450 
Hill and de Fraine . — On the 
A complicated series of anastomoses takes place between the cotyle- 
donary and plumular traces, which results in the formation of a closed 
vascular ring, enclosing a mass of parenchyma, of the same nature as has 
been described above for Dioon. The protoxylem rays are now organized, 
but not all at the same level. First, a ray is formed from the central bundle 
of one of the seed-leaves, and situated in the plane of the cotyledons ; then, 
at successively lower levels, of course not far distant one from the other, two 
other protoxylem rays are formed, each from the two lateral strands of the 
other seed-leaf, and inclined at an angle to the cotyledonary plane. The 
phloem-ring divides opposite each protoxylem group, and thus there is 
formed a triarch root-structure. 
This triarch arrangement persists for some little distance downwards 
towards the root-apex, but, at a lower level, a new protoxylem group comes 
into being and the band of phloem opposite it divides, thus a tetrarch 
structure results ; at a still lower level a similar occurrence takes place in 
a corresponding position on the other side of the central cylinder, so that 
a pentarch arrangement obtains. This increase in the number of poles in 
the root-structure appears to be a general feature of this plant, for in two 
other cases the initial triarch arrangement became tetrarch at lower levels, 
a character shared by Stangeria , Ceratozamia mexicana , and other plants . 1 
We have found no instance of the pentarch or tetrarch structure giving place 
to a triarch arrangement such as Matte described for Stangeria , Ceratozamia , 
and Encephalartos Barteri ; this is probably due either to the fact that the 
seedlings examined by us were either too young or, when sufficiently old, 
to the decay of the greater length of the root. It may be remarked here 
that the above account does not agree in certain respects with that given by 
Tansley and Miss Thomas . 2 They describe each cotyledon as having six 
vascular bundles which organize a tetrarch root-structure. In the examples 
examined by us the seed-leaves each had five bundles at the node, with one 
exception, when four were present and a triarch root-structure invariably 
was formed first. 
Matte 3 gives a relatively brief description of Encephalartos Barteri. 
The specimen examined by him had three cotyledons, of which one was 
larger than the others, this larger one had two vascular bundles in its tip, 
whereas the smaller seed-leaves had but one each. At a lower level more 
strands arose, so that at the base each cotyledon had four. These traces 
remained separate one from the other until they had entered the hypocotyle- 
donary axis, when those of each seed-leaf fused together to form a single 
concentric strand ; the three bundles thus produced fused with the plumular 
vascular tissue at different levels, and ultimately produced a pentarch root- 
structure, which, at a lower level, became reduced to triarch. 
1 Matte, Shaw, loc. cit. 2 British Association, Section K, York, 1906. 
3 loc. cit., 1904. 
