498 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
genetic connexion of this fungus with Gibberella moricola. Burning all affected 
shoots and old wood should be practised wherever the fungus appears. — E. A. B. 
Mushrooms, A Bacterial Disease of Cultivated. By A. G. Tolaas (Phyto- 
pathology, v. pp. 51-53, Feb. 1 915 ; pi.). — A bacillus (perhaps B. ftuorescens) 
producing spots at first pale yellow, but finally rich chocolate brown, on the caps 
of cultivated mushrooms is described. The discoloration is usually only on the 
surface, but where the attack is severe the flesh is frequently yellowish white. A 
similar attack has been described from near Paris. Fumigation of the beds 
with sulphur before spawning proved entirely successful, i£ lb. sulphur being 
used for each 1000 c. ft. of space in the caves. — F. J. C. 
Mussel Scale, Winter Treatment of. By A. H. Lees (Ann. Rep. Agr. Res. 
Stn., Long Ashton, 1915, p. 84). — Caustic soda (2 lb. to 10 gallons), paraffin 
emulsion (paraffin 10 per cent., soft soap 10 per cent.), and lime-sulphur (1 
gallon commercial concentrate to 12 gallons water) were used against mussel 
scale in winter, and the caustic soda alone proved effective, and that completely. 
F. J. C. 
Mycorhiza, Endotrophic, Recent Developments in the Study of. By M. 
Chevely Rayner (New Phyt. vol. xv. No. 8;. Oct. 1916). — This interesting paper 
is concerned chiefly with the Orchidaceae and Ericaceae and their respective 
symbiotic fungi, and is of particular importance with regard to the problems 
of soil ecology and in view of the edaphic peculiarities of Ericaceous plants. 
Noel Bernard was the first to demonstrate — (1) by germinating the seeds of 
orchids under aseptic conditions in sterilized media, (2) by isolating the root 
fungi, growing them in pure culture and identifying them with certainty — that, 
while the seeds of some species will germinate, in no case will they produce well- 
developed plants unless infected with an endophytic fungus and in most cases 
a specific endophyte must be present. The fungus at first vegetates actively 
in the living cells of the root, but to keep it within bounds, the orchid plant 
digests the mycelium in certain root cells and excludes all hyphae from the 
chlorophyllous tissues of the shoot. 
Of practical interest to Orchid growers is the evidence that in some cases the 
fungus isolated from endemic species will induce germination in the seeds of 
tropical species. 
The case of Call una is probably characteristic of Ericaceous plants in general. 
Here the root fungus not only forms mycorhiza, but extends into the tissues 
of the shoot and leaves ; it infects the seeds in the ovary chambers, and these, 
when ripened and shed, carry with them their fungal partner in the form of 
delicate hyphse on the surface of the testa. 
Gastrodia elata, a saphrophytic orchid and a native of Japan, is described 
by Kusano. It is a colourless tuber invested with a corky covering like a potato, 
is destitute of chlorophyll and has no root system. A remarkable case of sym- 
biosis exists between this orchid and the rhizomorphs of the fungus Armillaria 
mellea. The more striking features are as follows : Young tubers are uninfected 
and continue to grow only so long as they are attached to the parent tuber. 
Failing infection by the rhizomorphs of Armillaria mellea they never reach the 
flowering stage, and the majority die without flowering. The tuber is infected 
locally by a branch of the rhizomorph, a continuation of the mycelium outside, 
and only in this way can it gain food material from the soil. In one region of 
the plant the rhizomorph is parasitic, in another — which Kusano describes 
as the chief metabolic centre — the mycelium is itself ultimately digested after 
introducing an accumulation of food material upon which the flowers of the 
Orchid and the nutrition of its offsets are entirely dependent. At this stage 
the plant is seen to be completely parasitic on the fungus, It should be noted 
that the term mycorhiza must be extended to embrace a case of this kind where 
there is an association between a fungus mycelium and the shoot tissues of a 
flowering plant. Nothing is at present known as to the behaviour of the seeds 
of this orchid at germination. — G. D t L. 
Nematode, Root-knot, Experiments on the Control of the. By J. A. 
McClintock (U.S.A. Exp. Stn., Mich., Tech. Bull. 20, July 1915).— The root- 
knot eelworm, Heterodera radicicola (Greef) Muller, has for a long time been a 
serious pest to many crops, and the author records a large number of experiments 
on the control of this nematode. The experiments were devised to test the relative 
value of various chemicals, with the possibility of finding one that would be 
effective and economical to apply. Infected ground was treated with carbon- 
bisulphide, tobacco dust, formaldehyde, naphthaline, tobacco stems, ammonia, 
