No. 436.] LOCALIZED STAGES IN PLANTS. 259 



are much simpler than in the seedling as shown in Potcntilla 

 tridentata, Rides an rami Poterium canadensis and others. 

 Such extreme reversion may be compared to the young of other 

 species in the genus in which the first leaves do have more primi- 

 tive simplicity. 



This life history of a plant marked by stages in the leaves can 

 be made out in many, perhaps all plants where the leaves are 

 compound, notched or lobed and even sometimes where the 

 leaves are entire, by changes in venation and outline. 



Cambridge, Mass. 



