1()4 Hu ins. l{ep;oneratiün and its relatiou to trauniatrojjism. 



prolongod as ^vas nppareiitly shoMii liy (he seconcl set of ex- 

 pcrinionts. 



The otluT ([uostion linds it.s .sululiuii, as I belicwe, in the 

 tliircl set of experiments. Is the influence of the Stimulus con- 

 ducted to the elongatin<jj zone and there held until the root is 

 free to respond to it? This exporiment \vitli the glass tubes is 

 free from the objections cited bol'oro against tlie mothod of 

 cutting away the wounded tissue. Koots woundod and grown 

 in tubes grew as high as 6 cm and responded to the Stimulus 

 over two days after they wore wounded. If now the influence 

 of the Stimulus was conducted to the elongating area immodia- 

 tely and there held it must liave returned down the root as it 

 elongated. This seems highly improbal)lo although we have some 

 evidenee that the traumatropic Stimulus may be conducted toward 

 the tip as well as in the opposite direction. 



The work seems to justify the following conclusions: 



1. That the influence of the Stimulus is not conducted to 

 the elongating zone and there held from one to 

 eight days. 



2. That the latent period is not prolonged by mechanical 

 means. 



3. That the wounded tissue forms a constant irritant. 



4. That this irritant is removed when regeneration is 

 com]3lete, 



University of Michigan, January -i, 190-4. 



Literature. 



1) Prantl, Untersiicliuiigen über die Regeueration des Vegetatioiispiinktes 



an Aiio-iospermenwurzeln. (Arbeiten des Bot. Inst, in Würz- 

 bur^. Bd. 1. p. 546. (Older literature is cited liere. 

 Lopriore, Über die Regeneration gespaltener Wurzeln. (Nova Acta 

 Leop. Carol. 66. No. 5.) His other papers are cited here. 



2) Spalding, On the traumatropic curvature of roots. (Annais of Botany. 



Vol. 8. 1894.) 



3) „ I.e. p. 448. 



4) „1. c. p. 488. 



5) „ 1. c. p. 450. 



Explanatioii of flgures. 



No. 1. Pisum sativum six days after brau ding. The wounded tissue has 

 been regenerated and the root is turning down. 



No. 2. Pisum sativum. Eadical six hours after release from plaster-cast in 

 which it had been confined 72 hours after previous branding. 



No. 3. Pisum sativum. This radical, after being wounded, grew 4 cm in the 

 tube and developed a traumatropic curve on leaving it. 



No. 4. Pisum sativum. Small part of a longitudinal section of a root-tip 

 which was killed 48 hours after wounding. The process of rege- 

 neration is not complete. 



