blossoms or alone, display reduced floral parts. But there is no 

 evidence of suppressed members in this flower other than those 

 which occur also in the terrestrial species of Heteranthera. This 

 strengthens the view that its flowers are unspecialized as a water 

 plant and probably have undergone little modification in the 

 transition. 



Nor do the facts support Goebel's view (10) that cleistogamy 

 is correlated with conditions unfavorable for vegetative growth. 

 Heteranthera duhia surely suffers no lack of raw materials and 

 its light relation is no more difficult than other plants of the 

 same habitat. Such relation as exists between its vegetative 

 body and its habit of self pollination is due to the vigor of its 

 growth rather than otherv\dse. 



It seems therefore that the cleistogamy of Heteranthera duhia 

 is largely accidental and is due to the perfect flowers in relation 

 to the tardiness or failure of the flower buds to open. No doubt 

 this habit has operated to retard floral adjustment to the aquatic 

 habitat through its suppression of cross pollination. The effect 

 would be the same whether the habit of cross pollination was 

 acquired as a land plant or after it had shifted to the water. If 

 the species is now adjusted vegetatively to its new home its 

 homozygous reproduction may perhaps be advantageous rather 

 than otherwise. The species suggests itself as a favorable one 

 for experimental study in plant breeding since it grows readily 

 and if kept submerged sets seeds freely without further attention. 



56 



