GENERAL NOTES. 467 
from Otagoand Hawke's Bay, as to sheep eating thistle heads. 
Not only must the quantity of nutritious (chiefly saccharine) 
matter thus obtained be very considerable, but the number of 
flowers thus prevented from seeding must be enormous. Mr. 
Barker further draws attention to the fact that sparrows feed very 
largely on thistle heads, and that when one is driving along the 
roads in South Canterbury these birds rise in hundreds from off 
the thistle plants, and from those parts of the ground which are 
already covered with seeds. Probably numerous other small 
birds join the sparrows in consuming this supply of food, notably 
the goldfinches, whose common name of thistle-finch (Carduelis) 
bears testimony to their tastes. Opinions are divided as to the 
good or evil effects of thistles on the soil, some persons affirming 
that if cut and burned they improve the soil by the quantity of 
potash salts they contain. This is probably—to a great extent 
at least—an imaginary benefit, as they cannot add any salts to 
the soil, but only return those which they had previously with- 
drawn from it. It is possible, however, that they do return these 
salts in a condition more readily available by the plants which 
follow them. When thistles come in enormous numbers, so as 
completely to cover the ground, there can be little doubt that 
their ultimate effects must be beneficial, however objectionable 
they are at the time. I have myself seen large areas in the 
Oamaru district, which had been turned over by the plough for 
the first time, and had been completely taken possession of by 
thistles. The great mass of the vegetation thus raised died where 
it had grown, and thus added largely to the humus of the soil, 
and even where it was burnt off all the mineral matters were 
still of course left behind. But the greatest benefit was 
apparently conferred by the roots, which had penetrated into the 
soil below the furrow-cut to a depth of 3 or 4 inches in all direc- 
tions. These, decaying where they had grown, not only aided 
themselves in breaking up the lower soil, but also furnished by 
their decay considerable quantities of carbonic acid, which would 
further tend to liberate and render soluble various alkaline and 
earthy silicates. Whether the good thus done counterbalances 
the evil which they accomplish in other ways is a question which 
no doubt each one interested will answer for himself, but it is 
some comfort to know that even sucha generally condemned 
plant has something to be said in its favour. G. 
SEXUAL DIFFERENCES IN SPIDERS.—I would draw the 
attention of your readers to the peculiar differences in the struc- 
ture of the palpi of male and female spiders of the genus Sadticus 
(Leaping Spiders), which I procured from among the dead stalks 
of afern. The female, which is the larger, has long chelate 
palpi, with a claw like a lobster’s, while those of the male are 
short, stout, and shear-like. It would be interesting to discover 
what different purpose they serve: it may be that the claw is 
used for the transportation of the eggs. The appearance and 
colour of these spiders were such that it was most difficult to 
