496 JOURNAL OP THE ROYAL HORTICULTURAL SOCIETY. 



and its ramifications undergo a marked shortening. The con- 

 tractility spreads sometimes to the hypocotyl, which becomes 

 marked by transverse furrows. This type is illustrated by many 

 Uinbelliferae ; e.g. Carum Carvi (fig. 113), Composite, Atropa 

 Belladonna, Gentiana lutea, and other herbs with succulent 

 roots. With this contractility is probably associated the dis- 

 appearance under the soil at the approach of winter of the 

 persistent parts of the stem of many perennials, as well as certain 

 other peculiarities of this class of vegetation.* 



In the above cases the level occupied by the plant is materially 

 influenced by the behaviour of the roots ; there remains a large 



Fig. 116. — 1 Colchicum autumxale ' : (a) Young descending corm from near 

 the surface, (b) Young stationary corm from the normal depth. 

 (After Rim bach.) 



number of instances in which the roots do not appear to shorten, 

 but rather definite curvatures of the stem bring the plant to a 

 given level. 



II. — Special Curvatures of the Stem. 



This class is well illustrated by Colchicum autumnalc, which 

 has been the subject of detailed investigation by Rimbach. The 

 normal depth of the corm of this plant is about 15 centimetres ; 

 but this is only attained by a seedling after the lapse of a long 

 series of years. The seed germinates at or near the surface in 

 the usual way, and the young stem soon thickening forms the 

 primary corm. Each year a new corm arises from that of the 

 * Cf. Earner, Natural History of Plants, English edition, vol. i. p. 768. 



