i2a 



which we may take this character at one time or that at another. On the 

 other hand, groupa shown in the first half of the same quotation are charac- 

 terized by many characters (by these and at the same time also by those) ; 

 their limits and members do not change so manifestly as in the case of the 

 former groups, jilthough the characters taken as staudards vary. Sp3aking 

 generally, there ai'e, to be sure, some groups which are more dynamic and 

 others which are less dynamic. For examples, the Velloziaceae, Loganiacesa, 

 Myoporacese, Labiatae, Verbenacese, Euphorbiacese are more dynamic ; while 

 the Graminese, Qrcliidaceae are less dynamic groups. The latter certainly are 

 unchangeable within the limits of the variation of certain criteria ; but they 

 can not be exempted from Ixjing more or less dynamic, when all considerations 

 known as well as unknown to us are taken into account, as we sliall see 

 later on in the dynamic system and the explanation of it, to be given in this 

 paper. 



Now, let us take tha words, dynamic and static, in a comparative sense 

 and by " static " let us mean what is les3 dynamic. Then, there are two ways 

 of expressing the standing of all groups, namely : — 1, to regard all groups as 

 static forms, and treat dynamic forms as exceptional cases ; 2, to regard all 

 groups as dynamic forms and to treat static forms as exoeptions. Of these 

 two methods, the latter seems to me to be preferable to the former. The 

 reasonableness of my preference wiil be seen when we come to explain the 

 dynamic system. Spaaking generally, what I call a less dynamic group is 

 mostly represented by groups of the lower class, such as species or genera, 

 and what I call the more dynamic is iUustrated by groups of the higher 

 class, such as famihes or series. Such groujB as the Orchidaceaa and 

 Gramineae, just given as examples of less dynamic groups, somewhat correspond 

 to what we would have regarded as genera or the Hke, when compared with 

 more dynamic groups such as the Euphorbiacese or Myoporacese. 



What Engler says in § 4, may be taken as an illustration of the in- 



constancy of group3. In § 7'^ he go3S on to say : — 



Die Erfalirtmg, daS einzelne Merkmale zur Charakterisienmg groiSerer Pflanzen- 

 gemeinschaften verwendet werden konnen, andere nicht, fuhrte zu der Annahme von 



1) Enoleb, A. — 1. c. p. XL 



