96 



inverted ovule, of which the violet is an example the ovule is 

 inverted and the stem or funicle extends the full length, as the 

 raphe (Fig. 71). 



The ovules (Fig. 72), which are borne within the ovary, are 



Fio. 71. Types of ovules; (a) orthrotropous, (6) campylotropous, (c) amphitropous, 



(d) anatropous. 



to develop into the seeds. Each mature ovule is composed of a 

 mass of cells, which is known as the nucellus, and is surrounded 

 by one or usually two integuments, which are to 

 become the seed coculs (Fig. 73). The micopyle is 

 a very small opening in the integuments through 

 which the pollen tube penetrates to the nucellus. 

 The other parts of the ovule are the chalaza, or 

 point of union between the nucellus and integu- 

 ments ; the liilum, or point where the ovule is at- 

 tached to the ovary wall by means! of a short 

 stem-like structure known as the funicle or 

 funiculus; and the raphe, which is the exten- 

 sion of the funiculus along the side of the ovule. 

 An embryo sac,* consisting of eight nuclei, 

 is formed in the nucellus near the micropyle 

 73 and 74). In the mature embryo sac the 



section of ovary show- i, i j ,1 j.i ,1 



ing developing ovules, eight nuclei are so grouped that there are three 



at each end of the sac and two in the central part. The three 



nuclei at the micropylar end of the embryo sac constitute the egg 



* The formation of this embryo sac will be explained in Chapter XXVIII. 



