IO HEREDITY, AND THE ORIGIN OF SPECIES. 
there has been a sudden change, without any intermediate 
steps, from a plant with colored flowers to a pure white 
variety: such may be termed “negative” varieties, since 
their peculiarity is due rather to an absence of color, than 
to the presence of white. Not only does the flower show 
the characteristic absence of color, but the leaves, stem, 
and, in fact, the entire plant, are invariably of a lighter 
green; and if any red be normal to the stem (which is 
often the case), this will also be of a lighter shade. It has 
often been urged that these albinos are mere ‘sports’ of 
nature with nothing constant about them,...., and that 
there is nothing inherent in the constitution of the plant. 
Fortunately I have been able to test this,. .and found them, 
. not only constant in their peculiarities, but also that 
these are bred in the plant and capable of inheritance.” 
Three years later, about the time that De Vries began 
casting about to find material suitable for the demonstra- 
tion of his theory of unit-characters and their saltatory 
action, Mr. Thomas Meehan, a horticulturist of Phila- 
delphia, wrote as follows, in a discussion of some anomal- 
ous form of the oak: “The conclusion that I have been 
forced to is that the odd forms we often find in nature are 
not necessarily hybrids, but are as likely, if not more 
likely to be the outgrowth of some internal law of form 
with which we are as yet unacquainted. That they do not 
often perpetuate themselves is (not, plainly implied) re- 
markable when we remember that of thousands of seeds 
produced on any one tree, but a very small percentage 
ever gets a chance to form, and of those which do sprout, 
again but a small percentage survives to become bearing 
trees. As the number of trees reproducing the general fea- 
tures of the original may be as a hundred to one of the more 
strikingly aberrant forms, we may see that though indi- 
vidual instances may be common, we are never likely to 
meet many trees of one stamp. Once in a while an indi- 
a 
