374 



FOURTH GROUP. SEED-PLANTS. 



flower, as in the Ranunculaceae, Magnoliaceae and some other families, the portion of 

 the axis which bears them is usually elongated, in Myosurus, for instance, very 

 considerably elongated, and their arrangement is spiral. The monomerous ovary 

 when first formed is always unilocular, but it may subsequently become plurilocular 

 by luxuriant growth of the inner surface of the carpel forming ridges which divide 

 the cavity longitudinally, as in Astragalus, or transversely, as in Cassia fistula. Such 

 ovaries may be termed monomerous with false loculi or spurious dissepiments, but 

 ought not to be called polymerous. 



A polymerous ovary is in all cases produced by the union of all the carpellary 

 leaves of a flower, which are usually formed two, three, four or five together in a whorl, 

 in the centre of which is the apex of the floral axis. If the several carpels remain 

 open and cohere in such a manner that the right margin of one carpel unites with the 

 left margin of the adjoining carpel, the result is a unilocular polymerous ovary; 



FIG. 305. Dictamnus Fraxinella. A young flower-bud after appearance of the sepals s. B older bud after ap- 

 pearance of the petals p. C still older with the rudiments of the five stamens a between which five other stamens a' 

 have begun to be formed, three being already visible ; b the bract, b' the bracteole. D to H development of the ovary 

 ./ ; sk the ovules, gp the gynophore, g the style. 



such an ovary has parietal placentas, if the coherent margins project only a little 

 inwards, as in Reseda, Viola, &c. ; but if the margins project farther inwards, the cavity 

 of the ovary becomes plurilocular, but the compartments are open in the centre 

 towards one another, as in Papaver, where the incomplete partition-walls are covered 

 on both sides with numerous ovules. A bilocular or plurilocular polymerous ovary 

 is formed when the carpels push their lateral margins so far into the cavity of the 

 ovary that they meet or cohere in or about its axis, and to this the elongated floral 

 axis in the centre often contributes. There are variations in the mode in which the 

 carpels cohere to form a plurilocular ovary, according as their inflexed margins 



