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H. F. Wernham. 
derived them from a common ancestry. Examples of characters 
more or less fortuitous are provided by those often employed in 
systematic anatomy, e.g., structure of stomata, nature of indumentum 
mode of deposition of mineral contents, and so on. 
It may not he probable, nor is it impossible, that the same 
fortuitous character may appear as the result of mere coincidence 
in two plant-forms widely separated in descent. The multiplication 
of such characters, however, renders the possibility of coincidence 
negligible: whence, The occurrence of several common fortuitous 
characters in a series of pi ant-for ms is valid evidence of their mutual 
affinity ; and the greater the number of common characters, the closer 
the affinity. 
The groups of lowest rank with which we have dealt in general 
has been the family . 1 In our modern systems the critical characters 
of the families are largely biological, and the same applies to the 
higher groups. It is scarcely surprising that the vital functions are 
reflected to a considerable if not predominating extent in the 
structures of the individual organism; and it is very doubtful if, 
even in a state of perfect acquaintance with all the details, sufficient 
purely fortuitous characters could be found upon which to base a 
natural classification . 2 
It is to the principle of fortuity in connection with biological 
characters that we must turn in the search for critical features; in 
other words, to the consideration that the same biological end may 
be attained in more than way. In the case of the Dipsacales we 
pointed out that the capitulum is the product of cymose branching, 
whereas the inflorescence of Composite is essentially racemose. 
This distinction led us to associate the former with the rubialian 
and the latter with the campanal stock. Zygomorphy, we have 
seen, has been produced in at least two ways, and epigyny in more 
than one. In so far as a biological character may be acquired, or a 
vital function discharged, in several ways, then such a character is 
valid for phyletic purposes, if it has been acquired within the circle of 
forms of which phyletic unity is predicated in only one of those 
ways; and its validity is greater or less in accordance with the 
number and definiteness of those ways. In so far as the number of 
ways is without limit, the biological character tends to become 
fortuitous as well. A looser, but perhaps simpler, way of expressing 
1 Formerly referred to as “natural order”— e.g., Ericaceae, 
Rubiaceae, etc. 
2 See previous footnote No. 1. 
