44 ° Spalding . — On the Tranmatropic 
exclude absolutely the possible presence and continued action 
of some portion of the dead tissue without removing too much 
of the terminal portion of the root. 
Discussion and Conclusion. 
A review of the experimental work recorded in the pre- 
ceding pages, together with a comparison with what has been 
done by others who have investigated the subject from widely 
different theoretical standpoints, indicates that we are now in 
possession of the most important facts, and that regarding 
these there is a fairly general agreement. It is in the inter- 
pretation of the facts that extremely diverse views are still 
held by leading physiologists. It remains, therefore, to 
examine the whole evidence, and to determine, if may be, the 
conclusion to be drawn from it. The work of other observers 
will first be reviewed. 
Charles Darwin, with whom in this work Francis Darwin 
was associated, was the first to demonstrate the phenomena 
of traumatropism 1 . His ordinary method was to allow 
radicles of seedlings of different kinds to grow in moist air, 
and, while they were still very short, to fasten a bit of card 
laterally to the tip by means of shellac dissolved in alcohol. 
It was found that a large proportion of the radicles thus 
treated £ became bent, generally to a considerable extent, 
from the perpendicular and away from the side to which the 
object was attached.’ This was the case, for example, with 
fifty-two out of fifty-five radicles of Vicia Faba. He inter- 
preted this as a demonstration of the sensitiveness of the 
growing point to contact, but unfortunately did not pay 
sufficient attention to the action of the adhesive mixture 
employed, which later investigation proves to be an important 
factor. Various other experiments were conducted to prove 
in different ways the sensitiveness of the growing-point of the 
root. Thus ‘ thin slices were cut off parallel to one of the 
sloping sides of the apex, and out of the eighteen radicles 
1 Power of Movement in Plants. London, 1880. 
