On the Pollination Mechanism of Incarvillea 
Delavayi, Franch. 
BY 
E. M. CUTTING, M.A., F.L.S., 
Assistant, University of London, University College. 
With three Figures in the Text. 
T HE genus Incarvillea belongs to the Natural Order Bignoniaceae. 
The trumpet-shaped flowers are borne on a racemose inflorescence 
whose axis is about l j to % feet high. Most of the flowers are placed near 
the top of the inflorescence : the few scattered lower down are arrested ; 
they develop up to a certain stage, but grow no longer than about a third 
of an inch. The corolla tube of the ordinary flower is about two inches 
long, and directed slightly down- 
wards (Fig. i). 
My attention was first drawn 
to these flowers because they 
possess a large sensitive stigma 
of the Mimulus type (Fig. 2, C, D, 
and E). A closer examination 
showed that there was a further 
point of interest in that the 
anthers had attached to them 
curious stiff, downwardly directed 
(as the flower is naturally placed) 
prongs, and the opening of the anther-lobes and the consequent setting 
free of the loose pollen follows the manipulation of these. Each anther 
has two of these prolongations, one to each lobe (Fig. 2, E and f), and 
they are arranged so that one lobe of each anther must open and dis- 
charge some of its contents when the insect goes into the flower, and the 
other lobe is emptied of some of its contents on the insect coming out 
of the flower. The latter seems devoid of smell, at least in so far as it can 
be noticed by human senses, and the attractions that the flower has to offer 
are colour, conspicuous size, herding together at the top of the inflorescence 
axis, and a quantity of honey secreted by a large nectary situated round the 
base of the ovary. When the flower is quite open, the free portions widen 
l Annals of Botany, Vol. XXXV. No. CXXXVII. January, 1921.] 
Fig. 1 . Side view of flower of Incarvillea 
Delavayi (slightly reduced). 
