BOTANICAL SUBJECTS. 351 



only Mulimfutarv, as shown in Fig. 154, an<l is not unlike the 

 nndeveloped disk, or " would-be " sheath, of the Ruta ip-aveolens 

 (Fig. 139). 



Fig. 154. Disk (f/) of Pceoru'a officinalis (Le IMaout and Decaisne). 



It is from this disk that a large number of petals in the double 

 varieties are born. In the most double then the carpels alr^o turn 

 into petals. 



It might be said that the disk of the Citrus is distinct from 

 the peel. True. But this is only in the mature flower. In the 

 young flower, as the reader will see by referring to Fig. 149, the 

 disk is really what afterwards becomes the peel (r/), while (c), 

 which is only the base of the peel, afterwards swells out into the 

 disk proper (Fig. 150, c). Therefore, the disk of the Citrus, 

 and of the Ruta, the peel of the orange, and the sheath of the 

 P. Moutan appear to be one and the same thing, that is, all 

 homologous. In other words, they are all expansions of the bark, 

 just as leaves are. It may not be difficult now to see why in 

 teratological specimens of the Citrus the peel divides into fino-ers 

 as the bark might do into leaves. 



If the reader will refer to the sheath of the P. Moutan 

 (Fig. 153), he will see that it does not difl:'er from the sheath of 

 the accompanying Tangerine orange. The one partially enclosed 

 the carpels proper, while the other entirely does so ; the style, with 

 its stigma, in the orange ordiiuirily becoming deciduous, after 

 fertilization, at the point {a) in Fig. 15G. 



I have had the opportunity of examining a hirge number of 

 flowers of Fceonia Moutan, both of the single and double varieties. 



