THE ORANGE AtfD ITS ALLIES. 169 



distinguish the bitter kind of fruit, for which we have at 

 present no more suitable title than " Seville Oranges." 



The most complete treatise on oranges which has ever 

 appeared is contained in a folio volume by Eisso, published 

 at Paris in 1818, which furnishes coloured and life-sized 

 illustrations of above 100 kinds, with a full description 

 of every variety grown. This writer was the first to re- 

 mark the curious fact that a sweet orange may always be 

 infallibly distinguished at a glance from an acid or bitter 

 one, however similar in form or colour ; the vesicles con- 

 taining essential oil being in the former always convex, in 

 the latter concave. In Limes and insipid varieties the 

 vesicles are plane, and they become more or less convex 

 or concave according as the juice of the fruit is sweeter 

 or sourer. The orange tribe, he says, too, is distinguished 

 from all other known plants by several curious physiolo- 

 gical characteristics, which appear to depend on a peculiar 

 organization ; one of its peculiarities being that the pip 

 often contains several embryos under one integument, as 

 many as three or four being found in common oranges 

 and lemons, while in a Pommeloe Gaertner counted no 

 less than 20, though the majority were imperfect. 



The seed, when planted, germinates in about 10 or 15 

 days, and develops eventually into an evergreen tree with 

 greenish-brown bark, sometimes armed with thorns on the 

 young branches, the full-grown tree often reaching the 

 height of 25 ft. The leaf is technically considered as a com- 

 pound one with but a single leaflet, being thus not reckoned 

 in the same class with such as the plum or laurel, to which 

 a casual observer would be much more likely to assign it ; 

 but, on careful inspection, it may be seen that, instead of 

 the petiole or leaf-stalk being a mere ^uninterrupted con- 

 tinuation of the mid-rib of the leaf, as with other leaves 

 of similar shape, and which constitutes their claim to be 

 called simple, in the case of the orange it is a separate 

 piece, to which the part therefore called the leaflet is 

 articulated by a distinct joint, which is the special charac- 

 teristic of what are called compound leaves.* Though in 



* See Plate V., figs. 1,2, 3. 



