Morphology of the Citrus. 187 



importance, as the juice vesicles, for want of sufficient 

 space, must have naturally expanded in the direction 

 of least resistance. I have given them simply to show 

 that, even in their sizes, there is a certain semblance 

 of uniformity with the oil cells of the rind and leaves. 

 I have in vain endeavoured to discover whether any 

 author has treated of the morphology of the juice or 

 pulp cells of the citrus ; but all I can find about this 

 matter is the following in the " Outlines of Classifica- 

 tion, and special morphology of plants," by Dr. K. 

 Goebel ; at page 420, he says, " Allied to the berry is 

 the fruit of the species of citrus known as hesperidium* 

 the pericarp of which consists of a firm tough outer 

 layer, and a pith-like inner layer ; from the innermost 

 layer of tissue of the wall of the plurilocular ovary, 

 pluricellular protuberances are developed at an early 

 stage, which gradually fill the cavity of the loculi of 

 the ovary, as isolated closely packed succulent lobes of 

 tissue, and form the pulp."^ 



The above, of course, does not touch on their origin 

 or homology. Are they new creations, or a something 

 originally belonging to the carpel or leaf and modified 

 in course of evolution ? In the CEgle marmelos we 

 see, what I take to be homologous organs, instead 

 of becoming projections, forming depressions, with 

 their secretions poured into the common cavity of the 

 carpel, instead of being pent up in separate little 

 sacks. 



Of course my view would require that the citrus 

 fruit should have originated in two whorls of carpels, 

 the outer or rind-whorl and the inner or pulp-whorl^ 



* In the undeveloped ovary the juice-cells appear like hairs, but 

 at that stage they could not appear otherwise. 



t This I base mainly on the inner and outer rind whorls of the 

 digitate citrons. 



