M. J. DECAISNE — ELOEAL ORGANOGENY OE THE PEAR-TIIEE. 47 



the month of October, that is to say, in shoots which will not be 

 developed till the following year, we find that they are ovoid, 

 sessile, scarcely as large as the head of a pin, and crowned with 

 five appendages converging towards each other, which are the 

 rudiments of the sepals. On dividing them vertically, we remark 

 at the base and on the walls of the cup which is circumscribed by 

 the nascent calyx, slight protuberances or papillae, of which five, 

 more interior and arranged symmetrically round the ideal centre 

 of the cup, are presently distinguished from the rest by their more 

 rapid development. These are the carpels, which at first are in- 

 dependent of each other, and free from any adhesion witli the 

 surrounding organs. Almost from their first appearance a slight 

 channel is marked on their interior face, an indication of the line 

 of juncture of the borders of the carpellary leaf. A little later 

 the cell or cavity which each of them forms between its folded 

 edges becomes visible, and still later two ovulary papillae are dis- 

 cernible, springing at the base of the cell from the very borders of 

 the carpel. 



" I have just said that at first the carpels are free in the receptacle 

 of which they occupy the centre ; nevertheless, when the fruit is 

 perfect, they are deeply imbedded in the parenchymatous and 

 succulent tissue of the fruit. How then does this take place, 

 which seems in contradiction with what we had observed at first ? 

 This is what I am going to explain in a few words. 



" Almost at the time that the young ovaries spring from the base 

 of the receptacle under the form of obtuse cones, a new cellular 

 tissue is produced on the walls of the receptacle, which has daily 

 become deeper and more bell-shaped. This tissue gradually 

 thickens the walls, and forms what is called the perigynal disk of 

 the flower. This new parenchym reaches presently the central 

 whorl, moulds itself upon it and agglutinates the carpels, pene- 

 trating the little interstices which are left between them. Never- 

 theless it does not completely cover them, for their interior borders, 

 those which correspond to the suture, always remain free. This 

 additional tissue is easily recognized even in ripe fruit ; it is what 

 is called the heart of the pear ; it is always situated within the 

 inclosure traced by the stony granulations which characterize the 

 fruit. I have no need to add that at the time when this pheno- 

 menon is accomplished, the summit of the carpellary cones is 

 elongated into the style, and that the disk, increased in height as 

 well as thickness, carries the stamens and the petals very for from 

 the point at which they had originated. 



