HYBRIDISING AND CROSS-BREEDING. 123 



the colours are more pure and variable in the floral envelopes 

 than elsewhere. I shall confine my remarks mainly to the 

 flower, and it may be as well to remind practical hybridisers 

 that their efforts to produce any desired shade of colour will 

 be much facilitated if they understand a little of the theory 

 of colours, since colours not unfrequently mix or blend in 

 flowers just as they do on the palette of an artist. The three 

 primary colours are red, blue, and yellow ; and the tissues of a 

 plant in which these colours, or some combinations of them, 

 are absent are white. Now if red and blue blend together the 

 result is purple, the tint varying according to the proportion of 

 the red to the blue, or vice versa. Red and yellow mixed pro- 

 duce orange, and blue and yellow green ; and if there is more 

 yellow than blue, the result is a light or apple green ; but if 

 there is more blue than yellow, a dark or blue green is the 

 result ; and the least change in the proportion of one colour to 

 the other produces a different tint. If this is true, then orange 

 flowers may be produced by crossing a red -flowered variety 

 or individual plant with one which bears yellow flowers ; and 

 in many cases this can be done. Red and yellow flowered 

 varieties or species of Zinnia, if crossed, always yield a fair per- 

 centage of orange - coloured flowers, although they vary in 

 depth or richness according as the red or yellow elements pre- 

 dominate. Some plants naturally produce orange-coloured 

 flowers, and it is singular to note that when orange-flowered 

 plants are crossed with white-flowered ones, the yellow element 

 often disappears altogether, and the result is a hybrid or cross- 

 bred plant with red or pink flowers. We have an example of 

 this result in Begonia Weltoniensis, which is a rosy-flowered 

 hybrid from the white-flowered B. Dregeii, fertilised with pollen 

 from the orange-flowered B. Sutherlandii. Blue and yellow 

 flowered plants do not readily cross with each other, however 

 nearly related ; and if they do so, the colour of the progeny 

 reverts either to the male or female parent; indeed, if these 

 colours were to blend in the floral envelopes, the result would 

 be a green-flowered plant. If red and blue flowered varieties 

 of the common Hyacinth are carefully cross-fertilised, the 

 result is seed which produces seedlings of three kinds, part 

 having red flowers ; another group with blue ones, according as 

 they take most after either parent ; and a third set with inter- 

 mediate characters, and having purple flowers, some reddish- 

 purple, some blue-purple, and others of a delicate mauve 

 colour. Where purple and white flowered plants are hybrid- 

 ised, as Petunia (Phoenicia) violacea and P. nyctaginiflora, the 

 result is pale rose or rosy-purple flowered forms, others having 



