NOTES ON SOME CURIOSITIES OF ORCHID BREEDING. 459 



Darwin cites some very remarkable curiosities in sterility, 

 showing what slight causes affect the reproductive organs in the 

 genus Oncidium. (" Animals and Plants," ii. pp. 114-116.) He 

 shows from the observations and experiments of Dr. Fritz 

 Muller in Brazil that at least nine species of Oncidium, including 

 the well-known 0. flexuosum, are perfectly self-sterile: they will 

 not set seed if pollinated with pollen off the same plant, and yet 

 they are perfectly fertile both in their pollen and their ovules 

 when crossed with a distinct species, or, most curious of all, if 

 pollinated with pollen of the same species but off a distinct indi- 

 vidual plant. For instance, on the stigma of 0. flexuosum Dr. 

 Muller put the plant's own pollen side by side with pollen of 

 another plant of the same species ; in five days the latter was 

 quite fresh and yellow, while the former was dark brown and 

 decayed. Again, he placed on another stigma of 0. flexuosum 

 pollen of a distinct plant of the same species side by side with 

 pollen from a distinct genus, Epidendrum : both behaved alike, 

 and after eleven days could not be distinguished except by their 

 caudicles. Dr. Muller also found that the self-sterile pollen not 

 only turned brown and decayed itself, but that it also caused the 

 surface of the stigma to decay. 



A few experiments carried out by myself at home confirm 

 those made by Dr. Muller in Brazil. I pollinated seventy- three 

 flowers of 0. flexuosum with their own pollen : the stigma- 

 chamber folded itself up in every case and swelled slightly, but 

 in a few days withered from the stalk upwards and dropped 

 off. I had exactly the same result with 0. incurvum, having 

 pollinated many flowers. In all cases the pollen decayed quickly. 

 It was different with 0. flexuosum crossed with 0. Forbesii : six 

 flowers only were pollinated and two of them set pods, one of 

 which burst prematurely and was full of chaffy seeds, while the 

 other opened properly 133 days after pollination, and on exami- 

 nation was found to contain a few good plump seeds, which 

 under the microscope appeared to be healthy living germs full 

 of green colouring matter. The seeds were very small and 

 round, hollowed out on one side, not unlike a shell : they were 

 duly sown on April 12 of this year, but as yet show no signs of 

 germination. I have also set three apparently good pods of 0. 

 incurvnm crossed with 0. flexuosum, which have not yet ripened. 

 Hand-raised hybrids of Oncidium do not seem to have been 



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