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JOUENAL OF THE KOYAL HORTICULTURAL SOCIETY. 



since sixteen individuals are included in the series. Therefore the 

 participators in the fertilisation are — 



Pollen cells AB + AB + AB + AB + Ab + Ab + Ab + Ab + 

 aB + aB + aB + aB + ab + ab + ab + ab. 



E^£r cells AB + AB + AB + AB + Ab-hAb + Ab + Ab4- 

 aB 4- aB + aB + aB + ab + ab + ab + ab. 



In the process of fertilisation each pollen form unites on an average 

 equally often with each egg cell form, so that each of the four pollen cells 

 AB unites once with one of the forms of egg cell AB, Ab, aB, ab. In 

 precisely the same way the rest of the pollen cells of the forms Ab, aB, ab 

 unite with all the other egg cells. We obtain therefore — 



AB , AB AB AB Ab Ab Ab Ab 

 AB'^Ab aB ab AB Ab aB ab 



aB aB aB aB ab ab ab ab 

 AB Ab aB ab AB"^Ab aB ab' 



or 



AB + ABb + AaB + AaBb + ABb + Ab + AaBb + Aab + AaB + AaBb + aB -f 

 aBb + AaBb + Aab + aBb + ab=AB + Ab + aB + ab + 2 ABb + 2 aBb-h 

 2 AaB + 2 Aab + 4 AaBb.* 



In precisely similar fashion is the developmental series of hybrids 

 exhibited when three kinds of differentiating characters are conjoined in 

 them. The hybrids form eight various kinds of egg and pollen cells — 

 ABC, ABc, AbC, Abe, aBC, aBc, abC, abc — and each pollen form unites 

 itself again on the average once with each form of egg cell. 



The law of combination of different characters which governs the 

 development of the hybrids finds therefore its foundation and explanation 

 in the principle enunciated, that the hybrids produce egg cells and pollen 

 cells which in equal numbers represent all constant forms which result 

 from the combination of characters united by fertilisation. 



Experiments with Hybeids of other Species of Plants. 



"It must be the object of further experiments to ascertain whether the 

 law of development discovered for Pisum applies' also to the hybrids of 

 other plants. To this end several experiments were recently commenced. 

 Two minor experiments with species of Phaseoliis have been completed, 

 and may be here mentioned. 



A trial with Phaseohis vulgaris and Phaseolus nanus gave results 

 in perfect agreement. Ph. nanus had together with the dwai-f axis 

 simply inflated green pods. Ph. vulgaris had, on the other hand, an axis 

 10 feet to 12 feet high, and yellow coloured pods, constricted when ripe. 

 The ratios of the numbers in vrhich the different forms appeared in the 

 separate generationjs were the same as with Pisum. Also the development 

 of the constant combinations resiilted according to the law of simple 

 combination of characters, exactly as in the case of Pisum. There were 

 obtained — 



* [In the original the sign of equality ( = ) is here represented by +, evidently a 

 misprint. — W. B.J 



