1 9 1 2] JONES— Dl A N THERA 2 1 



The endodermal sheaths of the six branch bundles open up, each 

 connecting with that of the adjacent bundles, so as to form a 

 complete sheath around the leaf trace and the six branch bundles 

 (figs. 33-35). Where the central bundle is present, a connection 

 is made between the two pairs of side bundles and the central 



bundle 



becoming normally oriented. Then the ring of the six 



incoming leaf trace become 



common 



In the case of the inflorescence axis, the vascular ring shows a 



tendency to break up into six bundles. This ring opens on the side 



to allow the entrance of the leaf trace, or rather bract trace; the 



sheath then surrounds the ring and the trace (figs. 42-45). The 



structure so produced is in cross-section almost identical with that 



produced by the branch. The further history is the same for 



both types. 



The organogeny of the flower 



The apex of the inflorescence axis continues its activity all 

 through the flowering season, giving rise to opposite, decussate 

 bracts, in the axils of which are produced the flowers. The greatest 

 growth of the inflorescence axis is due to intercalary activity in 

 the basal internode. 



In the axil of each developing bract a slight mound develops. 

 On this mound, which is to be the flower, there appear first of all, 

 apparently synchronously, the five sepals (fig. 46), followed very 



by 



s five petals. At first the latter are separate, but s 

 form the corolla tube. About the same time that 



mounds appear, marking the primordia 



stamens 



more 



stamens (five occur in some of the Acanthaceae 



genera there are two stamens and three staminodia). The ovary 

 grows up as a ring (fig. 40) , the sides nearest and farthest from the 



plant being slightly (10-15 /*) higher (fig. 50). The petals 



the stahiens being carried up on the corolla tube 

 Le ovarian "ring" closes in over the top and continues its growth 

 form the pistil with its deeply two-lobed stigma. The placentae 



from the opposite walls of the ovary, near its base. Two 



vules arise on each 



gradually 



