ee Se ee a ee a eee eee a 
THE POTAMOGETONS OF THE BRITISH ISLES 187 
y P. 
pias Ga defined a A. R. Wales. “The limitation of we 
species is undoubtedly somewhat difficult, as some of them are 
exceedingly variable, being split up into petty varieties which are 
merely the description of individuals, whilst happily others will 
not a themselves to be so divided. Considered from the local 
point of view, tht splitting up into varieties is of value so long as 
they are held to be local variations ; studied in connection with 
d 
Fryer with so ma ny of we broad-leaved ones; and useful hints 
for os them are giv 
careful but concise bey to the species is followed by a shor 
nieack of the more important characters, in which due stress is 
laid on the value of ripe fruit for determination. After mentioning 
Koch’s five main groups, and pointing out that some species 
combine the features of two or more, Fryer goes on to explain his 
use of special terms:—Variety, for more or less permanently 
differing eaters of fertile species (hybrids appear to be, practi- 
cally, always sterile); state, for transient differences, dependen 
on individual or local conditions ; forma, for hybrids materially 
distinct from the plants originally described. ‘ No attempt is 
made at unravelling the intricacies of synonymy”; therefore such 
very uncertain names as P. compressus L. and P. gramineus L. 
are ciscarded, 
Brevity being desirable, I had better confine myself to a 
limited pedis of details ; it should, howe ever, be mentioned that 
Fryer rejected many of the all eged “varieties,” though he usually, 
and quite wisely, described the known hybrids (sometimes spoken 
of as “hybrid species”) with as much minuteness as the true 
specie 
: ¥; flwitans Roth is finally determined, in are tana with 
Beeby’s original investigations, as being P. natans x luc and 
P. Kirkit Syme “ls robably) P. natans x Sp acehifilias,: tt is 
pointed out that the resemblance between P. natans and P. poly- 
gonifolius is merely superficial, the hae possibly approaching 
P. lucens almost as nearly. Of the diffic . Drucei from Berk- 
shire, which “ has the most beautiful Salas of any of our British 
forms,” it is said that ghee Mr. Druce is correct in supposing 
of present evidence is in favour of its claim vf specific rank. 
P. serratus Huds. after nearly ten years’ observation, was found 
to be ‘merely a state which reverts on the same individual to the 
