CHAPTER XVII. 



VEGETATIVE REPRODUCTION. 



I. Fission and budding. 



301. Fission. — In single-celled plants cell division and 

 reproduction are practically identical, since shortly after divi- 

 sion occurs the two cells so produced separate and lead an 

 independent existence (C, fig. 18). Such a method of repro- 

 duction evidently interferes little with the processes of nutri- 

 tion, which probably are scarcely even suspended during the 

 process of reproduction. 



302. Budding. — A slight variation of the method of fis.sion 

 just described is to be found in those single-celled jilants, 

 such as the yeasts, whose growth is so localized as to form 

 upon one side a small enlargement which ultimately attains 

 the size of the parent, with which it is connected by a very 

 narrow neck (fig. 48). Across this neck the partition wall is 

 formed in the usual way. This becomes mucilaginous, ren- 

 dering the adhesion of the daughter cell at this point so weak 

 that it is easily separated from the parent. This method of 

 reproduction is known as budding. 



303. Fragmentation. — In those plants which consist of 

 a row of cells more or less closely united, the breaking up of 

 the filaments into separate pieces, either through external 

 force or the death of one of the cells, may produce a number 

 of smaller colonies or of new individuals, each of which may 

 grow to full size. In some of the more loosely organized 

 filament-colonies, such as Nostoc fsee ^ 13, and figs. 13, 

 14), there are specialized cells whose function seems to be 



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