64 IOWA ACADEMY OF SCIENCE 



This produces the four ovarian cavities, which are completed by the 

 fusion of the folds. 



Within each chamber two ovules arise, one from either edge of the 

 fold; they are thus foliar in origin (Figs. 18, 20). The ovules seem to 

 start simultaneously and the pair may be seen growing side by side, with 

 equal vigor. Up to this point, the two kinds of 'flowers have the same 

 history, but here they diverge, and must be taken up separately. 



The Pistillate Flower. 



These flowers, as stated, occupy the lower portion of the spike, and are 

 the first to develop. They may be first distinguished from the staminate 

 flower by the earlj'- checking of the stamens, which takes place about the 

 time the carpels begin to develop. The carpels, in contrast, make a 

 rather rapid growth. The stigmas are broad, occupying the entire top 

 of the carpels, and clothed with a mat of glandular hairs consisting of 

 4 to 8 cells each (Fig 3.). GrayV new manual gives as one of the char- 

 acterstics of this genus "stigma recurved." That certainly would not 

 apply to this species in which the stigma is practically sessile and uni- 

 formly covers the broad, rounded carpel. 



As the two ovules of each carpel develop, a vigorous competition en- 

 sues, due, no doubt, to a lack of space for both. One ovule gains the 

 dominance while the other aborts. This competition must be very keen 

 when the ovules arise simultaneously, and occasionally two of nearly the 

 same size are seen about the time the integuments begin to develop, 

 crowded tightly in the chamber (Fig. 15). No instance, however, was 

 observed in which one did not abort by the time the integuments had 

 begun to develop, and no case was seen in which both aborted. Thus 

 each carpel produces but one mature ovule (Fig. 22). The developing 

 ovule grows first downward (Figs. 18-20), then turns inward toward 

 the floral axis as the integuments bud out (Fig. 22), and finally turns 

 upward becoming entirely anatropous by the time the integuments close 

 together over the nucellus (Fig. 3). 



Eight persistent staminodia are generally found. These are better 

 developed in the upper pistillate flowers and more rudimentary in the 

 lower. In some of the lowest flowers of the spike no trace of the rudi- 

 ments was found. In others, only the inner four Were to be seen, the 

 outer whorl having been entirely suppressed. In others, though not 

 suppressed, they arise later than their usual order, sometimes after the 

 petals or even after the carpels. When both cycles of staminodia are 



2. Gray's New Manual of Botany, Seventh Edition. 1908. 



