vir.] THE FLOWER. 75 



duction, or it may be merely a protective organ ; but 

 whatever function it is designed to fulfil in other words, 

 whatever special organ it becomes it is modified appro- 

 priately to the function which it has to perform. Thus 

 we have the nutritive leaves, broad, green expansions, 

 exposing the fluids of the plant to the influence of light ; 

 the protective leaves, hard and scale-like, as the scale- 

 leaves of leaf-buds, or more delicate, and often showy 

 and coloured, as the enveloping leaves of the flower, 

 which have an attractive as well as a protective function 

 to fulfil attractive, that is, to insects ; just as is the sign 

 of a tavern to thirsty passers-by. 



The essential reproductive leaves invariably assume 

 one of two forms, either that of the staminal leaf, with 

 the blade (the anther) thickened and its tissue partially 

 transformed into pollen, or that of the carpellary leaf, 

 which is hollow, bearing a seed-bud or seed-buds (ovules) 

 usually upon its margin inside, and terminating above in 

 a stigma. 



That this is the correct view to take of the nature of 

 the leafy organs of a plant, we have incontestable external 

 evidence to prove. And this evidence is principally of 

 two kinds. Either we find one form of leaf passing by 

 insensible gradations into another, as foliage-leaves into 

 sepals, sepals into petals, petals into stamens or we find 

 some of the leaf-organs, especially those of reproduction, 

 under certain conditions assuming the character of other 

 organs. Thus stamens, in many plants, have a strong 

 tendency to lose their character as staminal-leaves and to 

 assume that of petals, as you may find if you compare 

 a Bachelor's Button with a wild Buttercup, or a double 

 with a single Rose. There is, indeed, a Rose in which 

 all the organs of the flower, excepting the sepals, so far 

 depart from their normal character as to become small 

 foliage-leaves, all coloured green, and firm in texture. In 

 the spring-flowering Double Cherry not only are the 

 stamens nearly all represented by petals, but the carpel 

 (often two carpels) is represented by a green leaf. 



The chief difficulty in the way of accepting the notion 

 of the essential unity of type or homology of all the leaf- 

 organs of a plant rests principally on the wide dissimilarity 

 existing, in the usual condition of things, between the 



