VEGETATIVE REPRODUCTION 209 
and planted in soil, will commonly give rise 
to new plants, and this faculty is taken 
advantage of in propagating new and valuable 
species. 
Sometimes young plantlets are produced 
by the development of a cluster of cells which 
still remains attached to the parent plant. 
This happens in many ferns, where bulbils 
are formed on the leaves or leaf stalks, and 
when they are set free they are already 
provided with all the organs necessary to 
start at once into growth. The process of 
propagation by gemmez and by young plantlets 
is essentially the same, the difference consists 
in the particular stage of development which 
is reached when the propagative body is cast 
adrift from the parent. The gemma is shed 
at an early stage, while the bulbil represents 
a gemma that has remained to develop on the 
parent plant, and has been fed at its expense 
during the early stages of growth. But there 
are advantages and disadvantages in both 
methods. The gemme are small, and are 
more readily dispersed over wide distances 
than the larger young plants. Furthermore, 
the latter by their very complexity are more 
liable to perish unless they speedily reach a 
spot in which they find conditions suitable 
for immediate development. 
But in spite of these numerous and elaborate 
kinds of vegetative reproduction, most plants 
still retain the primitive capacity of merely 
regenerating lost parts to a surprising extent, 
Oo 
