Manchester Memoirs, Vol. lix. (191 5), No %. 13 



the region of the grooves to a level higher than the tips of 

 the horns of the rhizophoric stele (cf. Fig. 2 E } F). The 

 leaf-bearing cortex surrounds the apical region of the 

 stem, forming there the whole of the cortex seen in trans- 

 verse section, and, after splitting has occurred, it forms 

 the upper portion of the two lobes. 



The shape of the vascular axis of the two-lobed plant 

 can be deduced from such a series of transverse sections. 

 The cylindrical primary stele of the upper portion of the 

 shoot narrows below where the stele of the young plant 

 persists. Below this region the rhizophoric stele broadens 

 out suddenly, being extended in the plane of the groove. 

 The meristematic line, by means of which additions were 

 made to the rhizophoric region, lay just outside the 

 convex lower edge and its ends coincided with the 

 meristem around the base of the stem stele. The more 

 or less upturned tips of the rhizophoric stele also coincide 

 in position with the meristematic layer which gives rise 

 to the secondary prismatic tissue. The expansion of the 

 rhizophoric stele was rendered possible by the develop- 

 ment of secondary tissue around the narrow basal region 

 of the stem stele. The upturned tips of the rhizophoric 

 stele may be more directly due to the secondary meri- 

 stem. These tips are well marked in this stock, but in 

 others may not be represented, the rhizophoric stele 

 simply broadening out below the base of the stem stele, 

 as allowed by the development of secondary tissue around 

 the latter. The shape of the whole primary vascular axis 

 may be compared to the edging iron used in horticulture, 

 the stem stele corresponding to the handle and the rhizo- 

 phoric stele to the half-moon-shaped blade. 



These inferences as to the shape of the vascular axis 

 are borne out, as was shown in Von Mollis figures, by 

 longitudinal sections in the planes of the lobes and of the 



