184 HETEROSTYLED TRIMORPHIC PLANTS. Chap. IV. 



heterostyled and trimorphic. This case is an interest- 

 ing one, for no other Monocotyledonous plant is known 

 to be heterostyled. Moreover the flowers are irregular, 

 and all other heterostyled plants have almost sym- 

 metrical flowers. The two forms differ somewhat in 

 the colour of their corollas, that of the short-styled 

 being of a darker blue, whilst that of the long-styled 

 tends towards violet, and no other such case is known. 

 Lastly, the three longer stamens alternate with the 

 three shorter ones, whereas in Lythrum and Oxalis 

 the long and short stamens belong to distinct whorls. 

 With respect to the absence of the mid-styled form in 

 the case of the Pontederia which grows wild in Southern 

 Brazil, this would probably follow if only two forms 

 had been originally introduced there; for, as we shall 

 hereafter see from the observations of Hildebrand, 

 Fritz Miiller, and myself, when one form of Oxalis is 

 fertilised exclusively by either of the other two forms 

 the offspring generally belong to the two parent- 

 forms. 



Fritz Miiller has recently discovered, as he informs 

 me, a third species of Pontederia, with all three forms 

 growing together in pools in the interior of S. Brazil; 

 so that no shadow of doubt can any longer remain 

 about this genus including trimorphic species. He 

 sent me dried flowers of all three forms. In the long- 

 styled form the stigma stands a little above the tips 

 of the petals, and on a level with the anthers of the 

 longest stamens in the other two forms. The pistil is 

 in length to that of the mid-styled as 100 to 56, and 

 to that of the short-styled as 100 to 16. Its summit is 

 rectangularly bent upwards, and the stigma is rather 

 broader than that of the mid-stvled, and broader in 

 about the ratio of 7 to 4 than that of the short-styled. 

 In the mid-styled form, the stigma is placed rather 





