FLOWERING PLANTS INTRODUCTORY 99 



a sharp knife and examined through a lens (Fig. 53, B). It will then 

 be clear that all these parts are borne laterally on the flower- 

 stalk, i.e. that they stand in the same relation to this as leaves 

 to the stem. The slightly widened, conical end of the flower- 

 stalk to which the floral leaves are attached is known as the 

 receptacle of the flower. As contrasted with the ordinary vegeta- 

 tive shoot, growth usually stops with the production of the 

 floral leaves, and the latter are not separated by internodes. 



The outermost series of floral leaves consists of five narrow 

 green structures, the inner face of which is concave and smooth, 

 while the outer surface is clothed with long whitish hairs. These 

 parts are more obviously leaf-like than the other parts of the 

 flower. They are called the sepals, and together form the region 

 of the flower known as the calyx. When the flower is young, 

 in the condition of 

 a bud, the sepals are 

 closely overlapped, 

 and completely en- 

 close and protect 

 the more delicate 

 parts within. Those A B 



edges Of the Sepals FlG> 53> _ F i ower O f Buttercup. A, whole flower ; B, flower 

 Which were thus cut in half. (After Baillon.) 



covered over can be 



distinguished by their thinner texture and yellow colour. When, 



as is the case with the sepals of the Buttercup, a number of leaves 



are borne at the same level on the stem they are said to form a 



whorl. 



The five conspicuous yellow leaves, which come next within 

 the calyx, are called petals, and together make up what is known 

 as the corolla. The petals also form a whorl, and stand higher 

 on the floral receptacle than the calyx. As is usually the case, 

 where the number of parts in the succeeding whorls is the same, 

 the five petals do not stand immediately above the five sepals, 

 but above the intervals separating the latter. The petals are 

 said to alternate in position with the sepals. The petals are the 

 parts which give the flower its prominent and attractive appear- 

 ance. Though flat and leaf -like in shape, they are very unlike 



