Ii6 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
the next morning, or 20 hours after the first closing, 10 were open and 3 
closed. At the time of the last record, 2 that had been open had closed, 
and 2 that had been closed had opened. 
Several potted plants of Torenia fotirnieri that were kept outdoors 
under fine nets were used in testing the action of Taka-diastase. On 16 
stigmas was placed a mixture of one fourth of the diastase whose enzyme 
had been destroyed by heating and three fourths corn starch. The mixed 
powder was dry when applied, and all stigmas were closed in the application. 
After one hour 10 were open and 6 closed; after 2 hours, 11 were open and 
5 closed; after 4 hours, 12 open and 4 closed. The next morning, 14 hours 
after the first closing, 13 were open and 3 closed. Sixteen other stigmas, 
used at the same time as the preceding 16 and on the same plants, were 
given a mixture of one fourth normal Taka-diastase and three fourths corn 
starch. After one hour, 5 were open and 11 closed; after 2 hours, 6 were 
open and 10 closed; after 4 hours, 7 were open and 9 closed. The next 
morning, 14 hours after the first closing, 12 were open and 4 closed. 
The foregoing tests with Torenia give a very good indication that the 
presence of the enzyme has an effect in keeping the stigmas closed longer 
than the same substance when the enzyme has been destroyed; but, after 
the lapse of 14 hours, about as large a proportion of stigmas opened with 
enzyme as with the de-enzymized material. 
Eight stigmas of Torenia on a plant outdoors under a fine net were given 
commercial casein and closed. The w^eather was sunny and fairly dry. 
All stigmas opened within 20 to 40 minutes of closing. Observations were 
not made to see how much earlier they may have opened. These stigmas 
were repeatedly closed by stimulating after the first closing, but all re- 
opened as often as they were artificially closed. Observations continued 
for 17 hours. 
Twelve stigmas of Torenia, weather cloudy and moist, were given a 
mixture of one fourth Witte's peptone and three fourths corn starch. All 
opened promptly and remained open for 4 hours at least, when observation 
was ended. 
III. Summary 
In all, 25 species and varieties of plants have been reported, 4 of them 
for the first time in the present paper, with sensitive stigmas. These 25 
plants are included in 4 families. The stigmas are composed of two tongue- 
shaped lobes of equal or unequal size which diverge 90° to nearly 360° when 
ready for pollination. The receptive region for pollen is the inner or apposed 
surfaces of the two lobes, except foi Utricularia in which only the lower lobe 
receives the pollen. 
The natural stimulus for the stigmas is the pressure of the body of the 
visiting insect or other animal, and the response consists in the closing 
together of the two lobes, so that the two lobes, except in the case of Utric- 
