8 INTROGRESSIVE HYBRIDIZATION 



those of Viosca. Meanwhile, the horticultural world took a 

 deep interest in the beautiful chance hybrids of these re- 

 mote pastures. Hardier and more generally satisfactory hy- 

 brids eventually were bred artificially, but until these man- 

 made hybrids reached the market in quantity there was 

 a brisk local business in the brilliant mongrel iris popula- 

 tions of these Httle agricultural communities of the lower 

 delta. 



Riley's intensive studies (1938, 1939a, 1939&) of these 

 hybrids were made at one of the localities where Viosca had 

 discovered a particularly brilliant group. An old abandoned 

 deltaic stream had built up two levees, one of which served as 

 a base for the public road. One of the bayous of the river 

 had swung out, cutting across these ancient ridges and form- 

 ing a wide marsh in which there were numerous plants of 

 HGC. Fulva occurred sporadically along the edge of the 

 abandoned stream for several miles along the road. At the 

 very point where these two habitats met, there was a series of 

 small, neighboring farms, their property lines stretching back 

 at right angles to the road and the abandoned natural levee. 

 Each family had managed its property a little differently, 

 and the holdings were all so narrow that the whole com- 

 munity was almost like a laboratory experiment. At several 

 places there were occasional iris plants that were tj^ical of 

 neither Fulva nor HGC and might possibly have been of 

 partially hybrid origin. On one farm, however, there were 

 great numbers of pecuhar irises, most of them resembling 

 the hybrids obtained by the iris breeders from controlled pol- 

 linations. They grew in two main groups (H-1 and H-2 in 

 Plate 1). The H-2 group w^as rather similar to HGC, and 

 some of its members wxre within the variation range of that 

 species. On the whole they looked like a population of HGC 

 slightly more variable than usual, but if one tabulated the 

 variation it was mostly in the direction of Fulva. That is to 

 say, the flower colors tended a little more towards red on the 

 average; there w^ere more small flowers; there were more 

 frequently several flow^ers on a stalk; and the petals w^ere not 



