44 



PISTILS AND STAMENS 



are three main structures involved in this development : (1) the 

 fertilized egg; (2) the fertihzed primary endosperm nucleus; 

 and (3) the parts of the ovule surrounding the embryo sac. 

 The development of each of these parts into their respective seed 

 parts takes place simultaneously. The fertilized egg becomes 

 the embryo, the endosperm nucleus has to do with the forming 

 of the endosperm, and a part of the surrounding portion of the' 

 ovule becomes the seed coat. Figure 52 shows a Tomato ovule 



Fig. 53. — A young ovary of Corn just after fertilization and a mature 

 ovary or kernel, both of which are sectioned lengthwise and the relation of 

 parts indicated. A, lengthwise section of the young ovary showing nucellus 

 in), egg (e), endosperm nucleus (ere), integuments (i), ovary wall {w), and 

 base of style (6). B, the lengthwise section through the kernel showing the 

 embryo {em), endosperm (end), seed coat (c), ovary wall {w), and the base 

 of the style (6). The dotted lines indicate the parts of the ovule from which 

 the different parts of the kernel have developed. 



in which the egg and endosperm nucleus have just been fertilized 

 and also shows the seed which develops from the ovule. The hues 

 indicate the parts of the ovule from which the different parts of 

 the seed have come. Study Figure 53 showing the development 

 of the ovule of Corn into a seed. Point out the different parts of 

 the kernel and the part of the ovule from which they came. 

 Notice that the heavy outer covering of the kernel is the ovary 

 wall, and does not come from the ovule. A kernel of Corn is a 

 seed closely jacketed by the ovary wall. Copy on a sheet of 



