The South Australian Naturalist. 59 



On three of the railway banks between Eden and Blackwood, 

 ten or eleven miles from Adelaide, there are a fairly large 

 number of Diuris growing and flowering every year. The 

 embankments are made with material from adjacent cuttings, 

 and are absolutely made-up soil. The first embankment from 

 Eden towards Blackwood is about 150 yards long and 15 yards 

 high, and on 14/9/18 had about twenty specimens of Diuris 

 pedunculata on it in flower. The second embankment, which 

 is about 200 yards long and twenty j^ards high in the middle, 

 has about 400 specimens on it. Most of these are Diuris peduncu- 

 lata — one hundred of which I actually counted, the rest I 

 calculated. Some of them are growing do^\TL the rocky sides of 

 the embankment, where they would have easily have grown from 

 seed, and where it is almost impossible for them to have spread 

 by their underground system. There were also a number of 

 Diuris palustris, and also several specimens of D. maculata. On 

 the third embankment I calculated about 100 specimens of 

 D. pedunculata on a stretch of 100 yards. 



How did these orchids originate on these embankments, 

 which were made up about thirty or forty years ago? It 

 seems impossible that plants were moved there in the soil and 

 continued to grow. The rough handling the soil would receive 

 in making up the bank would kill the tubers. Even if all were 

 not killed or destroyed, how many of them would be planted at 

 the right depth to ensure their living in the new situation. And, 

 again, if one or two survived all this and managed to grow on 

 the bank, how would you account for the wide distribution of 

 the plants along the embankment other than by seed dispersal? 

 It seems to me that the orchids growing in this particular situa- 

 tion did not originate from tubers, and the instances quoted 

 seem excellent arguments in favour of propagation by seed as 

 against increase by tuberous expansion and development. 



(1) B.A.A.S. Handbook of South Australia (1914). 



(2) ''Notes on the Reproduction of Terrestrial Orchids" in ''The 

 Victorian Naturalist," Vol. XXXIV. (1918), p. 161. 



