80 
EXHim'J'lD.N MKJ£T1N(;., 105O 
'I'lie exhibit iiicliuled 8 of the special Shetland si)ecies 
arranged in ]>airs, as follows, to demonstrate the characters 
used for identification. 
Series Dovrensia. 
R. pulchellifonnt (W. K. Linton) 
Pugsley. 
R. zeilandicum Beeby. 
R. psendo-protractum Pugsley. 
R. hethlandiae (F. J. Hanb.) Pugsley. 
R. austmlius (Beeby) Pugsley. 
R. subtruHcatum Beeby. 
R. praethidense Pugsley. 
R. vviKiceum (Beeby) Pugsley. 
. With the exception of R. psendo-protractum all the species 
are extremelj" local. They exhibit a surprising variation from 
phyllopodous to hypophyllopodous and aphyllopodoiis plants 
within a single group. 
J. E. Lousley. 
Series Protracta. 
Series Subeouosa X . 
B. 
specimens showing mint irregularities. 
Twenty-five sheets of Mentha were shown, chosen to illustrate 
irregularities in characters that rendered identification difficult, 
and to exemplify certain forms of freak growth. In the former 
category were hirsute forms of M. spicata L. em. Huds., and 
xM. gerdilis L., and a rare form of xM. verticillata L. in 
which the calyx-tubes and pedicels, usually hirsute, were glab- 
rous. An unusual example of freak growth was shown in a 
normal stalk of M. citrata< Ehrh., which, after a foot of upright 
growth had bent backwards to the ground, and had become a 
runner. 
R. A. CrRAHAM. 
EIODBA CALLITRICHOIDES AND ASSOCIATED TUVER PLANTS. 
Elodea callitrichoides (Planch.) Casp. (exhibited as a member 
of the genus Lag aro siphon owing to a misidentification) is a 
South American water plant which has recently become estab- 
lished in the Longford River, Middlesex. It is used extensively 
by aquarium enthusiasts and it has been suggested that its in- 
troduction may be due to material thrown out by an aquarist. 
It is very rampant in growth and, if the history of Elodea 
canadensis Michx. can be taken as a precedent, it is likely to 
spread rapidly over a considerable area. 
It was first noticed by me in the Longford River at Stanwell 
at the end of September 1950, but I understand that Dr George 
Taylor found it about two years earlier in the River Colne at 
Harefield. It may have spread from there to the Longford 
River. It is of interest that only female flowers have been 
found up to now. 
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