CHAPTER XII 



OVULE— FERTILISATION— SEED— FRUIT 



OVULE. 



An ovule (figs. io8, iii) is a more or less egg-shaped body 

 attached to the placenta by means of a stalk — the funide if). 

 The main body of the ovule consists of a central egg-shaped 



mass — the nucellus — 

 which is surrounded by 

 one or two coats — the 

 integuments (in). Each 

 integument is attached by 

 its base to the nucellus, 

 but elsewhere it surrounds 

 the nucellus like a narrow- 

 mouthed bag, which is 

 open at the top. The 

 opening at the top of the 

 integument or integu- 

 ments is the micropyk 

 (ni) ; it allows free com- 

 munication between the 

 nucellus and the chamber 

 of the ovary. In the 

 nucellus itself, near the 

 space. This is in reality 



Figs. 108-110. — Ovules. 

 Figs, iit-113. — ^Vertical sections through ovules. 



micropyle, there is a minute clear 



a closed bladder, and is termed the embryo-sac. 



There are three common types of ovules, whose forms are 

 best explained by the figures given, (i) An orthotropous 

 ovule is one in which the stalk (funicle) is in the same straight 

 line as the straight nucellus (figs. 108, 11 1). (2) An anatropous 

 ovule is one in which the nucellus itself is straight, but is 

 inverted, and consequently appears to be attached by its side 

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