BOTANY. 871 



nients in which various zones were marked off on the growing shoots, 

 and the growth of uninjured and decapitated shoots compared. Fiom 

 the experiments it is shown that decapitation always causes consid- 

 erable decrease of growth. This decrease is most marked in the zone 

 nearest the cut, where in some cases there is no growth shown, but on 

 descending toward the base of the shoot the difference between the 

 growth of the decapitated and sound plants becomes greatly reduced. 

 It was also shown that the decrease in growth was the strongest at the 

 beginning of the experiment and became less as the later measurements 

 were made. Decapitation decreases the normal rate of growth fully 

 one fourth, and this reduction in growth will be shown in the diminished 

 curvature when compared with the normal rate of growth in shoots 

 which causes strong curving in a few hours. 



The author conducted a series of experiments to determine why the 

 decapitated i^lants did not undergo hehotropic curving. A number of 

 plants in which hehotropism had been induced were decapitated and 

 compared with uninjured shoots, showing that it was due to decapitation 

 temporarily destroying the heliotropic sensitiveness. The remaining 

 part of the shoots is insensible to the irritation caused by one-sided 

 illumination. Decapitation in this case caused a strong diminution in 

 the rate of growth, and temporarily caused a total loss of sensitiveness 

 toward external irritants. 



A series of exi^eri nients was conducted in which vertical incisions in 

 or near the top of the cotyledon* were made to ascertain whether this 

 form of injury would have the same effect on heliotropism as decapita- 

 tion. But little effect was noticed, showing, in the asuthor's estimation, 

 that the phenomena described above are not due to the wounding of the 

 shoots, but are to be attributed exclusively to the removal of the con- 

 nection between the top and the remaining body of the cotyledon. 



Since the specific irritation produced by decapitation acts downward 

 from the cut along the cotyledon, the author made some experiments 

 to ascertain whether this irritation is transmitted to any considerable 

 distance or whether its effect is circumscribed within narrow limits. 

 He found that if the top is cut off for several millimeters the action 

 extends over the entire length of the shoots; but if J to 1 mm. is 

 removed the action is carried to a much less distance, the time which 

 transpires before the effect of decapitation manifests itself varying from 

 3 to 6 hours, and the heliotropic sensitiveness of the decapitated shoots 

 was reestablished within 24 hours. The characteristic unequal distri- 

 bution of the sensitiveness of the shoot was arrested and the upper end 

 became more sensitive than the lower part, showing that a regeneration 

 of the injured top had taken place in the upper end of the decapitated 

 shoot as soon as the physiological properties of the normal top were 

 restored, proving that these properties do not reside in any definite 

 morphological part of an organ and are not connected with any definite 

 anatomic structure. It is further shown that shoots decapitated after 



