MR. C. REID ON THE NATURAL HISTORY OP ISOLATED PONDS. 281 
those yet met with are plants that are not uncommon under such 
circumstances, or at any rate have been noticed in more than one 
pond. Taking the species in botanical order, the first in the list, 
Ranunculus aquatilis, happens to be by far the most abundant plant 
in isolated ponds, and is usually associated with Limncea pereyra. 
Though exact statistics have not been collected, I think that it 
may be said to occur in about one out of four of the isolated ponds 
which have neither completely dried up, nor been purposely cleared 
out, during the three or four seasons preceding the observation. 
Ranunculus flammula is common in pools or swampy places in old 
gravel-pits, but seldom occurs in dew-ponds on the Downs, probably 
because around these ponds there is no swampy margin such as 
this plant loves. The same remark applies to Ranunculus sceleratus , , 
which, however, is somewhat more rare. Calllta has not yet been 
noticed in ponds entirely surrounded by dry ground, and both 
Nuphur anil Nymphiea are also absent, except where purposely 
introduced. 
Nasturtium officinale occurs occasionally, but, as far as observed, 
only in the few isolated ponds which happen to be fed by springs. 
It is a plant we could not expect to find in stagnant water. 
Myriophyllum spicatum has been met with once, and so also, 
I beliovo, has Hippuns ruh/aris, though no note was taken of the 
locality. CalHtnche is one of the most abundant genera, being 
second to Ranunculus aipiatilis in its number of occurrences. 
Piplis portula, though not a truly aquatic plant, is found under 
somewhat similar conditions ; it occurs on the wet iloors of 
sand-pits which, though surrounded by perfectly dry heaths, 
have been deepened till the water-level has been reached, and 
consequently have their Iloors always moist. Various marsh plants 
occur under such circumstances, indulging Hydrocatyle, Anayallis 
tenellu, Peilicularis palustrts, and several sedges and rushes. 
Conditions are seldom favourable around dew-ponds for the 
growth of our aquatic Umbellifers, for most of them would easily 
be broken down by the cattle, and their fruit cannot ripen in the 
water. In ponds in old sand-pits a few are occasionally seen, but 
the species have not been noted. 
Both our species of Bnlens have been seen on the margin of 
ponds, but neither is common. Hnttonia, Samolus, Menyanthes, 
and Limnanthemum are all absent as far as observation has yet 
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