Atnpkicarpaa monoica, 359 



also the sharp dimorphism previously noted as existing in 

 the winter between plants developing from aerial and sub- 

 terranean seeds, is due to a want of sufficient light intensity . 



1 8. The purple aerial flowers (a) are produced on the upper 

 part of the plant from the latter part of July on to Septem- 

 ber. The green aerial (b) do not appear until the latter 

 part of August, and they may be found in all stages— flower 

 to fruit— as late as October. They are not so definitely 

 located upon the plant as the purple flowers are. The pro- 

 duction of the subterranean type begins in June and con- 

 tinues throughout the entire season. 



19. The purple flowers (a) possess 10 diadelphous stamens, 

 the filaments of the 9 being united almost the entire length ; 

 their anthers are similar and perfect. The green aerial (b) 

 flowers have 10 stamens, distinct or with the filaments 

 united into a short tube; these anthers exhibit varying 

 degrees of imperfection. The winter flowers (d) have 10 

 stamens, which are distinct ; four of these usually bear 

 perfect anthers, the remaining stamens being quite rudi- 

 mentary. The terrestrial flowers (c) have indications of 10 

 stamens (many of them exceedingly rudimentary), those 

 which develop anthers vary from 6 to 4, and usually but 

 2 possess perfect anthers. 



20. The thickened hypodermal layer (endothecium) pre- 

 sent in the anthers of {a), is absent in anthers of the 

 remaining types. 



21. The microspores and macrospores of the three types 

 of flower exhibit a gradual reduction in size. 



22. A very complete series illustrating transitional reduc- 

 tion in styles and stigma may readily be obtained from a 

 study of types 0, b, c. 



23. Flowers of type (a) are probably close fertilized, 

 although there are present several devices associated with 

 insect fertilization. The remainder are cleistogamic flowers; 

 the pollen not being discharged from the anthers, but send- 

 ing forth tubes toward the stigma. 



24. Flowers of type (a) do quite frequently produce 



