412 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
Cotyledon oppositifolia Ledeb. By R. A. Rolfe {BoL Mag. t. 8822 ; 
Dec. 1919). — At one time called Umbilicus oppositifolius, this native of the 
Caucasus is hardy in English rock gardens. It produces branched spikes of 
yellow flowers in an open panicle on erect stems bearing fleshy, flattish crenate 
leaves. — F. J. C. 
Crataegus Wattiana Hemsl. et Lace. By W. J. Bean {Bot. Mag. t. 8818 ; 
Sept. 1919). — Attains size of a small tree. Native of Baluchistan. Distinguished 
from C. sanguinea by truncate or cordate base of leaf (not cuneate), foliage and 
summit of ovary glabrous. Flowers white in May ; fruits globose, clear trans- 
lucent yellow. — F. J. C. 
Cucurbits, Bacterial Wilt of. By F. V. Rand and Ella M. A. Enlows {U.S.A. 
Bur. PI. Ind., Bull. 828, May 1920, pp. 1-43 ; 9 figs.). — The study of the bacterial 
wilt on cucumbers, caused by Bacillus tracheiphilus (E. F. Smith), has been 
continued since 191 5, and an exhaustive study of the relation of soil and insects 
to the distribution and control of the disease has been made by the authors. 
The disease occurs in thirty-one States and affects^cucumbers, cantaloups, squashes 
and pumpkins, but not water-melons. The severity of the attack varies from a 
single plant to 95 per cent, of the crop. Very little direct relation between 
percentage of infections and severity of the disease is due to weather conditions, 
but the chief carriers of the disease in summer-time are the striped cucumber 
beetles, Diabrotica vittata and D. duodecimpunctata. Infection of the plant is 
due to wounds on surface. The disease cannot winter in the soil. Cucumbers 
are the most susceptible and water-melons are the least susceptible to the disease. 
Control measures suggested are some strong insecticide and some protective 
spraying fluid for the plants. — A. B. 
Currant Grapes, Growing. By George C. Husmann {Am. Pom. Soc, 191 7, 
pp. 66-69 4 plates). — Their profitable growth in the United States has been 
demonstrated. Two conditions are necessary — they must be grafted on 
phylloxera-resistant stocks and incised while in blossom, the latter operation 
consisting in making two parallel incisions through the bark, around either the 
trunks, arms, or cones of the vines, and taking out the bark between the cuts. 
A. P. 
Daphne tangutica Maxim. By W. J. Bean {Bot. Mag. t. 8855, Sept. 1920). — 
R. Fairer distributed a Daphne under his No. 271 , which, while related to D. retusa, 
is distinct in its longer narrower leaves, less markedly ciliate bud scales, and 
glabrous stigma. It flowers in spring and appears to be perfectly hardy, 
although not transplanting readily. The flowers are pinkish [and exceedingly 
sweet-scented]. — F. J. C. 
Delphinium Pylzowii Maxim. By O. Stapf {Bot. Mag. t. 8813 ; Sept. 1919)- — 
This plant has been known in cultivation since 1876, but was reintroduced by 
Mr. Farrer, who collected it in the Min-Shan range (Journal R.H.S. xlii. p. 332). 
It is a perennial requiring the same cultivation as D. grandiflorum, with dark 
azure-violet, pale rose, or rose-lilac flowers. — F. J. C. 
Derris as an Insecticide, By N. E. Mclndoo {Jour. Agr. Res. 17, Aug. 1919, 
pp. 177-200). — An historical review is given of the discovery of Derris as an 
insecticide. Several species of Deguelia (Derris) are known, but only D. elliptica 
and D. uliginosa have proved sufficiently toxic and useful. 
Although these plants have long been known as a fish poison, it is only in 
recent years that its value as an insecticide has been discovered. It acts both 
as a contact and a stomach poison, but is useless as a fumigant. 
Experiments are described, with tables showing results of the application 
of Derris as a powder and liquid spray. 
Several methods of extracting the toxic property are given, and denatured 
alcohol proved a good solvent. The toxic principle is thought to be a resin, 
known as Derrid, and appears to kill insects by motor paralysis. 
In the dusting experiments described it was found that the nerve tissue 
of the insect was first affected, and only small quantities got into the mouth 
to act as a stomach poison. 
Derris powder was found efficient against several insects, including Aphis 
rumicis L., A. pomi de Geer, and Myzus persicae Sulz. ; but of no use against 
Red Spider, Mealy-bug, Cockroaches, etc. 
In proprietary washes, Derris extract is mixed with soft soap, and can be 
dissolved in water and used at once. — G. F. W, 
