SECTION 11.] 



OVULES. 



Ill 



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

 three or four different ways, and tliereby are distinguished into 



Orthotropous or Straight^ those which develop without curviug or torn- 



'1, 



_/ 



344 345 346 347 



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

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

 ovule. 



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



355 



352 353 ■ 354 



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 foruiiug 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. Tlierefore 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 ; c, 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; tlie parts lettered as in the last. 



Fig. 348-3.50. 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 aua- 

 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; 

 6, inner co-vt; c, nucleus; d, rhaphe 



