THE DEVELOPMENT OF THE FLORAL WHORLS. 197 



the Gladiolus and Alstroemeria, where they are very numerous 

 and follow the rule of commencing to emerge in the middle, 

 and then proceed upwards and downwards. Though parietal 

 placentas seem generally to have their ovules developed from 

 below upwards, yet, as seen above, it is not uncommon with 

 an axile placentation. If any interpretation be sought, I 

 should feel inclined to associate it somewhat with a more 

 primitive state of things, since a parietal placentation presents 

 a more rudimentary character than an axile. But why they 

 are developed thus, sometimes upwards, sometimes down- 

 wards, or both ways at once, is at present as inexplicable as 

 the fact that leaves develop both basipetally and basif ngally, 

 either in their entirety, or as to their lobes and notches, which 

 may be formed on either plan. Perhaps there may prove to 

 be a common cause for both. 



