Ernest Warren 
125 
8. General Conclusions. 
In the various characters that have been dealt with in the crossing of different 
strains of the garden foxglove we have seen that in pclorism, colour of corolla and 
colour of spots, the mode of inheritance is Mendelian with reference to the 
qualities : peloric and non-peloric, purple and white corolla, purple spots and 
brown spots. If, however, there are any marked differences in the intensities 
of these qualities, the mode of inheritance of the intensity of the quality was 
found to be of the blended type. 
The other characters examined were quantitative in nature, such as degree of 
the development of purple spots and the ratio of breadth to length of corolla, and 
these characters blended completely. 
When the intensity of a quality is very slight and approaching zero the 
difficulty arises as to which category the individual should be referred. When 
Mendelian inheritance is in evidence the critical point may apparently be determined 
by the occurrence of segregation. Thus, if a homozygous plant with a very faint 
tinge of purple (say an intensity of about 4) is crossed with a homozygous strongl}' 
coloured plant, segregation occurs in the so-called F., generation, and we obtain 
on the average 1 faintly tinged plant to 3 much more darkly coloured plants. 
When, however, the pale plant has a somewhat greater intensity (say about 10), 
the and subsequent generations are intermediate, and definite segregation does 
not occur. In accordance with this procedui'e a plant with flowers having an 
intensity of general coloration which did not reach 5 of the scale was classed as 
" white." Without employing such a line of demarcation the results obtained 
were wholly unintelligible. 
From the strict Mendelian standpoint, in the example given above, it would 
probably be affirmed that the faint tinge of piirple on " white " flowers is not 
really a fractional part of the general purple coloration of coloured plants, but is 
a distinct character governed by a different factor or set of factors in the chi'omo- 
soraes. To one who has grown the plants this view appears an artificial one. 
In my previous account I stated that there appeared to be a distinct gap among 
my plants between "" white " plants and coloured plants, and that colorations of 
about 8 — 25 of the scale were extremely rare or almost absent, but I have sub- 
sequently obtained a number of plants having such intensities of coloration, 
passing imperceptibly down to absolute whiteness. Consequently it is (juite un- 
likely that the faint tinge of purple on " white " flowers is anything else than the 
last remnant of a general purple coloration. 
It is quite similar in the character of pelorism, but the difficulty in finding a 
suitable method of measuring this character renders the matter less obvious. 
Thus, it would appear that if a character is not present beyond a certain minimum 
or unit quantity it may be unable to blend on crossing witli a ])lant possessing the 
character in a well-marked degree. 
