I02 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9. 
be due to the forcing of cell sap into the stigma when crushing the style, 
for the response came too long after the crushing to be so accounted for. 
The stigma of Mimulus glahratus var. Jamesii also could be stimulated 
by crushing the style 2 millimeters from the insertion of the lobes, though 
the closing was never complete, and the lobes started to retrace their course 
2 to 3 minutes aftei the crushing of the style. 
2. Relative Sensitiveness and Transmission of Stimuli in Various Species 
Meckel (8) attempted to arrange the 9 species that he studied in a series 
according to the sensitiveness of the stigma, citing Martynia and Mimulus 
as among the most sensitive and Tecoma, Bignonia, and Catalpa among 
the least sensitive. The Martynia stigmas he saw complete their closing 
in 3 seconds after stimulation, while the stigmas of the 3 genera named 
above as less sensitive required 60 seconds. 
During the several years of my observations, I have watched the closing 
of thousands of stigmas, with not fewer than scores of observations in any 
of four genera and nearly a score in each of two species in another genus 
(Mimulus). Though I have made no special study of the relative reaction 
time of various species, I am certain that the response of Catalpa hignonioides 
is, under favorable conditions, completed in 7 seconds, that of Torenia 
fournieri in 2 seconds; of Tecoma radicans in 3 seconds at 30°; of Mimulus 
glahratus var. Jamesii in 10 seconds at 21°; while even the slowest of the 
eight species I have observed has shown individual closures within 12 
seconds of stimulation. I have seen, on one tree of Catalpa hignonioides 
growing in good soil, stigmas close in 7 seconds, while on another tree, 
stunted and in poor dry soil, the stigmas required 60 seconds or more to 
close. The following season, flowers were found on the latter tree whose 
stigmas closed in 10 seconds. The responsiveness of the stigmas, as is the 
case with sensitive reactions generally, is so influenced by external and 
internal conditions, that only a special study can determine the relative 
sensitiveness of the stigmas of species; and such a study has not yet been 
made. 
Perhaps it is remarkable that so few species of the Scrophulariaceae have 
been reported to have sensitive stigmas, seeing that there are so many 
that have the two-lobed form of stigma characteristic of those that are 
sensitive. It would seem probable that search will discover other species 
sensitive, and different degrees of sensitiveness. A little attention on 
my part has been given to the testing of other species for sensitiveness, but, 
of the several examined, only Digitalis purpurea and a hybrid, Digitalis 
purpurea 9 D. lanata d^, have given any response. The response is 
relatively feeble in both cases. In D. purpurea, generally no movement of 
stigma lobes could be detected. On one occasion, when the stigmas of 
seven flowers were given the pressure always bringing a response in Mimulus 
and the other plants already mentioned, four stigmas showed a slight closing 
