THE PISTIL. 105 



HILUM. The scar left by the separation of a seed 

 from its placenta. 



It is not supposed that pupils will find all these parts 

 of the ovule in plants. Some of them are usually discern- 

 ible, and they may all be understood in their proper rela- 

 tions by studying the diagrams. 



EXERCISE XLVIL 

 Kinds of Ovule. 



The STRAIGHT, or ORTHOTROPOUS OVULE, has the 

 base of the nucleus and the base of the ovule in the same 

 position, while the micropyle is at the apex (Fig. 329). 



Micropyle- 



Hilumand %^ Chalaza._JSgf HB*-- MLropyle. 

 Chalaza -^^ 



FIG. 329. FIG. 330. 



Straight, or Orthotropous. Curved, or Campylotropous. 



In the CURVED, or CAMPYLOTROPOUS OVULE, the mi- 

 cropyle, or apex, is bent over close to the base (Fig. 330). 



In the INVERTED, or ANATROPOUS OVULE, the funicu- 

 lus lengthens, and bends round, growing fast to the coat, 



Rha P he --i mm I. ^1-Micropyle. 



Chala Z a.___^||f __._ Micropyle. Rhaphe '* >^~ 



FIG. 33 1 - FIG. 332. 



Inverted, or Anatropous. Half-inverted, or Amphitropous. 



until the base of the nucleus is at the apex of the ovule 

 (Fig. 33i). 



In the HALF-INVERTED, or AMPHITROPOUS OVULE, the 

 funiculus only lengthens till the ovule turns a quarter of 

 the way over, as in Fig. 332. 



