CH. XIIl] 



CALTHA. 



173 



anatropous. The biological meaning of the inversion of 

 the ovule is not clear, but, like many other characters of 



FIG. 80. 

 LONGITUDINAL SECTION THKOUGH OVULE OF CALTFJA. 



c, wall of ovary. ov, cavity of ovary. /, funicle. 



t, integuments of ovule. TO, micropyle. n, nucellus. 



s.e, secondary nucleus of embryo-sac. o, egg-cell. 



s, one of the synergidaB. a.c, antipodal cells. 



unknown physiological importance, it is a distinction of 

 value to the systematic botanist. Thus certain groups of 

 plants are characterised by possessing an anatropous 

 ovule, others by the presence of an orthotropous ovule, i.e. 

 one in which the funicle and the axis of the ovule are in a 

 straight line. 



