THE TRIMORPHISM AND INSECT VISITORS 
OF PONTEDERIA 
By Tracy E. HAZEN 
Barnard College, Columbia University 
(WITH PLATES I4 AND I5) 
The family Pontederiaceae is notable as containing the only 
known heterostyled species among monocotyledonous plants 
(with one possible exception*) and is further remarkable among 
heterostyled plants as furnishing the only recorded examples of 
distinctly zygomorphic or irregular flowers in such plants. 
Fritz Мег, writing in 1869 from Santa Catharina in southern 
Brazil, described a Pontederia which had for several years been 
introduced as an ornamental plant in the colony of Blumenau, and 
which increased with incredible rapidity by asexual propagation; 
the species he thought to be P. crassipes, and from the fact that 
the flowers showed the same relative positions of long and short 
stamens and style found in the mid-length-style form of the well- 
known Lythrum Salicaria, he was convinced that he was dealing 
with a trimorphic species of which only the mid-styled form had 
been introduced. He found another species growing wild on the 
banks of the Itajah$-mirim, which presented long- and short- 
styled flowers, but no mid-styled form could be found there. 
From the finely toothed petal segments shown in Müller's figures 
of this second species (loc. cit. f. 1-3) it almost immediately oc- 
curred to me that it was the plant which I have regularly seen 
labelled Piaropus azureus (Sw.) Rat., growing with the more 
famous water-hyacinth at the New York Botanical Garden, and 
later I discovered that it is so identified by Müller himself (as 
* It is stated by Kerner (Pflanzenleben 2: 369. 1891; Eng. Ed. 2: 374) that 
flowers cf Colchicum autumnale present three style lengths, but his brief ZA 
does not indicate any corresponding difference in stamen lengths such as alwa 
accompanies truly trimorphic species. 
+ Müller, F. Ueber den Trimorphismus der Pontederien. Jen. Zeitsch. 
Naturwiss. 6: 74-78. 1871. 
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