Chapter 6 



THE GYNOECIUM 



The ovule-bearing organs of the flower, the carpels or megasporo- 

 phylls, make up the gynoecium. They range in number from many to 

 one and, in arrangement, from spiral to whorled. The carpels may be 

 free from fusion with one another — the gynoecium apocarpous — or 

 connate in various degrees — the gynoecium sijncarpous. In the early 

 decades of die twentieth century, the term coenocarpous has been ap- 

 plied by some authors to gynoecia with connate carpels that ai-e several- 

 chambered, with axillary placentae; and the term paracarpous to syn- 

 carpous gynoecia with a single chamber and parietal, basal, or free 

 central placentation. This distribution has morphological value, but 

 paracarpy has perhaps arisen in more than one way: by phylogenetic 

 union of open carpels, and by modification of coenocarpic gynoecia. A 

 line between apocarpy and syncarpy is difficult to draw, because fusion 

 may be slight and even developed late in ontogeny. Syncarpy is dis- 

 cussed later in this chapter. 



The gynoecium perhaps shows more simply than the androecium 

 and the perianth the major changes in the evolution of the flower. 

 Especially prominent are the advances from spiral to whorled arrange- 

 ment, from free to fused members, and from many to one which is 

 pseudoterminal. 



Numerous spirally arranged carpels characterize rather few families 

 — Magnoliaceae, Annonaceae, Eupomatiaceae, many of the Ranuncula- 

 ceae and Rosaceae; usually apocarpous, they may become syncarpous in 

 fruit — Annonaceae. Gynoecia with few, spirally arranged carpels are 

 few, but, in syncarpous forms, the spiral arrangement may be de- 

 terminable only anatomically — Berheris. The flower of Scheuchzeria 

 has been cited as an example of the spiral placing of a few carpels, but 

 this "flower" is perhaps an inflorescence. Spiral arrangement is difficult 

 to determine in gynoecia with only two carpels, but, in these gynoecia, 

 one carpel overtops the other — Jeffersonia, Epimeditim. Oblique adna- 

 tion to the receptacle by individual carpels brings about "false coeno- 

 carpy," a type of union difficult to determine morphologically, because 

 distinction must be made between the tissues of the receptacle and 

 those of the carpels. False coenocarpy is discussed further under 

 Syncarpy. Reduction of fertile carpels to few and to one is common. 



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