1882 .] 
435 
[Trelease. 
This, however, is prevented from realization by a very effective 
device. The style is very irritable, and after being touched its 
tip quickly straightens or even becomes recurved so as to press the 
stigma closely against the lower lip of the corolla. Apparently 
the style is excitable for some distance from its tip), but the 
seat of motion is in the part which bears the stigma. In a 
comfortably warm room the movement occurs very promptly 
after the style is touched, so that in three seconds or less, if vig- 
orous, it is completely recurved. At a lower temperature and 
under less favorable conditions the motion is slower and the 
reflexion less complete, but the time given may be safely taken as 
the average duration of the movement when well pronounced. 
So great is the excitability that not only direct contact, but a 
shock to the plant may cause the motion, and the power of move- 
ment is even retained for some days by styles that have been 
broken from the ovary by falling corollas ! Morren has also 
shown that it occurs in G. anisopbylla when a sudden and consid- 
erable change of temperature is experienced, as well as when the 
flower is suddenly blown upon (2, 24-25). 
If undisturbed after the first irritation the style assumes its 
original position after a time, and it is capable of repeating these 
motions a considerable number of times. I have not determined 
the exact time required for the return movement. Several styles 
experimented upon were found curved again at the end of half 
an hour. Morren (2, 17) states that the movement takes over a 
quarter of an hour in G. anisophylla. Under favorable condi- 
tions it probably takes from twenty to twenty-five minutes, requir- 
ing a longer time at unfavorable temperatures and after the style 
has already been excited several times, as is the case with the 
first movement. 
The bearing of this motion upon the crossing of the flowers is 
evident. A bee enters a flower and causes the depression of the 
style. This occurs so rapidly that before the insect has finished 
gathering nectar the stigma is safely pressed against the corolla 
and receives none of the pollen from this flower. It remains 
in its retreat until the bee has gone to other plants, when it rises 
again. A bee laden with pollen from other flowers could not fail 
to deposit some of it upon the stigma before its movement 
occurred. 
