Marcu 24, 1923] 
NATURE 
411 

map shows great improvements on former maps of 
this part of the Sahara. 
_ DistripuTion or Ice rn Arctic SEAs.—The pub- 
lication by the Danish Meteorological Institute of 
“The State of the Ice in the Arctic Seas, 1922,” 
directs attention to a somewhat unusual year, but 
unfortunately information is almost entirely lacking 
from Siberian waters and very scanty from the Beau- 
fort Sea. By April the extent of pack in the Barents 
Sea was much smaller than usual. Bear Island, 
which had been free from ice all winter, was clear 
and open water almost reached to Novaya Zemlya. 
The edge of the ice continued to retreat. In July 
the whole west coast of Novaya Zemlya was clear, 
and in August Franz Josef Land was probably access- 
ible by open sea. Early in the year conditions in 
Spitsbergen were about normal. In May and early 
eee an unusual amount of ice drove round the South 
pe before continuous easterly winds, but this re- 
sulted in the west coast being practically free from 
ice for the remainder of the summer. On the north 
coast conditions were particularly favourable, and a 
vessel reached lat. 81° 29’ N. Some sealers circum- 
navigated Spitsbergen, a feat that is not possible in 
most years. In the Greenland Sea the belt of pack 
lay more westerly than usual, and though the east 
coast of Greenland does not appear to have been 
clear of ice, open water touched the coast in about 
lat. 74° N. during August. Jan Mayen and the coast 
of Iceland were free from pack from May onwards 
throughout the summer. On the Newfoundland 
banks both pack and icebergs were abundant in early 
spring, but July was clearer than usual. In Davis 
trait the winter ice was thinner and the “ west ice ” 
less abundant than usual. In Bering Strait condi- 
tions were fairly normal, but along the north coast 
of Alaska the pack pressed hard and navigation was 
much hindered. 
Earty History oF THE BLAcK CuRRANT.—The 
Gardeners’ Chronicle has recently commenced a very 
interesting series of notes under the heading “‘ Early 
Botanic Painters.’ In the issue of February 17, the 
figures of the Black Currant reproduced from the 
paintings by Jean Bourdichon (1457—? 1521) are 
extremely interesting, and raise the query whether 
the cultivation of the black currant may not be of 
longer date than is usually supposed. R. G. Halton 
of the East Malling Research Station has recently 
described existing varieties of the Black Currant, and 
to judge from his brief account of its early history 
(Journal of Pomology, vol i. No. 2, p. 68), it receives 
scant notice from the earlier chroniclers of horti- 
cultural effort. 
A New Cutture Mepium ror BacTEertaL Count 
Worxk.—For bacterial counting work, in which the 
plating method is used, a first essential of accuracy is 
that the medium used in plating should give uniform 
results. There are two respects in which a medium 
should display this uniformity. In the first place, it 
should be reproducible, that is to say, different batches 
of medium should give similar results. In a medium 
recently developed at Rothamsted (H. G. Thornton, 
Annals of Applied Biology, vol. ix. p. 241, 1923), this 
reproducibility has been achieved by using pure 
chemical compounds as food constituents and especi- 
ally by selecting those compounds that were found 
not to alter the reaction of the medium during 
sterilisation. In the second place, parallel platings 
of a suspension of organisms made on a single batch 
of medium should develop the same number of 
colonies (within the limits of random sampling 
variance). Uniformity in this respect involves the 
NO. 2786, VOL. 111] 
independent development of each colony on the plate, 
and on agar media this is frequently prevented by the 
development of bacteria that form rapidly spreading 
colonies which interfere with the development of 
other bacteria. A special study was therefore made 
of a common “ spreading ’’ organism with a view of 
limiting its growth. It was found that the organism 
spread over the agar surface by active motility and 
that the factors controlling its spread were (1) the 
existence of a surface film of water on the agar, and 
(2) the rate of multiplication previous to the drying 
of this film. In the present medium this rate of 
multiplication has been much reduced, so that 
spreading colonies are greatly restricted. 
SILKWORM DISEASES IN INDIA.—The subject of 
silkworm diseases is not a new one in India, but 
notwithstanding the fact that sericulture is probably 
a much older industry in that country than in Europe, 
there are no corresponding early records of disease, 
The whole problem is very fully discussed in a recent 
memoir by Dr. A. Pringle Jameson (Report on the 
Diseases of Silkworms in India, Calcutta, 1922. 
pp. 165 and 8 plates). It appears that all the re- 
cognised diseases are prevalent, and those of the mul- 
berry, muga, and eri worms are the same. Pebrine 
is only of importance in mulberry worms : losses are 
still heavy, mainly because the majority of rearers use 
unexamined eggs or “‘ seed.’’ Muscardine is almost 
confined to mulberry worms and is a most serious: 
complaint, whole rearings being frequently lost. 
Flacherie is of less importance in mulberry worms, 
while grasserie is stated to cause loss to all species. 
Conditions in India make the control of disease con- 
siderably more difficult than in temperate countries, 
but there is no reason why the industry should not 
be placed upon a surer footing. The crux of the 
whole question lies in the “ ryot,’’ and, if improve- 
ment is to be effected, the village rearer must be 
instructed as to the causes of disease and induced 
to go in for better methods of rearing. Since the 
industry is carried on by cottagers, the latter should 
be encouraged to use disease-free ‘‘seed.’’ The 
extension of the Government nursery policy will avail 
little unless the rearer can be induced to educate 
himself to adopt better methods. The most im- 
portant work of the Government sericultural officers 
should be instruction and supervision, while seri- 
cultural schools should be established. The seri- 
cultural department officials themselves should 
conduct research work on a practical scale, and 
an attempt should be made to provide them with the 
chief literature on this subject in order that they may 
keep abreast with sericultural research. Improve- 
ments are to be looked for from the work of the 
provincial sericultural departments being extended 
among the villages. 
FIBRES FROM THE TrRopics.—A noticeable feature 
of journals recording activities in tropical agriculture 
is the interest at present being taken in the subject 
of fibre production. The Tvopical Agriculturalist, 
issued from Peradeniya, records promising experi- 
ments with cotton, and in its December issue (1922) 
devotes considerable space to a paper by E. Mathieu, 
superintendent of the Government Plantation, Kuala 
Kangsar, upon the cultivation of the ‘‘ Kapok”’ tree, 
Eriodendron Anfractuosum, In the fruits of this 
plant, hairs grow freely on the inner side of the valves 
of the capsule but not upon the seeds themselves, 
so that the separation of the fibre from the seed is 
a relatively easy matter. The export of this fibre 
from Java in 1912 exceeded 10,000 tons, and owing 
to the increasing demand from Europe and America, 
its cultivation seems likely to extend in Ceylon. 
