NATURAL HISTORY QUERIES 
137 
for a tuber to produce heads two years in succession. I am wondering if the 
wet summer last year had anything to do with it. Perhaps some reader of 
Nature Notes who has studied this group will give me some information. 
The Nurtons, Titttern, Mon. J. F. Bird. 
April 30, 1908. 
634 . Russian Thistle. — A correspondent, who has lived twenty years in 
Colorado, writes of this troublesome weed : “ With regard to the Russian 
thistle, it is a plant ot altogether different character from the Scotch thistle, 
which stays at home and attends to its business, merely disseminating itself with 
a little harmless down. The Russian, when full-grown, is globular in form, 
composed of innumerable hard stems, with thousands of prickles and millions 
of seeds. When dry it detaches itself from the ground and rolls before the wind, 
climbing fences and seeding the cultivated ground within; so that however 
thoroughly a man works his place he is liable to visits from the thistle from 
windward at any season. I have seen a single plant 4 feet in diameter, and 
travelling five miles an hour.” 
[The so-called “ Russian Thistle,” which has attracted considerable attention 
of late years as an agricultural pest throughout Western North America, is no 
thistle but Salsola Kali var. Tragus, one of the Chenopodiacete, a typical halophyte, 
extending its area from the sea-shore into salt deserts or steppes, but by no 
means exclusively Russian. — Ed., N.N.\ 
NATURAL HISTORY QUERIES. 
144. Silver Fish. — The kitchen part of this house is invaded by those 
little insects which are about the size of an earwig, are of a silvery grey, and 
shaped like a tiny fish. I cannot find them in any book I possess. Can you tell 
me what they are, and whether they are in the habit of frequenting houses? Do 
they live in old stone walls ? And are they destructive in any way — as weevil in 
wood, or plaster ? Is it likely to be merely a temporary incursion, or will they 
dwell and multiply in the house? I have been four years in this house and have 
not found them indoors until quite lately. 
Milverton, Somerset, E. M. Beechey. 
fune 8. 
[Lepisma saccharina, one of the Thysanura, one of the latest orders of insects, 
will live in old sash-frames, brick floors or damp sculleries, feeding on crumbs, 
sugar, or other vegetable matter. They apparently do little harm, but are not 
easily dislodged. Their bodies are covered with minute scales, which have long 
been used as tests of the penetrating and defining powers of the objectives of 
microscopes. — Ed. N.N.'\ 
ASTRONOMICAL NOTES FOR JULY, 1908. 
Mercury will be visible as a morning star during the last week of July 
arriving at his greatest elongation west of the sun on the 25th. He will be close 
to Neptune on 28th. 
Venus, Mars, and Jupiter will be practically invisible in July owing to their 
proximity to the sun. 
Saturn rises just before ii p.m. at the middle of the month and, coming 
above the horizon four minutes earlier each night, will soon be perceptible 
throughout the evenings. He will be near the moon on the morning of the 19th, 
on which occasion he will be 3 degrees to the northward of our satellite. 
Uranus will be in opposition to the sun, and very favourably visible, on July 
7. He will be in conjunction with the moon on the morning of the 13th, when 
the distance separating the two objects will be only half a degree. 
On July 16 a star of 4I magnitude will be occulted by the moon between 
10.59 p.m. and 12.3 a.m. 
Shooting Stars will be numerous from the direction of Aquarius and Perseus 
during the last week of the month. 
W. F. I). 
