CHAPTER IV. 



J3 



S 



THE PRINCIPLE OF AEEANGEMENT. 



SuPEEPOsrrioN and Alternation of Whorls. — It has been 



already observed that leaves are arranged on two methods, 



either being on the same plane, i.e. opposite and verticillate ; 



or with only one at a node, i.e. alternate. If the fibro-vascular 



cords passing from the leaves into 



the stem be traced downwards, >« ^^- mmis km , 



those belonging to the leaves i^- 



situate in one and the same ver- to 



tical line always have their lower 



extremities inserted laterally and 



not actually confluent in that line, 



as will be seen in Fig. 7, taken 



from Hanstein's researches.* 



This fact is tme, not only for 

 foliage and bracts, but also to 

 some extent for sepals and petals. 

 When, however, we trace the az -* a/ a 3.a.s. 



fiT-iCTiTi nf stampriR nnr) fjlTnpla wo Fig- ' —Wogram of the foliar conjB in 



origin 01 siamens ana carpeis, we ^^^ ^^^ ^j ti,^ ArabU aUMa (after 

 find that their cords, instead of ^Hanstein). 

 being inserted separately into the fibro-vascnlar cylinder, 

 generally arise by branching, or by the so-called "chorisis" 



• De la Connexion qui existe entre la Disposition des Feuillea et la 

 Structure de la Zone Ligneuse des Dicotyledons, Ann. des. Soi. Nat., 4" 

 ser., torn. 8. 



