6 2 Sargcint . — Theory of the Origin of Monocotyledons 
show how readily a tetrarch root-stele may become diarch by 
suppression of opposite protoxylem rays. 
The hypothetical vascular system at which we have now 
arrived corresponds very closely to the Ranunculaceous type 
(Diagram IX). In this two cotyledonary traces only enter the 
hypocotyl, but they give very clear evidence of their double 
origin, as M. Dangeard has already remarked (9). In every 
other respect the schemes are identical. 
Returning to the hypothetical Dicotyledon, whose seedling 
has a fourfold symmetry throughout its vascular system, let 
us suppose the development of the plumule to be arrested 
rather than accelerated, and secondary thickening to disappear 
altogether from the axis. This development of the vascular 
scheme leads to a symmetry closely resembling that of 
Anemarrhena. The latter indeed possesses but two cotyle- 
donary traces, but each gives very clear indications of its 
double origin when it enters the hypocotyl. 
To derive the vascular system of Eranthis hiemalis from 
our four-partite ancestor, we must suppose the plumule to 
have increased in importance up to a point at which the tetrarch 
symmetry of the root has almost disappeared. The whole 
vascular system was developing on Ranunculaceous lines. 
But at this point the ancestor of Eranthis parted company 
with its fellows. The plant perhaps had to adapt itself to 
different climatic conditions. These postponed the develop- 
ment of the plumule, and led to the formation of a tuber from 
the hypocotyl by the increase in mass of cortex and conjunctive 
tissue. This process gradually put a stop to secondary 
thickening by isolation of the bundles within the tuber, and 
the vascular system became what we see it in Eranthis . 
Little weight can be attached to hypothetical genealogies 
of this kind. They are valuable only as suggesting lines of 
research. In this case the investigation of forms allied to 
Anemarrhena on the one hand and to Eranthis on the other 
may yield valuable results. The seedlings of other species of 
Eranthis are, I believe, still undescribed even in their external 
characters. Their vascular structure is entirely unknown. 
