OECHID CONFERENCE. 



441 



pigments in art, or the colours of the spectrum, and (in a broad sense, 

 bearing in mind that some colours are more powerful than others) 

 I believe that the same combination of colours takes place in 

 Orchids. 



The dictionary definition of white is " reflecting to the eye all the 

 rays of the spectrum combined," that is to say, " having all the con- 

 stituent colours so blended that no colour is predominant," and I believe 

 that this is the correct definition of the white in Orchid flowers. 



Now, whilst the perfect blending of all the colours of the spectrum 

 produces perfect white, where the blending of the colours is not perfect, 

 a perfect white is not produced. 



The synthetic white oi the physics laboratory produced from pig- 

 ments resembling all the colours of the spectrum, and combined, does 

 not give perfect white. 



In the same way there are various whites in Orchid flowers com- 

 parable to Paper White, Snow White, Milk White, and Cream White, 

 each of which is distinguishable from the others. 



In a lecture at the Central Technical College, Sir William Abdy 

 caused to be thrown upon a sheet, by means of a lantern, three super- 

 imposed photographic pictures, projected through three coloured 

 screens, thereby obtaining a coloured picture upon the sheet. The 

 white objects in the view which had been photographed were repro- 

 duced white upon the sheet, notwithstanding that the light had passed 

 through three coloured screens ; that is to say, white (not necessarily 

 perfect) had been produced by means of colours. 



Now, considering that almost every Orchid known to us has a 

 white variety, there must be some logical reason for its existence, 

 and if the perfect combination of colour produces white, I think I am 

 justified in concluding that it is the combination of colour which 

 produces the white (more or less perfectly) in Orchid flowers. 



This opinion seems to drive me still further away from the desired 

 object of obtaining white Orchids from seed, because I can never hope 

 to blend red, yellow, and blue flowers by crossing so perfectly as to 

 produce white flowers. 



Experience, however, tells me that white can be built up by 

 choosing purple flowers upon one side and yellow upon the other, 

 and the fainter the purple colour is, not only the more nearly do 

 the flowers of the seedlings approach white, but the proportion of 

 white over coloured flowers is greater. 



The parents of the following examples contain purple on the one 

 side and yellow upon the other, and the nearer these colours are to 

 pure pale purple and pure yellow the greater is the proportion of whites 

 obtained. 



Dendrohium Wiganiae xantliocliilon, crossed with D. Thwaitesiae, 

 produced flowers, some with rose, some with violet, some with yellow, 

 j and some with white sepals and petals — showing that there were not 

 I only two, but several, factors involved. 



I The same results were obtained by crossing Dendrohium Wiganiae 



