Darwin- Wallace Celebration. 71 



happen to grow intermixed. Approximately parallel cases are now 

 known among artificial hybrids of 0. crispiim with species which 

 grow in different localities, particularly with 0. Harryanum. All 

 these hybrids are completely fertile. 



Thus we have evidence that 0. crispum grows naturally with five 

 other species, with all of which it hybridises, and that the resulting 

 primary hybrids again cross with the original species, yielding 

 secondary hybrids, some of which are not distinguishable from what 

 have usually been considered as spotted forms of 0. crispum. All 

 this has long been suspected, and now the details are being filled in 

 by cultural experiments. It is believed that the process extends 

 much further, for the agencies by which these puzzling intermediate 

 forms have arisen have been in existence for ages. For a long time 

 their origin was a matter of inference, after comparison with the 

 original species; but recent experiments, while confirming these 

 inferences, have carried the matter further, and revealed a new 

 complication, in the existence of what is known as " reversion." 



In the case of secondary hybrids, at least, seedlings out of the 

 same capsule often show a remarkable polymorphism, and some of 

 them so closely resemble the original species that in the absence of a 

 knowledge of their origin they would be referred to them. A 

 single example may be mentioned. Some time ago M. Peeters, of 

 Brussels, crossed the natural hybrid 0. Adriance with a blotched 

 form of 0. crispum, and from the resulting capsule raised a large 

 batch of seedlings, which have now flowered. During a recent visit 

 to Brussels I had the good fortune to see them, and I was astonished 

 at the range of variation, which seemed almost incredible. There 

 were forms with white, light yellow, and deep yellow ground-colour, 

 with the greatest possible amount of variation in the size of the 

 flowers, and in the size, number, arrangement, and colour of the spots. 

 Without a knowledge of their origin some would have been referred 

 to 0. Adriance and others to spotted foims of 0. crispum, and yet 

 all are technically forms of 0. Fascinator, which had previously 

 been raised. 



Hybrid Odontoglossums are not by any means confined to the 

 regions just mentioned. 0. triumphcms and 0. gloriosum extend 

 into the Ocana district, where they cross, giving 0. Leeanum, and 

 here the former with 0. nobile yields 0. excellens (whose parentage 

 has been proved), and the latter with 0. nobile produces 0. 



