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BOTANICAL GAZETTE 



[FEBRUARY 



retained.. In this manner possibly as many as 50 stamina te flowers 

 may be caught in a single depression, thus forming conspicuous 

 white patches on the surface of the water. It is interesting to 

 note how successfully these areas of associated flowers hold together 

 even when the water is quite rough. Cowles (5) mentions these 

 film pockets, but gives no details other than to compare them with 



those of Elodea canadensis. In this 

 latter form, as previously described 

 (2), the floating pollen grains are 

 caught in the depressions that are 

 formed about the tiny pistillate 

 flowers. Svedelius speaks of a sim- 

 ilar " capturing" of the pollen-bearing 

 flowers in Enalus ac oroides, but does 

 not attribute this to the influence of 

 the surface film, although obviously 

 the case closely parallels that of 

 Vallisneria. 



The sepals of the innermost of 

 the captured stamina te flowers in 

 Vallisneria are of course in contact 

 with the margins of the pistillate 

 flower (fig. 2), but later arrivals are 

 held back as they form only a single 

 layer in the depression. It should 



Fig. 2* — Flowers floating on 

 surface of water in a small aqua- 

 rium surrounded by black paper; 

 pistillate flower in center. 



be noted at this time that contact between flowers on a level water 

 surface, such as Kerner figures, could not lead to pollen transfer, as 

 the pollinia are upraised over the center of the flower. But with any 

 slight declination of the film about the pistillate flow r er, even in quiet 

 water, there might be contact between the innermost pollinia 

 and the stigmas (fig. 2). Obviously, however, any movement 

 resulting in a further depression of the pistillate flower would cause 

 the surface film to become more abruptly declined r thus tipping 



the staminate flowers more sharply inward 





and thereby 



2-6 



flowers floating at surface of water when subjected to submergence by pulling on scape 

 of pistillate flower. 



