IOWA ACADEMY OF SCIENCE 63 



spike are commonly staminate, and the lower usually pistillate. There 

 is generally an abrupt change from one kind of flower to the other (Fig. 

 6), but the variation, however, in this respect is very great, and perfect 

 or neutral flowers may be found between. Sometimes, on the other 

 hand, the entire spike is either staminate or pistillate, i. e. dioecious. 

 Often there is a gradual transition from one kind of flower to the other, 

 though perfect flowers in this species are not common. 



The developing spike resembles very closely the tip of a vegetative 

 branch. Each consists of a number of very short internodes and nodes 

 bearing the leaves and bracts, in the axils of which the buds develop. 

 The flower bud may easily be distinguished from that of the vegetative 

 bud by its greater lateral development, resulting in a comparative thick- 

 ness. Then, too, the origin of the lateral members of the flower is near 

 the broad tip, while in the vegetative shoot, they arise back a consider- 

 able distance from the growing point. 



The lobes of the sepals are the first members of the flower to be devel- 

 oped (Figs. 7, 8). These are four in number and arise near the tip of 

 the broad growing point. Their growth is checked very early and they 

 never become more than one or two mm. in length. This rudimentary 

 or dwarfed condition of the sepals is probably due to the fact that they 

 are no longer needed for protection, as the developing flower is entirely 

 enclosed by the three heavy bracts. 



Next after the sepals comes the inner row of stamens (Figs. 9 to 11). 

 These appear as broad elevations just inside and opposite the sepals. The 

 stamens of the outer whorl alternate with those of the inner and arise 

 soon after the inception of the first whorl. These eight stamens make 

 a rapid growth and appear very vigorous, especially in t^ie staminate 

 flowers. 



The four petals are next to develop (Fig. 10). These alternate with 

 the sepals and are thus opposite the outer whorl of stamens. They grow 

 rapidly from the start, and before the stamens are half grown, they have 

 reached the top and soon overlap one another at the apex of the flower 

 (Figs. 13, 14). The petals are free and imbricated. Eichler^ states 

 that they are convolute, often absent in the pistillate flower, or else so 

 small that they do not touch one another. In this species, I find they 

 are imbricated, always present in ])oth kinds of flowers, and always over- 

 lapping. 



The carpels are the latest to develop. They alternate with the inner 

 row of stamens. Arising as small protuberances near the center of the 

 flower, they soon begin each an infolding toward the center of the axis. 



1. Eichler, A. W., Bluthendiagramme. Zweiter theil, Leipzig, 1878. pp. 463-464. 



