TIIFIR NOMENCLATURE. A27 
Unfortunately, they are not the novel segregates only which are 
thus difficult to trace. The severance of any one of these from an 
older species, as previously recognized in books, must usually 
nullify all the past records about that old species, if the object now 
be to shew also its own distribution apart from the severed 
novelty ; such former records having been made for the undivided 
aggregate, not specially for either of its severed portions, that is, 
neither for the segregate nor for the remnant. When aggregate 
species AB comes to be made into two by the severance of B from 
it, leaving A equally alone, what are we to do with all its old 
recorded localities? None of them were reported for A or for B 
specially by itself; and often the places must be re-visited, or 
authentic specimens be re-examined, in order to determine the 
doubtful alternative between A and B for each locality. 
Such is the difficulty, at present almost an insurmountable 
difficulty, to be met in this division of the ‘Compendium.’ It 
must take inclusive notice of segregate species and varieties, 
familiar to few of us, and some of which are certainly ill-understood 
even by their own proposers or introducers into English books ; 
and the localities for which are at best very sparingly recorded, if 
not in some cases already misrecorded for the wrong thing. A 
commencement only can be attempted here, by putting into an 
abbreviated form so much or so little as is yet known to the writer 
concerning the distribution or localities of the segregates. Some 
half-century henceforward, when new Local Floras and Lists and 
other records have accumulated, a successful attempt will become 
possible to the botanists of that future time. As to now tracing 
their distribution through other countries (which has been 
advised), the attempt to do so would be only a futile mockery of 
the former portion of this work, so meagre and uncertain would 
any such enumeration of foreign habitats unavoidably become. 
Before proceeding to the brief summary alluded to, some pages 
will be devoted to expositions of the manner in which the 
aggregates (the recognized species of the older botanists, and still 
accepted in the same character by influential botanists of the 
present time) have passed into the modern segregates ; which too 
