67 
Incarvillea Delavctyi , Franck. 
but little doubt that they are responsible for the presence of the foreign 
pollen on the stigmas. That they do not seem to have pollinated the 
Incarvillea plants with their own pollen is no proof, however, that they 
are unable to set the mechanism in motion for the discharge of the pollen- 
grains, nor does it show that the grains are unable to adhere to their 
bodies. There were only three Incarvillea plants growing in my garden, 
and although I placed these close together, the chances of a bee’s 
visiting two of these flowers, one after the other, were exceedingly 
small, because there were but a few flowers out at a time, probably 
never more than four. The stigmas are covered with papillate hairs 
that are doubtless used in pollen fixation. The flower is sufficiently 
preserved from 'self-pollination by the closure of the stigmatic lobes on 
stimulation. In the flower of Thunbergia alata (8, 11), which in mechanism 
comes closer to Incarvillea than any other plant known to me, it is curious 
to find that Darwin reports (3, 4) ‘ spontaneously self-fertilized fruits ’. The 
stigmas of Thunbergia are not, as far as I am aware, sensitive ; their position, 
however, and the method of shedding pollen in this plant suggest either that 
Darwin’s plants were parthenogenetic or that insects did visit them and cause 
pollination, although they may not have been the insects that usually bring 
about the transference of pollen in this genus. The figure of the flower of 
Thunbergia alata copied from Hildebrand’s paper and figured in Loew’s 
‘Bliithenbiologie’ suggests that the anther-lobes are smooth and all the spines 
backwardly directed from the anthers. Lindau’s figures (9) bear this out 
for Thunbergia reticulata , and it will be found that here the anther-lobes 
remain parallel, and the spines are so arranged that an insect only causes 
pollen to be shed on its emerging from the flower. 
The flowers of Incarvillea had been found, in previous years, to be 
visited commonly by earwigs, and though it is not suggested that these 
creatures brought about the pollination in these cases, the plants undoubtedly 
bore fruits containing what looked like quite well-developed seeds. These 
seeds have not, however, germinated. This year, besides the earwigs, other 
visitors have been noticed, mostly a large garden ant — attracted by the 
honey — aphides, and an occasional humble-bee. I see no reason why the 
last named should not be able to bring about the pollination of these 
flowers, and, indeed, I should think that the setting of seed in the cases men- 
tioned above was probably due to their agency. The humble-bee has about 
the right-sized body for the corolla tube, and also (I should imagine) the 
strength necessary to move the anther spines. I cannot, however, think 
how the pollen adheres to his body except one postulates that, as happens 
in other cases, a sticky secretion from the stigma is deposited on it as the 
bee passes into the flower. The stigmas I examined, however, were not 
sticky. The flowers, which grew in my garden and gave rise to fruit, had 
all been hand-pollinated ; and all the flowers that had not been so treated 
