MENDEL'S LAW. 



(except in a single individual). Hence the cross VB X GS gives 

 us the hybrid VgSb. When this hybrid produces pollen and ovules, 

 the pair of characters V and G separate, V going to half the pollen 

 grains and ovules, and G to the other half. S and B do the same 

 thing, but without reference to V and G. Hence we have four kinds 

 of pollen grains and four of ovules, as shown in the following diagram : 



VB 



GS 



VgSb 



Pollen. 



f VB 



vs 



GB 

 GS 



Ovules. 



VB 



VS 

 GB 

 GS 



Here we have a mixture of 

 four kinds of pollen offered to 

 four kinds of ovules. On the 

 average, one fourth of each kind 

 of ovules will be fertilized by 

 each kind of pollen, giving six- 

 teen equally numerous fertiliza- 

 tions, as follows: 



l. 

 2. 

 3. 



4. 

 5. 



6. 



7. 

 8. 



VB X 

 VS X 

 GB X 

 GS X 

 VBX 

 VS X 

 GB X 

 GS X 



VB = VB. 



VB = VSb. 

 VB = VgB. 

 VB = VgSb. 

 VS=VSb. 



VS = vs. 



VS = VgSb. 

 VS = VgS. 



9. 

 10. 

 11. 

 12. 

 13. 

 14. 

 15. 

 16. 



VB X 



vsx 



GBX 

 GS X 

 VB X 

 VSX 

 GB X 

 GS X 



GB = VgB. 

 GB = VgSb. 

 GB = GB. 

 GB = GSb. 

 GS=VgSb. 

 GS = VgS. 

 GS = GSb. 

 GS = GS. 



Here it will be noticed that (2) and (5) give the same result. 

 Similarly, (3) and (9); (8) and (14); (12) and (15); and (4), 

 (7), (10) and (13). We may, therefore, represent the hybrid and 

 its progeny thus: 



VB \ 



GS ] 



VgSb 



16 parts. 



This diagram may easily be extended 

 to later generations. VS will produce 

 VS. The progeny of the type VSb will 

 all have the character V, but one fourth 

 of it will have the character S, two 

 fourths Sb, and one fourth B; thus, 



VSb J, 



1 VS 



2 VSb 

 1 VB 



4 parts. 



In like manner the progeny of the other types may be written out. 



Of the nine types produced from the hybrid, four of them, VS, 

 VB, GS, GB, are pure, and will reproduce true to seed. They have 

 no characters hidden in them to crop out in later generations. It 

 will be noticed that each of these pure types constitute one sixteenth 

 of the progeny of the hybrid. Four other types, VSb, VgS, VgB 



VOL. lxii. 18. 



