The Hypothesis of Transmission 181 



develops into a plant which is similar to the twining P. 

 multiflorous, but remains smaller than the latter. The 

 flowers of the hybrid are of a pale red, being a tint midway 

 between the two parents, as I had the opportunity of 

 convincing myself personally. The red coloring matter 

 is found in solution in the vacuoles of the cells of the 

 petals. 



The ability of the vacuoles to form the red erythro- 

 phyll comes from the father, in this instance. But the 

 vacuoles of the hybrid originate morphologically from 

 those of the mother. The power of producing erythro- 

 phyll must therefore have been transmitted in a latent 

 condition in the sperm-nucleus of the father to the nu- 

 cleus of the egg-cell, and must have been communicated 

 sooner or later to the vacuoles of the hybrid. 



The same thing is taught by many other hybrids, as, 

 for example, Digitalis lutea 9 x purpurea $ , Linaria 

 vulgaris 9 x purpurea $ , Linaria genistaefolia ? x pur- 

 purea $ , et cetera. 2 * 



The yellow color of the flow r ers behaves in the same 

 way. Digitalis lutea-purpurea forms the best illustra- 

 tion. The two forms D. purpurea $ x lutea $ and D. 

 lutea $ x purpurea $ are quite alike, with the exception 

 of some slight variations in the color of the flowers. 24 

 Naudin gives an illustration of the hybrid ; the flower has 

 a pure yellow color in one cluster, while in the other one, 

 yellow is mixed with pale red. 25 Of the two mentioned 

 hybrids of the Linaria I do not find any record of the 

 reciprocal forms. 



23 Cf. Focke, Die Pflansenmischlinge, pp. 311, 315, and other 

 passages. 



24 Focke, loc. cit. p. 315. 



25 Naudin. Nouvelles recherches sur 1'hybridite. Nouvelles Ar- 

 chives du Museum d'histore naturelle de Paris, p. 95, PI. 2. 1869. 



