98 THE ORCHID REVIEW. [APRIL, 1903. 
composite one, made up of three distinct characters, namely, (1) the ground 
colour; (2) the various markings upon the ground colour; and (3) the 
median band, bar or stripe. These three characters are considered to be 
inherited independently of each other, with hardly any correlation, and 
the different combinations of these characters serve to make up the colour 
of the dorsal sepal. It is further pointed out that in order to afford a fair 
test of Mendel’s principles the characters must not only be single, but also 
differential (that is found in only one of the species under investigation), 
and constant. It is considered that these conditions are fulfilled in the case 
of across between P. X Leeanum and Boxallii. 
Now, if Mendel’s theory as to the purity of the single character deter- 
minants in the germ cells of hybrids be correct, the hybrid P. x Leeanum 
contains determinants which are either pure Spicerianum or pure insigne 
(these are termed S and I for convenience and brevity), and the union with 
P. Boxallii (termed B) will result in B S or BI (on the average in equal 
numbers, according to the law of chance), but not in B SI, or even in S I. 
A table is given in which the 49 hybrids which have hitherto flowered 
are analysed, and the results are summarised as follows :—Ground colour of 
dorsal sepal, 20 B 5, 29 B I; markings on the ground colour, 26 B S, 
23 BI; and, Median Band, 30 B S, 19 BI; or a total, when the 
single characters are added together, of 76 B S, and 71 B I; which, 
considering the small numbers used, is claimed as a fair approximation to 
the equality which Mendel’s theory presumes. 
As thirty of the 49 hybrids are figured, readers may compare for 
themselves the analyses with the figures, and here we may point out that 
nine of the thirty forms figured are given as B S only in all three characters 
(Nos. 3, 4, 5, 23, 24, 32, 33, 42 and 43), and six as B I only (Nos. 6, 22, 40, 
41, 48, and 49). - That is to say there are nine forms which in the three 
characters analysed are identical with P. x Calypso (Boxallti X 
Spicerianum), and six with P. x Schlesingerianum (Boxallii x insigne), 
which collateral hybrids were available for comparison when the analyses 
were made. As to whether these forms are really pure, the author remarks 
that the biologist would further require them to be “self-fertilised for 
several generations to see if they remain pure B S and B I in those 
characters, as they appear to be on the surface.” It is interesting to find 
that the experiment is being followed up. 
The author summarises his conclusions as follows :—‘‘ While from the 
biological point of view, we cannot yet say with certainty that Mendel’s 
principles are proved beyond doubt, yet so far as the matter has been 
carefully tested in many different genera, and by several independent 
observers in several countries, there can be no doubt that there is 4 
substantial agreement with the principles laid down by Mendel.” 
