1898 | COMPARATIVE MORPHOLOGY OF PISTILS 305 
36). Within a very short time the position of the ovule becomes 
permanent, with the apex of the nucellus directed towards the 
receptacle (fig. 37). Subsequent changes are mostly those in 
size and such modifications of shape as are caused by the pres- 
sure of the surrounding pistils. 
ALIsMA PLanTaGo aguatica. In the very young flowers of 
this species the receptacle is much broader above than below, 
and has a rounded top. It is from the narrower basal part that 
the stamens arise, while the pistils are produced at the edge 
where the receptacle is widest. They appear as projections, at 
first small, later larger (fig. 38). This gives the receptacle, 
viewed from above, the appearance of a toothed wheel. The 
receptacle grows rapidly in height, as do the apex and sides of 
each pistil, thus forming a hollow in the upper side of each 
(fig. 39). Into this rapidly deepening cavity, there pushes out 
from the receptacle a rounded mass of cells (fig. 40). The 
apical part of the pistil grows very rapidly until the laminae 
connecting it with the receptacle at each side of the ovular out- 
growth are in sucha position that their edges are nearly vertical. 
The ovule continues to elongate and curve towards the bottom 
of the pistil, eventually gaining a position in which its apex is 
directed downwards. During this process the nucellus has 
become differentiated and the two integuments have appeared. 
The funiculus has also been clearly distinguished (figs. 47, 42, 
43). Up to the time of fertilization there has been no organic 
connection between the edges of the two laminae, although for 
a little while they have been in contact for a part of their dis: 
tance. At the time of pollination there is still an opening 
between the laminae at the bottom of the line of meeting. This 
is due to the fact that the laminae arise with enough distance 
between them to allow for the formation of the ovule. Now, 
when their margins approach each other they are separated 
furthest at the bottom and require a longer time to come fully 
together (fig. 44). Inthe mature pistil the funiculus. is long 
and ascending, carrying the ovule well up into the cavity of 
the pistil. In the young pistil the funiculus is short, and it Is 
