the truo meanings of these 

 two terms. What are called important characteristics clearly must include 

 those which were taken voluntarily or conventionally as the criteria for the 

 erection of a group and for determining the limit of the latter, or those which 

 come in linkage with the above qualities. In other words, they designate 

 those which characterize what we had habitually regarded as a group. 

 The term " unweseutliche " points out those characteristics which are just the 

 opposite of the above qualities. Thus interpreted, there could originally have 

 been no such difference in characters as is expressed by the words " wensent- 

 liche" or " unweseutliche." All characters show natural relations in respect of 

 themselves, no matter whether they be taken or not taken as criteria or whether 

 they come or do not come into linkage relations with the other features, that 

 is to say, regardless of whether they characterize or do not characterize the 

 conventional groups. They should all, therefore, be taken into account in any 

 system denoting natural relations. 



What ENGLER states in 8 l , may bo taken as an illustration of the 

 statement that he applies the term " wes3utliche " to a character that is 

 helpful in justifying the present system, and that he applies " unwesentliche " 

 to one that stands in the way of our doing so. 



His statement in 9 is in my opinion altogether impossible. For 

 phylogenetic development is not a matter that can bo made clear through a 

 comparison of the plants of the present age ; and even if it could be done, 

 the difficulty would remain that the order of progression or the stage of 

 development is not the same for all plants, but is possibly different for every 



1) ESGLEB, A. 1. c. p. XL 2) EXGLER, A. 1. c. p. XIL 



