136 THE THEOEY OF EVOLUTION 



Even within the class of Club-mosses a similar 

 procedure is to be observed. 1 



Heterospory finally i.e. the peculiarity of forming 

 small and large spores for separated male and female 

 prothalli (which has been regarded as a progressive 

 stage in the evolution of the whole plant world) is found 

 in the most varied plant groups ; there are homosporous 

 (with spores of only one kind) and heterosporous forms 

 among the Ferns the Equisetae and the Club-mosses. 

 The present EquisetaB are even exclusively homosporous 

 (therefore ' lower ') forms ; the Calamariaceae were 

 heterosporous. 



Thereby is it demonstrated by evidence that differ- 

 ences in the spore formation and reduction of the sexual 

 generation are not phenomena which by themselves 

 can be taken as transitional stages towards other 

 ' types ' or as constituting a general higher formation. 3 



5. On whatever principles we may proceed in the 

 systematic classification of the present organisms, 

 so far we always arrive at the result that the plants 

 and animals fall into a few larger groups which exist 

 separately but close to each other. 3 Are these groups 

 also really types, i.e. primary animal and plant forms ? 



1 E. Warnung : Handbuch der systematischen Botanik, p. 153. 



2 J. Reinke agrees to this when he says (Einleitung in die, fheoretische 

 Biologie, p. 471) : ' If in this sketch I have put forward the results of com- 

 parative examination, without further remarks, as evidence of the genetic 

 connection (between Ferns, Gymnosperms, and Angiosperms) of phylo- 

 genetic evolution, the reader will not be in doubt with regard to the 

 manifold hypothetical elements in this partly fanciful description.' 



3 With regard to the various botanical divisions see the very instructive 

 chapter on the Stdmme des Pflanzenreiches by Kerner v. Marilaun (Pflanzen- 

 leben, II, p. 488. This chapter is not in the second edition. 



