xvi. A PPL ES OF SOD OM. 283 



sect gives rise to the numerous red spines which are 

 well known to all. Upon many of our indigenous 

 plants and trees a great variety of curious and in- 

 teresting galls is formed, the history of which in many 

 cases is still imperfect; but the oak-tree is more infested 

 than all others. Upon it the nests of upwards of 

 twenty different species of insects of this kind may 

 be found. One attacks the young shoots, originating 

 the well-known oak-apples ; another develops flower- 

 like leaves like a little brown artichoke on the buds ; 

 a third gives rise to a series of galls resembling a 

 small bunch of red currants on the catkins ; while 

 every one is familiar with the little round oak-spangles 

 which cover the under side of almost every leaf, con- 

 sisting of a crowd of greenish or reddish hairs, as if 

 they had been cut out of a piece of velvet, and 

 looking so like the shields of a fern or the cups of a 

 fungus that they were at one time supposed to belong 

 to these orders. They change their colour with the 

 growing and fading foliage, and during the winter 

 they may be found on the red fallen leaves with the 

 same rusty hue, the flies being developed from them 

 in the following spring. A gall is produced on the 

 willow called the rose-willow, which is like the oak 

 artichoke, and consists of a cluster of short leaves 

 arranged like the petals of a rose. 



Some very extraordinary galls occur in foreign coun- 

 tries. I saw, in the neighbourhood of Nice, several 

 elm-trees whose topmost branches were covered with 

 large clusters of black pear-shaped bags, looking like 



