88 Sargent, Westratian Form of Prasophyltum australe. l^j^fJ^^ 



L Vol. X-X.^. 



organ with pollen. I have never deliberately watched the 

 flowers, but I have spent a good many half-hours moving about 

 amongst them. So far I have not had the good fortune to 

 observe an insect visit. 



In 191 1 I made an attempt to estimate the percentage of 

 fruits produced by the flowers. I visited a locality where I 

 had seen numerous scapes earlier in the year — on the 8th of 

 November. Most of the scapes had vanished ; probably they 

 had been trodden down, or perhaps eaten, by horses or sheep. 

 Diligent search discovered eleven scapes, with fruits just 

 dehiscing — four with complete racemes and seven with the 

 apices missing. This collection totalled just 100 flowers, of 

 which 42 had produced fruit. Only one raceme was intact 

 when I reached home. It bore 21 fruits and 24 infertile, 

 withered flowers (46 per cent, of fruits). The lowermost 

 fourteen flowers were all fertile, and the topmost few fruitless. 

 It seems to be the rule that the early flowers are most successful 

 in securing pollination, and the chances decrease as the season 

 advances. So I judge from the fragments, and from scapes 

 seen in other years late in the season. This suggests that the 

 activity or prevalence of poUinators early in the season is a 

 contributory cause of the earlier flowering of the Western 

 form. It has triumphed in the struggle for existence, because 

 it has found pollinators for its flowers sufficiently early to 

 enable it to occupy the dry situation available. (Active life 

 would be impossible for it after about the end of October.) 

 That the pollinators are most active early in the season seems 

 an advantage : the earlier flowering individuals stand the best 

 chance of reproduction, and so the form tends to become better 

 fitted for its arid home. Even now the last few flowers some- 

 times wither without unfolding. From this I conclude that 

 the later flowers have small chance of maturing fruit, even if 

 pollinated. If my ideas are correct, the Western form is really 

 a distinct section of the species — distinct physiologically, but 

 not morphologically. There has been no change of form, 

 because structurally the flower was at the start (when the 

 Western plant struck out on its own path) already perfectly 

 efficient for its purpose. It seems we have here material for 

 some interesting and useful experiments. Whether the 

 Western plant has really altered at all is capable of determination 

 by attempting to grow it in a swamp, preferably in South Aus- 

 tralia or Victoria. The Eastern form should simultaneously 

 be transferred to dry conditions. Many small details would 

 require careful attention ; but the difficulties are far from being 

 insuperable. 



