JANuaRY, 1923.| THE ORCHID REVIEW. 7 
POLLINATION OF SATYRIUM_ BICALLOSUM. 
HE issue for September, 1922, of Annals of the Bolus Herbarium, South 
Africa, contains an interesting article on the pollination of Satyrium 
bicallosum, by S. Garside. In the literature consulted by the author no 
record has been found of an insect having been seen to enter an Orchid 
flower and remove the pollinia from any South African Orchid. This lack 
of information is somewhat remarkable, considering that many of the 
numerous species which occur in the south-western region of South Africa 
are very common. The possibility that many of the highly-scented 
greenish Orchids might be pollinated by night-flying insects might account 
for our scant knowledge of these. It is stated that observation of such a 
brightly coloured Orchid as the scarlet Satyrium coriifolium, a species with 
both attractive colour and abundant nectar, shows that the visits of diurnal 
insects are by no means frequent. 
Mr. Garside’s attention was first directed to Satyrium bicallosum by the 
following statement by Dr. H. Bolus (Orch. Cape Pen., p. 129): ‘In the 
structure of the column this species differs from any other known to me. 
The anther, instead of hanging vertically under the rostellum with its 
glands pointing forward, as is the typical structure in the genus, appears as 
if pushed up against the apex of the column, so as to lie nearly horizontal, 
with the glands turned to the back of the flower, and the stigma completely 
covered and hidden from view. The economy of its fertilisation is a puzzle 
to me, for the appearance is as if the process were carefully prevented. But 
I have not had the opportunity of watching it, and have never seen any 
insect or trace of insect work on the plant.” 
After describing the reproductive organs, Mr. Garside remarks: ‘‘ It will 
be realised that each half of the flower has its own entrance, with its 
alighting place for insects ; its own pollinium, with adhesive disc projecting 
laterally into the passage, and its own stigmatic surface, placed just above 
the adhesive disc. Each half of the flower also has its own spur. The 
possibility of the separate functioning of the halves of a zygomorphic flower 
is of great interest.” Search was then made for the pollinating insects, and 
the author was fortunate enough to discover them by the following method. 
The plants were growing in a moist place were there was a trickle of water 
through the soil. Numerous plants of Drosera hilaris were in the same 
locality, and it occurred to Mr. Garside that if a Satyrium plant could be 
found in the centre of a group of Drosera, the pollinating insect would be 
seen captured. The required combination was soon found: a fine Satyrium 
almost entirely surrounded by Drosera. On examining the leaves of the 
latter, no less than a dozen small black flies were seen to have become stuck 
to the tentacles, each fly with one, two or even three pollinia attached to it. 
