Mar. 1S09.] BOTANICAL SOCIETY OF EDINBUEGH 197 



Last Xovember I found a Scotch pine on which a 

 witches' broom was growing. The tree was seventy years 

 old and forty-five feet high, with diameter of one foot at 

 breast height. It occurred in an old mixed plantation 

 which occupied a steep slope with an eastern aspect. The 

 condition of the wood may be described as distinctly open. 

 The soil was light and sandy, with a covering of blaeberry 

 and moss in some places. The part of the trunk from 

 which the branch bearing the broom arose was seventeen feet 

 above the ground, and showed forty-one annual rings, so 

 that infection had occurred when the tree was forty-one 

 years old. The broom itself was four feet long and three 

 feet broad. It had a peculiarly dorsiventral structure, 

 and all parts of it were extremely brittle. The needles, 

 though numerous, were short, thin, and pale in colour, 

 indicating a lack of chlorophyll. The average length of 

 the needles of the same tree was two inches, while those 

 on the broom averaged only I'd inch. All the needles of 

 the broom were of this year's formation. This is some- 

 what similar to what we find in the broom of the silver 

 fir, with this difference, that the needles of the abies 

 broom are shed annually, while those of the pine broom 

 persist till the year after their formation. 



Some doubt exists as to whether this broom is caused 

 by a fungus or an insect ; but on examining the twigs 

 microscopically, I found abundant traces of a mycelium 

 in the wood and bast. I was able to trace the hyphaj to 

 the base of the bud, but found no evidence of it in the 

 bud itself, nor in the leaves. I have, therefore, come to 

 the conclusion that in spring the mycelium grows on, 

 keeping just behind the extending apex, and at the same 

 time sending branches out into last year's needles, there 

 to form its fructifications ; and these needles being shed 

 in summer or autumn, would leave nothing on the broom 

 but this year's needles, which is the condition I found it 

 in last Xovember. As the tree has been cut down, there 

 is no hope of making any further observations on this 

 broom : but I am trying some artificial mycelium-infection 

 experiments with a view to obtaining more material. 



