450 DR. ERIC DRABBLE ON THE 
side where the last fusion has occurred. The wedge-shaped internal projections of the. 
fibrous ring still mark the limits of the originally free cylinders. 
In Pl. 50. fig. 82 the root-cylinder is normal and the internal boundary of the fibrous 
ring, though sinuous, has lost its wedge-shaped projections. The medullary strands now 
each contain only a single vessel. The scattered internal vessels of the fibrous zone 
represent the metaxylem-elements of the internally orientated xylem-groups. 
Sometimes the fusion of the cylinders of Pl. 50, fig. 77 takes place in a different 
manner. Instead of peripheral cylinders only fusing, fusion may involve some of the 
more internal cylinders also, as in Pl. 50. fig. 83. In this way the inrolled ares of so 
many palm-roots are produced. Internal fusion of the edges of these arcs leads to the 
formation of cylinders enclosing parenchymatous ground-tissue, one of which is shown 
in Pl. 50. fig. 84 and a second in Pl. 50. fig. 85. Thus Cormack’s “ polystelic” structure 
is realized. While this has been progressing the internal protoxylem-groups have been 
disappearing, leaving only the large metaxylem-elements. 
Distally these closed rings open out internally and the enclosed parenchyma is again 
in direct continuity with the common ground-parenchyma. Fusion of the edges of 
adjacent ares now occurs, leading to the formation of a lobed ring, at first incomplete on 
the adaxial side, but later fusing here also. 
Complete rounding of the external surface of the root-cylinder now occurs accompanied 
by loss of the internal wedge-formations, and thus normal root-structure is attained 
. (PI. 50. fig. 82). 
The aecompanying text-figure (7) illustrates the method of union of root and stem. 
Fig. 7. 
A 
| Lateral Rootlets. ' 
e The small lateral rootlets of the Palms, such as those shown in Pl. 48. fig. 11, a, have 
— SP uy normal origin in the pericycle of the relatively main root. The endodermis 
1s ruptured and the cortex of the lateral root attains considerable thickness during its 
passage outwards. The endodermis is connected at its origin with that of the cylinder 
