162 



ASCOMYCETES. 



into the inner tissues of newly-formed twigs and leaves. The 

 mycelium of Ex. alpinus passes the winter in the buds, spreading 

 thence in spring into young twigs and leaves. 



Fig. 57. — Exoascus cerasi on Prunns Ceratm. Cherry-tree in blossom, with the 

 exception of four witches' brooms. The tree is as yet leafless except the brooms, 

 which are in full foliage and show up dark. (v. Tubeuf phot.J 



Exoascus carpini Eostr. is common on Carpinus JBetulus (horn- 

 beam) (Fig. 55). The brooms produced are bushy and densely 

 leafed ; the twigs are thickened and much branched ; the leaves 



