98 
NATURE NOTES 
A Bird Poisoner’s Bag. — A neighbour has seen a sack full of dead birds • 
killed by a professional poisoner in these parts, and has described its contents to 
me. There were some rooks and a few pigeons ; common buntings, greenfinches, 
chaffinches, and linnets were in numbers ; yellow-hammers and mountain finches 
were the most numerous of all ; sparrows were about 15 per cent, of the whole. 
Market IVeston, Thetford, Edmund Thos. Daubeny. 
April, 1902. 
Snow Buntings. — We have had a flock of these pretty little birds on the 
golf links at Littlehampton this winter for a number of weeks. Is not this a 
long way south for them ? I did not send you a note at the time, as these notes 
are sometimes copied into the local papers, and we should probably have had 
everyone who could muster any sort of a rusty old firelock trying their best to kill 
them all. 
I observed a large butterfly settle on a sign-post on March 6, and on going to 
see what it was, found a fine specimen of the scarce tortoiseshell in a wonderfully 
good state of preservation. He was still a little sleepy after his lengthy nap, and 
gave me time for a good long inspection at the distance of a foot before he flew 
lazily away. 
Lyviinster, Arundel. H. S. Cleather. 
Crows and Sparrows. — Last Sunday I went out in the garden to feed 
the birds, when flying just above my head came two crows pursuing a sparrow, 
and the crows trying to cover the unfortunate sparrow with their wings, and one 
crow flying slightly in advance of the other. Can any reader of Nature Notes 
say if crows do attack full-grown birds for food ? The frost was very severe. 
I scatter rough food for the crows in a field close by, as these large birds are very 
shy, and I have never before seen them so near the house. 
Little Kussells, Sutton, Surrey. M. T. Cuthuert. 
February, 1902. 
[Were they not rooks? — E d. W.A.] 
“ Knaurs” ? in Trees.— I am much obliged to you for your reference to 
Prof. Marshall Ward’s notes on knurs. After perusing them I am convinced 
the disease he refers to is altogether different to the peculiar tumours, as boys, 
we used to knock out of the cortex of various trees. For the last three or four 
years when on holiday I have been observing and collecting these tumours, and 
have now some very interesting specimens by me. 
I have found them in beech, holly, lime, oak, and other trees. Unlike the 
irregular excrescences Prof. Ward speaks of, they never bear branches or buds. 
At an early stage they are tiny, hard, woody tumours, growing between the layers 
of the cortex, probably between the soft and hard bark. They receive their 
nourishment from their capsules, and so increase at their periphery. If you excise 
a small piece of cortex over the growth, decay starts at that spot. 
I have often found one the size of a walnut perfectly surrounded by cortex, not 
even in contact with the wood of the tree, though in structure resembling the 
wood. The strip of cortex lying between the tumour and the tree microscopically 
resembles normal soft bark and cambium layer. Sometimes after they have grown 
to the size of a walnut or larger, this posterior part of their capsule gives way, and 
decay may start at this point, or what sometimes happens, the tumour may form 
an adhesion to the wood of the tree. I have never found these adhesions very 
firm, making it difficult to knock off the tumour from the tree. 
So much for facts. The cause can only be a matter of theory, and I venture 
to put forward this hypothesis. At some period of the tree’s history cells from 
the cambium layer become displaced between the soft and hard bark, or between 
the various layers of the soft hark, and these take up their normal function of 
wood-forming. Such accidents are far from common in the fortal life of many 
animals. By a folding inwards of the epiblast, cells which normally form skin 
and its appendages become displaced into abnormal positions, and in after life 
form skin, hair, &c., in this hew position. Such tumours are easily recognised at 
the time of the operation, and are called dermoids. 
The close analogy will appear on a moment’s reflection. In the Animal 
