ROOT FORMATION 



187 



The production of a similar substance by bacteria would 

 explain the results of Nemec (1930), who obtained formation 

 of new roots on root cuttings of Cichorium intyhus by 

 smearing the cut surface with a culture of Bacterium tume- 

 faciens (cf. XIII C). 



In a later paper Nemec (1934) confirmed the fact that 

 cotyledons and buds store not only food materials but also 



h 



i>k^ 



Fig. 52. Determination of root-forming activity. Basal end of cutting 

 marked +. A, 7-day old etiolated pea seedling; B, cutting; C, D, preparation; 

 E, slit apically; F, inverted in test solution; I, root formation after 14 days. 

 (From Went, Proc. Kon. Akad. Wetensch., Amsterdam 37: 445-455, 1934.) 



special root-forming substances or ''rhizogenes." He placed 

 isolated hypocotyls of Helianthus or Lupinus in aqueous 

 extracts of cotyledons, terminal buds, or stems. All these 

 extracts increased the number of roots formed at the base 

 of the hypocotyls, distinction being again made between 

 number and length of the roots. 



For quantitative experiments neither woody cuttings like 

 Acalypha nor hypocotyls with hormone-storing organs 

 above them are suitable. Went (1934a) therefore introduced 

 etiolated Pisum seedlings as test objects; the shoots, when 

 10-12 cm. long, are cut off just above the first scale-bearing 



