The Morphology of Ruppia Maritima. 83 
3. Stem Structures in the Floral Region. 
Three forms coming under the category of stem are found in 
connection with the production of flowers and fruit: .(a) the peduncle, 
or the stalk of the inflorescence, (using this term in its narrower 
sense); (b) the rhachis or axis of the inflorescence, which is joined 
to the apex of the peduncle and bears the sessile flowers; (c) the 
stipe, a stalk which acquires its full development subsequent to the 
fertilization of the ovule and bears the mature fruit at some dis- 
tance from the rhachis. 
These three parts will be considered in order. 
a. Peduncle. 
(1) General Characters. 
At the time of blooming the peduncle is short, about 2.5 cm., in 
length, and is raised nearly its whole length vertically above the 
surface of the water. About the time that the pollen is shed 
and the anthers fall off, the peduncle becomes horizontal, floating 
on the surface of the water. From now on it commences to 
elongate, presumably by simple stretching of its cells, as no merist- 
ematic regions were found to prove the contrary. It elongates 
until in some cases it attains great length. One specimen I measured 
was 18.2 cm. long. Elongation takes place whether fruit is matured 
or not, and the length is apparently just as great in either case. Indeed, 
the specimen just men- 
tioned bore no fruit. The 
average length of the 
peduncle when no fruit 
was matured was 5.39 
cm. The average length 
in 80 specimens when 
ovules were matured x. 
was 49 cm. On the 
whole, therefore, the 
average length of the ex- 
tended peduncle is about 
5 cm. or about twice that 
pO 

: : eee 
at the time of flowering. a 
Figure 9.—Cross section of peduncle, showing 
at x the apparently double epidermal cells; 
ture. ep, epidermis; /a, lacunae; c, cortex; axb, axial 
Ingeneral, the anatom- bundle. >< 185. 
ical structure of the ped- 
uncle is very similar to that of the leafy stem (Text-fig. 9; Pl. VI, 
fig. 34). The following points, however, are noteworthy :— 
(2) Anatomical struc- 
