Bree te The External Form of Plants. ‘AAS | 
(Fig. ae In a few cases the whole of the interior wall of 
the ovary or of the loculi serves as a placenta, as in the 
poppy ; or a single placenta stands in the centre of the un1- 
locular ovary like a column, as in Primulacez [when the 
placentation is free central]; more often certain portions of 
the inner walls of the loculi, corresponding in number to the 
carpels and often projecting, bear the ovules, and are then 
called parietal placentee [as in Viola or Rzbes| ; |or the ovules - 
are attached to the common axis of all the loculi of a multi- 
| locular ovary, as in the apple or /77zs, 
when the placentation is axzle.| As re- 
spects the mode of attachment of the 
ovules to the loculus, they may be either 
erect, |lateral|, or pendulous. 
Fic. 299.—Ovary of the Fic. 300.—I. Orthotropous ; II. anatropous ; III. cam- 
ash ; the single seed at- pylotropous ovule; @ nucleus with the embryo-sac 
tached toa long funicu- coloured dark ; 4 primine ; c secundine ; de chalaza; 
lus, and still enclosed in J micropyle (represented diagrammatically). 
the ovary ; A, adetached piece of the wall of the ovary. 
If a section is made through the longer axis of an ovule, 
and the surfaces examined under a magnifying-glass, it is 
seen that the ovule consists of a [cellular] muceus (Fig. 
300 a) enclosed in a single or more usually in a double coat 
or zutegument (b,c), [the outer coat being designated the 
primine, the inner coat the secundine|. At the apex of the 
ovule is a small orifice through the integuments, called the 
micropyle or foramen ; [and in the interior of the nucleus 
is a large cell called the embryo-sac|. With regard to their 
form, ovules may be classified into three kinds—the ortho- 
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