SPECIAL TECHNIQUES 97 



ilarly the other hybrid population H-1 (Fig. 22) in the same 

 way we can demonstrate that these correlations hold for it 

 and are even more strongly apparent there. 



Having demonstrated the repeated existence of these 

 complex correlations, we now proceed on the hypothesis that 

 they are the result of introgression from a species in which 



R 



RV 



m 



c 

 •a 



0) 



OS 



BV 



VB 



5 6 7 8 9 10 11 



Petal size >- 



Fig. 22. Pictorialized diagram of Hybrid Colony H-1 of Plate 1, plotted 

 from Riley's data, using the symbols of Fig. 23. 



all these characters were united. We can, therefore, extra- 

 polate our data on the correlates in the hybrid population 

 and produce a conception of what species would have been 

 required to create such an effect. Population H-2 was very 

 similar to HGC on the whole, and even H-1 bore a strong 

 resemblance to it. Therefore, w^e need to imagine what kind 

 of iris when crossed with HGC would yield such variants. 

 If it produced reddish blue descendants in its cross with 

 HGC, then it must have been redder still. If it produced 

 small flowers in combination with. HGC, then it must itself 

 have had very small flowers. In this way we may extra- 



