905] McCALLUM—REGENERATION IN PLANTS 99 
be made, for occasionally in some species, e. g., Salix, the axillary 
buds on the first year’s growth instead of remaining dormant until 
the following spring will develop at once into shoots. 
It will be quite apparent that as regeneration merges so insensibly 
into ordinary vegetative growth, the necessary limitations as to the 
use of the term must be entirely artificial. Prerrer (8) restricts 
the term to those cases where an organ directly replaces that portion 
of itself that has been removed; all others he would call mere repro- 
duction. GOEBEL, Kress, MorcAn, Ktsrer, and most other writ- 
ers on the subject, give it a broader meaning, so as to include the 
replacement of parts or organs, whether by means of entirely new 
growths, or from the development of latent buds. The advantage in 
having some general expression to cover all these phenomena, and 
the fact mentioned by Morean, that they all accomplish the same 
result and are probably due to the same cause, make it @ matter of 
convenience to use the term in its wider application. Fe : 
A certain amount of confusion has arisen because it has not 
been kept clear that regeneration is not really different from ordinary 
vegetative growth. Most plants naturally tend to grow and branch 
indefinitely, the new members arising usually in definite places, the 
shoot primordia, for example, in the embryonic parts of the shoot, 
and the root primordia ordinarily in the younger regions of the root. 
The fact that this is the general rule has led to an unjustifiably ngid 
limitation of the origin of new members to specified regions. As a 
matter of fact, the ability to produce new members is distributed 
throughout the plant body, and in many even of the higher plants 
almost any part is able to produce any other vegetative part. Nor 
is this ability limited to embryonic parts, for in very many plants it 
's exercised by the older cells, as in the production of shoots on roots 
of Taraxacum or on leaves of Begonia. That certain conditions 
are Necessary to bring this latent ability into activity does not make 
it in the least different from ordinary vegetative growth, for the latter 
also is dependent on definite conditions. 
The whole plant body of mosses and liverworts, and many roots, 
stems, and leaves of the vascular plants have this capacity, and it 
Tequires only the proper conditions to become manifest. 
In spite of the extensive investigations into this question, ranging 
