84 



PRACTICAL BOTANY 



76. Reproduction by bulblets and by underground stems. 

 Many plants bear small aerial bulbs or tubers on some portion 

 of the stem and are commonly reproduced by these. Familiar 

 examples among cultivated plants are the onion and the tiger 

 lily. The bulblets known as " onion-sets " are for sale at every 

 seed store, and in some parts of the country are almost exclu- 

 sively planted by onion growers, while in other sections the 

 seed is more generally planted. The black bulblets of the tiger 

 lily are borne in considerable numbers along the stem, in the 



FIG. 67. Roots, rootstocks, and a tuber of the Jerusalem artichoke 

 (Helianthus tuberosus) 



A, base of a plant with two long rootstocks, about one twelfth natural size ; B, a 



full-grown tuber, beginning to sprout, slightly reduced ; st, aerial stem ; r, roots ; 



rh, rootstocks ; I, lateral buds of tuber ; t, terminal bud of tuber. A, modified 



from report of Kansas Agricultural Experiment Station 



leaf axils, and may be found on the ground, rooting in the late 

 autumn and the following spring. Some of our wild plants, 

 including certain, ferns, are propagated by bulblets. 



Underground stems of various kinds are so common as means 

 of reproduction that only a very few of them need be mentioned. 

 Some of the worst weeds are those which have running root- 

 stocks, like the couch grass or quack grass and the Canada thistle, 

 which may be cut up by the hoe and produce a new plant from 

 every node ; and the nut grass (Cyperus), which produces 

 many little tubers. Among cultivated plants a great number 



