AUGUST, 1922.] THE ORCHID REVIEW. 233 
Although we have found evidence to indicate that Orchids are by no: 
means so incapable of holding their own in biological competition as the 
facts of distribution in a balanced flora have seemed to prove, we are still 
likely to be puzzled by the astonishing profusion of seeds per capsule and 
the sparse distribution characteristic of Orchids in general. And yet, it 
seems to me, that in profusion of seeds the Orchids overcome one of the 
chief obstacles in the way of success which their association with mycorrhiza 
created. Granted that our present day knowledge is trustworthy, profusion: 
of seeds seems to be a sine qud nem if desirable distribution is to be achieved. 
Reduce the number of seeds and extinction would be almost inevitable, not 
because a low percentage of germinative capacity is characteristic of the 
Orchids, but because the mycorrhizal relationship demands a prodigality of 
seeds. Only those Orchid seeds enjoy a fair prospect of successful 
germination in places far removed from a flourishing Orchid population 
that have become inoculated after initial dissemination. For every seed! 
that becomes inoculated millions must fall where there is no likelihood of 
symbiosis being established. 
If, at this point in our discussion, we attempt to piece together briefly 
the probable story of the Orchids in evolution, basing our assumptions on 
what we now believe to be true in the life history of existing species, we 
begin with those ancestral forms which were characterized by the capacity 
to yield an abundance of seeds. These ancestral Orchids in the struggle 
for existence were attacked by a fungus. They not only withstood the 
attack, but emerged from it with profit. The fungus became a useful 
partner and a symbiotic condition was established. As the Orchids evolved,. 
their seeds gradually lost the capacity to germinate without the aid of the 
fungus, that is, they lost the capacity to render the soluble organic’ 
compounds of the substratum assimilable. The accomplishment of this. 
work became the function of the fungus. The fungus in the meantime 
became more and more dependent on intimate association with Orchids: 
and gradually ceased to live autonomously for any length of time. It took. 
on the peculiarity of passing from one generation of Orchids to another, 
rarely reproducing itself by spores. It ceased to carry on an independent 
existence. At this point a condition was reached which would militate 
against the success of the Orchids, because seeds which fell far removed 
from a parent plant would be unlikely to meet with the normal and: 
indispensable symbiont. Such a condition would only be favourable to: 
those Orchids which continued to yield a large number of seeds, and 
those species would be best adapted to successful competition which were 
characterized by an increase in seed yield and by slow germination. We 
find, for example, that it is not among the less highly differentiated species- 
of the family (such as those of Habenaria, Orchis and Cepalanthera), that 
