49 ° Tans ley and Lid ham « — A Shidy of the 
xylem. Soon after this the first arm of the trace (turned towards the mid- 
dorsal line of the stele) departs, and meanwhile the thickened portion 
of the pith disconnects with the rest on the outer side and becomes the pith 
of the leaf-trace, the xylem of the inner cylinder becoming confluent with 
that of the outer immediately below the base of the outer arm of the trace. 
This outer arm of the trace now departs and the trace-pith is opened to the 
cortex of the stem. Shortly afterwards the inner cylinder again separates 
from the outer. 
After the departure of the fourth trace, the strand of phloem in the 
centre of the second (inner) cylinder becomes constant, and increases in size, 
being sometimes isolated and sometimes in connexion with the external 
phloem of the second cylinder. In the course of the seventh internode a strand 
of endodermal cells appears in the midst of this internal phloem, but dis- 
appears again before the departure of the next leaf-trace. The eighth trace is 
the first in this plant showing a true ‘ leaf-gap ’ in a single transverse section, 
i. e. the pith of the base of the trace opening to the cortex before it is discon- 
nected from the pith of the stele (PL XXXIII, Figs. 27, 28 right). Before 
the eighth node is passed another endodermal rod appears in the internal 
phloem, consisting this time of but a single cell in cross-section. It dies out 
again almost at once. The ninth trace shows a reversion to an earlier type, 
passing off much more suddenly and showing no gap, while the xylem 
of the inner cylinder joins that of the outer between the bases of the arms 
of the trace (PL XXXIII, Fig. 28 left). The tenth internode shows a third 
endodermal rod, which rapidly increases in size, joining the outer endodermis 
of the inner cylinder, and then disappears again. The eleventh internode 
shows yet another, which persists through the rest of the stem. 
(2) Starved Intermediate Plants. 
The next advance in complexity we found in certain plants, already 
alluded to, which were growing in a deeply shaded crevice below an 
overhanging rock close to the top of Gunong Ledang. The smallest 
of these scarcely exceeded F in stoutness of rhizome or size and complexity 
of leaf, though they have longer petioles ; while others are considerably 
larger, though in all respects much smaller than typical vigorous plants 
growing in the open. They were, no doubt, plants of some age which 
had been unable to attain anything like their full growth, owing to 
want of soil and light. Their vascular structure is of interest, since it 
leads up from that of the six young plants to that of the typical 
adults. 
In the simplest one, which we wiil call for convenience G, the stelar 
system of the rhizome is identical with that of the distal part of F, 
i. e. it consists of an outer solenostele and an inner cylinder, the xylem 
