46 Sargant . — Theory of the Origin of Monocotyledons 
A single trace from the plumule approaches the double 
cotyledonary trace, and with it forms a diarch root-stele. 
The transition from stem to root takes place precisely as 
in Zygadenus (PI. V, Figs. 9-12). 
These facts certainly suggest that Anthurium is a form 
intermediate between the typical Liliaceous type and that of 
Arum and Arisaema , and this is the position assigned to it 
by systematic botanists on the evidence of its floral structure. 
If the relationship between Arum and the primitive Lily- 
type be admitted, we have still to decide which of the two 
is the older. Does the line of descent start from the mother- 
form of the Lily family and end in such genera as Arum and 
Arisaema , or do these represent a type earlier than that of 
the Lilies ? 
The succession suggested by the structure of their seedlings 
is from Anemarrhena , through forms perhaps resembling 
Chlorogalum and Arthropodium , to others like Allium and 
Zygadenus ; thence to Anthurium. We may hope that future 
research will fill up the gap between Anthurium and Arum. 
Should it do so, would it be possible to read the chain 
backwards with equal probability ? 
If we make the attempt, we must suppose the point at which 
Anthurium approaches the Liliaceae to be that of greatest 
antiquity. A form resembling Zygadenus in the structure of 
its seedling must be accepted as the primitive type of that 
family. But the comparative study of seedling forms within 
the Liliaceae has shown that types of vascular symmetry 
differing so widely from each other as those of Eremurus , 
Zygadenus , and Eucomis can all be referred to a single scheme 
— that which I have called type 4 (Diagram VI, p. 26). It is 
incredible that these genera should possess three distinct types 
of vascular structure in their seedlings, each of which should 
be modified through three distinct lines of descent until they 
all reached the same well-marked form — a form, moreover, 
which then appears in two genera such as Anemarrhena and 
Albuca , which have been always placed in separate tribes owing 
to the difference in their mature characters. 
