536 



THE DICTIONARY OF GARDENING, 



Ovary continued. 



that of a leaf, and the arrangement of the veins is 

 readily seen to be similar in both. Along the back of 

 the pod (dorsal suture) is a large vein, corresponding to 

 the midrib of the leaf, and along each half of the 

 placenta runs a vein, corresponding to the marginal 

 arched veins in leaves, but strengthened to give a 

 branch to each ovule. The carpel is seen, in the Pea, to 

 be situated nearer the tip of the receptacle than is any 

 other part of the flower. The carpels of Actcea (see A, 

 Fig. 791), and of Pceonia (see B, Fig. 791), show a very 

 similar cross section to the pea-pod. 



The pea-pod may be taken as an excellent example of 

 a carpel in which the Ovary is quite typically formed, 

 and remains so throughout its growth; but this simple 

 structure of the carpel is widely departed from in various 

 ways, and it is necessary to look now at some of the 

 less typical forms to ascertain to what extent they 

 differ from it. 



1. In most plants the pistil is made up of two, or 

 more, carpels. These may be, as in Pceonia. and 

 Ranunculus, free from one another down to the base, 

 or they may be united to any extent, from near the 

 base almost, or altogether, to the top of the Ovary, 

 and even the styles and stigmas may be completely 

 united to each other. The Ovaries may be united only 

 by their outer surfaces, each being closed, and remaining 



FIG. 792. (A) CROSS SECTION OF OVARY IN FLOWER OF GOOSE- 

 BERRY, formed of two Carpels, joined near their edges, the 

 edges themselves being turned inwards to form the Pla- 

 centae. (B) CROSS SECTION OF YOUNG OVARY OF POTATO, 

 formed of two Carpels meeting in middle, and completely 

 united into one mass, with axillary Placentae. 



distinct from the rest internally, or they may open 

 into a central space common to all. The ovules may be 

 borne along the edges of the neighbouring Ovaries, 

 either on projecting upright plates, e.g., Poppy, or in 

 rows along the inside of the wall of the Ovary, as in 

 Gooseberry. In all these cases, it is easy to recognise 

 that the compound Ovary is really made up of as many 

 simple Ovaries as there are placentae, and that the 

 ovules are borne on the edges of the Ovaries. This 



FIG. 793. THREE CROSS SECTIONS FROM OVARY OF HYPERICUM 

 HIRSUTUM, to show transition in the three united Carpels, 

 from marginal Placentae in A to axillary Placenta; in C. A 

 is from upper part, B from near middle, and C from base of 

 Ovary. 



will be better understood by a reference to Figs. 792, 

 793, and 794. In all fresh Ovaries, cross sections prove 



Ovary contin ued. 



most instructive for study. In the Primrose and its 

 allies, there occurs what is known as free-central 

 placentation ; i.e., the Ovules are borno on a head 



FIG. 794. CROSS SECTION OF OVARY OF FI.OWKR OK IRIS, showing 

 three Carpels joined at centre into a mass, in which three parts 

 are clearly traceable, each formed of two united Placenta 1 , 

 each of which bears an Ovule. 



(placenta), which looks like a direct growth upwards of 

 the receptacle; and the carpels form only a covering to 

 the head and ovules, which latter do not adhere 



FIG. 795. CROSS SECTION FROM OVARY OF PRIMROSE FLOWER. 

 The Carpels are completely united, and form a ring in the 

 section, quite separate from the free central mass of Placentas 

 on which the Ovules grow. 



to any part of them (see Fig. 795). It is not pos- 

 sible here, in the flower, to tell the number of carpels 

 that unite to form the Ovary, though the number may 



FIG. 7%. CROSS SECTIONS OF OVARY OF RED CAMPION (LYCHNIS 

 DIURNA) A, from Flower, showing tive Carpels, joined, as in 

 Iris, into a central mass bearing the Placentae, the various 

 Carpels of which are indicated by the dark lines ; B, from half- 

 grown Ovary, showing central mass bearing Ovules apparently 

 free, as in the Primrose (remains of broken partitions are 

 seen ; otherwise as in A). 



be inferred. In Lychnis (see Fig. 796), and other Caryo- 

 phyllece, the structure is almost like that of the Prim- 

 rose in the mature flower ; but it is possible to trace a 

 connection, at a very early stage, between the placenta? 

 and the carpels; and this connection, and the number of 

 carpels, are indicated by lines radiating from the middle 

 of the central mass ; and the number of rows of ovules 

 also indicates the number of carpels. The shape of the 

 Ovary, when made up of two or more carpels, usually 

 depends on the number that form it, and is best seen 

 in a cross section of the Ovary made when fresh. 



2. Care must be taken not to confound, with truly 

 compound or united Ovaries, a condition sometimes met 

 with e.g., in Astragalus (see Fig. 797), with a simple 

 carpel, and in Flax, with the Ovary composed of several 

 united carpels in which each carpel is divided, or 

 nearly so, into two cavities, lengthwise, by a partition, 



