230 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
they are attached to dies ; and there is no migration from unsuitable to suitable 
hosts. Descriptions are given of the egg, nymphal and adult stages, together 
with the life-history. A list of food plants is given ; the most favoured 
being tomato, potato, cucumber, French beans, and marrow. 
The remedies given are fumigation of market houses with hydrocyanic acid 
gas, using i oz. sodium cyanide (98 per cent.), i£ oz. sulphuric acid, and 3 oz. 
water to 4,000 cubic feet. 
This strength kills adults and nymphs, but not the eggs, so that a second 
fumigation must be performed some days later. 
For conservatories and small houses, the use of tetrachlorethane is recom- 
mended, at the rate of \ pint to 1,000 cubic feet for 24-36 hours, if possible. 
G. F. W. 
Wilting, Determination of. By Arthur L. Bakke (Bot. Gaz. vol. lxvi. No. 2, 
August 1918, pp. 81-114 ; 5 figs.). — The exact wilting point occurs when there 
is a serious rupture in the water columns of the plant. 
" During the daily march of foliar transpiring power obtained by making 
consecutive hourly readings for twenty-four hours, the maximum is attained 
at a time previous to the greatest evaporation. During the time of approximate 
maximum evaporation there is a marked fall in the foliar transpiring power 
index, followed shortly by a rise. The ratio between the maximum and minimum 
is more or less definite, but not sufficiently so for the formation of any law. 
When the ratio is reduced to the point where it is in the neighbourhood of unity, 
the plant is in a state of intense incipient drying. When the maximum value 
does not exceed the usual minimum, the plant is in a soil environment which 
is critical from the point of water supply, or almost at its wilting coefficient. 
It is then merely a question of time before the plant wilts." 
Although evaporation gives an increased transpiring power value, yet during 
the process of wilting, the index of foliar transpiring power comes to be in- 
dependent of evaporation. 
During the process of the march of wilting an equilibrium point is reached, 
where the indices of foliar transpiring power do not show much variation. It is 
suggested that the duration of the equilibrium gives a measure of the com- 
parative drought resistance of different plants. Helianthus grown in 1915 
during a rainy season was different from Helianthus grown during 1916, when 
the season was unusually dry. The equilibrium period of 1915 was much shorter 
than for 191 6. 
Older leaves wilt long before the younger ones. Stomatal movements are 
not important factors when the plant is in an intense state of wilting. — R. J. L. 
Wireworms, On the Life-history of, of the Genus Agriotes, Esch., with some 
Notes on that of Athous haemorrhoidali>, F. By A. W. Rymer Roberts, M.A. 
(Ann. Appl. Biol. vol. vi. Nos. 2 and 3, Dec. 1919, pp. 1 16-135 ; plate and text 
figs.). — The paper represents the results obtained at Rothamsted Experimental 
Station in the biology and life-history of Agriotes, and leaves the results of research 
work to secure an adequate insecticide for control purposes for a future paper. 
Its general life-history and habits are dealt with in detail, and notes on the 
relative abundance of species in the British Isles are given. The larvae feed on 
almost any crop, and apparently on many weeds apart from grasses, which are 
probably their original food plants. They can subsist for " very lengthy periods 
on no other food than humus and decaying vegetable matter." The great value 
of birds in reducing the number of wireworms is confirmed, and a suggestion is 
made that poultry might be run on newly ploughed grass land with advantage. 
Wireworms are apparently parasitized to some extent by insects and fungi. 
The article concludes with a reference table. — R. C. S. R. 
Wireworms of the Genus Agriotes, with some notes on that of Athous haemor- 
rhoidaiis, On the Life-history of. By A. W. R. Roberts (Ann. App. Biol. vol. viii. 
Nos. 3-4, Nov. 1921, pp. 193-215 ; 4 figs., 1 plate). — A continuation of a paper 
which dealt with the Biology and Life-history of Agriotes in vol. vi. pp. 116- 
135- 
The present paper gives minute descriptions of the Oval, Larval, and Pupal 
stages of Agriotes obscurus L. — G. F. W,. 
Wistaria venusta Rehder et Wilson. By J. Hutchinson (Bot. Mag. t. 881 1 ; 
Sept. 1919). — This plant has been confused with both W. sinensis and W. brachy- 
botrys, but is quite distinct in the soft covering of short hairs upon its leaves, 
the rather short and very wide racemes, with large flowers on stout velvety 
pedicels. The form grown in England (it made its first appearance from Japan 
at the International Exhibition of 191 2) has white flowers, but coloured forms 
are known. — F. J. C, 
