520 TRANSACTIONS OF THE CANADIAN INSTITUTE [Vou. VIII. 
neither pith nor gap, but at the next node there is a repetition of the 
events of the eighth. Above the twelfth there is a shallow, then a narrow 
gap, only a cell wide, reaching in to the heart of the xylem, that is about 
four cells deep. A pith of three or four cells is again enclosed. The 
leaf-traces are now concentric, but as yet there is apparently only meta- 
phloem on the ventral side. Above the thirteenth node, the narrow 
pith widens to two or three cells in breadth, and the gap formed overlaps 
that originating at the fourteenth node. Before the fifteenth node 
is reached, however, all gaps are closed, and there is a narrow pith of two 
or three cells in width and consisting of twelve cells in all. The gaps 
corresponding to the fifteenth and sixteenth nodes overlap. At the 
seventeenth node a pocket of parenchyma is formed as a diverticulum 
from the narrow pith, which soon opens to the outside as a gap of the 
seventeenth leaf-trace. 
This seedling may be considered as the most nearly typical of all in 
regard to the sequence of events that take place in the course of its de- 
velopment. 
F.—The base of the stem was lacking, and presumably about ten 
leaf-traces were missing. ‘The roots occur with considerable regularity, 
but at the fifteenth node there was none. Above the eleventh node there 
Was a deep narrow gap, and farther on a narrow pith. A separate pocket 
of parenchyma cells forms at the next node, but there is no leaf-gap above, 
and almost simultaneously the stele becomes a solid bulky mass of tra- 
cheids, round in section. In preparation for the next leaf-trace there is 
again a parenchyma pocket, but the gap above the thirteenth node is 
shallow and there is no pith. Above the fourteenth node a deep narrow 
gap appears, reaching to the centre of the core of xylem, and the next gap 
opens before this closes. ‘The pith is about one cell in width. A pocket 
of parenchyma now forms, corresponding to the sixteenth leaf. ‘This pocket 
opens out into the gap above the sixteenth node and connects at the same 
time with the already existing narrow pith. There isan overlapping of the 
last two gaps. The phenomena of the seventeenth node are nearly iden- 
tical with those of the preceding. But above the seventeenth node there 
is a broad shallow gap which soon fills up with tracheids and the pith 
disappears. Once more there is a “‘solid”’ stele. At the eighteenth node 
there is a transitory pocket of parenchyma, but no gap or pith above. 
At the next node there is another pocket and a pith of four or five cells. 
These join, and above the node there is a deep narrow bay. The gaps of 
the nineteenth and twentieth internodes overlap. Above the twentieth 
leaf-trace there is a fairly deep bay in the xylem, four or five cells wide, 
and into which the external phloem clearly dips. A pocket of parenchyma 
