6 3 
neither of these takes place. (A flower lasts about ten days, if 
not previously fertilised ; it must last at least four to reach the 
second stage.) The inference is that the papillae are not broken. 
If flowers be left for several hours in a moist chamber a clear 
colorless liquid rich in glucose appears in the nectaries of many. 
This is doubtless due to the fact that under such conditions — a 
warm, moist atmosphere — osmosis is not checked, while transpira- 
tion is, so, the cells becoming hyperturgid, sap exudes to relieve 
the tension. I examined several petals just after secretion com- 
menced ; but I could not determine whether the nectar exuded 
from the papillae or elsewhere. In one case it was plainly exuding 
only from the disc, a small green fleshy ring surrounding the base 
of the ovary. Flies could not obtain nectar from the disc as it is 
hidden completely by the stamens. Possibly the “ mosquitos ’’ 
thrusting their slender probosces between the stamens obtain 
nectar from this source. I pressed several nectaries carefully 
with a smooth blunt needle, but no sap exuded. Still the fly 
doubtless exerts a different and more efficient pressure. The 
spiral thickening of the wall of the papilla is of value, I think, in 
enabling it to quickly regain its shape after being pressed. It 
may also help in liberating sap, for the ridges round the side of 
the bulbous top would diverge when the papilla was pressed 
down, and stretch the thinner membrane between them, thus 
making it more penetrable. The pollinator fly is doubtless able 
to apply suction as well as pressure. I have no evidence as to 
how the occasional visitors obtain juice (I think they do obtain it.) 
Of what use are the purple lines on the petals ? Chiefly, I 
think, that with the ground color of the petals they produce a 
tint more pleasing to flies than a pure white or cream would be 
Indeed, I see no other use for them. They are superfluous as 
“ honey guides ” — the shape of the corolla cannot fail to guide 
the fly correctly. House flies as often walk across them as along 
them, when not seeking nectar. Each line stands immediately 
over one of the main veins of the petal ; so the question arises, 
is it a screen to cut off actinic rays ? The color is, however, as 
strongly developed on petals in the shade as on those in full 
sunlight ; and this seems contrary to the idea. 
The flower is zygomorphic, but bears traces of descent from 
an actinomorphic blossom. The bases of the petals still occupy 
almost a complete circle, only the anterior two being slightly 
separated. If a bud be opened a few weeks before it is due to 
unfold the stamens will be found equal in length arranged in a 
circle round the pistil with anthers all facing inwards. These 
facts point clearly to an ancestor with bell-shaped corolla, and 
regular and equal stamens. In this connection it is worth noting 
that the buds are erect, only becoming horizontal shortly before 
anthesis. One is tempted to speculate how the oblique flower 
may have arisen : it looks so like a mutation. I am not prepared 
