CHAP. V. 
ORIGIN OF WOOD. 
323 
the grafting of plants. The second is the opinion commonly 
entertained in France, and adopted by De Candolle in his 
latest published work. 
The objections to the views of Turpin need hardly be 
stated. Those which especially bear upon the view taken by 
De Candolle are, that his theory is not applicable to all parts 
of the vegetable kingdom, but to exogenous plants only ; and, 
that endogens and cryptogamic plants, in which there is no 
secretion of cambium, nevertheless have wood. 
Such is the state of this subject at the time I am writing. 
To use the words of De Candolle, “ The whole question may 
be reduced to this — Either there descend from the top of a 
tree the rudiments of fibres, which are nourished and deve- 
loped by the juices springing laterally from the body of wood 
and bark ; or new layers are developed by pre-existing layers, 
which are nourished by the descending juices formed in the 
leaves.” 
I would only add, that, after attentively considering the 
various arguments adduced in connection with this difficult 
question, it appears to me that the two greatest objections to 
the theory of Du Petit Thouars are, 1st, the existence of 
Dutrochet’s embryo buds, already described, p.79.; and, 2dly, 
M. Decaisne’s statement {Comptes rendus, vii. 944.), that in 
the Beet-root, where new vascular tissue is produced, it, in 
the beginning, is distinct from the previously formed vascular 
tissue. These two points deserve to be carefully considered 
and re-examined. 
Y 2 
