So Oliver . — On the Structure , Development , 
The Flowers. 
These are borne solitary in the leaf-axils, one only as a 
rule being developed at each node. Those which reach the 
surface open normally, but many — found especially in the 
axils of the submerged leaves, occasionally also in those of 
floating ones — remain quite small and closed. These are 
the cleistogamic flowers, to be described hereafter. 
The pedicels reach a length of about 25 mm. and show 
a slight thickening at their distal end, corresponding to the 
inferior ovary, which becomes more prominent after the fall 
of the corolla. Immediately below the calyx-lobes, and 
alternating with them, are already visible rudiments of the 
five fruit-spines. These are one anterior ( a . si) and two small 
posterior tubercles (p. .?.), and a minute elevation on either 
side (l. si); these are seen in Figs. 10 and 11, which are anterior 
and posterior views of the ovary at this period. The free 
part of the calyx is inserted just above them, and is divided into 
five acute segments, with imbricate aestivation in bud. The 
outer surface of the calyx, and of the pedicel, is densely 
covered with 4-rayed epidermal glands (indicated in Fig. 16), 
similar to those on the leaves described on p. 101. The 
corolla is infundibuliform with spreading limb ; the two 
posterior lobes forming the upper, the three anterior the 
lower lip. The anterior median lobe ( a.p . Figs. 3, 4, 5) is 
inside in aestivation, the two posterior (/. pi) outside, and the 
two lateral lobes {l pi) half inside, half outside. The tube and 
lobes show a beautiful pencilling well rendered in the Figures. 
The curious stamens are inserted in the corolla-tube (Fig. 
5) and are visible at its mouth, though not projecting. The 
posterior pair (^. mi) alone are fertile, and their structure is 
interesting enough to be described. The connective has the 
form of a flat circular disc, attached to the filament in a 
peltate manner (Figs. 6 a and b are front and back views of 
a single stamen), the anther-cells being inserted at its upper 
edge, a trifle to the outer side of the median line. The cells 
are slightly divergent, with longitudinal dehiscence. In Fig. 23 
