72 Darwin- Wallace Celebration. 



which has several synonyms. 0. triumphans also grows with 

 0. blandum, the two producing 0. Cookeanum ; and 0. Lindleyanum 

 extends into the Yaramal district, and crossing with 0. Harryanum 

 yields 0. Watticmum (whose parentage has also been proved 

 experimentally). Other hybrids occur in the Ocaria district, some 

 in Ecuador, and some in Mexico. Our knowledge of them depends 

 largely upon the popularity of the species as garden plants, and the 

 frequency with which they are imported, for they almost invariably 

 appear accidentally among importations of the parent species, and 

 their presence is not detected until they flower. Our knowledge of 

 0. crispum is almost entirely due to its popularity as a garden plant, 

 and to the enormous quantities in which it has been imported, and 

 to the same popularity is due the successful efforts to i-aise it and 

 the allied forms from hybrid seed. Without such popularity our 

 knowledge of the facts adduced would have been practically nil. 



These facts, it is believed, could be paralleled in the genera Salix, 

 Rosa, Rubus, and various others, if their history could be investigated 

 in the same way. Again, it may be remarked that natural hybrids 

 are known in many other Orchid genera, and are common in a few, 

 and in some cases they have been described as species, in others as 

 varieties of one of the parents. The facts are well known in a large 

 number of cases, and in a few the parentage has been proved 

 experimentally. The subject is worthy of increased attention, for 

 crossing increases variability, and variation is the material on which 

 natural selection works. Many hybrids are completely fertile, and 

 spontaneous hybrids often possess such distinctive features as to 

 have been described as new species or as varieties of one or the 

 other parent. Their permanence is a matter for further study and 

 experiment. Crossing may lead to or hasten the appearance of 

 distinct races, for there are many races of "florist's flowers" and 

 other garden plants which are known to be of mixed origin. Thus 

 hybridisation is a question of great biological importance, and one to 

 be taken into consideration in discussing the very origin of species, 

 indeed it is probably of more importance than has yet been 

 realised. 



