CH. IV, 12] MONSTROSITIES OF STEMS 



199 



Spruces and some other trees. Here, instead of the usual 

 development of a few buds with inhibition of others, many 

 or all of the buds on the 

 branches affected develop 

 equally, and more or less 

 independently of the 

 others. It is known 

 that this condition is 

 produced by the pres- 

 ence of a parasite, the 

 obvious effect of which 

 is to paralyze the mech- 

 anism of growth correlation by which the buds are ordinarily 

 controlled. 



Closely analogous to these cases in buds is the unregulated 

 growth of tissues. Thus, the large burls or gnarls which ap- 



FIG. 146. A twin-fruit, of Mandarin 

 Orange ; X . (Drawn from a photo- 

 graph.) 



FIG. 147. A typical Witches' Broom, caused by an ^Ecidium, a Fungus, on 

 a branch of Fir. (From Kerner.) 



