THE FLOWER 



229 



ovules ; one, several, or even a great number as in the 

 poppy. The elongated part, the style, is occasionally 

 traversed by a canal ; but in most cases the style is solid, 

 though its tissue is porous and spongy, its cells not 

 coming into close contact with each other but having 

 spaces between them. This style ends at its apex in a 

 broadened part called the stigma, which may be flat 

 like a button, delicately branched like a feather, or in- 

 deed of almost any shape. The surface of the stigma is 

 generally covered with short hairs and secretes a sticky 

 fluid. The ovule enclosed within the cavity of the ovary, 

 if split longitudinally, presents the following structure : 

 the central part, the so-called nucellus, is surrounded 

 by a double wall, through one end of which a canal 

 passes right down to the nucellus. This canal may be 

 directed upwards, or downwards as in fig. 65. In the 

 part of the nucellus near the canal, a very big cell 

 attracts our atten- 

 tion. This cell 

 has been called 

 the embryo-sac 

 (fig. 65), because 

 it is here, as we 

 shall see later on, 

 that the embryo 

 of the plant de- 

 velops. 



Such in general 

 terms is the struc- 

 ture of these two 

 flower organs — 

 the stamen and the 

 pistil. Their most 

 essential parts are 

 the ovule, which 

 has to undergo fertilisation, and the pollen grain, by 

 which the process of fertilisation is efi^ected. 



Fig. 65. 



