212 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
Cabbage Maggot, Biology and Control of the. By W. J. Schoene (U.S.A. 
Exp. Stn., New York, Bull. 419, March 1916, pp. 99-160 ; 8 plates, 3 figs.). — 
For more than eighty years the cabbage maggot (Phorbia brassicae Bouch6) has 
been regarded as the most important injurious pest of cruciferous vegetables, 
such as cabbage, radish, cauliflower, and turnip. The damage it causes fluctuates 
from year to year. Like its host, it attains maximum development in a cool, 
moist climate. A full description of the various life stages of the insect is given. 
The egg is deposited on or near the plants, and three to five days later the larva 
appears and attacks the root or part of the plant devoid of chlorophyll. The 
larva matures in eighteen to twenty days, and then enters the soil to pupate. 
The pupal stage may last from twelve to eighteen days or may be prolonged for 
several months (the insect hibernating). The females begin to oviposit soon 
after emerging, probably within three to five days. Adults may live for five 
or six weeks. With favourable conditions, there are three broods and perhaps 
a partial fourth. For the maggot to occur in great numbers, the presence both 
in spring and autumn of large acreages of succulent cruciferous roots is necessary. 
As regards treatment, the use of cheesecloth screens proved very satisfactory 
in securing cabbage seedlings free from injury, provided that the coverings were 
fly-proof. Tar-paper discs also proved effective, but in the open field the sticky 
surface soon became covered with dust and ceased to be of use. The removal 
of all crop remnants and the destruction of cruciferous weeds will lessen the 
numbers of the insect. — F. G. A. 
Calcium and Magnesium Compounds, their Influence on Plant Growth, By 
F. A. Wyatt [Jour, Agr. Res~. vi. pp. 589-620 ; July 1916 ; plates). — The author 
refutes the magnesium-calcium-ratio theory of plant growth, but shows that 
certain magnesium salts added to soils may produce the condition known as 
magnesium sickness characterized by the yellowing of the uppermost leaves 
of plants, the lower remaining green. — F. J. C. 
Calcium Cyanamlde as a Manure, Some Conditions affecting the Value of. 
By T. D. Mosscrop (Jour. Agr. Sci. viii. pt. 2, pp. 178-181 ; March 1917). — 
An important drawback in the use of calcium cyanamide as a manure is its 
injurious effect upon germinating seed when it is first applied to the soil. Seeds 
of cos lettuce, turnip, and barley were germinated on porous tiles under bell- 
jars water-sealed from the outer air. Inside the bell-jars was placed calcium 
cyanamide mixed with water, with soil water, and with moist earth. The let- 
tuce seeds did not germinate, and microscopic examination showed a blackening 
of the cotyledons within the testa. With 1 gram only of calcic cyanamide within 
the jar the germination of the turnip and barley seeds was not greatly affected, 
but with as much as 4 grams marked inhibition was observed. The blackening 
action is by the condition of the experiment due to some volatile decomposition 
product of nitrolim, and further experiments showed that the action is not due 
to cyanamide, nor to dicyanamide, nor to cyanamide carbonate, but simply 
to ammonia, which with carbon dioxide and acetylene (a trace) is the gaseous 
product resulting from the action of water on nitrolim. Pot experiments showed 
that the injurious action had ceased eight days after application of the nitrolim 
to the soil. Oily seeds are affected little or not at all. — /. E. W, E. H. 
Calcium Phosphates, The Solubility of, in Citric Acid. By A. A. Ramsay 
(Jour. Agr. Sci. viii. June 191 7). — It is generally held that these phosphates 
exist in the state of mono-calcic phosphate soluble in water, di-calcic phosphate 
or reverted phosphate soluble in citric acid, and tri-calcic phosphate soluble 
in neither water nor in citric acid. The author was unable to purchase the 
pure tri-calcic compound : the calcic phosphate of the British Pharmacopoeia 
was found to be a mixture of the tri- and di- compounds ; di-sodic phosphate 
added to ammoniacal calcic chloride does not give it, but a mixture of the di- 
and tri- compounds, together with calcic hydrate and a similar mixture, is given 
by bone ash dissolved in hydrochloric acid and precipitated by ammonia. The 
author finds that pure tri-calcic phosphate is obtained by acting on one equivalent 
of pure pentoxide of phosphorus with three equivalents of calcic oxide. If, how- 
ever, only two equivalents of calcic oxide are added, the product is not the di- 
calcic salt but a mixture of di- and tri-calcic phosphates. The pure tri-calcic 
compound is found to be completely dissolved by four separate thirty-minute 
extractions with 2 per cent, citric acid solution, but the separate extracts do not 
contain phosphoric acid and lime in the proportions required by the formula for 
tri-calcic phosphate. The citric acid in fact is more correctly a solvent for lime 
than for phosphoric acid, as is shown by the fact that by the simple addition 
of calcic carbonate to the tri-calcic phosphate the solubility of the latter in citric 
