15 
of the past summer, but the action has been a double one. In 
the first place a very much reduced quantity of fresh water has 
been drained from the Thames basin down the river. The river 
throughout its entire course has been relatively sluggish and 
this would tend to greater evaporation for any given mass of 
water and consequent increase in salt-content. The salinity of 
Thames water,’ however, is due mainly to carbonates and these 
have not been considered in the work summarised above. The 
small quantity of fresh-water coming down has meant that at 
Kew the salt tidal water has come up higher and in greater 
quantity than is normally the case. Whether mixed with fresh 
separate layers, the salt sea-water coming up the Thames 
estuary at high tide, and most especially at spring tides, is the 
ultimate source of the salt in the Kew water supply. In this 
connection it is interesting to note that during the last summer 
seaweed came up as far as Kew Bridge. Thus at extra-salt tides, 
just now and again during the summer, decidedly salt water was 
let into the Kew Lake. This is a shallow basin giving the 
contained water a relatively large superficial area for evaporation 
compared with its bulk. This helps to account for a marked 
concentration of salt in the Lake itself during last summers’ 
heat. It is probable that the water as supplied for watering 
purposes in Kew Gardens is often more salt, especially in summer, 
than fresh river-water, which in the case of the Thames normally 
contains very little sodium chloride. The conditions of drought 
and heat aggravated this state during the past year by reducing 
the quantity of fresh water coming down, and therefore increasing 
both the relative and actual amount of salt sea water coming up, 
and also by increasing the concentration of salt through evapor- 
ation of the water in the Lake, which for the time being was 
tending to become a miniature Dead Sea. 
IV.FURTHER NOTES ON THE AUSTRALIAN 
SPECIES OF STIPA.* 
D. K. Hueues. 
In response to the communication of a copy of Miss Hughes’ 
paper “ A Revision of the Australian Species of Stipa,”’ published 
in the Kew Bulletin of last year, pp. 1-30, Mrs. A. Chase, on the 
behalf of the United States National Herbarium, asked for the 
revision of their Australian Stipas by Miss Hughes. The propo- 
sition was all. the more welcome as the Washington collections 
* See Kew Bulletin, 1921, 1. 
