60 Double Petunias 



malformed, the corolla being split and the segments curled ; the ovary 

 was not opened. The remaining flowers on the plant showed the usual 

 degree of doubleness. Among the flowers of single plants only two were 

 observed in which there was any approach to doubling, and in each case 

 the remaining flowers on the individual were normal singles. In one of 

 these flowers a single large petaloid structure had developed in the 

 corolla tube ; in the other a similar structure arose near each of the five 

 stamens, the line of adhesion to the corolla coinciding with that of 

 a stamen and forming a common decurrent ridge. It was noticed that 

 in single plants kept through the winter under unfavourable conditions 

 the first flowers produced in the following spring were often deformed, 

 the corolla being split and infolded but without showing any tendency 

 towards doubleness. 



B. Results of breeding experiments. 



The general results of the experiments carried on during the last 

 five years may be briefly stated as follows : — 



1. When a single is crossed with a double, doubles as well as 

 singles occur in the first {Fi) generation. 



2. When such F^ .singles are self-fertilised' or fertilised inter se the 

 resulting offspring are all single. Doubles in fact are only obtained 

 when the pollen of doubles has been used to fertilise the seed-parent, 

 so that this operation must be repeated in each generation. 



3. The proportion of singles in a mixed family is probably always 

 in excess of the doubles. 



Details of the experiments are given in the accompanying Tables. 

 The results recorded in Tables I and II show that singles, whether 

 belonging to one of the type forms or derived from a previous cross, 

 when fertilised with pollen from a double yield a mixture of singles and 

 doubles in the first generation. Out of a total of 41 families thus bred, 

 40 included some doubles. As regards the remaining case in which no 

 doubles were recorded there is little doubt that their absence is due 

 solely to the small size of the family (4), and that a larger sowing 

 would have given the usual mixture. 



■ If protected under muslin or glass and left undisturbed violacea and hybrida rarely 

 set seed ; even wlien artificially self-fertilised many pollinations give no result. On the 

 other hand nyctaginiftora, under the same conditions will often set seed, and does so 

 readily when artificially fertilised with its own pollen. Further experiments concerning 

 the sterility of these forms are now in progress. 



