Morphology of tJie Citriis. 201 



further decided progress could have occurred without 

 the intervention of the seed-buds. By their help, and 

 with the already enlarged oil-cells of the inner whorl, 

 we can take another step. It is easy to imagine that 

 breaks occurred, in which the enlarged oil-cells con- 

 tained first a mixture of bitter and sour juice, and 

 subsequently by further selection a sour and sweet 

 juice, or an acidless secretion. 



Figs, d and , pi. 140, show us how a further step 

 may have occurred. The free and digitate ends of 

 the carpels finally curved inwards, like closed fingers, 

 and by their cohesion, completed the outer casing of 

 the citrus. Then, after becoming further improved, 

 human selection for the sake of the pulp, completed 

 the perfect modern orange and lemon. Risso, in his 

 " fruits cornus et cornicules," gives us some idea of 

 how many experiments nature may have made, through 

 the means of the seed, before she succeeded in giving 

 us a break with the beautiful and perfect cricket-ball 

 orange we now possess. 



There must have been a stage in the descent of 

 the citrus, in which birds probably parrots have 

 played a prominent part. The colours of the lemon 

 and orange I take to be nothing but those of decaying 

 or ripening leaves. In many decaying leaves of trees, 

 first yellow and then orange hues come out, and it is 

 not impossible that the yellow-coloured citrus was 

 anterior to the orange-coloured variety. Even the 

 orange is first yellow, and then orange. Anyhow, 

 both are green like the foliage, before they take on 

 their special colours. What the brilliant crimson 

 Hibiscus, against its green foliage, or any similar 

 brilliant flower, is to the insect, the brilliant yellow 

 and red fruit is to the bird, nothing less than an 

 advertisement, and an invitation to come and taste. 



