164 Hill. — On the Seed l ing- Sir tic In re of certain Piper ales. 
axis in a straight line, and obviously occupy positions between the phloem 
masses : thus a triarch root is produced. These changes do not end 
here : normally, of course, two seed-leaves are present, and the root is 
diarch ; in this case there are three cotyledons, and the root is triarch. 
On the examination of the root at a lower level it is seen that the 
triarch structure becomes diarch. The changes leading to the alteration 
are illustrated in Diagram II. 
Diagram II. 
Terming the xylem and phloem groups X. r, X. 2, X. 3,/. 1, p. 2, and p. 3, respectively; one 
xylem mass, X. 3, temporarily disappears, and this is followed by the obliteration of the group X. 2. 
So that, at this stage, there obtains, as regards the xylem, a monarch structure. The phloems p. 1 , 
p. 2 now approach one another to form a single strand, and, at the same time, the xylem ray, which 
was the first to disappear, reappears. Thus there results a diarch root. 
Piper genicidatum, Hort. ex Link., follows a precisely similar course, 
even to the behaviour of the epicotyledonary traces. 
Peperomia eburnea , Linden. At the distal end of the petiole of each 
cotyledon the bundles of the blade fuse together to form a single strand, 
the behaviour of which is not necessarily the same in each petiole. In one 
seedling it was found that in one petiole there was a normal collateral 
bundle with endarch protoxylem ; tracing this strand downwards, no 
bifurcation of the phloem occurs, but the strand, as a whole, becomes 
somewhat obliquely orientated with the greater mass of phloem on one 
side, and also with the smallest xylem element somewhat more exarch 
than its neighbours. Immediately above the cotyledonary node this 
bundle shows its xylem tangentially arranged, and its phloem in an early 
stage of bifurcation. 
Turning now to the other cotyledon, the bundle is found, at the distal 
end of the petiole, to be somewhat ^/-shaped, the xylem forming a tan- 
gential row of elements between the two groups of phloem elements. At 
a lower level, the xylem of this strand undergoes rotation, so that by the 
time the node is reached the bundle has its protoxylem exarch and its 
phloem in two masses. These differences will be realized by the exami- 
nation of Figs. 7, 8, and 9, of which the two first illustrate the appearance of 
the two bundles at the same level. As the cotyledonary traces pass 
inwards towards the centre of the axis, the phloem of the bundle first 
described separates into two well-defined masses, corresponding to what 
obtains in the other. The course now followed is the same as in Piper , 
except that as regards the bundle first described no rotation of the xylem 
