64 
WRIGHT : THE GENUS DTOSPTROS 
by the descending epicotyledonary trace, and thus indicated 
one of the possible stages in the establishment of a new root 
symmetry. 
Splitting of Xylem Traces ,—Another point which indicates 
most markedly the unstable conditions of the seedlings is 
seen in the splitting of the xylem of the leaf traces. This is 
best seen in seedlings which are very young and in which 
vascular cambium has not made its appearance, and for the 
sake of clearness a description of the behaviour in D. 
Embryopteris is here given. At the cotyledonary node three 
vascular bundles make their exit on each side and persist as 
three separate strands in the petiole of each cotyledon. At 
right angles to the cotyledons, two strands from the epicotyl 
leaves appear, one on each side. As these strands are traced 
through the hypocotyl they are seen to separate from one 
another, and on reaching the collet area where the parenchy¬ 
matous system is large each xylem strand separates into two, 
three, or more parts. At the collet area I have counted as 
many as twenty-two groups of xylem resulting from the 
scattering of the original eight traces. Traced below the 
collet into the primary root a fusion occurs, but whether 
this takes place between parts of dissimilar bundles or other¬ 
wise is very difficult to determine. The fusion goes on 
gradually, and at certain levels the number of strands is seen 
to be sixteen, later twelve, and through eight and six on to 
a final four. In no species are there ever less than four 
strands in the apical portion of the primary root. 
Owing to the highly scattered nature of the xylem 
elements it is often impossible to ascertain the exact area 
wherein the inversion of orientation is effected. 
In seedlings of the same species there is a great yariation : 
sometimes only one lateral cotyledonary trace undergoes 
division, sometimes all three ; the epicotyledonary traces 
when present may remain compact, or each may separate 
into two or three strands. In a general way it may be stated 
that the type of xylem in the seedlings is one where a split¬ 
ting is seen in any of the cotyledonary traces into two or 
