March, 1922] NEWCOMBE — BEHAVIOR OF SENSITIVE STIGMAS lOl 
the Stigma of Catalpa hignonioides toward ammonia vapor. By normal 
pressure stimulus, my Catalpa in first class condition at 29° C. will begin 
closing in 2 seconds and completes its closing in 7 seconds from the moment 
of stimulation. In strong ammonia vapor, at 29° C, the stigmas began 
closing in 15 to 20 minutes. One flower, on removal from the vapor after a 
5 minutes' stay, showed its stigma normally sensitive to pressure. The 
stigmas of the other flowers left in the ammonia vapor were still closing 
slowly 55 minutes after being placed in the vapor, and were completely 
closed and dead 70 minutes after being placed in the vapor. Lloyd's results 
with heat and alcohol and my own with ammonia vapor raise the question 
whether Heckel's (8) results, obtaining closing with these same agents and 
others, were really sensitive responses, as he thought, or rather the result 
of the death of the protoplasm. Of course, one must bear in mind the 
fact that many contractile organs, like the leaves of Mimosa, respond in 
a sensitive way to ammonia vapor and to other poisonous vapors and gases; 
so that, a priori, one might expect the stigmas to close in the presence of 
various vapors and gases. 
Another method of stimulating for Catalpa hignonioides consists in 
crushing a portion of the style. Burck (12) states that the styles of the 
species he worked with could be cut through without causing the stigma to 
close. Many trials of the same kind were made with the Catalpa I worked 
with and no closing ensued, if the knife was sharp, no matter where the 
style was cut. If, however, scissors were used, and the cut was not more 
than 2.5 millimeters from the insertion of the stigma lobes, the most sensi- 
tive stigmas at 30° would close after the lapse of 5 to 15 seconds. Crushing 
the style with forceps whose tips were one millimeter wide was a much surer 
way of causing closing. In one series of 21 pistils, the style crushed with 
the forceps 10 mm. from the insertion of the lobes, temperature 29°, the 
stigmas closed at periods 15 to 120 seconds from the time of crushing. In 
another series of 10 pistils, style crushed as above noted at a distance of 
2.5 mm. from the insertion of the lobes, temperature 29°, closing took place 
in 5 to 16 seconds from the time of crushing. These two series with their 
results are fairly representative of the whole number of tests. Pinching 
the style between finger and thumb will often, but not always, cause the 
stigmas to close. As a result of the pinching, no injury to the style could 
be detected — no deformation nor infiltration. 
When one considers the time of the response when the style was crushed 
at 10 millimeters, and again at 2.5 milHmeters from the stigma lobes, it 
would seem that the closing, probably due to sudden increase of water- 
permeability in the cells of the stigma lobes, must have been induced by an 
impulse received from the injured protoplasm of the style. The change 
in permeability of the contracting cells in the stigma could hardly be due to 
the sudden flow of water toward the crushed spot of the style, for there 
was no closing when the style was cut through with a razor; nor could it 
