Manchester Memoirs, Vol. lix. (191 5 ), No. 8. 37 



be made from transverse sections selected from complete 

 series. Thus Photos 5-8 are from a plant which had well- 

 marked secondary growth, while Photos 9-13 are from 

 another plant in which the primary stele was larger, but 

 had little, if any, secondary growth. 



Photos 5-8 are from the series of transverse sections 

 already illustrated in outline in Text-fig. 2 of the preceding 

 paper. Photo 5 shows an older region of the stele where 

 the secondary prismatic zone is fully developed. It shows 

 the innermost portion of the cortical tissue, the cells of 

 which are arranged in radial rows. The ill-marked 

 secondary meristem lies at the inner limit of this, just 

 outside the clear looking zone of prismatic tissue. The 

 latter is almost entirely composed of cells with small 

 nuclei (secondary sieve-tubes) arranged in radial rows con- 

 tinuous across the cambium from the cortex. Embedded 

 in the secondary tissue is the primary stele from which 

 the bases of old leaf-traces diverge. The entering leaf- 

 traces consist of phloem and xylem separated by con- 

 junctive parenchyma. The phloem of the trace as will 

 be shown more clearly below, was continuous with 

 the innermost layer of phloem of the stele ; this primary 

 phloem was differentiated before any secondary meristem 

 was established. The conjunctive parenchyma of the 

 trace was continuous with the parenchymatous xylem- 

 sheath of the stele. The xylem of the leaf-trace can be 

 traced some depth into the xylem of the stele, coming 

 into contact with the central region of this. The outer 

 xylem, only slightly developed in this plant, fills up the 

 intervals between the entering traces and renders the 

 outline of the xylem in cross section almost circular 

 instead of stellate. 



The structure of the stele of this plant is better shown 

 in Photo 6, taken at a level where the primary tissues are 



