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TEXTBOOK OF BOTANY 



propagation among cultivated plants by collecting, storing, and trans- 

 planting naturally occurring vegetative propagules; and by cuttings. 



Among the vegetative parts of a plant that may become separated 

 naturally and develop as separate individuals are the branches that grow 

 from runners, rhizomes, and roots; oflFsets or sprouts that grow from the 

 bases of stems; plantlets that develop from leaves; and the familiar 

 bulbs, corms, and tubers with terminal and lateral buds from which new 

 shoots and roots develop (Chapter XXVI). Methods by which plants 

 multiply vegetatively from these naturally occurring vegetative propa- 

 gules will be described first. 



Abscised leaves and stem segments. Under natural conditions the 



abscised stem segments of some plants and 

 abscised leaves of others are vegetative 

 propagules. Embryos develop from vege- 

 tative cells in the notches of the leaves of 

 bryophyllum and kalanchoe (Fig. 176). 

 From these embryos roots develop first in 

 leaves of Bryophyllum calyciniim, and 

 shoots develop first in leaves of Bryophyl- 

 lum crenatum ( Fig. 194 ) . The plantlets on 

 the leaves of some varieties of kalanchoe 

 abscise before the leaves do. On falling to 

 the ground they continue growth, forming 

 a clone beneath the larger plant. 



Abscised lateral buds of some species of 

 sedum and lily fall to the ground and new 

 individual plants develop from them. Simi- 

 larly abscised stem segments and fruits of 

 certain cacti become vegetative propagules. 

 In pastures where these cacti are weeds the 

 stem segments may be scattered rather 

 rapidly by grazing animals. The abscised stem segments of such plants 

 as willow and cottonwood appear to be of no importance in propaga- 

 tion. Vegetative multiplication of some water plants, such as elodea, 

 occurs frequently from broken fragments of leafy stems. The elodea in 

 the canals and rivers of central Europe is said to have been dispersed 

 vegetatively from clones introduced from America about 1840. 



Runners and other "creeping" stems. Runners are common means of 

 vegetative multiplication of strawberry, of some ferns and grasses, of 

 water hyacinth, and of numerous other plants ( Fig. 177 ) . As many as a 



Fig. 176. Kalanchoe leaves. 

 Young plants have originated 

 from cells near the margin of 

 the older leaf on the left. 

 Photo from P. W. Zimmerman. 



