Morphology of the Citrus. 191 



The transformation of the oil-cells of the citrus rind 

 into the vesicles of the pulp would be no more difficult 

 to understand than the transformation of the mandibles 

 of the caterpillar into the sucking apparatus of the moth, 

 which may be several inches long, and, in one case, 

 probably more than a foot long. 



In plants the same organ is now fashioned into 

 leaves for purposes of breathing and digestion, then 

 turned into petals and sexual organs, and so forth. 



To sum up, my view of the matter is this. The 

 pulp consists of a series of pods or carpels,* folded on 

 themselves and placed side by side, and imperfectly 

 agglutinated together, so that each pod is easily sepa- 

 rated from its neighbours. These carpels have their 

 seed edges or crenations turned towards the centre of 

 the fruit, with seed buds developing from the abortive 

 axillae of their abortive crenations. Sometimes the 

 pulp carpels remain open towards the centre, or are 

 burst open by the expansion of the juice cells like 

 those of the turunj in pi. 152, fig. b, and others, but 

 usually the two edges are united together and form 

 a regular closed pod, like those of most oranges and 

 lemons. The contained juice vesicles then I look 

 upon as transformations of the oil cells of the rind 

 carpels and homologous with them, and with the oil 

 cells of the leaves and bark. 



In studying the relationship between the juice vesi- 

 cles and the rind oil-cells, I have endeavoured to 

 find support for Risso's theory that the shape of the 

 oil-cells of the rind (or their openings) was " en rap- 

 port " with the quality of the juice in the pulp. At 

 page 24 he says : " Nous avons les premiers remarque 



* I have tried to explain elsewhere one way by which their number 

 might have been increased. Vide pis. 223 and 224, and also Appen- 

 dix, No. 62. 



