6 IOWA STUDIES IN NATURAL HISTORY 
PLACENTA AND OVULES 
The globular free central placenta rising from the base of the 
flower is covered with ovules (Fig. 1). The number as counted 
in seven flowers ranged from 175 to 250 with an average of 
227. Of these seven flowers, five showed abortive ovules, twenty- 
eight of them being recognized, all told, but of these, nineteen 
were in one flower. 
The ovules are anatropous and each possesses a single massive 
integument which arches over and comes into contact with the 
placenta (Fig. 6). At first rather delicate (Fig. 2), the integu- 
ment thickens and soon, as seen in sections, becomes similar to 
the opposing funicular part, each being hemispherical, with the 
embryo-sae as a central axis between these halves (Fg. 11). 
These spherical ovules are tightly packed together, complete- 
ly covering the free central placenta and thus appearing as a 
globular mass which, however, is closely invested externally at 
all stages by the ovary wall. 
In the growth following fertilization the ovules become sharp- 
ly angled together. The seeds are commonly six sided (Fig. 
17) and are clearly flattened dorsiventrally, due to compres- 
sion between the placenta and the investing ovary wall (Fig. 
10). 
The funiculus, early massive and typical of this type of ovule 
(Fig. 6), diminishes relatively during the development of the 
seed and finally consists of merely a slender rudimentary struct- 
ure (Fig. 16). No vascular elements are developed in the 
funiculus, or in any other part of the ovule, though they are 
soon prominent in the placenta as discussed below. It should 
be kept in mind that the funiculus of the ovule of Utricularia 
vulgaris thus early aborts and that the embryo is nourished 
through another structure, the micropylar haustorium, the de- 
veloping seed meanwhile being held in position by the pressure 
of surrounding parts. 
The tissues of the free central placenta undergo considerable 
specialization. A tree-like vascular supply is developed which 
sends a branch to a point near the base of each ovule. The tip 
of this branch is directed towards the funiculus but stops 
alongside the micropylar haustorium (Fig. 1). 
