MODIFICATIONS OF FORM 



197 



leaves .ire fully formed, as in the Christmas Rose [Helleborus), the 

 Crocus, and Snowdrop. 



For the disposal of their store a slight distension of the tissues is 

 pften sufficient in these herbaceous perennials. This is seen in the 

 Iris (Fig. 129), where the short stock grows onwards from year to year, 

 bearing fresh leaves each season and axillary buds, and storing each 

 year's surplus in the massive stem. In other cases the various parts 



Fig. 130. 

 Tuberous roots of the Dahlia, (After Figuier.) 



Fig. 131. 



Corm, or storage stem of Crocus. 

 (After Figuier.) 



may be considerably changed in their proportions. Thus the roots 

 of the Dahlia are swollen to hold inulin (Fig. 1 30), and root-storage is 

 also seen in the native Orchids, in Ranunculus Fkaria, and in Spiraea 

 Filipendula. But it is more frequently the stem, or rhizome as it is 

 called when underground, that is distended for storage. The familiar 

 corm of the Crocus is the base of an upright stem of the previous 

 season's growth, which is swollen for storage. The store is depleted 

 in the spring by the development of leaves and a terminal flower upon 

 a new axillary bud. The foliage leaves on that axillary bud serve to 

 nourish it as the season progresses, and its distended base then remains 



