io8 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
the air was cooler and more moist than outdoors. The open stigmas were 
polHnated all from a mixture of pollen from two anthers of another flower. 
Five stigmas were caused to close at once by stimulating, and four were 
pollinated without closing. All the stigmas maintained, till microscopical 
examination the next day, their original closed or open position. The 
five closed stigmas showed their pollen well 'germinated, but the four open 
stigmas showed no germination of pollen. 
With Mimulus cardinalis, only one experiment is pertinent for entry 
here. Four stigmas were given pollen and closed by the pressure stimulus. 
The plant bearing the flowers was in the garden, and was covered with a 
cheesecloth net. The weather for the first three days was moist and 
ranged from 12.5° to 21°. The first stigma remained closed throughout; 
12 days after pollination the ovary was large and had abundant ovules. 
The second stigma was closed on pollination but opened after two and a 
half hours, remained open a day and then closed finally; twelve days after 
pollination the ovary was about two thirds full size and had about half the 
normal number of ovules. The third stigma was closed on pollination and 
remained closed throughout; examination twelve days after pollination 
showed a normal-sized ovary filled with ovules. The fourth stigma was 
closed at the time of pollination, but opened in an hour and did not close 
again ; at the end of the twelve days, the ovary had grown to less than half 
the size of the preceding one, and had one fourth as many ovules. In the 
last case there must have been germination of some of the pollen on the 
open stigma. This germination could be accounted for by the moist 
atmosphere which prevailed for the two days following pollination. 
From the results obtained with the foregoing four species, representing 
four genera, there can be no doubt that the continued closure or the sec- 
ondary closure of the pollinated stigmas serves the plant in securing ger- 
mination of pollen on the stigma. Of the eight species which have been 
under my examination, only Utricidaria vulgaris has shown fluid on the 
stigma. Lloyd (14) reports Diplacus as having no stigmatic fluid. The 
value of the closure of the stigmas in promoting pollen germination would 
seem obvious, and the experimental results confirm the assumption. 
3. Cause of Secondary Closing 
As stated before in this paper, the stigmas of some of the two dozen 
species of plants known to possess sensitive stigmas reopen in less than an 
hour after they have been closed at the time of pollination. These stigmas, 
except in Mimulus glahratus and Utricularia vulgaris, close again within 
2 to 14 hours, unless the weather is unusually damp. Some stigmas in 
several of the species do not open after the primary closing at the time of 
pollination, and hence the effect is the same as though there were opening 
followed by secondary closing. The question now to be considered is the 
cause of the continuance of the primary closure, and of the secondary 
closure when there has been an opening after the primary closure. 
