NOTES AND ABSTRACTS. 
211 
2. Stimulation by atmospheric electricity brought to the soil by metallic 
conductors. 
3. Potatos grown between two large sheets of zinc and copper in the soil, 
200 yards apart and connected by an insulated wire, were said to give a better 
yield. (A priori one would not expect the small current so generated to have 
much effect.) 
4. Stimulation by a current passing through the soil and generated bv a 
cell. 
5. Stimulation by high tension discharge from overhead wires. This method 
has been widely used and increased yields have been obtained, but the expense 
of installation is great, and the results are not certain. 
6. Treatment by passage of a constant current through the soaked seed before 
sowing. Mr. Rae quotes this process as being a commercial success, but he 
does not mention the adverse report on the results, made by Dr. E. J. Russell. 
Sir A. D. Hall also stated at the British Association in 1920 that no such process 
has proved of real use. — H. Waller. 
Evaporation and Transpiration, Studies in. By Geo. F. Freeman (Bot. Gaz. 
lxx. No. 3, Sept. 1920, pp. 190-210 ; 5 figs.). — 1. As a result of evaporation 
experiments carried out by means of a porous cup atmometer enclosed in a 
glass cylinder of one litre capacity, through which an air current is passed, an 
evaporation formula is offered which may. take any of the following forms : 
z (t-t); (b) y = \~t\n ; 
v 1 y 1 J 1 + c (w) 
t — t x 
1 \ a 
c (w) , 
1 a 
In these formulae y = rise in the dewpoint of the air caused by the loss of water 
to it of a given evaporating surface ; t = temperature of the air ; t 1 = dew- 
point of the outside air ; z = the constant used when the area and wind move- 
ment remain constant ; n = exponent of w, used when the area remains con- 
stant ; c = constant coefficient of w, used either when the area is constant 
(when a does not appear in the formula) or when a varies and hence appears 
in the formula ; a = area of the evaporating surface which is always expressed 
as the ratio of the surface exposed to that exposed when c and k were determined ; 
when c and k are determined, the area then used is taken as unity, and all other 
areas expressed in terms of it ; k = constant used in the exponent of w to adjust 
the area unit to the wind movement unit. 
2. These formulas appear to be general in type, and capable of use in any 
situation where y is measurable. It is possible that with some modification 
these formulae may also be of use when y cannot be measured, but where it is 
possible to measure directly the actual evaporation per unit area. 
3. Under temperature changes only, alfalfa leaves appear to act as physical 
evaporating surfaces. 
4. Changes in the dewpoint of the air result in profound changes in evapor- 
ating efficiency of leaf surfaces. This is probably a result of the opening and 
closing of the stomata. 
5. It is possible to make use of these formulae in comparing the evaporating 
efficiency of different species of plants and interpreting results which would 
otherwise appear hopelessly confusing. 
6. Distinct pure races of alfalfa exhibit measurable differences in the rate 
of evaporation per unit area of their leaves. Such differences may be of economic 
value in semi-arid or irrigated regions where production depends principally 
upon the efficiency of the use of the available water supply. — R. J. L. 
Fern-Growing. By H. Drury {Irish Gard. 14, pp. 7, 25 ; Jan., Feb., 1919)- — ■ 
Full directions for the construction of a fern garden. — F. J. C. 
Fruit-Butters, Homemade. By C. P. Close (U.S.A. Dep. Agr., Farmers' 
Bull. 900; Bureau of Plant Indusi., Sept. 1917 ; plates). — Careful instructions 
in the preliminary equipment, and the preparation of the so-called " fruit- 
butters," so popular in the United States. Recipes for various. forms of apple- 
butter, for pear, peach, plum, and ' Garfield ' butter are given. — M. L. H. 
Fuchsia, Notes on the Cytology and Genetics of the Genus. By R. Beer (Jour. 
Gen. 11, pp. 213-227 ; 1921 ; 3 plates). — The author reviews the investigations 
previously made upon the cytology of Fuchsias and recounts his own, together 
with an account of crosses made between different" species and varieties of the 
(3)y = 
(c)y = 
