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TEXTBOOK OF BOTANY 



Vegetative multiplication not limited to leaves, stems, and roots. Vege- 

 tative multiplication occurs more frequently in stems and roots than in 

 other organs of seed plants. Experiments have shown, however, that it 

 may occur also in bulb scales, fruits, cotyledons, hopocotyls of embryos, 

 zygotes, endosperms, and in the coat and nucellus of an ovule. Later on 

 it will become evident that the development of embryos from unfertilized 







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Fig. 190. Stages in the development of an embryo-like bud from the epidermis of 

 Crassula. From Ilda McVeigh. 



eggs in dandelion is genetically equivalent to vegetative multiplication. 

 Whether the new individual develops from a single cell or a group of 

 cells, both root and stem primordia resembling those of an embryo soon 

 become differentiated ( Fig. 190 ) . Among the bacteria, fungi, and algae, 

 vegetative multiplication by single cells is a regular phenomenon. 



Cuttings. Man, however, is not limited to naturally occurring vege- 

 tative propagules, because he has learned how to utilize cuttings from 

 various parts of the plant. Among ornamental plants propagation by cut- 

 tings alone greatly exceeds that by all other methods. Trees and shrubs 

 cultivated for their fruits are usually started from cuttings used as grafts. 

 A few of them, such as black raspberry and hazel, are started by layering. 

 Red raspberry, banana, and pineapple are started by offsets and sprouts 

 from the base of the stem or from roots. Sugar cane is started from short 

 stem segments bearing several lateral buds. Cuttings may be made from 

 stems, leaves, or roots and are valuable means of insuring the propaga- 

 tion of varieties that do not reproduce true from seeds. 



Stem cuttings. Shoot primordia are already present in the terminal 

 and axillary buds of a stem cutting. Preformed root primordia may also 

 be present, as in branches of willow, cottonwood, and flowering currant. 

 Adventitious root primordia may develop from parenchvma cells in the 



