xxvi PROCEEDINGS OF THE ROYAL HORTICULTURAL SOCIETY. 



particular variety in this case was 1 Pink Beauty,' and the present is the 

 second year in which the trouble has occurred, though in different spots 

 in the same garden. 



Insects on Oleander, dc. — Mr. Saunders, F.L.S., reported that he had 

 examined the insects found upon various plants in a greenhouse, and sent 

 by Mr. Stanton Brown, A.R.H.S. They belonged to the family Psocideae, 

 and were specimens of the uncommon species Caecilius Dali. This species 

 is not known as a plant pest, but is said to feed upon fungoid matter of 

 various kinds, mould on palings and rust fungi on leaves, &c. They are 

 most frequent upon the bark of trees. 



Scientific Committee. March 3, 1908. 



Sir John T. Dillwyn-Lleweltn, Bart., in the Chair, with seventeen 

 members present and numerous visitors. 



Inheritance of Albinism in Orchids. — The following communication 

 was received from Mr. Hurst, F.L.S. : — Two distinct and definite cases of 

 albino orchids producing coloured forms when crossed were recently 

 brought before this Committee by Mr. Chapman. Such facts, accepted by 

 the Mendelians, are important, inasmuch as they go to show that 

 albinism in orchids is inherited in a similar manner to albinism in sweet 

 peas and ten-week stocks, and in accordance with Mendel's law. An 

 albino orchid is distinguished from a coloured one by the absence of 

 purple sap. For instance, the well-known Paphiopedilum (Cypripcdium) 

 insigne Sander ae is an albino form from which the purple sap of the type 

 has disappeared. Recent experiments with sweet peas and stocks, 

 carried out by Mr. Bateson, F.R.S., Mr. Punnett, and Miss Saunders at 

 Cambridge have fully demonstrated that the appearance of sap colour 

 depends on the simultaneous presence of two colour factors. If both of 

 the colour factors are present the sap is coloured, but if either (or both) of 

 the colour factors is absent the sap is colourless. With regard to the 

 cases of Paphiopedilum (Cypripcdium) brought forward by Mr. Chapman 

 for the sake of simplicity we w T ill call the two colour factors C and P. 

 The typical coloured forms of P. insigne, P. hellatulum, P. callosum, and 

 P. Lawrenceanum will therefore be carrying both of the colour factors 

 C and P. Their albinos will, on the other hand, be carrying either the 

 C factor alone or the P factor alone (or neither). The known facts of 

 the breeding of albinos of these four species seem to be in accordance 

 with the conception that P. insigne Sanderac and P. hellatulum album 

 are carrying the factor C alone ; while P. callosum Sanderac and 

 /'. Lawrenceanum Ilyeanum are carrying the factor P alone (or vice 

 versa), as the following table, comprising all the results known to me, 

 shows : — 



Table A. 



1. /'. ivsiqiir Sanderac (C) x P. insigne Sanderac (C) gives albinos (C C). 



2, /'. eaUo um Sanderas (P) x P. callosum Sanderac (V) gives albinos (P P). 



:i. /'. hawrenceawum HyecmumQ?) x /'. Jjaicrenccanmn Hycannm (P) gives albinos 

 il' P). 



I. /'. hammekam/Uim ffyeamum (P) x T>. callosvm Sanderac (P) gives albinos (P P). 



