entirely loses this quality when grown in North Dakota and sub- 
jected to the same disease. The tall trees of one climate may be 
the dwarfs of another. The obscure and little known insects and 
wild plants of one country may be the scourges of another, and 
the weeds of the tropics may become in part the hothouse plants 
of America and Europe. 
On the other hand, certain individual organisms are so strik- 
ingly alike that we are able to group them roughly into varieties, 
species, genera, etc , realizing, however, that this represents but 
a convenient method of keeping track of them, for, no one who 
has really studied the subject thoroughly believes in the reality of 
species. And yet the individuals composing some varieties and 
species are remarkably alike, and especially is this true of man}’ 
garden varieties of plants. We are told that a certain Dutch 
bulb-grower was able to distinguish 1200 varieties of tulips from 
each other by observations on the bulbs alone, and it is a common 
thing for nursery employees to be able to separate many varieties 
of plum and apple trees as they lie piled in the storage cellars, 
devoid of leaves. Practically all the navel oranges from the 
thousands of California groves represent fruit from the parts of a 
single tree discovered near Bahia, Brazil. How they differ in size, 
taste and flavor, and yet how similar to each other in color, in 
lack of seeds and in the presence of the navel! Naturalists find 
our little shepherd’s purse and a variet}'- of brake-fern all over the 
world, and they have no difficulty in recognizing them. Other 
plants, such as our wild asters and thorn apples, refuse to be 
specified, and no one, not even the greatest specialists on these 
groups, are certain that they can correctly identify them. When 
we attempt to define a species by. placing all the individuals from 
a single ancestor or a pair of ancestors under the same name, we 
are again face to face with variation. In the natural world, like 
only produces like when we are speaking superficially. Blue- 
flowered chicory gives rise to white-flowered plants, as well as to 
forms differing in many less striking characters; spotted beetles 
produce plain-colored beetles; twenty-four leaved typical tobacco 
plants are parents of plants with 150 leaves; round-stemmed weeds 
have both round and flat-stemmed descendants. Examples such 
as these are a matter of common observation among students of 
experimental botany. It is only when one carefully isolates 
single plants or animals and puts them and their descendants 
through a purifying process that like begins to produce like, and 
this is what the breeder of new varieties of animals and plants 
attempts to do. 
For centuries, scientific men have grappled with this problem 
of variation, attempting to find some law or order in all the seem- 
