326 
Breeding Experiments ivith Foxgloves 
hybrids, and by defining the unit-character in a suitable manner the familiar 
ratios so well known to Mendelians do appear in the case of certain characters. 
The above expression "defining the unit-character in a suitable manner" is well 
illustrated in the case of the general colouration of the foxglove flowers. Provided 
we define a "purple flower" as meaning a flower in which the corolla is more or 
less uniformly tinted all over we obtain a simple Mendelian relationship; but 
many of the white flowers, on being closely scrutinized, were seen to possess an 
excessively faint tinge of purple over small isolated areas, the remainder of the 
corolla being dead white. If these plants had been included under the category 
of "purple flowers" no Mendelian relationship would be apparent. There is, 
however, a certain justification for excluding such from the category of "purple 
flowers," since there is a distinct gap in the series between the flowers which are 
tinted faintly purple all over and the white flowers with an extremely slight 
blush of purple over small irregularly placed areas. 
A similar relation occurs in connection with the brown spots. Provided the 
spots are examined with the naked eye they are very generally either brown or 
purple ; brownish purple spots were seldom observed, and a simple Mendelian 
relationship occurs, brown spots being recessive. If, however, the purple spots 
are examined under the microscope the distinction between the two kinds of spots 
is seen to be not so sharp, since a certain amount of decomposition product may 
be present, although not as a general rule in sufficient quantity to give a spot 
a brownish purple appearance to the naked eye. Here, again, we have a distinct 
gap in the series ; it occurs between a small amount of decomposition and total 
decomposition. A strict Mendelian might hold that in the flrst case the slight 
tinge of purple occurring in the white flowers was a character distinct from the 
purple colouration of the general surface of the corolla, and was controlled by a 
different determinant or group of determinants; but such a supposition could 
scarcely be applied to explain the occurrence of the gap between the small amount 
of decomposition and the total decomposition of the anthocyanin of the spots. 
By presupposing the existence of many factors controlling a character and the 
linkage of factors it may be possible to express in Mendelian terms almost any 
experimental result that may be obtained, but it must be confessed that there 
is an artificiality about the process which does not inspire confidence in the 
interpretation. 
With regard to the peloric character, in order to obtain a simple Mendelian 
relationship, it is necessary to include in the peloric category all plants which 
exhibited any distinct tendency tovi^ards the peloric condition. There is a gap in 
the series between flower-axes which exhibit some shortening of the internodes 
of the upper flowers and a marked shortening resulting in a distinct abnormality; 
and it is this gap in the series which gives the clue as to where the line of division 
should be drawn between peloric plants and non-peloric plants. 
The question arises as to how far a so-called unit-character is capable of change. 
In the course of evolution any given character must of necessity have arisen in some 
