MOKPHOLOGY OF EEPEODUCTIVE OEGANS 149 



ovules are not developed upon the carpellary leaves, the thala- 

 mus becomes prolonged into the cavity of the ovary and forms 

 the placenta {fig. 438). At other times the thalamus becomes 

 prolonged beyond the ovary, as in the Geraniaoeffi and Um- 

 belhferse ; this prolongation is terraed a carxoophorc . In the 

 species of Geranium (fig. 443, c), this carpophore forms a 

 long beak-hke process, to which the carpels, car, are attached, 

 and from vifhich they separate when tlie fruit is ripe. In 

 many cultivated flowers, as in the Rose, the thalamus some- 

 times acquires a monstrous development, and becomes extended 

 beyond the flower into a branch bearing foliage leaves fig. 279). 

 To this prolongation of the axis beyond the flower the term 

 median prolificat Ion is usually applied. 



In some plants the last internode of the thalamus becomes 

 elongated and forms a stalk to the ovary, to which the term 

 gynopliore has been applied ; this sometimes happens also 

 between the perianth and the sporopliylls. Examples may 

 be seen in some of the Capparidacese (fig. 280, thai) ; in the 

 Pink {fig. 405, g), Dictamnus {fig. 427, g), and Xanthoxylon 

 {fig. in, g). 



Sometimes the thalamus presents certain modifications of 

 form which are seen between the floral whorls. They are due 



Fia. 281. Fig. 282. 



Fi(/. 281. Tflo\veroithe'Feraiel(^Fi<-'/iictiIumcapiUacenm). The ovarj' is sur- 

 mounted by a disc, d. Fig. 282. Flower of the Rue (Ruta graveolens). 



The pistil is surrounded by a disc iu the form of a fleshy hypogynoiis ring, 

 ou the outside of which the stamens are inserted. 



to changes in particular internodes, and generally occur above 

 the perianth leaves. Any such modification of the thalamus is 

 known as the disc. Under this term we include all bodies of 

 whatever form, except sporophylls, which are situated on the 

 thalamiis between the calyx and gynoecium, or which are upon 

 or in connection with either of these organs, but which cannot 

 be properly referred to them. 



The disc is developed in a variety of forms ; thus, in the 



