SECTION a.] 



OVULES. 



Ill 



321. The Kinds of Ovules. The ovules iu their growth develop in 

 three or four different ways, and thereby, are distinguished into 



Ortkotropoits or Straight, those which develop without curving or turn- 



347 



ing, as in Fig. 344. The chalaza is at the insertion or base ; the foramen 

 or orifice is at the apex. This is the simplest, but the least common kind of 

 ovule. 



Campylotropous or Incurved, in which, by the greater growth of one side, 



the ovule curves into a kidney-shaped outline, so bringing the orifice down 

 close to the base or chalaza; as in Fig. 345. 



Amphitropous or Half-Inverted, Fig. 346. Here 

 the forming ovule, instead of curving perceptibly, 

 keeps its axis nearly straight, and, as it grows, turns 

 round upon its base so far as to become transverse to 

 its funiculus, and adnate to its upper part for some 

 distance. Therefore in this case the attachment of 

 the funiculus or stalk is about the middle, the chal- 

 aza is at one end, the orifice at the other. 



Anatropous or Inverted, as in Fig. 347, the com- 

 monest kind, so called because in its growth it has 

 as it were turned over upon its stalk, to which it has continued adnate. 

 The organic base, or chalaza, thus becomes the apparent summit, and the 



FIG. 344. Orthotropous ovule of Buckwheat : e, hilum and chalaza; /, orifice. 



FIG. 345. Campylotropous ovule of a Chickweed: c, hilum and chalaza ; /, orifice. 



FIG. 346. Amphitropous ovule of Mallow:/, orifice; h, hilum; r, rhaphe; c, 

 chalaza. 



FIG. 347. Anatropous ovule of a Violet; the parts lettered as in the last. 



FIG. 348-350. Three early stages in the growth of ovule of a Magnolia, showing 

 the forming outer and inner coats, which, even in the later figure have not yet 

 completely enclosed the nucleus ; 351, further advanced, and 352, completely aiia- 

 tropous ovule. 



FIG. 353. Longitudinal section, and 354, transverse section of 352. 



FIG. 355. Same as 353, enlarged, showing the parts in section : a, outer coat ; 

 ft, inner coat i c, nucleus ; d, rhaphe. 



