212 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
genus. He reports several cases of the occurrence of false hybrids showing 
only maternal characters, and makes suggestions as to the meaning of the 
phenomenon. — F. J. C. 
Galls: The Zoocecidia of North-Eastern United States and Eastern Canada. 
By B. W. Wells (Bot. Gaz. vol. lxv. No. 6, June 1918, pp. 535-542). — Some 
interesting statistics concerning the plant galls of this phyto-geographic region 
are given. Of 792 known, 2 are caused by worms {Nematodes), 87 by mites, 
and the remainder by insects, chiefly flies of the family Itonididae. Their 
distribution amongst the plant families is extremely irregular. Although such 
large families as the Cruciferae and Caryophyllaceae contain no gall-bearing 
species, yet in the small family of the Fagaceae they are extremely numerous ; 
in Quercus alone 176 have been described. " The intimate and constant relation 
between specific insects and specific plants forms one of the most significant 
phenomena in the field of cecidology." — R. J. L. 
Grape-Berry Moth in Northern Ohio, Control of. By H. G. Ingerson and 
G. A. Runner (U.S.A. Dep. Agr., Bur. Entom. y Bull. 837, June 1920 ; 4 plates, 
1 fig.). — -The grape-berry moth (Polychrosis viteana Clem.) is the most destructive 
insect pest the grape growers of Northern Ohio have to contend with. Arsenate 
of lead , 1 £ lb. of powder to 50 gallons of water, is the active killing agent with resin, 
fish-oil soap, 1 lb. to 50 gallons for a spreader and adhesive — the first application 
to be made when the grapes first " set," and the second when the berries touch 
in the clusters. — -V. G. J. 
Growth in Plants, Effects of Relative Length of Day and Night upon. By 
W. W. Garner and H. A. Allard (U.S. Jour. Agr. Res. xviii. No. 11, March 
1920, pp. 553-606 ; 16 plates). — Three primary factors enter into the action 
of light upon plants, namely, the intensity of light, the quality, i.e. the wave length 
of the radiation, and the duration of the exposure. In the present investigation 
we are concerned with growth and reproduction as affected by the daily duration 
of light exposure. The relative length of the day is a factor of the first importance 
in growth and development of plants. From the species studied it was found 
that the plants can attain the flowering and fruiting stages only when the length 
of day falls within certain limits, and these stages of development are ordinarily 
reached only during certain seasons of the year. Some species respond to 
relatively long days, while others respond to short days, and still others are 
capable of responding to all lengths of the day which prevail where the tests 
were made [in Washington]. The absence of favourable length of day for bringing 
into expression the reproductive processes favours the development of vegetative 
growth (gigantism). On the other hand, a suitable length of day induces pre- 
cocious flowering and fruiting. Thus certain species may be early or late 
maturing, according to the length of day to which they are exposed. " Ever- 
blooming " or " ever-fruiting " may be induced for an indefinite period when 
exposed to a day favourable to both growth and reproduction. 
The relationships between annuals, biennials, and perennials are dependent 
on responses to the prevailing seasonal range in length of day. Therefore by 
artificial regulation of length of daily exposure to light, it is found that the 
normal yearly cycle can be greatly shortened in time or indefinitely lengthened. 
All species studied showed a rate of growth directly proportional to length of 
day. The seasonal range in length of day is an important factor in natural 
distribution of plants, and the inter-relationships between length of day and 
prevailing temperatures of the winter season largely control successful repro- 
duction. The relation between length of day and time of flowering is of great 
importance in crop yields in many instances. 
A short bibliography is appended. — A. B. 
Grub-infested Soils, Arsenic for. By J. F. Illingworth (Journ. Econ. Eniom. 
vol. xiv. pp. 238-239 ; April 1921). — A. brief account is given of several pot 
and field experiments with crude white arsenic (arsenious acid) as a remedy for 
grub-infested soils. The experiments were mostly conducted with grubs of the 
gauger beetle (Isodon puncticollis, Macleay) which were feeding on the roots 
of cucumber plants. Application of white arsenic is recommended at the rate 
of 80 lb. to the acre. The poison is said to have no detrimental effect on the 
plant. It was applied in excessive quantities (200 lb. an acre) to land growing 
sugar-cane, and careful chemical tests on the juice obtained from this cane 
showed " not a trace of arsenic in the juice." — G. W. G. 
Hawthorns, Wild, as Hosts of Apple, Pear, and Quince Pests. By W. H. 
Wellhouse (Jour. Econ. Entom. vol. xiii. pp. 388-391 ; Oct. 1920). — The author 
reports that he has a list of 374 species of insects which have been found to feed 
on the hawthorns (Crataegus sp.). Several of these are widely distributed and 
