GOEBEL: REGENERATION IN PLANTS 201 
ever, we have to do, not with previously laid-down primordia, but 
with a disposition on the part of the tissues of the leaf; and we 
have actually brought about a form-relation present in other spe- 
cies but normally absent from Begonia Rex. 
2. When a part of a plant is removed direct restoration occurs 
only when we have to do with embryonic tissue, such as that of 
the vegetative point. When parts of plants which have assumed 
their permanent character are concerned the rupture and wound- 
ing have the effect of inducing a portion of the cells to return to 
the embryonic condition and to produce structures which give rise 
to one or more new plants. Many seedlings have a remarkable 
power of regeneration. 
There is no important and invariable difference in the phenom- 
ena of regeneration in plants and in animals, but the course of 
procedure that has been described is highly characteristic of plants. 
While in animals the parts that have been lost must be replaced 
directly, this is the exception in plants. A few illustrations will 
make this clearer. 
(2) Embryonic tissue. It has long been known that vegetative 
points of roots and shoots, if wounded, easily regenerate what has 
been lost. Fern-fronds have, as is known, the peculiarity that the 
tip remains in an embryonic condition for a long time, while it soon 
passes into permanent form in most spermatophytes. I split young 
leaves on Polypodium Heracleum \engthwise into two similar or 
dissimilar halves. When the parts were alike the tips of each 
regenerated a perfect leaf; when the parts were unequal, the regen- 
eration on the smaller was much less marked. Similar phenom- 
ena are to be observed in the tips of roots or shoots, 
(6) On the other hand when the parts of a leaf which have as- 
sumed permanent form are removed, the restoration does not take 
place ; a separated leaf of Begonia for example does not regenerate 
a new shoot-axis with roots which continue life as a part of the 
regenerated plant, but there develop on the leaf new plants which 
soon become entirely independent of the original leaf. The cells 
of the leaves of many plants are easily induced to develop new 
plants ; they contain all the necessary germ-plasm, but are not in 
a position to codperate with one another in such manner as to 
directly replace what was lost by newly constructed tissues. 
