157 



naeus' classification depended on the number of stamens. He 

 began with one stamen; now the sequence must be reversed. 

 Plants with many stamens have in numerous cases also other 

 primitive characters. Stamens in part sterile, or pollen grains 

 more or less united are specialized characters. 



Perianth 



1. Sepals and petals nearly alike^clearly differentiated 



2. Perianth parts many— >few 



3. Sepals and petals free— >more or less united 



4. Arrangement spiral-H>hemicyclic— >cyclic 

 This fourth series is questioned by Sprague. 



5. Regular (actinomorphic) — irregular (zygomorphic) 



Comparatively few changes occur in the calyx. Separate 

 sepals are the exception, they occur chiefly in the Magnolia and 

 Parietales groups. In the corolla of insect pollinated flowers the 

 changes are in the direction of improved adaptation to insect 

 visitors. The evolution of flowers must have proceeded parallel 

 to that of insects. Petals with claws, etc. as in many Cruciferae, 

 or flowers with special structures, such as a corona, must be 

 considered as specialized forms. 



Receptacle 



1. Convex— »flat—>concave 



2. Disk absent— ^present 



Inflorescence 



1. Flowers solitary — ^inflorescence loose— ^inflorescence con- 

 densed 



2. Flowers alike^more than one kind of flower 



3. Flowers perfect— >polygamous—>monoecious—Kiioecious 



Vegetative Parts 



1. Leaves simple— ^compound (?) 



2. Lacunae at nodes below leaf bases, 3— >1 (Sinnott) 



3. Trees or shrubs— ^herbaceous perennials^annuals 



4. Vessels scalariform^pitted 



Finally, in addition to the evidence from ontogeny, other 

 and entirely independent lines of investigation may throw light 

 on floral evolution. First of these comes paleobotany. It is of 

 special interest that the dicotyledonous genera from the Cre- 



