260 Hill and de Frame. — A Consideration of the 
TABLE I. 
No. of Root-poles. 
No. of Species 
examined. 
Percentage. 
2 
3 i 
40*8 
3 
16 
21. 1 
2 or 3 
5 
6-6 
3 or 4 
8 
10.5 
4 
7 
9.2 
2, 3 or 4 
2 
2-6 
4 or 5 
2 
2-6 
5 
2 
2-6 
6 
1 
i -3 
3 , 4 or 6 
1 
i -3 
8 
1 
i *3 
Triarchy, tetrarchy, and combinations of these occur in association with 
the third type of transition — which is correlated with a diarch root-struc- 
ture — owing to the disturbing influence of polycotyledony or, in other 
cases, to a marked increase in the size of the seedling. And it is worthy of 
remembrance that even in those cases where the root-structure is to begin 
with 4-, 5-, or 6-arch, reduction to diarchy very commonly takes place. 1 
Thus although, for obvious reasons, young seedlings, whenever possible, 
only were examined, no less than fourteen species were found to exhibit 
such a reduction. On the other hand, it is only fair to point out that the 
initial number of poles showed an increase, on being traced downwards, 
in seven species ; but this obtained chiefly in the Cycadaceae, and in 
certain cases a subsequent reduction took place. In fact, this local 
variation in the number of poles of the root-structure is very commonly 
found in plants which have a tuberous hypocotyl ; several Cycads show it, 2 
also Araucaria 3 and other plants. The explanation of this is, we think, to 
be found in the fact that the swollen axis requires a greater dispersal of the 
vascular tissues, and this, possibly, is the explanation of the Anemarrhena 
type in Eranthis 4 and certain other plants. 
The diarch root-structure in the Ferns is associated with single leaf- 
trace bundles of the two first foliage leaves, 5 and this also obtains in 
numerous Angiosperms and Gymnosperms. And in many of these cases 
the transition-phenomena, which are of Type 3, show resemblances to the 
Ferns ; the cotyledon-traces are undivided, and their vascular rearrange- 
ments are very obscure, that is to say, the cotyledonary bundles do not 
show a well-marked bifurcation and rotation either in the petioles or in the 
axis, but run into the central region, where a rearrangement of the vascular 
1 Hill and de Fraine : Gymnosperms, Pts. I, II, and III, loc. cit. 
2 Matte : Sur le d^veloppement morphologique et anatomique des germinations des Cycadacees. 
Hill and de Fraine : Gymnosperms, Pt. Ill, loc. cit. 
3 Shaw, F. J. F. : The Seedling-structure of Araucaria Bidwillii. Ann. Bot., xxiii, 1909. 
4 See Tansley : Reduction in Descent, loc. cit. 
5 If the cotyledons are foliar members and are homologous with Fern leaves, a comparison, if 
drawn, must be made with the first-formed leaves of the Ferns. 
