68 Double Petunias 



The material used in these experiments included the following 

 forms : — 



(1) P. violacea {phcenicia). Flowers deep magenta with very 

 dark throat. Pollen blue. 



(2) P. nyctaginiflora. Flowers white with yellow flush in the 

 throat. Pollen yellow. Of stouter habit than the preceding species 

 and with larger flowers. 



(3) P. hyhrida grandiflora. Garden hybrids, (a) Flowers magenta 

 or magenta and white, variously striped or blotched. Corolla plain 

 edged. Pollen blue, (h) Var. fimhriata. Flowers nearly pure white. 

 Corolla fringed. Sepals broad and slightly curled. (Lady of the 

 Lake.) 



(4) Countess of Ellesmere. A garden variety. Flowers rose- 

 coloured with throat nearly white. Pollen white. 



The plants were raised from seed. The two species P. violacea and 

 P. nyctaginiflora and the garden form Countess of Ellesmere are all 

 single-flowered. The seed from which the grandiflora plants were 

 raised was stated to yield a proportion of doubles, and a mixture of 

 singles and doubles was duly obtained. In growers' catalogues it is 

 generally stated that the seed which is guaranteed to produce doubles 

 has been obtained from flowers (i.e. singles) artificially fertilised with 

 the pollen of doubles. This, as will appear presently, seems to be the 

 only method of producing double-flowered plants from seed (see p. 60). 

 The proportion of doubles obtainable is variously quoted as 20 — 40 per 

 cent. The object of the present experiments was to discover under 

 what circumstances doubles may be expected to occur, and also, if 

 possible, to determine whether the proportion of doubles obtainable 

 was constant. 



A. Description of the double flower. 



The plants which will bear double flowers may be recognised before 

 the flower expands by the shape of the bud which is short, thick and 

 blunt, whereas that of the single is long, slender and pointed. In the 

 single flower we have a simple funnel-shaped corolla, five epipetalous 

 stamens, and an ovary with a slender style terminating in the expanded 

 disc of the stigma (see fig. 1). In many cases the connective is pro- 

 longed above the anthers in the form of a petaloid structure varying in 

 size from a short process so small as to be easily overlooked after the 



