i in; I'AUAsmr KXOA-M I-:AK. 



159 



duchii,' the broom> liy artificial infection of alder. The di-.-ase 

 is common and epidemic, and a single tree may carry as many 

 as a hundred l>rooins. 



The witches' brooms are 

 composed of many thickened 

 twills, beset with an alumr- 

 mal number of lentieels, 

 and the point of infection 

 show- a distinct swelling, 

 from which the broom tends 

 to turn directly upwards. 

 The leaves are somewhat 

 modified, they are larger and 

 thicker than the normal, 

 they unfold later and wither 

 earlier, while their stipules 

 remain attached for SOUK- 

 time. The brooms of alder 

 only survive a few years, 

 and by their decay cause 

 tin- death of larne liranche-. 

 and freipieiitly of tin- whole 

 tree. 



Tin- asci, which are sunk 

 in a depression of their 

 stalk -cell, form a white 

 nut inn on In. tli surfaces nl' 

 tin- Leaves. The mycelium 

 hiliernates in the lunU. 



Exoascus turgidus Sad. 

 causes the formation of 



witches' lil'ooms oil l' lulu 



verrucosa. The |r;i\-;^ tunn- 

 ed mi the lirooms are some- 

 what crumpled, and the asci 

 are produced un their lo\\er 

 -in face. 



Exoascus betulinus 



pr.idllre- Witrh. 



on I'.ilnlii jnil'1 sr. /rs and //. 



- 







.!>.._ 



\- 1 



ti.in. 'l'l , .niinii. 



till' ll"l-lll.ll -till ll-lll.llll 

 v. Till 



