REPEODUCTION 417 



that this is the regular method of the multiplication of the 

 yeast-plant, where each division of the protoplasts brings 

 into being a new individual. The process can be noticed 

 through all the families of the vegetable kingdom, though 

 us 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 rnulticellular ; 

 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 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 cut- 

 tings, which are pieces of the stem, bearing buds ; these 

 when detached and planted in suitable soil, put out adven- 

 titious roots from the base of the cutting and develop into 

 plants like the original one. Other instances are afforded 

 by the buds which many leaves, notably those of Bryo- 

 pliyllum and certain Begonias^ 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 Cwlebogyne 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 bud- 

 ding of certain cells of the nucellus of the ovule, which grow 

 into the interior of the embryo sac, and develop into embryos. 



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