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 gemmae 

 of certain Algae 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 pinnae 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 conns ; 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 Begonia, 

 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 Ccelebogyne 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 



