474 
Notes . 
by the formation of a branch passing from b 3 \.od r, for example. Finally, however, 
the branching stops, the strands d 1 and d 2 having combined with one of the bundles 
situated on their flanks, and g definite rotation of the protoxylems b 2, b 4, and b 1, 
b 3 takes place. The condition now obtaining is that of a tetrarch root ; this last 
movement, however, is too late, for almost immediately the phloem and metaxylem of 
b 2, b 4, and b 1, b 3 fuse together, enclosing in their meshes the exarch protoxylem 
which was derived from these same bundles. Thus the groups of tracheids c 1 and 
c 2, which have been gradually increasing in number, form the protoxylem of the 
diarch root. 
Mirabilis divaricata, Lowe, follows a similar course. 
Amarantaceae : Amaranthus hypochondriacus, L. — Each cotyledon has a single 
bundle. Bifurcation of the phloem and the rotation of the xylem towards the exarch 
position commence some way up the petiole. On the central region of the axis 
being reached, the rotation of the xylem is seen to be complete, the metaxylem 
elements speedily pass inwards and, at a lower level, the opposing masses of phloem 
fuse together. A diarch root is thus formed. 
The same changes occur in A. caudatus , L. 
The transition-phenomena in all the following plants are essentially of the same 
nature as in Amaranthus : — 
Aizoaceae : Teiragonia expansa , Murr., Mesembryanthemum crysiallinum , L. 
Caryophyllaceae : Corrigiola litoralis, L., Lychnis Vise aria, L., Polycarpon 
tetraphyllum , L., Silene Otites , Sm., and Silene pendula , L. 
Portulacaceae : Portulaca oleracea , L., Calandrinia Menziesii , Torr. et Gray. 
Chenopodiaceae : Airiplex hastata , L., Chenopodium Bonus-Henricus , L., 
Spinachia oleracea , L. 
T. G. HILL. 
