HOW PLANTS MULTIPLY WITHOUT SEEDS 



153 



goes on its way underground. The elm, the poplar, 

 the plum, and the pear are among the trees that throw 

 up suckers. 



15. The tuber. Sometimes the underground stem 

 swells into a tuber, as in the potato. The potato that 

 you eat is not really a root, but a part of the stem ; 

 and I need hardly say is not grown by the plant for 

 our use but to make new plants. The "eyes " of the 

 potato are just leaf-buds in the swollen stem. 



16. The bulb. Sometimes, again, the underground 

 stem swells out into a bulb. Very many of our 

 spring wild flowers, like the Victorian crocus and the 

 harbinger of spring, have bulbs. Sometimes, as in 



the onion, the bulb can be broken 



up into thick scaly leaves. These 



scales, indeed, are just disguised leaves. 



Now, you know that in the angle 



between a leaf and the stem there is 



always a bud. The little bulbs, then, 



that form at the base of the scale-like 



leaves are just underground buds. 



Sometimes again, as in the gladiolus, 



the bulb is solid and cannot, like 



the onion, be broken up into 



scaly leaves. In such cases 



the little bulbs have to be 



formed above the old one, or at 



the side. Take up a bulb of the 



gladiolus, and you will often see 



the bulb of last year below the 



bulb of this- year. You might 



think from this that in a year 



Solid bulb (gladiolus) , t , 



showing the withered bulb or twO the Dulb 01 the gladlOlUS 

 of last year below this ^ 



year's bulb. 



Fi& 111, 

 Scaly bulb with 

 little bulbs— a, a. 



