INTRODUCTION. 13 



that some plants of Caltha palustris produce only male 

 flowers, and that these live mingled with the her- 

 maphrodites. The rarity of such cases as this last one 

 is remarkable, as the presence of hermaphrodite and 

 male flowers on the same individual is not an un- 

 usual occurrence; it would appear as if Nature did 

 not think it worth while to devote a distinct indi- 

 vidual to the production of pollen, excepting when 

 this was indispensably necessary, as in the case of 

 dioecious species. 



I have now finished my brief sketch of the several 

 cases, as far as known to me, in which flowers differing 

 in structure or in function are produced by the same 

 species of plant. Full details will be given in the fol- 

 lowing chapters with respect to many of these plants. 

 I will begin with the heterostyled, then pass on to cer- 

 tain dioecious, sub-dicecious, and polygamous species, 

 and end with the cleistogamic. For the convenience of 

 the reader, and to save space, the less important cases 

 and details have been printed in smaller type. 



I cannot close this Introduction without expressing 

 my warm thanks to Dr. Hooker for supplying me with 

 specimens and for other aid; and to Mr. Thiselton Dyer 

 and Professor Oliver for giving me much information 

 and other assistance. Professor Asa Gray, also, has uni- 

 formly aided me in many ways. To Fritz Miiller of St. 

 Catharina, in Brazil, I am indebted for many dried 

 flowers of heterostyled plants, often accompanied with 

 valuable notes. 



