398 AURANTIACE^E, OR ORANGE TRIBE. 



more. It is also due to certain qualities in the fruit itself, which 

 allow it to be kept for a considerable time, with less alteration 

 than fruit of any other kind. Of these qualities, one of the most 

 remarkable consists in the thick spongy rind, which resists 

 changes of temperature by its non-conducting power ; and in the 

 large amount of minute oil-receptacles by which the surface is 

 occupied, the contents of which almost entirely prevent the 

 evaporation of the watery fluid within, and, by their acridity, 

 resist the attacks of insects, &c. from without. Hence internal 

 decay is the only accident by which oranges are liable to be 

 destroyed ; and this does not happen for a long time, if the rind 

 remains uninjured, so as completely to exclude the air from the 

 interior, and if they are well ventilated, and kept free from 

 moisture, which would cause the exterior to decompose. 



564. If we examine any plant of the Orange tribe, grown 

 in a hot-house in this country, or in the open air in its native 

 clime, we may at once observe that it has a peculiar aspect, in 

 consequence of the surface of its leaves being covered with minute 

 yellowish dots. These dots are little receptacles for secretion, filled 

 with an essential oil very fragrant to the smell, though acrid to 

 the taste ; the leaves possess some fragrance in their natural 

 state, but, if they be crushed between the fingers, this is very 

 much increased, part of the receptacles being then ruptured. 

 These little cavities exist not only beneath the surfaces of the 

 leaves and fruit, but also in the leafy parts of the flower, which 

 owes most of its fragrance to them. On further examining the 

 leaves, it will be observed that they are articulated or jointed at 

 the junction of the blade with the petiole, and that the latter is 

 expanded (more or less in the different species) into a sort of 

 small supplementary leaf, by the development of a narrow blade 

 from each side. In some species the leaves are pinnate ; and 

 it occasionally happens that the leaflet of one side only is deve- 

 loped, or that even both are absent ; so that the petiole, which is 

 then much enlarged, has to perform the functions of the true 

 leaf, as in some other cases (. 228). The calyx has the shape of a 

 cup, being formed of five sepals (in some species only three) 

 united at their lower portion, and separating above into as many 



