278 THE FLOWER. 



HILUM, takes also this latter name in the ovule. In the simplest 

 form of ovule (as in Fig. 582, 580), hilum and chalaza are one. 

 So also in cases where the body of the ovule incurves, as in Fig. 

 583. But very commonly the place of attachment, which becomes 

 the hilum, is more or less distant from the chalaza ; as in Fig. 584 

 and 587, where the hilum is lateral, but the chalaza at the larger 

 end, the two being connected by a short ridge ; and in Fig. 588 

 the two are separated by the whole length of the ovule. 



519. The simplest and most rudimentary ovule is that with- 

 out a coat, as in Mistletoe and the whole order Loranthaceae, and 

 in Santalaceae and Gnetaceae. This has been called a naked 

 ovule ; but long before ovules of such simplicity were known 

 this term had been appropriated to those of Gymnosperms, in 

 the sense of destitute of ovarial or pericarpial covering, i. e. to 

 uncovered ovule, not to uncovered nucleus. The ovule consist- 

 ing only of nucleus may be termed (after Alph. DeCandolle) 

 simple, or better achlamydeous. 1 



520. The tunicated or chlamydeous ovule is of three principal 

 kinds, with one or two subordinate modifications. These are 

 the Orthotropous, campylotropous, and anatropous, and the modi- 

 fication called half-anatropous, or amphitropous.* 



521. Orthotropous (Fig. 580, 582, 585), or straight o^ule, is 

 the simplest but least common species, being that in which the 



chalaza is at the evident base, and the orifice at the opposite 

 extremity, the whole ovule straight (as the first part of the name 

 denotes) and symmetrical. Atropous, meaning not turned at 

 all, is a later and etymologically much better name, but it has 



1 An epidermal stratum or tegument may not be wanting to such ovules, 

 forming a sort of adherent covering ; but this in nature and origin is not 

 similar to the ovular coats. 



2 In Latin form, orthotropa, campylotropa, anatropa, amphitropa, names given 

 by Mirbel, and referring to the way in which the ovule is turned either on 

 itself or on its support. Some English botanists incongruously write ortho- 

 tropal, campylotropal, &c. 



PIG. 685. Orthotropous or Atropous ovule of Buckwheat. 586. Campylotropons 

 ovule of Chickweed. 587. Amphitropous ovule of Mallow. 588 Anatropous ovule of a 

 Violet. The letter h indicates the hilum ; c, the chalaza, which in 585 and 586 corre- 

 sponds to the hilum; /, the foramen or orifice; r, the rhaphe. 



