PHYTOGENY. 235 



The spathe- or stalk-leaf appears in the tubular-shaped 

 or Monopetalous corolla. It is a leaf-bud, which has 

 only ruptured at the apex, like most calyces, unto which 

 it corresponds spathoid corolla. Lastly, in the poly- 

 petalous corolla the reticular or petiolated leaf appears 

 upon its highest stage reticular or phylloid corolla. 

 The rank of the leaves consequently determines also that 

 of corollse. 



1205. Although we regard the corolla as a whorl of 

 leaves, namely, as several leaf-buds approximated, a yet 

 clearer insight into its numbers and positional relations 

 is attained, by viewing it only as the lobes of a single 

 leaf. 



1206. If we regard the petals of a polypetalous corolla 

 in the import or light of pinnate leaflets, the legitimate 

 regularity of their numerical relations, and the so-called 

 irregularity of their arrangement is easily explained. 

 The papilionaceous corollse have been manifestly con- 

 structed according to the plan of the pinnate leaf; the 

 vexillum or vane corresponds to the odd leaflet, the alae 

 or wings to the two anterior, the carina or keel to the 

 two posterior pinnate leaflets ; and hence their consecu- 

 tive ratio of decrease in respect to size. 



1207. All irregular corollse admit of being referred to 

 the papilionaceous form. One petal is always found, 

 which separates from the others, is either larger or smaller, 

 or entirely ablated, and consequently corresponds to the 

 odd pinnate leaflet or vane. 



1208. The irregular monopetalous or tubular corollas 

 admit also of being referred to the papilionaceous form. 

 They need only be regarded as a confluence of petals. 

 The labiate carollse are one of the same character ; but, 

 on the contrary, the lower lip is trifid, the upper, and 

 thus the keel, bifid. Here the papilionaceous corolla 

 stands, properly speaking, reversed. 



NUMERICAL LAW. 



1209. The number of petals in the corolla ranges pa- 

 rallel with the mode of development of the pinnate leaves. 



