O ELEMENTS OF STRUCTURAL BOTANT. 



in colour. Each of these is called a sepal, and the five 

 together form the calyx of the flower. If you look at 

 a flower which is a little older, you will probably not 

 find any sepals. They will have fallen off, and for this 

 reason they are said to be deciduous. So, in like manner, 

 the leaves of most of our trees are deciduous, because 

 they fall at the approach of winter. You will find that 

 you can pull off the sepals one at a time, without dis- 

 turbing those that remain. This shows that they are 

 not connected together. They are therefore said to be 

 free, and the calyx is described as polysepalous. 



Inside the circle of sepals there is another circle of 

 leaves, usually five in number, bright yellow in colour, 

 and much larger than the sepals. Each of them is 

 called a petal, and the five together form the COFOlla of 

 the flower. Observe carefully that each petal is not in- 

 serted in front of a sepal, but in front of the space be- 

 tween two sepals. The petals can be removed one at a 

 time like the sepals. They, too, are free, and the cor- 

 olla is polypetalous. If you compare the petals with one 

 another, you will see that they are, as nearly as possible, 

 alike in size and shape. The corolla is therefore regular. 



6. We have now examined, minutely enough for our 

 present purpose, the calyx and corolla. Though their 

 divisions are not coloured green, like the ordinary leaves 

 of the plant, still, from their general form, you will have 

 no difficulty in accepting the statement that the sepals 

 and petals are in reality leaves. It will not be quite so 

 apparent that the parts of the flower which still remain 

 are also only modifications of the same structure. But 

 there is good evidence that this is the case. Let us, 

 however, examine these parts that remain. There is 



