426 VEGETABLE PHYSIOLOGY 
that this is the regular method of the multiplication of the 
yeast-plant, where each division of a protoplast brings 
into being a new individual. The process can be noticed 
through all the families of the vegetable kingdom, though 
as we advance upwards in the scale the separated body 
becomes more and more complex. We have the gemmex 
of certain Alge and Bryophyta, which are multicellular ; 
we have in certain Mosses branches which become detached 
by the dying off of the shoot behind them. Many Ferns 
develop buds upon the pinne of some of their leaves, which 
when separated from the latter grow into complete ferns. 
Among the Phanerogams we notice a great variety of this 
method of reproduction, many structures being developed 
normally to secure it, while others can be made to lead to 
it by artificial means. We have the propagation of plants 
normally by the formation and separation of tubers, buds, 
and corms; by the young plants which are developed from 
the nodes of runners and stolons. The artificial method of 
bringing it about is illustrated by cuttings, which are pieces 
of the stem, bearing buds ; these, when detached and planted 
in suitable soil, put out adventitious roots from the base 
of the cutting and develop into new plants. Other in- 
stances are afforded by the buds which many leaves, 
e.g. those of Bryophyllum and certain species of Begonta, 
put out when wounded. These also develop adventitious 
roots, and young plants arise which become independent. 
This method, in which we never meet with the prepara- 
tion of cells which are specialised in the direction of 
reproductive powers, is usually spoken of as vegetative 
reproduction or vegetative propagation. ° 
Some curious cases of it are known. In the embryo sac 
of Celebogyne there is no fertilisation of a sexual cell in the 
manner which will shortly be described, but still one or 
more embryos arise. This is caused by a vegetative budding 
of certain cells of the nucellus of the ovule, which grow into 
the interior of the embryo sac, and develop into embryos. 
A feature of vegetative propagation which may here be 
