Sargent.— N otes on the Life-History of Pterostylis. 273 
formulate the above hypothetical account of the adventures of a dipteran, 
because at present it is only a working hypothesis. 
I think I have shown that the flowers are very cunningly devised. 
Intoxicating juice and irritable labellum seems a remarkably good combina- 
tion. But the best laid schemes do not always succeed, and the question 
arises : how effective is this one ? How shall we judge ? If seed production 
is to be the criterion, we shall receive an indefinite answer. Some species 
(e. g. P. reflexa , constricta , and rufa) are very shy seeders, but others seed 
freely, P. recurva sometimes gets over ninety per cent, of its flowers fertilized. 
But even supposing that the majority of species usually get but a small 
proportion of their flowers fertilized, it does not necessarily follow that the 
method of pollination is to blame. It might be thought that the sensitive 
labella would frequently be excited to close the flower by causes other than 
the alighting of desirable insects ; but this is not the case. Very seldom is 
a blossom found with its labellum closing the lower chamber. Wind, unless 
perhaps a very strong one, does not affect the labellum. The fact that over 
forty species of this genus are in existence, scattered over a vast continent, 
is surely strong evidence that their reproductive mechanism has proved 
effective in the past. As to the future ; five years’ close observation has 
given me the impression that the species I know are well able to hold their 
own in their native wilds. I have no data for forming an opinion as to the 
effect civilization will have on them. 
I have not exhausted the resources of my notebook, but I think I have 
said enough for the present. I have sought in this paper to give a clear 
idea of the impressions I have formed, so I have not tried to demonstrate 
any of my statements. Much that is interesting I have reluctantly omitted. 
I am continuing my observations and experiments, and I hope from time to 
time to deal with individual points in full detail. 
In conclusion, I wish to express my indebtedness to Professor Oliver, 
Dr. A. B. Rendle, and Dr. R. S. Rogers (of Adelaide, S.A.), for much help 
and encouragement in various ways. 
Literature. 
R. D. Fitzgerald : Australian Orchids. Sydney, 1882. 
J. D. Hooker : Flora of Tasmania, vol. ii, p. 18. 
B. W. Oliver: On the Sensitive Labellum of Masdevallia i?wscosa, Rchb. f., Ann. of Bot., vol. i, 
p. 246. 
