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JOURNAL OF TPTE ROYAL HORTICULTURAL SOCIETY. 



amount of purple sap-colour in the flowers and leaves, and consequently 

 are not true albinos, though for practical purposes they are usually 

 called " albinos," and in many cases are quite as beautiful and as 

 much sought after as the true albinos. In these false albinos both 

 the colour factors C and E are present, and consequently they give 

 quite different results in breeding from the true albinos. These false 

 albinos are really dilute coloured forms, and the fact that they usually 

 behave as Mendelian recessives in breeding shovv^s that their condition is 

 due to the absence of a factor for dense or full coloration, which factor 

 is present in the typical coloured form. 



The different kinds of dilution found in most species suggest that 

 more than one factor is concerned in the typical dense form. This 

 application of Genetics to Orchid breeding explains a good many 

 apparent mysteries. For instance, it explains why the false albino 

 Cypripedium insigne Sanderae breeds true to its special dilute form 

 or throws true albinos when selfed, and yet behaves as if it were an 

 ordinary C. insigne when crossed with the true albinO'S C. x Maudiae, 

 C. Lawrenceanum Hyeanuvi, and C. callosum Sanderae. These true 

 albinos arose originally by the loss of a colour factor (C), but the factor 

 for dense coloration (D) would still be present in those albinos, though 

 not manifested on account of the albinism. When this factor for densfe 

 coloration (D) is brought in by the cross, it naturally causes the parent 

 C. insigne Sanderae tO' behave as if it were an ordinary C. insigne. 



If these so-called " reversionary " forms were to be self-fertilized 

 or crossed inter se, both the recessive dilute coloration (dd) and the 

 albinism (cc) would appear in certain individuals. On the average, the 

 dilute forms would be expected to appear in three out of sixteen plants, 

 and the albino forms in four out of sixteen plants. The recent cases re- 

 ported in which the true albinO' Cypripedium Lawrenceanum Hyeanum., 

 crossed with the false albino C. niveum, gave typical coloured plants 

 of C. x' Aphrodite,' and in which the false albino C. niveum, crossed 

 with the false albino C. Lawrenceanum Gratrixianum^, gave the false 

 albino 0. x * Antigone ' album, are of course easily explained in the same 

 way. To the student of Genetics such cases as these present no diffi- 

 culty, as numbers of similar cases are well known in other plants and 

 in animals. 



The Ee-making of a Blotched Ceispum. 



In 1909 the writer showed that the ' ' blotched ' ' character in 

 Odontoglossums behaves as a Mendelian dominant to^ the " plain " 

 character, which is recessive. Since then further evidence has given 

 ample confirmation. The logical consequences of this application of 

 Genetics to Orchid breeding lead one to support Mr. de Baeri 

 Oeaw shay's idea, expressed many years ago, that blotched crispums 

 first appeared in a wild state through natural hybridization wuth other 

 species. 



From the point of view of Genetics, a dominant character is due 



* " Mendel's Law and its Application to Horticulture," Gard. Chron. 1909, i. 

 p. 303. 



