RECHERCHES SUR LE TRADESCANTIA VIRGINICA. 231 
i hypocotyl at all. What happens in the transition from the 
arch to the endarch type in the two cotyledon-traces here is not 
cling from M. Gravis’s description or figures, but it is almost 
certainly not ‘“ rotation.” The primary fact in all cases is the 
traces, and sometimes also with those of the first epicotyledonary 
leaf. This sR: is in direct relation to the first physiological 
xylem about aie’ wii strand doc different parts of its 
course is a matter of secondary impor 
in the present case the si eiologial utility of the primary 
dintziliaic of the strands is clear enough. The primary root is 
first placed in direct relation with the cotyledon by the initial 
differentiadlitic of two precrseee protoxylem-strands. This ser 
for rapid water-supply to the cotyledon in performing its function of 
first foliage leaf. The first epicotyledonary leaf, on the other hand, 
developed a little later, is placed in immediate relation with the 
later-formed absorbing organs, viz. the three rootlets, as well as, 
— of the organism 
It follows from all ‘this that the organs of transition between 
root ee stem are in need of a general restatement in vi 
ots already known. We want a thoroughgoing rational treatment 
they ae eeeitt a y claseientiod of oe which appear ‘0 
be ‘of secondary importance. Whether the treatment suggested 
would disclose a . e. ancestral—as distinct from 
one type is substituted for the 
not, however, enable us to 
exarch to endarch orientation in the cotyledon-traces occurs suddenly, 
which is rather what his language would seem to suggest. Such a 
sudden change is certainly not the rule. 
The sa of the bundles in the meeed stem is fully worked ir 
the most important being the de : : 
‘** cauline’”’ yeriaice of earlier observers are in reality the ot by Me 
formed by the bases of the leaf-traces. The alled by M. 
Gravis “ faisceaux anastomoti iques” when the system of s 
traced downwards from the leaf into the stem, eatibondois’ term 
