A Study of the self-pollination of Thelymitra venosa 

 R.br. and Some Notes on its Implications 



hy David L. Jonhs 



flwlxiiulia venosa R.Br, has been 

 oK ,usly reported as a sclf- 

 polliiwtiny species by Rogers and 

 Nicholls'', and its mechanism has been 

 lilnil K,hly dealt with by Rogers'. 

 Both autlWCS stated that the species 

 jj. v ;||-poilmating in bud and by 

 ,hc time the flower opens the pro- 

 cess is well advanced It is diflicult 

 10 see how this species can be 

 llA „hcd m natural hybridization, 

 ,,pj vol this has been staled by 

 authors" As well I have seen speci- 

 mens ot a possible hybrid involving 

 IHvlxmiini viiuiui and 7. ixioitics 

 from Rocky Plain in North eastern 

 Victoria. Pickled material was col- 

 lected by Ti & Mv&C of the Mel- 

 bourne Herbarium and the collection 

 has been reported on hy Peterson . 

 Subsequent collections of the same 

 hybrid have been made by A. C*. 

 Beauuleholc at Rocky Plain, and 

 other plaees in North-eastern Vic- 

 toria. 



In an attempt to determine how 

 H species thai is self-pollinated early 

 in the bud can be involved in hybri- 

 ilualion. I made a comprehensive 

 flltdy ot 7. VenoSH in the field at lake 

 Mountain on 25 January IJJTQt. The 

 results are verv interesting and will 

 he leported in this paper. 



The temperature on 25 January 

 was about 75"F: one of the warm 

 balmy da\s thai make (be sub-alpme 

 areas so mviiing dining early Sum- 

 mei. Hie Sun-orchids were al Iheir 

 peak with the majority being wide 

 open while a few of Ihe earlier ones 

 had just finished and some of ihe 

 later ones were still bud The 

 survey involved a study of the pol- 

 BhUlOlJ supe of buds, open flowi-rx 



Auguit, 1971 



and withered flowers. Two hundred 

 open flowers were examined and 

 fifty buds and withered flowers were 

 collected for later dissection. 



The examination of open flowers 

 revealed that 35-4098 of them had 

 ni> pollen on the stigma. A closer 

 examination of these Mowers showed 

 lhat in about 20% the anther sacs 

 were completely empty: in 10T« the 

 anther iLself was abortive while the 

 stigma was still functional and Ihe 

 remaining 10% had anthers which 

 had not yet shed their pollen. 



These reSUlfS show that nearly half 

 of the Thelymitra venosa flowers 

 examined at I ake Mountain have not 



Thetynihin fPROW 



Pholo; I ft ftpthpllMH 



217 



