i2 A. G. Tansley. 
With regard to the earlier, the stele passes through a definite 
Lindsaya- phase, and then through a phase with internal endodermis 
alone, before a pith appears and the solenostelic condition is reached 
(Fig. 60, B, G, J), The phenomena are however complicated by 
the very early appearance of the internal thickening of xylem which 
ultimately leads to the development of the second (internal) 
cylinder. This first appears while the stele is still in the Lindsaya- 
phase (Fig. 60 D) and the internal ridge even separates from the 
Fig. 100. Lnmeria Spicant. Ontogenetic evolution of dictyostely directly 
from the Lindsaya -type without the interposition of the solenostelic condition. 
The ground-tissue pockets (5) and (6) are unconnected with one another. The 
sixth and seventh leaf-gaps overlap. From Chandler. 
main xylem-cylinder and runs free in the internal phloem through 
part of the internode, joining the external xylem at the next leaf- 
insertion. When the solenostelic condition is reached this internal 
strand becomes surrounded by its own phloem, pericycle and endo¬ 
dermis (though it is confluent with the main cylinder for a con¬ 
siderable part of its course), and thus- becomes a protostelic 
accessory internal cylinder. At later stages it successively passes 
through the Lindsaya -phase and the phase with internal endo¬ 
dermis, eventually in its turn reaching the solenostelic condition 
(Fig. 61, P, Q, T). 
