148 ELEMENTS OF BOTANY. 
three-celled ovary, seen in cross-section. The ovules are not 
borne indiscriminately by any part of the lining of the ovary. 
In one-celled pistils they frequently grow in a line running 
along one side of the ovary, as in the pea pod, Fig. 176. The 
ovule-bearing line is called a placenta; in compound pistils 
there are commonly as many placentas as there are separate 
pistils joined to make the compound one. Placentas on the 
wall of the ovary, like those in Fig. 132 A, are called parietal 
placentas ; those which occur as at B, in the same figure, are 
Silene 
Sf. Sere ee 
OU, Sees S 
Fic. 125. — Tubu- Fic.127.— Parts Fic. 128.— Parts of the 
lar Corolla,from Fic. 126. — Labiate of a Stamen, Pistil. 
Head of Bache- orRingentCorolla a, filament; 5, ov., ovary ; sty., style; 
lor’s Button. of Dead Nettle. anther. stig., stigma. 
said to be central, and those which, like the form represented 
in C of the same figure, consist of a column rising from the 
bottom of the ovary, are called free central placentas. 
185. Union of Separate Circles. —'The members of one of 
the circles of organs of which the flower is composed may 
join each other or become adnate, adherent, or consolidated. 
In Fig. 117 the calyx-tube is adnate to the ovary. In this 
case the parts of the flower do not all appear to spring from 
the receptacle. Fig. 133 illustrates three common cases as 
regards insertion of the parts of the flower. In I they are 
