4 IOWA STUDIES IN NATURAL HISTORY 
promise between these opposing tendencies and one comes to 
feel that it is held rather sharply in check by environing cir- 
eumstances. That it tries frequently to escape its bonds is 
evidenced by the numerous departures from the typical story. 
There are recorded observations of unusual behavior by each of 
the seven nuclei associated with the egg, and there are various 
modifications of the gametophyte as a whole. Granted favorable 
opportunity one might expect to find it taking on highly modi- 
fied forms. 
In the Bladderwort (Utricularia) an unusual combination of 
parts is found within the ovary, and associated with it are 
striking specializations of both the female gametophyte and its 
successor in place, the endosperm. The protruding embryo-sac 
of Utricularia has long been known, as it was figured by Mertz 
(7) twenty years ago. Similarly, Kamienski (5) long since 
outlined quite fully the remarkable behavior of the endosperm 
in this genus. Lang (6) finds in the closely related Poly- 
pompholyx a series of events parallel to those in Utricularia, yet 
displaying interesting points of difference of peculiar signifi- 
cance in this connection. The present writers have undertaken 
this study feeling that the unusual behavior of these structures 
merited fuller investigation and perhaps warranted further con- 
clusions. 
Living vegetatively as a submersed aquatic, Utricularia has 
long been of interest because of the peculiar bladders produced 
upon its leaves. These organs, which function as floats and in- 
sect traps, have suggested both the common name of the plant 
and the scientific name of the genus. While belonging to the 
limited group of seed plants that flourish vegetatively beneath 
the surface of the water, its flowers are brought to the surface 
of the water for pollination, and pollen transfer is accomplished 
in the air by insects. 
Utricularia vulgaris americana Gray thrives in our Iowa lakes 
and ponds. In the vicinity of the Iowa Lakeside Laboratory 
on the Okoboji lakes in northwestern Iowa the smaller bodies of 
water are often yellow with its bloom. The flower stalk begins 
its development beneath the surface but later pushes up out 
of the water to a height of four to fifteen inches, bearing a 
raceme of beautiful flowers. As the period of flowering passes, 
