132 
position by the tubular calyx. The rectangular bend of the 
standard necessitated to secure these relative positions occurs 
just at the end of the blade. The four lower petals project 
horizontally past this point, concealing the staminal sheath, and 
the ovary, style and stigma which it contains. At the point 
where the base of the wing- and keel-petal blades leave the 
standard owing to its upward bend there are two prominent 
ear-shaped callosities close together at the middle of the base 
of the standard blade. These hold between them the upper 
edges of the lower petals just as the fingers and thumb may 
hold together the pages of a book. A weight such as that of 
an insect alighting on the lower petals will depress them and so 
liberate them from the callosities which hold them together. 
They are thus enabled to open and to slide down on each side 
of the stiff genital core. This brings the under side of the insect 
on to the brush of stamens or if the staminal sheath has split 
(which it does after the pollen is used), on to the exposed stigma. 
After each insect-visit, the petals, according to a field note by 
Mr. Keith on a sheet of Canavalia from Siam in the Singapore 
Herbarium, rise again, protecting the genitalia. The correct 
position of the insect is presumably encouraged by the offer of 
nectar round the disc which can only be reached through the 
slits in the upper side of the base of the staminal sheath. The 
position of the flower is not, however, always standard upwards 
as indicated above. Mr. I. H. Burkill records observations 
made by him on the fertilisation of Canavalia rosea as follows :— 
“The flowers oe dae ea upside down, but sometimes face 
upwards. Xylocopa aestuans was visiting and in either case 
stood on the its He and caused the stamens to dust the back 
of its thorax as it does in Hriosema.’’ But in each case the 
deposit of pollen occurs of course on a different surface of the 
visiting insect. 
Our thanks are due to the Director of the Royal Botanic 
Gardens, Kew, and to the Keeper, Botanical Department, 
Natural ‘History Museum, London, for leave to use the material 
in the establishments under their charge, to the Director of the 
Singapore Botanic Gardens for the loan of all the Canavalia 
sheets in the Singapore Herbarium, and to Mr. H. N. Ridley 
for notes and for a collection of specimens specially made for 
us on a recent visit to the Malay Peninsula. 
Key To THE OLD Worxtp CANAVALIAS. 
1. Pod with two oP fomer soais 2s ribs ee to the ore 
suture 
Pod with two papplemedtary ribs 5 mm. or more distant 
from the upper su 13 
2. Upper lip of calyx equal to the tube: flowers 4 cm. long 
(Polynesian plants) % 
Upper lip of calyx shorter a the tube - - ‘ 
