10G 



SIMPLE PISTILS. 



[SECTION 10. 



305. Carpels. It is convenient to have a name for each flower-leaf of 

 the gynoecium; so it is called a Carpel, in Latin Carpellum or Cari>'ututm. 

 A simple pistil is a carpel. Each component flower-leaf of a compound 

 pistil is likewise a carpel. When a flower lias two or more pistils, these 

 of course are simple pistils, that is, separate carpels or pistil-leaves. There 

 may be only a single simple pistil to the flower, as in a Pea or Cherry 

 blossom (Fig. 271) ; there may be two such, as in many Saxifrages ; or 

 many, as in the Strawberry. More commonly the single pistil in the 

 centre of a blossom is a compound one. Then there is seldom much 

 difficulty in ascertaining the number of carpels or pistil-leaves that com- 

 pose it. 



306. The Simple Pistil, viewed morphologically, answers to a leaf- 

 blade with margins incurved and united where they meet, so forming a 

 closed case or pod (the ovary), and bearing ovules at the suture or junction 

 of these margins : a tapering upper portion with margins similarly iurolled, 

 is supposed to form the style ; and these same margins, exposed at the tip 

 or for a portion of the length, become the stigma. Compare, under this 

 view, the three accompanying figures. 



307. So a simple pistil should have a one-celled ovary, only one line of 



attachment for the ovules, a single style, 

 and a single stigma. Certain variations 

 from this normal condition which some- 

 times occur do not invalidate this mor- 

 phological conception. For instance, the 

 stigma may become two-lobed or two- 

 ridged, because it consists of two leaf- 

 margins, as Fig. 324 shows; it may 

 brcome 2-locellate by the turning or grow- 

 ing inward of one of the sutures, so as to 

 divide the cavity. 



308. There are two or three terms which primarily relate to the parts 

 of a simple pistil or carpel, and are thence carried on to the compound 

 pistil, viz. : 



VENTRAL SUTURE, the line which answers to the united margins of the 

 carpel-loaf, therefore naturally called a suture or seam, and the ventral 

 or inner one, because in the circle of carpel-leaves it looks inward or to the 

 centre of the flower. 



DORSAL SUTURE is the line down the back of the carpel, answering to 



FIG. 323. An inrolled small leaf, such as in double-flowered Cherry blossoms is 

 often seen to occupy the place of a pistil. 



FIG. 324. A simple pistil (of Isopyrum), with ovary cut across ; the inner (ven- 

 tral) face turned toward the eye: the ovules seem to be borne on the ventral suture, 

 answering to leaf-margins : the stigma above seen also to answer to leaf-margins. 



Fio. 325. Pod or simple pistil of Caltha or Marsh-Marigold, which has opened, 

 and shed its seeds. 



323 



