ORIGIN OF ROOT 221 
interest in any discussion of the origin of a subterranean absorptive 
system.! 
But the presence of such “rhizophores” does not greatly assist the 
solution of the problem of origin of the roots themselves. There is, in 
fact,” no sufficient or decisive evidence how the root came into existence 
in Vascular Plants ; but on the facts as they stand two alternative opinions 
are possible. Either that it resulted from the transformation of a leafy 
shoot by loss of the appendages, followed by other special adaptations in 
relation to its life, and to its absorptive function in the soil. Or that it 
fr Ce 
[i ~ 
Fic. 113. 
Plant of Selaginella spinulosa, with root system springing from swollen knot at base of 
the upright hypocotyl. 14 natural size. 
arose as a new type of haustorial outgrowth, not originally of shoot-nature ; 
but nevertheless that in’ its first and less differentiated condition it 
resembled the shoot from which it arose, in its structure, and in the 
character of its branching. That those features which were helpful in its 
absorptive and conducting functions were permanently. maintained, and 
they became distinctive characters of the differentiated root: other charac- 
ters, such as the root-cap and endogenous branching, may have been added 
in accordance with the underground habit. This latter view seems to me 
the more probable alternative. 
Applying it in the case of the Lycopodiales, the root at its inception 
would, like the stem of these plants, be exogenous, with exarch xylem 
1Compare Goebel, Organography, vol. ii., p. 230. 
