THE ORCHID REVIEW. 
[August, 1921. 
DISPERSAL OF ORCHID SEEDS. 
I T is a matter of no little surprise to all who consider the question 
why the pods of Orchids contain such countless numbers of seeds, 
and why, having regard to the large size of many of the flowers, the seeds 
should be so very mihute. The characters of our cultivated plants are 
inherited from the imported species, and to obtain anything like a clear in¬ 
sight into the why and the wherefore of the microscopic nature of the seeds, 
we must consider the natural conditions under which these forms of veger 
table life exist. If the seeds upon ripening merely fell directly to the earth, 
the following generation would be injuriously affected by the restricted area 
in which the resulting plants attempted to exist. Also, the ground beneath 
the parent plant might not be suitable for the germination of the seed, in 
which case, there would be little prospect of further life. Thus we see why 
the dispersal of seeds over a wide area becomes a necessity, and although a 
certain proportion may be lost, a number ultimately find favourable condi¬ 
tions for germinating. Although larger seeds would be carried up by the 
wind in fairly open country, the vertical wind-currents in the forests are 
weakr and on that account but few of the heavier type would find their way 
to the higher portions of the trees. To ensure the seeds settling on suitable 
material, minute dust-like seeds are the most easily dispersed by wind, and 
these, floating through the air, possess all the qualities for settling on fit 
places, and at an approximate level to the parent plants. It must not be 
forgotten that many Orchids only thrive well when situated under suitable 
conditions of diminished sunlight. Near the tops of the trees they might 
be scorched by excessive heat, while in the dense shade near the ground 
they would suffer from insufficient light. 
Mr. H. N. Ridley, late Director of the Botanic Gardens, Singapore, has 
observed that it is not all trees that bear epiphytes. On some of those 
with smooth bark or with longitudinally groved bark epiphytes are seldom 
if ever to be found. Whether a tree does or does not bear epiphytes 
depends on the flow of rtpn down the branches and stem. Where in 
smooth-barked trees like Macaranga the rain flows quickly off, vegetable 
debris and spores cannot rest, and no epiphytes are borne. A notch in 
the bark of one these may, however, retain a little soil, and epiphytes then 
usually appear. Ficus Benjamin a is a smooth-barked tree, but liable to 
cracks and other injuries, so that it carries epiphytes readily in parts. 
The roots of the Orchids and creeping rhizomes of the ferns retain the 
vegetable debris washed down and blown by wind, and the plants increase 
until the bough may be covered with epiphytes. 
Darwin, in his well-known work on the “ Fertilisation of Orchids," 
remarks that what checks the unlimited multiplication of the Orchideae 
