Within the last tvventv-five years there has grown up among 
scientists a desire to add to the comparative and geological 
evidence of evolution that of experimental proof. If plants and 
animals of today have really arisen from those of yesterday, as 
the geological record indicates, it should be possible somewhere 
and somehow to detect a species in the act of origin. It should 
even be possible to examine the specific causes which may lead to 
the appearance of new forms, and perhaps to control or guide 
these causes so that new species might be produced at will. With 
these aims in view, the last two decades have seen increasing- 
attention paid to the study of experimental evolution, and in the 
course of this time, much controversy has arisen regarding the 
minutiae of the evolutionary process. In some of these disagree- 
ments the anti-evolutionist has thought to find the basis for 
refuting the whole theory, misunderstanding the relative insig- 
nificance of the disputes as to method. 
What have been the results of this experimental study? Have 
new species been seen in birth ? Have they been experimentally 
produced ? The answer hinges upon the definition of the term 
“species.” It will be worth while to consider in an elementary 
way just what is meant by a species. Probably no two scientists 
agree exactly upon the definition of the word species, but it will 
not be necessary here to go into the details of the difficulty. It 
is, perhaps, sufficient to say that a species includes all such 
individuals which, in plants, resemble each other so closely that 
they might have been raised from the seeds of one parent plant. 
What experimental evidence can ferns offer relating to the 
appearance of new species ? We may answer this best by con- 
sideration of the history of the common house plant known as the 
Boston fern. Up to about 1895 one of the common ferns of the 
commercial greenhouse was the so-called sword fern {Nephrolcpis 
exallaia), common in Florida and in the tropics, and reasonably 
uniform in its characteristics wherever found. It had been culti- 
vated by florists for about a half a century and had come to be 
rather common about twenty-five years ago. About that time a 
florist near Cambridge, Massachusetts, found among his sword 
ferns a new sort, in many respects like the sword fern, but differ- 
ing in several particulars which made it a better house plant. 
For example, its leaves were softer and more graceful, and it 
produced more leaves in a pot of a given size, making a more 
compact, bushy plant. Becker, the florist concerned, thought he 
had a species entirely different from exaltnta and sold it at first 
under the name of another known form. Later, the error was 
corrected, and the Boston fern, as it came to be known, was 
distributed very widely among liorists, and grown in increasing- 
numbers until the annual production reached many hundreds of 
thousands of plants. 
As thus grown throughout the country, the Boston fern re- 
mained the same, and plants from the southern states, and from 
the western, northern or central part of t Lie country, could not be 
distinguished from those of eastern Massachusetts. Six excep- 
