4, ab 
STRUCTURE OF ‘THE FRUIT. 53 
‘one carpel' only. If this is split open a row of ovules is seen 
along one of the edges. This portion is called the ventral 
‘suture of the carpel, and represents the margins of the carpel- 
lary leaf; while the back of the pod is termed the dorsal suture, 
and represents the midrib. If you cut out a piece of paper of 
ane the form shown in the figure,* marking it 
in the manner indicated, and fold the two 
edges together, you will obtaih a rough 
model of a pea-pod, and will see that the 
_ legume is only a leaf with :the two sides 
of the blade folded together. .A ‘section 
through | this carpel > = : 
- would present some- 
thing of this appear- 
ance, In which ds re- 
presents the midrib, 
or dorsal suture, and 
vs the infolded mar- 
gins, or ventral suture. 
. , Wherever, in any _. _ 
Big. 82. Dingram- ovary, we find the Pip St Competiny 
matic figure of a ovules we have a clue mate fe 
simple carpellary. to the position of (at 
least a portion of) the ventral sutures of 
‘the carpels composing it. 
Now take three pieces of paper of a somewhat similar 
form, and, folding a thin strip of the margins inwards, fasten 
' 
ars 
ep 
(by pins ‘or otherwise) the three 
together, edge to edge. You will 
thus ‘get a rough representation of: 
such an ovary as occurs in thé violet 
‘—viz., 1-celled, with three parietal 
placente. This is clearly made up 
of three united carpellary leaves, the . ° 
placentz (vs) marking the line of 
union (or the ventral sutures) of 
two adjacent carpels; the midribs 
(ds) being half-way between these ‘Fig. 85. Transverse sec- 
points. tions of three carpellary 
__ Next take two or more large pieces reat : abe Seite 
of paper of the form originally shown, placentation. : 
‘and first make a fold at right angles : 
down the direction of the dotted lines; then fold the margins 
together as in the model of the pea. If now you fasten the 
‘ * The form best suited to shaw this is most readily ascertained by 
practice. No model cut-out of a sheet of paper can do more than show 
this structure very approximately, / 
