INTRODUCTION 



l'"or inst.^Ilce, the underground stems of quack grass and bind- 

 weed are capable of producing a new plant from every joint, as 

 every farmer and gardener knows to his sorrow. Again, should it 

 be deemed necessary, the California big tree which at the estimated 

 age of 5,000 years is steadily becoming extinct, thanks largely to 

 human activity, might be given another 5,000-year start by propagat- 

 ing it from its buds by cuttings (Fig. 99). The process might again 

 be repeated 50 centuries later and so on without a limit. 



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FIG. 2— TIGER LILY AND BULBLETS 

 1. Notice bulblets in leaf axiles. 2. Bulblets rooting a few days after failing off 



plants. 



5. Life cycles of plants. — Every plant normally passes 

 through a lite cycle or history. The seed germinates or 

 sprouts; the plant vegetates, blooms, bears seed and 

 sooner or later dies. Life cycles vary in duration from 

 a few days or weeks (peppergrass and portulaca) to many 



