9i8 



A TEXTBOOK OF THEORETICAL BOTANY 





arise in the meristem as purely stem structures without relation to the leaf 

 rudiments has not been settled. 



Medullary bundles 



I 



Fig. 899. — Piper cliisii. Transverse section of stem 

 showing accessory bundles in the medulla. 



I 



Fig. 900. — Cucurbita pepo. Transverse section of stem 

 showing two rings of vascular bundles. The central 

 cavity represents the space previously occupied by 

 the pith. 



3. Scattered Bundles in Dicotyledons. These cases are only separated 

 from the above by the fact that there is no normal ring of bundles, but all 

 are irregularly scattered, or arranged in two or three irregular zones. Such 

 cases are known chiefly in Ranunculaceae (Fig. 901) {e.g., Thalictriim) and 

 Berberidaceae {e.g., Podophyllum) and also in Papaver. They seem to be 

 associated with leaves with wide bases and numerous trace bundles. 



