246 The Phenomena of Morphogenesis 



gests that this is a case of reproductive regeneration rather than of 

 restoration. 



The stems of most monocotyledons lack a cambium, and this somewhat 

 limits the possibilities of regeneration of lost parts in them. Axillary buds 

 are often present, however, and the nodes and bases of leaves remain 

 somewhat meristematic. New roots commonly arise in these regions. Meth- 

 ods of regeneration and of vegetative reproduction are generally very 

 specialized. Some members of the Juncaceae and Cyperaceae reproduce 

 vegetatively from tips or nodes of culms, as in Eleocharis rostellata, where 

 buds grow from the sterile culm tips ( La Rue, 1935 ) . 



Fig. 9-6. A young adventitious bud which has grown from epidermal cells on a de- 

 capitated hypocotyl of flax. Note the cell divisions in the cortex which will give rise to 

 a vascular connection with the stele. (From Crooks.) 



Factors in the rooting of conifer cuttings have been discussed by 

 Deuber (1940). 



The physiological basis of such regenerative processes has been widely 

 investigated. Gardner ( 1929 ) observed that, in both deciduous and ever- 

 green trees, cuttings from 1-year-old stems rooted more readily than those 

 from older ones. The influence of auxin and of various synthetic growth 

 substances has been much emphasized ( p. 391 ), particularly in root forma- 

 tion. Van der Lek (1925) found that cuttings rooted better if there were 

 buds on them, presumably because of the production of root-stimulating 

 substances by the buds. Discovery of the effectiveness of various organic 



