20 INTROGRESSIVE HYBRIDIZATION 



partially fertile progeny with species of Epidendrum and of 

 Sophronitis. The Milto-Ondontiodas similarly may be 

 crossed with species of the genus Oncidium. Some of the 

 widest known crosses have been produced artificially be- 

 tween exceedingly distinct genera in the grass family. 

 Mangelsdorf and Reeves produced hybrids of Zea with 

 Tripsacum, genera so distinct that the homologous parts of 

 the inflorescences in the two are still matters of dispute. 

 Hybrids between sugar canes (Saccharum) and other grasses 

 having been demonstrated, Dr. Janaki-Ammal attempted a 

 whole series of intergeneric crosses. She succeeded (1941, 

 1942) in obtaining hybrids and second-generation descend- 

 ants between Saccharum and Erianthus and between Sac- 

 charum and Imperata. She even obtained weak F/s be- 

 tween sugar cane (Saccharum) and maize (Zea). Other 

 sugar-cane breeders produced useful crosses between Sor- 

 ghum and sugar cane and between sugar cane and Narenga. 

 These amazing results were first received with considerable 

 scepticism, but Janaki-Ammal's detailed descriptions and 

 photographs left room for little doubt. Similar results have 

 since been obtained by other sugar-cane breeders. 



One of the widest fertile crosses known occurred in England 

 (Osborn, 1941), where the Monterey Cypress, Cupressus 

 macrocarpa, and the Yellow Cedar from the Pacific Coast 

 of North America, Chamaecyparis nootkatensis, were grown 

 near each other on a private estate and both reached fruiting 

 size. Among the seedlings that were raised from both parents 

 were a few which differed from their siblings to such a de- 

 gree that they were noticed and kept track of. As they de- 

 veloped, both sets were found to be intermediate between 

 Cupressus and Chamaecyparis, and the two sets were es- 

 sentially alike. There was then little doubt that an inter- 

 generic hybrid had occurred. Specimens of the hybrid 

 (known horticulturally as Cupressocyparis Leylandii) have 

 been grown to fruiting age and seedlings have been raised 

 from them, demonstrating that under certain conditions gene 

 exchange is possible between these distinct genera. 



