Morphology of the Citrus. 183 



are at certain distances from each other, and that the 

 intermediate spaces are filled with smaller and smaller 

 oil cells. What the object or origin of these three or 

 more sizes of .oil cells can be, I do not know, but this 

 I know, that every leaf of every kind I have examined 

 has this peculiarity, and it is repeated in the edge of 

 the leaf, the large oil cells occupying the angles 

 between the large crenations, and the smaller ones, 

 those between the small crenations. It is curious to 

 note that in the rind of many citrus fruits, a similar 

 disposition of large and small oil cells is maintained.- 

 This might be taken as another proof that the rind 

 consists of modified leaves called carpels. Fig. a, pi. 

 1 8 1, shows a new and fully developed leaf of the Malta 

 lemon, full size, thin and transparent. There are on 

 this sketch three sizes of dots, indicating the relative 

 positions of the different sized oil cells. The largest 

 sized ones were less numerous along the midrib. The 

 crenations, large and small, are exact copies of the 

 original, and they also show the three sizes of oil 

 cells. 



The outer, or rind surface of a citrus fruit often 

 resembles that of a lump of dough, studded with large 

 and small pinholes* It is interesting to note that in 

 cases of large fruit, where the oil cells have plenty of 

 space to develop in, the three sizes are distinct, the 

 larger depressions corresponding to the larger oil 

 cells, the smaller depressions corresponding to the 

 cells of the second magnitude, and those of the third 

 magnitude are represented by little miliary eminences. 

 In short, a longitudinal section of any part of the 

 rind would very closely, in many cases, resemble 

 the edge of the leaf of the Malta lemon given 



* If the reader will substitute " foveoli " for pinholes^ he will have 

 their botanical term. 



