106 THE PISTILS, OB GYNO3CIUM. 



520. THE PLACENTAE are usually prominent lines or ridges extending 

 along the ventral suture within the cell of the ovary, and bearing the 

 ovules. They are developed at each of the two edges of the carpellary 

 leaf, and are consequently closely parallel when those edges are united, 

 forming one double placenta in the cell of each ovary. 



521. THE SIMPLE CARPEL, with all its parts, is completely exemplified in the pea- 

 pod. When this is laid open at the ventral suture, the leaf form becomes manifest, 

 with the peas (ovules) arranged in an alternate order along each margin, so as to 

 form but one row when the pod is closed. In the pod of columbine the ovules form 

 two distinct rows : in the simple plum carpel each margin bears a single ovule, and 

 in the one-ovuled cherry only one of the margins is fruitful. 



522. THE STIGMA is the glandular orifice of the ovary, communicat- 

 ing with it either directly or through the tubiform style. It is usually 

 globular and terminal, often linear and lateral, but subject to great va- 

 riations in form. It is sometimes double or halved, or 2-lobed, even 

 when belonging to a single carpel or to a simple style, as in Linden, 

 where these carpels are surmounted by three pairs of stigmas. 



523. THE COMPOUND PISTIL consists of the united circle of pistils, 

 just as the monopetalous corolla consists of the united circle of petals. 

 The union occurs in every degree, always commencing at the base of 

 the ovary and proceeding upward. Thus in columbine we see the car- 

 pels (pistils) quite distinct ; in early saxifrage cohering just at base ; in 

 pink as far as the top of the ovaries, with styles distinct ; in evening 

 primrose to the top of the styles, with stigmas distinct ; and in Rhodo- 

 dendron the union is complete throughout. 



SS7, Ovary (follicle) of Larkspur, composed of single carpeKary leaf. 388, Ovaries of the Col- 

 umbine, five, contiguous but distinct 3S9, Compound ovary of Ilypericum, of carpels united 

 below with distinct styles. 390, Ovary of another Hyperictim of three carpels completely united. 

 391, Ovary of Flax ; carpels five, united below, distinct above. 392, Dianthus (Pink). ' 393, 

 Saxifraga. 



524. To DETERMINE THE NUMBER OF CARPELS in a compound ovary 

 is an important matter. It may be known, 1, by the number of styles ; 

 2, by the number of free stigmas (remembering that these organs are 

 liable to be halved, 522) ; 3, by the lobes, angles, or seams of the 

 ovary ; 4, by the cells ; 5, by the placenta. 



