66 
IOWA ACADEMY OF SCIENCES 
known exceptions such as the adventitious flowers of Nepaul-harley, but 
it does not appear that the systematist, especially in this day of morpho- 
logical and physiological enlightenment, is in great danger of taking, for 
his species marks, any of the few characters that have no physiological 
significance. Indeed, in the field in which the present writer has done 
most of his taxonomic work, it is not easy to find a functiouless organ 
or tissue. The spores of higher lichens are thought by many to be 
functionless or nearly so, but if this be true, they have become so 
highly developed and characteristic in former stages of phylogenetic 
development, in which they surely functioned, that they are now impor- 
tant characters in the determination of lichens, and cannot be ignored. 
The podetia of the Cladonias have doubtless arisen through hypernutrition 
and, if the spores be functionless, can perform no other function than 
that of carrying squarnules and scredia up into the air where they may 
be more readily dispersed. Yet we can scarcely see just how the tact 
of relatively unimportant function would detract from their value as 
species characters. 
In certain recent papers, the binomial nomenclature has been attacked 
as detrimental to scientific progress and likely to be replaced. The 
drudgery and uncertainty of matching characters in the herbarium is also 
'bewailed. There is much of reality in all this complaint, and the pres- 
ent writer has had experience enough to know that, in the field of 
lichenology at least, the worker who has not at different times deter- 
mined specimens from the same collection as two or more species has 
had a very limited experience in the work or has been very fortunate 
in always terming the same judgment. Yet the question arises as to how 
we are ever to know the elementary or biological species among lower 
plants so that we may replace our often-compound sytematic conceptions. 
Again, if tnis ever becomes possible, it may still be doubted whether 
these biological species will serve any purpose in determinations, or 
make the v/ork of matching characters any easier. Whatever new plan 
of classification may be in store for the future, its realization is far 
enough av/ay, so far as lower plants are concerned, so that we may profit- 
ably consider what light all this discussion of morphology and evolution 
throws on our conception of systematic species. 
Those who have followed the recent discussions provoked by de Vries’ 
announcement of the mutation theory cannot have failed to note that it 
has been confined almost exclusively to higher plants and animals, 
principally the former. This onesided consideration will never settle 
the difficult questions involved, and those of us who work on lower plants, 
where studies similar to those of de Vries on the seed-plants will be much 
more difficult of carrying to a successful conclusion, may well begin to 
stir ourselves. There seems to be no doubt that certain phases of the 
question of evolving of species may be experimented upon by direct 
observation and cultural methods ammng algae, fungi and lichens, though 
in many of these plants, the unit characters must be very obscure and 
often physiological rather than morphological. Indeed, the work of 
Salm®n on Agaricus and certain studies of JJredineae point to the possi- 
bility ©f establishing elementary species among fungi, while it is quit* 
