10.] CHAPTER II. SPECIAL MORPHOLOGY OF THE MEMBERS. 



41 



larger proportion of space than that of the bulb, and is invested by only a few 

 scaly leaves. It occurs in Crocus and other Iridaceae. 



The Tuber is likewise a shortened shoot, with a swollen stern and small scaly 

 leaves ; it is usually developed underground, as in the Potato and the Jerusalem 

 Artichoke (Hclianthus tuberosus, Fig. 22 A). 



The morphological nature of the tuber is readily demonstrated by uncovering 

 the underground shoots of a Potato-plant, when they develope into ordinary 



FIG. 22. Various forms of shoots. A Tubers of Helianthus tuberosus (} nat. size); 

 s lower part of the stem springing from last year's tuber 7c'; in the axils of the upper 

 leaves arise the buds 1m, and in those of the lower leaves the tubers 7: with very small 

 scaly leaves and buds. B Bulb of Hijacintlius orientalis (reduced) ; 7c the discoid stem, z 

 the scaly leaves, s the stalk which subsequently elongates and bears the flowers above 

 ground, with the buds b ; I foliage-leaves, w roots; 7oi an axillary bud which becomes 

 next year's bulb. C Elongated rliizome of Carex arenaria () ; scaly leaves n ; o erect 

 shoot with scaly and foliage-leaves I. D Runner s of the Strawberry, Fragaria (reduced), 

 springing from the plant a, with scaly leaves n, from the axil of which a new plant 6 

 arises. E Creeping stem of the Ground Ivy, Gleclioma hederacea (reduced) ; // decussate 

 leaves; the internodes are twisted; a axillary shoot; w root. 



