40 ELEMENTARY BOTANY 
shows the ovules attached to the centre, but the walls of the 
carpels are entirely disconnected with the placenta; the 
placentation is then described as free central, in order to 
distinguish it from axile placentation, in which the placenta 
is connected with the wall of the ovary. 
In the sweet pea, the ovules are borne alternately by the 

Fig. 40.—Dock (SEcTION Tic. 41.—CARPELLARY LEa¥F 
- or FRvit). OF PINUS. 
p.l, perianth leaves (per- 0, ovule. 
sistent) ; , wall of ovary ; 
st, style ; 0, basal ovule. 
margins of the carpel, where they unite ; this is the form of 
parietal placentation known as marginal. (Plate LV., Fig. 71.) 
‘An ovule may be attached to the floor of the ovary, as in the 
~ dock (Fig. 40), the placentation is then basal, or it may hang 
from the roof, and is then said to be pendulous. (See Fig. 44.) 
In one group of Flowering Plants the ovules are not enclosed 
in an ovary, but are naked on the sporophyll. This is well 
seen in the Scotch fir (Pinus). 
