CHAPTER IV. 



THE PRINCIPLE OP AREANGEMENT. 



m. 1520. n22M.w msf 



Superposition 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, 



those belonging to the leaves ^^ 



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 true, not only for 

 foliage and bracts, but also to 

 some extent for sepals and petals. 

 When, however, we trace the 



nricrin nf <?fnmpn«! anri pm-npla wp Fig. 7 —Diagram of the foliar cords in 

 origin OI stamens ana caipeiS, we the stem of the Arabis aWida (after 



find that their cords, instead of Hanstein). 



being inserted separately into the fibro-vascular cylinder, 



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



* De la Connexion qui existe entre la Disposition des Feuilles et la 

 Structure de la Zone Ligneuse des Dicotyledons, Ann. des. Sci. Nat., 4® 

 ser., torn. 8. 



2.Z 4i 3 J & 3.8^S. 



