ESSENTIAL ORGANS — THE PISTIL. 



239 



Fig. 416. 



Fig. 417. 



while the margins of the outer rows are arranged on the back of the 

 inner ones ; if the receptacle is convex, the outer carpels are lowest, as 

 in the Strawberry; if concave, the outer 

 ones are uppermost, as in the Eose. 

 At other times the carpels are united, 

 as in the Pear, Arbutus, and Chick- 

 weed, so that the pistil becomes syn- 

 carpous (eiiv, together or united). In 

 Dictamnus Fraxinella (fig. 416) five 

 carpels unite to form a compound pis- 

 til. In Scilla italica (fig. 283) the o^ 

 three carpels form apparently only one ; 

 but on examination it will be found 

 that the pistil consists of three carpels 

 alternating with the three inner sta- 

 mens. The union, however, is not al- 

 ways complete ; it may take place by 

 the ovaries alone, while the styles and 

 stigmata remain free, the pistil being then gamogastrous {yd(Mi, union/ 

 and yaSTn^, ovary) ; and in this case, when the ovaries form apparently 

 a single body, this organ receives the name of compound ovary ; or the 

 union may take place by the ovaries and styles, 

 while the stigmata are disunited ; or by the 

 stigmata and the summit of the style only (fig. 

 414). Various intermediate states exist, such 

 as partial union of the ovaries, as in the Eue, 

 where they coalesce at their base ; and partial 

 union of the styles, as in Malvaceae (fig. 417). 

 The union is usually most complete at the 

 base ; but in Labiatse the styles are united throughout their length, 

 and in Apocynacese and Asclepiadacese the stigmata only. 



When the union is incomplete, the number of the parts of a com- 

 pound pistil may be determined by the number of styles and stigmata 

 (fig. 417 s) ; when complete, the external venation, the grooves on 

 the surface, and the internal divisions of the ovary, indicate the 

 number. When the grooves between the carpels are deep, the ovary 



Fig. 416. Portion of the pistil of Dictamnus Fraxinella. Two of the five carpels have 

 heen removed in order to show how the styles, s, produced on the inner side of the carpels, 

 and at first distinct, approximate and become united into one. o. Ovaries, two of which 

 ia front show their dorsal surface, d, and their lateral surface, I. At the hase of the 

 gynophore, g, are seen the cicatrices, c, marking the insertion of the calyx, the petals, and 

 the stamens. Fig. 417. Pistil of Malva Alcea. o, Nine ovaries, united so as to form one. 

 *, Column formed by nine styles united to near their summit, where'they diverge and separate. 

 Bach of the divisions of the style is terminated by a stigma, s. Fig. 418. Horizontal 

 section of the four-celled {qiiadrilocndar or tetratliecaT) ovary of Fuchsia coceinea, c c cc^ 

 Wall of the ovary, which is formed by four carpellary leaves, a, Quadrangular axis to which 

 the carpels are united, o. Ovules attached to the inner margin of the carpels. 



