THEIR NOMENCLATURE. 435 
and not distinguishing the circinatus even as a mere variety from 
the tenuifolius of the ancient botanists, the pantothriw of their 
successors. As to the distinctions of this latter in England into 
Drouetit and trichophyllus, perhaps that may be found a matter of 
more or less confervoid growths in the water. Certainly such an 
intermixture often causes the finely divided leaves of tenuifolius 
and heterophyllus to cling together when drawn out of water; thus 
producing that valuable specific distinction of “collapsing seg- 
ments.” 
And now, looking back to the dates of our first acquaintance 
with the eight species recently made out of aquatilis, will the 
Reader be pleased to declare how it is possible to trace their 
geographic or topographic distribution apart from each other ? 
The older segregates fluitans and circinatus having become known 
to botanists before the present century, and having usually been 
distinguished in books indifferently well, a goodly number of 
localities are now found on record for them; although some 
confusion has occurred from time to time between those two and 
the plants now called pseudo-fluitans and trichophyllus or Drouetii. 
It is with these three and their five other congeners that the 
impossibility begins ; for not only are the plants themselves ill- 
distinguished as species, but their names are contradictory and 
chaotic in their meanings, that is, in their applications to the 
plants. 
In example, the botanists who have sought to follow the 
nomenclature of the ‘Manual,’ in its successive editions, must 
unavoidably have been using the same names with diverse 
meanings. Under what name, for instance, was the R. floribundus 
recorded in local lists before 18562 How are we to know, when 
meeting with an earlier record for a “ peltatus,” whether the 
peltatus, or the floribundus, or the pseudo-fluitans of later editions 
is intended by that name? And so on with the other names; 
each one in turn including more forms as we go back in dates, 
fewer forms as we go forward. This uncertainty will meet us 
even while keeping to the one single book, the ‘ Manual’ only. 
And if we look to the records of botanists who name their plants 
