EXPERIMENTS IX PLANT HYBRIDISATION, 



23 



Constant 



Axis. 



Colour of 



Form of 



combinations. 





the unripe pods. 



the ripe pods. 



1 



long 



green 



'Hit 



]nnateu 



2 



)> 





constricted 



3 



j> 



yellow 



inflated 



4 



?j 



J) 



constricted 



5 



short 



green 



inflated 



6 



?j 





constricted 



7 





yellow 



inflated 



8 



J) 





constricted 



The green colour of the pod, the inflated forms, and the long axis were, as 

 in Pisum, dominant characters. 



Another trial with two very different species of Phaseolus had only a 

 partial result. Phaseolus nanus, L., served as seed parent, a perfectly 

 constant species, with white flowers in short bunches and small white 

 seeds in straight, inflated, smooth pods ; as pollen parent was used Ph. 

 multifloTUs, W., with tall winding stem, purple-red flowers in very long 

 bunches, rough, sickle-shaped crooked pods, and large seeds which bore 

 black flecks and splashes on a peach-blood-red ground. 



The hybrids had the greatest similarity to the pollen parent, but 

 the flowers appeared less intensely coloured. Their fertility was very 

 limited ; from seventeen plants, which together developed many hundreds 

 of flowers, only forty-nine seeds in all were obtained. These were of 

 medium size, and were flecked and splashed similarly to those of Ph. multi- 

 florus, while the ground colour was not materially different. The next 

 year forty-four plants were raised from these seeds, of which only thirty- 

 one reached the flowering stage. The characters of Ph. nanus, which 

 had been altogether latent in the hybrids, reappeared in various com- 

 binations ; their ratio, however, with relation to the dominant characters 

 was necessarily very fluctuating owing to the small number of trial plants. 

 With certain characters, as in those of the axis and the form of pod, it 

 was, however, as in the case of Pisum, almost exactly 1 : 3. 



Insignificant as the results of this trial may be as regards the deter- 

 mination of the relative numbers in which the various forms appeared, it 

 presents, on the other hand, the phenomenon of a remarkable change of 

 colour in the flowers and seed of the hybrids. In Pisum it is known that 

 the characters of the flower- and seed-colour present themselves un- 

 changed in the first and further generations, and that the- offspring of the 

 hybrids display exclusively the one or the other of the characters of the 

 original stocks. It is otherwise in the experiment we are considering. 

 The white flowers and the seed-colour oiPh. ^^/^/^s appeared, it is true, at 

 once in the first generation in one fairly fertile example, but the remaining 

 thirty plants developed flower colours which were of various grades 

 of purple-red to pale violet. The colouring of the seed-coat was no less 

 varied than that of the flowers. No plant could rank as fully fertile ; 

 many produced no fruit at all ; others only yielded fruits from the flowers 

 last produced, and did not ripen. From fifteen plants only were well- 

 developed seeds obtained. The greatest disposition to infertility was seen 

 in the forms with preponderantly red flowers, since out of sixteen of these 

 only four yielded ripe seed. Three of these had a similar seed pattern to 



