96 



COLLEGE BOTANY 



inverted ovale, 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 



Fig. Tl.^Types of ovules; (a) orthrotropous, (6) campylotropoua, (c) amphitropoua, 



{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 siirrounded 

 by one or usually two integuments, which are to 

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

 a very small opening in the int-eguments through 

 which the pollen tube penetrates to' the nucellus. 

 Thp other parts of the O'Vule are the chalaza, or 

 point of union between the nucellus and integu- 

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

 tached to the ovary wall by meansi 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 

 m^a'ti J'i7n?Sn"I (^^g^- '^^ and 74). In the mature eahbryo sac the 

 fng developing ovute" eight uuclei are so grouped that there are three 

 at each end of the sac and two in the central pai't. The three 

 nuclei ^t the micropylar end of the embryo sac constitute the egg 

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



