The Comparative Structure of the Flowers in 



PolygaJa polygama and P. paucifiora, 



with a Review of Cleistogamy. 



(.WITB PLATES XVI-XVII.) 



By Charles Hugh Shaw, Ph. D., 



Professor of Botany in Temple College. 



[Submitted to the University of Pennsylvania in Partial Fulfillment of the Requirements for 

 the Degree of Doctor of Philosophy.] 



In the genus Polygala only two species, so far as known, 

 exhibit cleistogamy. Both are natives of the Eastern United 

 States. One is P. polygauia, often abundant along our sandy 

 coasts, the other is P. paitcifolia, the beautiful so-called 

 Flowering Wintergreen of more interior districts. 



The former, alike from the abundance of the cleistogamic 

 flowers it produces, and the presence of intermediate types 

 now for the first time described, has been the chief subject of 

 the present study and will be first dealt with. 



The detailed description of the various types of flower may 

 best be prefaced by recapitulating what is known of the 

 flowers of the genus. 



Conspicuous blooms are borne by all members of the 

 genus. These are generally in racemose clusters, and are 

 sometimes very showy. The typical aerial flower is very 

 irregular. In the calyx the two lateral, interior sepals are 

 greatly developed as petaloid wings. The corolla consists 

 of three petals, one anterior and two posterior, the two lateral 

 of the theoretical five being suppressed. Of the three the 

 anterior one is greatly developed as a hood covering the 

 stamens and pistil. The stamens are eight in number, 

 the anterior and posterior ones of the theoretical ten being 

 wanting. They are monadelphous, being united below, and 



