MINUTE STRUCTURE OF PLANT HYBRIDS. 253 



cell sap, slight chemical change may produce marked colour effect. Yellow, on the other 

 hand, being a pigment intimately united with and formed in protoplasmic masses, is less 

 liable to rapid change. White we naturally consider to be due to refraction of light from 

 cell surfaces, from walls which bound intercellular spaces, &c. If, therefore, a cross is 

 effected between two parents, one of which has large richly-coloured petals or other parts, 

 the other parent smaller and pale-coloured parts, the hybrid may appear to have a greater 

 resemblance to the first, though exactly intermediate, for half of the large amount of rich 

 pigment from the one parent which will be diffused throughout its cells, will apparently 

 give an exceptional richness of effect. A good example of this is furnished by Rhodo- 

 dendron Nobleanum, which was raised from the scarlet, rather large-flowered R. arboreum 

 and the greenish or pinkish white, smaller-flowered R. Caucasicum. To a casual observer 

 the hybrid seems to take wholly after the first. An arrangement of the three blossoms 

 side by side effectually demonstrates how nearly the hybrid ranks between the parents. To 

 take another illustration from vegetative parts, the fine hybrid Nepenthes Mastersiana is a 

 cross of 2V. sanguinea, the pitchers of which when mature are of large size and vary in colour 

 from greenish-scarlet to crimson, and of N. Khasiana, which bears long narrow pitchers, 

 varying from yellowish -green to dull red-green. The hybrid accordingly presents a 

 corresponding latitude in colour effect, though on the average it is greenish-crimson. 



The opposite relation equally holds true, as proved by the dark purplish crimson 

 Rhododendron atrovirens, when crossed by R. ciliatum, giving the bright crimson- 

 pink R. prcecox, and similarly the small-flowered dull pink R. glaucum, when crossed 

 by R. ciliatum, gives the pale pink R. Grievei. 



Though cases have been recorded of peculiar and apparently inexplicable colour blend- 

 ing, there are few, I am persuaded, which will not yield to ordinary methods of analysis. 

 A very interesting series of crosses and recrosses of East Indian Rhododendrons has been 

 studied by Professor George Henslow,* and some of the colour combinations described 

 are such as one would scarcely have expected, but it is quite possible that the evolution 

 of some new chemical product through hybrid combination may simplify or quite explain 

 the apparent anomalies. 



If we are to put any trust in colour statistics as hitherto given, we are bound to con- 

 clude that the balance of evidence is in favour of a hybrid inheriting half the amount of 

 colour effect from each parent, whether due to union of the same or another colour series. 

 Even when colours belong to opposite ends of the spectrum, evenly balanced fusion seems 

 to result, though the day is not long past when this was regarded as almost or quite im- 

 possible. Thus the brilliant scarlet-flowered Delphinium nudicaule has been crossed in 

 the Edinburgh Botanic Garden with the dark blue-flowered D. cashmirianum, the hybrid 

 product being of a lurid purple-red hue, which, when set between the parents, is the per- 

 fection of blending. Though Gartner failed to cross the blue and red varieties of 

 Anagallis, this has since been effected. It is also true that few if any allied species, 

 even though very different in colour, resist steady and repeated attempts to cross. 



* Gardeners? Chronicle, vol. ix. p. 618, 1891 ; Trans. Boij. Hort. Soc, 1891. 



