224 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
It is frequently found that a few colonies surpass all the others in honey 
production, gentleness, comb-building, resistance to disease, general hardiness, 
and length of life ; but, owing to the inability to select the drone, these and 
similar desirable qualities may not be perpetuated. 
Numerous experiments in artificial mating have been tried since about 
1870, but with small success. Cages of varying size up to 30 ft. high by 30 ft. in 
diameter in which selected drones and queens are released, have only partially 
succeeded. The only feasible plan for mating queens with select drones, 
according to E. R. Root, is to prevent the escape of drones other than select 
drones, by placing zinc over the entrances of all colonies not having choice 
drones, leaving only select drones the freedom of the air. — G. W. G. 
Razoumofskya, Experimental Investigations on the Genus. By James R. 
Weir (Bot. Gaz. vol. lxvi. No. 1, July 191 8, pp. 1-31 ; 19 figs.). — Culture 
experiments carried out by the writer show that many of the characters em- 
ployed in the classification of the false mistletos vary with such factors as 
change of host, geographical location, and environment. " This indicates that 
only the broader and plainly evident lines of demarcation should be employed 
in their classification." 
Attention is drawn to the danger of introducing the following parasites 
into Europe : — 
(1) Razoumofskya campylopoda, infecting Pinus resinosa, P. sylvestris, and 
P. montana. 
(2) R. laricis parasitic upon Larix europea, L. leptolepis, Abies grandis, 
Pinus ponderosa, and P. contorta. These are new hosts for this species, with 
the exception of the last. This parasite is only of economic importance mt 
present upon Larix occidentalis. 
(3) R. americana is of importance only on Pinus contorta and P. Banksiana. 
It will infect P. montana, hence its importance to European forests. — R. J. L. 
Red Spider (Genera Tetranyehus and Oligonychus), Revision of the English 
Species of. By S. Hirst (Proc. Zool. Soc. London, 1920, pp. 49-60 ; 5 figs.). — 
A short account of the native species of plant mites, better known as Red Spider. 
Keys are given to the two genera mentioned, and to the species — 8 species of 
Tetranyehus and 3 species of Oligonychus. The most important species from an 
economic point of view are T. telarius, the well-known Red Spider of carnations, 
peaches, melons, cucumbers, etc., and O. ulmi, whose host plants are apples, 
pears, plums, etc. 
This latter has been a serious pest of apples in most counties during the 
exceptionally hot summer of 1921. — G. F. W. 
Rhododendron ciliicalyx. By A. O. {Irish Gard. 14, p. 18, fig. ; Feb. 1919). 
— Notes on this Chinese sp. as grown in the temperate house at Kew and in its 
wild habitat. Flowers 4 in. in diameter, white, with yellow blotch inside, and 
flushed rose without ; very fragrant. — F. J. C. 
Root-Cuttings and Chimaeras, II. By W. Bateson, M.A. (Jour. Gen. xi. p. 90 ; 
April 192 1, plates). — Cases in which two dissimilar plants have been obtained 
from sister root-cuttings in Pelargonium, and Bouvardia are described. A 
variegated plant of Spiraea Ulmaria, quite sterile, has produced numerous buds 
upon its roots, but all have formed white shoots. — F.J.C. 
Root Rot of Fruit Trees due to Armillaria mellea. By W. A. Birmingham 
(Agr. Gaz. N.S.W. xxxi. pp. 669-673 ; 4 figs.). — Armillaria mellea is a most 
destructive fungus, attacking the roots of trees. In its early stages its presence 
can only be recognized by examining the roots. It will then be found that 
the bark below the ground is rotten and can be peeled away, exposing the white 
fungus with black rhizomorphs running along the surface of the roots. In 
citrus trees the rhizomorph is firmly attached to the roots, but in apples and 
stone fruit it runs free. Spore-bearing toadstools may appear in autumn. The 
fungus spreads from the spores, from old stumps left in the ground, and from 
infected roots. It is difficult to cure, but in the early stages copper-sulphate- 
lime paste may be applied" to the diseased roots. — S. E. W. 
Root Variations induced by Carbon Dioxide Gas Additions to Soil. By 
H. A. Noyes, J. F. Trost, and L. Yoder (Bot. Gaz. vol. lxvi. No. 4, October 1918, 
pp. 364-373 ; 9 figs.). — Experiments were carried out by introducing carbon 
dioxide subterraneously into soil in Wagner pots. The effects of the gas 
varied with the different plants used, but a constant treatment of 650 c.c. of 
carbon dioxide per hour was apparently preventive of normal root develop- 
ment. " Decaying organic matter is held to be beneficial to growing plants. 
Cases have been cited by others where turning under immense amounts of green 
