2 R. H. Howe: MANUAL OF THE GENUS USNEA 
floridus, here named in order of pagination * priority, all seem 
to intergrade and belong to one species ; with a broader conception, 
however, true transitional examples are in reality rare, if in some 
cases occurring at all. 
The difficulty has been that too many purely contingent 
varieties have been described and recognized, so that the Linnaean 
conception and nomenclature has been embarrassed ; whereas, for 
the papillate species (all he considered), it was exceedingly near 
the proper elucidation. Each of the following species represents 
a variable, but a distinct, plant, found both fruited and sterile. 
Though true intergrades may appear occasionally, they are not im- 
portant enough to make it necessary for us to blind our under- 
standing by adopting a special nomenclature to explain their 
presence ; if we should do this and should follow the present rules 
of nomenclature, we must cast aside appropriate names, applicable 
original descriptions, and good recognizable figures, and the general 
procedure of nearly two hundred years, and use the names simply 
as handles with no other significant connection whatever. This, 
it is plain, would be distinctly undesirable. 
That there must come a reaction from the naming of contingent 
phases in lichenology is evident. There is no halting if once it is 
begun, and the inevitable result is, names standing for unique 
individuals, and type localities reduced to certain fallen logs or 
crumbling ledges. The law of variability is being sadly over- 
looked. A study of the limits of variation in species will throw 
hundreds of names already given into a now tangled synonymy. 
Two distinct types of subspecies have been recognized, only 
one of which has a proper claim to recognition. The first type is 
what I have termed in my former paper ‘“ contingent phases,’ 
states of development brought about by very local and temporary 
conditions ; as a result of separations thus based we have in our 
synonymy such subspecies and forms as /urta, rubiginea,etc. The 
second type of subspecies, based on the results of actual morpho- 
logical differentiation, due to the fixed but varied environmental 
effects of wide geographical distribution or of altitude, are, it is 
needless to say, scientifically grounded and worthy of recogni- 
tion, if the separations of this nature are well defined and not of 
* Unrecognized by the Vienna Rules. 
