INTRODUCTION. 15 



otyledons, and Triandria and its multiples among 

 Monocotyledons, as compared to the indefinite 

 number of parts occurring in related members of 

 the same classes. 



3. A well established and persistent reduction 

 of number in parts, indicates a progress as com- 

 pared to their correspondence ; for the correspon- 

 dence must have existed before the exception could 

 establish itself as a rule. For instance Ainygdalese 

 with one ovary developed into a drupe, as compar- 

 ed with the nearly related Spirseese, with several, 

 usually five, ovaries. 



4. A well established morphological law is a 

 progress ; i. e. a well-defined difference of calyx, 

 corolla, stamens and seed leaves, is a progress as 

 compared to the spiral development, with its tran- 

 sitional forms intermediate between sepals and pe- 

 tals — petals and stamens, as they are found in 

 Nymphfeaceee, Magnoliacese, Banunculacese, etc. 

 Even where the circles are well defined but similar 

 in structure, they indicate a lower stage of evolu- 

 tion than when the structure differs. For instance, 

 the calyx of the Kanunculacere, compared to the 

 well defined calyx of the Caryophyllaceae, or the 

 entirely differentiated and transformed one (Pap- 

 pus) of the Composite. 



5. A difference in the proportion of parts, indi- 

 cates a progress, when the disproportion is well 

 defined and persistent, as in Didynamia, or Tetra- 

 dynamia, because an established disproportion can 

 only be developed out of an established equality. 



