214 
Lang . — Studies in the Morphology and 
While the first leaf-gap is closing and the second is forming, an internal 
endodermis appears in the pith. It is at first incomplete {4 a ), but soon 
becomes a complete tube {4 b). The external and internal endodermis become 
continuous as the second leaf- 
trace separates (/, 6). As the 
trace departs a root is given off 
from the stele to one side in the 
usual fashion (j). The second 
leaf-gap is a long one. The gap 
in the external endodermis re- 
mains open for some distance 
(6, 7) and then closes, the exter- 
nal endodermis again becoming 
a complete tube {8, 9). The in- 
ternal endodermis is for some 
distance a complete tube (9), but 
then becomes incomplete ( 10 - 
18). Before the second leaf-gap 
in the xylem closes the third gap 
opens {11,12), the internal endo- 
dermis being present as an in- 
complete arc opposite to the new 
gap. As the preparations for 
the departure of this leaf-trace 
advance, endodermal markings 
appear on the cells bridging 
across from the internal to the 
external endodermis. Then the 
trace separates {13 a, 13 b ) with a 
complete sheath of endodermis, 
the adaxial portion of which is 
continuous below with the in- 
ternal endodermis ; the external 
endodermis at the leaf-gap is 
continued inwards for a short 
distance by the side portions of 
the arc of internal endodermis 
(13 b). The outer endodermis 
almost at once becomes con- 
tinuous across the gap {13 c ), 
and at this level a root-trace is attached, followed by another on the other side 
of the gap {1 y), The third gap then closes in the xylem ring, and the fourth 
leaf-trace prepares to separate {14-16), The next root-trace is attached 
Text-fig. 8. Reconstruction of the stele of plant F. 
Description in text. The divisions on the left correspond 
to the numbers in Fig. 9. 
