330 THE .TOT'RXAL OF T30TAXT 



It is siio^gested that a more natural division into sections, founded 

 on constant morphological and functional characters, ^vould be as 

 follows : — 



A. Eusrj)al(P. 



Outer divisions of perianth sepaloid, ?. e. firm and rather rigid in 

 texture, green in colour, ])rotective in function. 



E. Pseudo-pefaliB. 



Outer divisions of perianth petaloid, ?'. e. thin and translucent in 

 texture, brightly coloured or white, and having as their object the 

 attraction of insects for the fertilization of the flower. 



IVrhaps the reason why some such arrangement has not been 

 adopted long ago is that it is so obvious. There is a not unnatural 

 tendency to regard the obvious as superficial, and to look for dee])er 

 characters. Probably it was assumed that the differences in the 

 sej)als* of the two sections were only a question of colour, and 

 therefore of no account : hence their inward meaning and importance 

 were overlooked, or not fully ap])reciated. I hope to show that they 

 are deep, and go to the root of the matter. 



The difference between the two sections is first of all a morpho- 

 logical one, analogous to that which exists between a typical calyx 

 and a typical corolla. Take, for instance, the calyx and corolla of 

 Rosa canina. Both no doubt are modified leaves, but they have been 

 modified in different directions, and have become differentiated to 

 such a degree as to be structurally distinct. So it is also in the case 

 of the two sections of Opliri/s. The sepals in the first section have 

 retained their original form. They are true sepals, comparativeh'- 

 thick and firm in texture, more or less rigid and semi-opaque, rich in 

 chlorojilndl, and so to speak built for strength and resistance to 

 weather. In the Pseudo-petahe, on the other hand, they have been 

 carried to a more advanced stage of development. A higher note has 

 been struck : a still higher purpose is in view. So we find them fine 

 and thin in texture as the petal of a rose ; translucent, so that the 

 sunlight shining through them may light up the brilliance of their 

 colour ; with no chloro])hyll except on the midrib or nerves which 

 strengthen their delicate expanse. The dull green of the sepal has 

 given ])lace to the colours of a corolla. They are clearly designed for 

 beauty and attractiveness, rather than for protective purposes, and 

 have been raised to the dignity of a higher plane in the evolution of 

 the flower. 



Secondly, the difference between the two sections is a functional 

 one. The main object of the sepals is to protect the young and 

 tender corolla from injury before expansion. This is well seen in the 

 ])oppies, in which the calyx is deciduous, and falls off as soon as this 

 service is accomplished. Similarly their function in the Eu-sepalae is 

 to envelop the unexpanded bud in a protective covering impervious to 

 weather, and later on to give shelter from rain or excessive sunshine 

 to the essential parts of the flower, the anther and the stigma. For 

 tliis reason the up]jer sepal arches over the column, and the lateml 



* The term sepal will be used liereafter instead of the conventional " outer 

 divisions of the i)erianth '" for the sake of brevity and clearness. 



