147 
GHitches’ Brooms. 
By C. R. Srraton, F.ES. 
i lt aici! ieee 
[Read at the Salisbury Meeting of the Society, 1896.) 
4 URIOUS plant structures, which go by the name of witches’ 
brooms, are frequently seen growing on Birch, Abele, 
Hornbeam, and Silver Fir. They are not unlike bird’s nests, or 
bunches of mistletoe ; they are, however, not parasites like mistletoe, 
but distorted parts of the tree itself. When a Birch tree is affected 
a bud will be found here and there larger and looser than the 
others; if the loose scales be shaken off it will be seen that the 
contained shoot is stunted and a circle of buds surrounds the un- 
_ developed central bud. ach bud of this circle undergoes the same 
development, without waiting for the returning seasons of growth, 
_ and crop after crop is thrown out until the work of five or six years 
has been crowded into one. The leaves and shoots dwindle, but 
_ the woody base goes on increasing. If one of these brooms be 
tapped gently over a sheet of paper a number of small gall-mites 
may be shaken out. These phytopti are not, properly speaking, 
insects, but belong to the same class as spiders. Their cylindrical 
bodies are + of an inch in diameter, and they have four short legs 
placed close to the head. Their eggs are found under the scales of 
the bud. It is the influence of the phytoptus that produces this 
_ rapid bud formation, and as a result an enormously increased supply 
of food for its young. I need not enumerate the many trees which 
gall-mites tuft in this way. Sometimes the flower bud only is 
attacked, and many of those flowers that “run back” to green leaves 
