438 Spalding. — On the Traumatropic 
at the end of this time the radicles were straight. They were 
then placed in water at approximately i8°C. Twenty-four 
hours later three of the seven were strongly deflected, two 
were straight, and two doubtful. One of the doubtful ones 
afterwards became deflected. Exact measurements were not 
made, but it appeared that the specimens that failed to curve 
did not grow, probably having died while in the ice-cold water. 
2 6. Two suppositions (if we exclude mechanical hypotheses) 
are possible in connexion with the foregoing experiments : 
first, that the injured tissue of the tip acts as a constant 
irritant ; or second, that by induction an influence is promptly 
transmitted to the zone of rapid growth, where it remains 
effective long after the infliction of the wound, it may be for 
a period of some days. To obtain evidence on this point the 
following experiment was conducted : — 
Seven specimens of Lupinus albus with healthy radicles 
about 1*5 cm. long were branded in the usual way and 
immediately placed in casts. At the end of twenty-four 
hours they were removed from the casts and decapitated, 
care being taken to remove just enough of the tip to be sure 
to take away the burnt tissue and as little more as possible. 
Directly after decapitation they were again placed in casts for 
twenty-four hours. At the end of this period they were 
removed from the casts, their length measured, and then they 
were allowed to grow in water at the temperature of the 
room. All were perfectly straight except No. 7, which was 
slightly bent away from the burnt side. The table gives 
their length when placed in water and also twenty-four hours 
later. 
No. 
Length. 
Length after 24 hours. 
I 
14-5 mm. 
26 mm. 
2 
vs 
25 „ 
3 
13-5 » 
itf -5 » 
4 
!5 » 
3 ° » 
5 
15 .. 
32 „ 
6 
16 „ 
18-5 „ 
7 
I 5'5 » 
20 „ 
