io6 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
being left a small open chamber between the two lobes. This motile lobe, 
however, soon begins to retrace its course, so that in 20 to 30 minutes it is 
near or in its first position. Mimulus glahratiis var. Jamesii is another 
species — -this one with the usual two subequal and motile lobes — that, in 
its usual behavior, opens its stigma lobes a few minutes after the first closing 
at the time of pollination. Lloyd (14) found the same behavior with 
Diplacus glutinosus. We thus know of three species that, in their usual 
behavior, open their stigmas soon after the first closing at the time of 
pollination. Possibly other species will be found to behave in the same way. 
In preceding pages, I have reported four species whose stigmas do not 
always open after the first closing with pollination, but may open and later 
show secondary closing. 
Of the 24 species and varieties now known to possess sensitive stigmas, 
15 have been tested to determine whether pollen could be placed on the 
stigma without causing the stigma to close immediately, and with all 15 
the test has been successful. In 13 of the 15 species, however, the majority 
of the stigmas of each species in usual weather close 2 to 5 hours after the 
application of the pollen. Stigmas, therefore, may show the secondary, 
without showing the primary, closing. 
2. Significance of Secondary Closing 
An extensive series of experiments in my own work with Catalpa higno- 
nioides and with Torenia fournieri, as well as less extensive tests with several 
other species, have demonstrated the fact that the pollen does not germinate 
on the stigma, unless the stigma lobes are closed, except in unusually moist 
air. 
A number of tests of the time of germination of the pollen of Catalpa 
resulted in showing that in 10 percent sugar solution at 29°, initial pollen 
tubes could be found after 3 hours, at 23° after 2>H hours, good germination 
with long tubes after 6 hours at 23°, and 80 percent germination at 26° after 
Sy2 hours. Pollen from freshly opened anthers germinates well, and 
pollen adhering to open anthers retains its viability for three days or more 
after dehiscence. 
The great majority of stigmas of Catalpa left on the tree close whether 
pollinated or not. If the blossoms are brought into the house and placed in 
a damp chamber, some stigmas will close, but some will remain open con- 
tinuously even though pollen may be placed on the lobes. In a series of 
eight experiments, the stigmas of 48 blossoms were cross-pollinated so as 
not to cause closing of the lobes, and the blossoms were kept with their 
stalk? in water in a moderately moist chamber at 22° to 26°. Of the 48 
stigmas used, 22 remained open continuously for 24 to 26 hours, when 
they were examined for germination of pollen. There was no germination 
of pollen. Eight flowers had their stigmas cross-pollinated without closing 
the stigmas, and the flowers, dipping into water, were kept in a chamber 
