162 BUTTERCUP. 



Such an arrangement makes possible the increase in 

 diameter of Dicotyledonous plants throughout the grow- 

 ing season. In perennial trees or shrubs this increase 

 takes place annually, as is shown by the so-called " annual 

 rings." The strong supporting shafts of our trees are 

 due chiefly to the great development of the xylem bundles. 

 In Dicotyledons underground stems of all kinds are 

 less common than in Monocotyledons; while distinctly 

 fibrous roots, and tap-roots with secondary root systems, 

 are the usual subterranean organs. 



The flower of Ranunculus is a relatively simple one. 

 The carpels are numerous and separate, each carpel 

 here forming a separate pistil. The stamens are numerous 

 and spirally arranged. Numerous carpels and stamens, 

 and spiral arrangement of floral organs, are characteristic 

 of the simpler Dicotyledons. The placing of the other 

 floral organs below the ovary (hypogynous arrangement) 

 is also indicative of the lower members of the group. 



The classification of Ranunculus in the manual should 

 be done with the idea of learning how to study the classi- 

 fication of plants rather than with the idea that an exten- 

 sive work in classification is to be done in this course. 1 



1 See"A contribution to life-history of Ranunculus," by John M. 

 Coulter, Bot. Gaz. 25 : 73-88. 



