MENDEL'S PRINCIPLES APPLIED TO ORCHID HYBRIDS. 619 



minajits of any single character in its germ-cells, which will be either S 

 or I, but not SI. 



Then, if SI be crossed with B, the progeny will come out for any 

 single character, either BS or BI (on the average in equal numbers, 

 according to the law of chance) ; and on the other hand they cannot come 

 out as BSI or even SI, if Mendel's theory is correct. 



In order to test the matter thoroughly it is evident therefore that, in 

 addition to the above-mentioned species and hybrids, we must also know 

 the characters of the collateral hybrids BS and BI, so as to be able to 

 compare them with our hybrids of SI x B. Fortunately this is com- 

 paratively easy, as large numbers of both BS and BI have been raised, 

 figured, and described. The former BS, the hybrid between P. Spicerianum 



