March, 1922] NEWCOMBE — BEHAVIOR OF SENSITIVE STIGMAS IO5 
assumed that the closing of the stigma serves the plant in preventing its 
own pollen from reaching the stigma, the visiting insect causing the stigma 
to close before the insect reaches the pollen of the same flower. This view 
would seem to express the obvious significance of the phenomenon. The 
only objection to this interpretation has been raised by Burck (12) who 
states that in Torenia fournieri the visiting bee encounters the pollen before 
touching the stigma. I have examined the position of anthers and stigma 
in hundreds of flowers of Torenia fournieri, and have never seen a case in 
which a visiting bee would touch the pollen before the stigma. This does 
not imply that Burck may not have seen such cases; for the species of 
Torenia, Catalpa, Tecoma, and Mimulus that I have examined show con- 
siderable variation in the position of anthers and stigma, though in the 
great majority of cases the well known relation is present of one pair of 
anthers far above, the other pair below, and the stigma between the two 
pairs and projecting in front of them; or the stigma rises above all the 
anthers, and projects forward into the open throat of the flower. In 
flowers of Catalpa hignonioides and Mimulus cardinalis, I have seen in a 
few instances stigmas covered with pollen from anthers pressing in between 
the open stigmatic lobes. But these unusual relations cannot be cited as 
evidence against an hypothesis supported by the evidence of the usual 
behavior. F. Miiller (4) found the flowers of Tecoma sp., Elrod (13) found 
those of Tecoma radicans, and Batalin (6) those of Mimulus guttatus infer- 
tile to their own pollen. On the other hand, I found Torenia fournieri, 
Mimulus cardinalis, and Utricularia vulgaris readily self-fertile, and one 
case of self-fertilization in Catalpa hignonioides. 
II. The Secondary Closing of Stigmas 
As stated earlier in this paper, the opening of stigmas, which often 
occurs after the primary closing at the time of insect pollination, has not 
been generally observed. The usual statement is that the stigmas remain 
permanently closed provided pollen has been deposited at the time of 
closure. This statement is true for some species only; for other species, 
under certain conditions there may be an opening of stigmas following the 
first closing, and later another closing without a second stimulation. 
I. Phenomena as Observed in Nature 
The species Utricularia vulgaris differs in its stigma structure from all 
other species so far reported to have sensitive stigmas, in that it has but 
one motile lobe. Only the lower lobe is long and motile, while the upper 
lobe is short and rigid. A description of this stigma may be found in Hilde- 
brand's (5) paper. When the lower lobe of the Utricularia stigma is mechan- 
ically stimulated and pollen is deposited upon it, it immediately rises through 
an arc of 180° or more, but does not close against the upper lobe, there 
