Ig15] BURLINGAME—ARAUCARIANS 103 
THOMSON’S discovery of these bars of Sanio in the ordinary wood of 
araucarians (70). They have also recently been reported in the 
cycads (56). In this group they are said to occur when the pits are 
scattered, but not when alternate and crowded. 
THOMSON (70) has suggested that the araucarian affinities of 
some of the mesozoic transitional forms with traumatic resin canals 
would be equally well explained as having descended from the 
cordaiteans as by the assumption that they are acquiring araucarian 
characters. If I understand this suggestion correctly, it assumes 
that these forms are not directly related to araucarians at all, but 
are really abietineans that still retain some cordaitean characters 
and have acquired or are in the process of acquiring the characters of 
- modern abietineans. 
On the principles of evidence 
After having set forth the evidence that has been adduced by 
various writers in support of the several theories, it is now pertinent 
to return to the problem originally proposed by the quotation from 
Jerrrey. Are there any general principles of evidence or are there 
not? Are all sorts of evidence of equal value? Shall any class of 
evidence be excluded, as is done in our law courts? Such questions 
as these must be answered by every botanist before he can properly 
proceed to sound inferences from the facts uncovered by his investi- 
gation. The arguments set forth in the preceding sections may be 
conveniently grouped under the following heads: (1) resemblance 
or likeness, (2) geological sequence, (3) vestigial structures, (4) onto- 
genetic recapitulations, (5) traumatic reversions, (6) abnormalities 
or monstrosities. 
1. Resemblance or likeness means relationship——This appears 
to be the most fundamental principle in the minds of the great 
majority of writers on this and other phylogenetic problems. That 
this is a sound principle is unquestioned. No fact in our biological 
experience is better grounded than that “like begets like.” That 
the parent and child may differ in minor points is an everyday 
experience, but that they ever differ by large differences is not 
believed. The theory of evolution itself is founded firmly on these 
two well known facts of general likeness with slight variations. 
