156 The Philippine Journal of Science ms 
tion, it is genetically associated with the scope of our idea of 
a species; and approaching the subject from this point, I may 
come again into agreement with Doctor Willis, and this time 
on his own ground. There is a constant tendency among both 
botanists and zoologists to place an ever finer construction on the 
idea of a species. Each decade sees the recognition as species 
of many groups of plants which previously were combined with 
other groups, either as varieties or without even varietal dis- 
tinction. In some cases, this change is due to more careful in- 
vestigation of resemblances and differences, but frequently it 
is merely the expression of a change in attitude as to what a 
single species should include. The extreme in this direction 
was reached years ago by Jordan, in the recognition of what are 
commonly referred to as Jordanian, in distinction to Linnaean, 
species. As a matter of fact, no botanist of to-day holds himself 
to the Linnaean idea. If the present tendency continues un- 
checked, our descendants will all find themselves following 
Jordan’s policy. In practice, I do not expect the tendency to 
extend so far. Such a practice applied to all plants would make 
systematic botany a subject inconveniently vast and cumbersome, 
even for the larger number of botanists that may be expected 
in future years. In the case of the very great majority of plants, 
the recognition of Jordanian species, supposing that they exist, 
would serve no useful purpose. In the case of such plants as 
rice, and other plants of great industrial importance, it will be 
worth while, and will surely be done, whatever the nomenclato- 
rial rank the forms may be given. 
Our nomenclatorial divisions — families, genera, species, and 
varieties or forms — are, as I have repeatedly pointed out, in 
part functions of the diagnostic peculiarities of plants, and in 
part functions of our convenience. The old idea, that a species 
is a group of plants distinct from any other group, in the sense 
that we know no practically continuous series which connects it 
or has connected it with any other group, was never anything 
but an expression of contemporary ignorance, and is as dead 
to-day as the idea that the species were separate manifestations 
of the Creator’s activity. This is as true of genera and families 
as it is of species. “We would still want to recognize genera 
and species, if the tree of life could be reproduced in every 
detail.” 5 
As we fill in our skeleton structure of the tree of life, it is 
convenience that must determine what genera, species, and other 
5 Philip. Journ. Sci. 8 (1913) Bot. 153. 
