Morphology of the Citrus. 207 



also a trifoliate leaf. In the Feronia elephantum 

 and Limonia acidissima, we see still more compound 

 leaves ; vide pi. 244, figs, b and c, and pi. 245, figs, a, b y 

 and c. 



Moreover, in more than one instance in seedling 

 citrus which I grew, trifoliate leaves were developed 

 among the secondary leaves ; vide pi. 246, figs, d, e, f 



The leaf stalk of the citrus varies from a wingless 

 short petiole, like that of the Malta lemon (fig. a, pi. 

 181), to the enormous wings of the C. hystrix (fig. d, 

 pi. 225). In many cases, the winged petiole of the 

 latter is larger than the blade of the leaflet, such as is 

 shewn in the same figure. 



The leaflets of the citrus are emarginate. Even if 

 the general shape be acuminate, they usually have an 

 emarginate point, a mere indentation at the tip. Not 

 impossibly this indentation has a meaning. 



Had the remote ancestors of the citrus simple or 

 compound leaves ? In the embryology of the verte- 

 brata it has been found that, up to a certain point, the 

 embryos so resemble each other that they are practically 

 indistinguishable. Afterwards they become differen- 

 tiated, and each species progresses in its own way. 



The embryology of the citrus leaves can possibly be 

 studied in the primary and secondary leaves of its 

 seedlings after germination, and also, perhaps, in the 

 first leaves of each branch. They are different from 

 the typical leaves of the adult tree. 



The cotyledons of the citrus in germination remain 

 under ground. In all, the first pair of leaves that show 

 themselves above the ground are opposite and have no 

 sign of joint between the petiole and the blade, and no 

 sign either of margins or wings on the petiole. In 

 many citrus, the first three or four leaves are also 



