such a plant as described above, has from 40 to 180 leaves, a flat 
stem and from 6- to 20-petaled flowers. This new type or muta- 
tion, as it would be called, bred true to these characteristics from 
the first. This new mutant type, in addition, excellently illustrates 
a case of how one sort of hereditary unit may express itself as a 
number of distinct characters, for the number of leaves per plant, 
the character of the stem, and the number ot petals per flower, are 
looked upon by those who classify plants as separate characters. 
They are inherited however as though they were all tied together. 
In order to demonstrate the statements cited above, the char- 
acter of the material cannot be too strongly emphasized. Many 
misunderstandings have arisen, even among investigators, owing 
to their use of very complex material, material that would neces- 
sitate attacking these problems on their most difficult front. 
Human beings, for example, present such difficult material, and 
one tackling the problems of heredity, variation and environment 
solely by means of this material reminds us of those people who 
are determined to do things in the most difficult manner possible. 
One of the elements of Mendel’s claim to greatness is the foresight 
with which he reduced his problems to their simplest form. The 
steam engines of today are comparatively simple to those trained 
to build and operate them, but to the inventor of the first steam 
engine, their complexity would be appalling and incomprehensible. 
O. E. W. 
