1915] 



BURT THELEPHORACEAE OF NORTH AMERICA. IV 629 



enlarged and have turned pale and slightly pink under the 

 stimulus of the infecting fungus. In figs. 10-15 the lateral 

 axillary buds along the infected stem have abnormally en- 

 larged by the stimulation of the fungus and have developed 

 in several instances short, delicate, wax-like or coralloid 

 branchlets of carmine color. Such branchlet shoot galls are 

 beautiful objects in their vegetative condition; they consti- 

 tute a noteworthy type of gall which is quite different in ap- 

 pearance from the more common leaf galls, produced in re- 

 sponse to local infection of leaves. Nevertheless, the common 

 cause of these different gall forms is well brought out by 

 Woronin's illustrations, especially by figs. 11, 12, 13, and 15. 

 Upon shoot galls similar to the above, there have been pub- 

 lished Exohasidium Andromedae Karst. non Peck for the 

 shoot galls of Andromeda polifolia, E. cassiopes Peck for the 

 shoot gall of Cassiope Mertensiana, and E. Oxycocci Rostrup 

 for that of Oxycoccus palustris. 



Figures 16-18 show the flower type of gall of Vaccinium 

 vitis-idaea, that is, the abnormal growth form made by indi- 

 vidual flowers in response to the stimulation of their tissues 

 by the fungus. That both the flower gall and the leaf gall 

 have a common cause has been brought out well by the selec- 

 tion of the specimens used for figs. 16 and 17. In fig. 18 there 

 is presented local infection of a single flower. This is import- 

 ant because isolated flower galls upon a new host have in some 

 cases been regarded as prima facie evidence that they have 

 been caused by a new species of Exohasidium. 



Other host plants produce some types of galls, when in- 

 fected with Exohasidium, which were not figured by Woronin 

 for Vaccinium vitis-idaea but which are more or less common. 

 Such gall types are : 



(a) Leaf type in which scattered whole leaves of the host 

 are infected. These leaves redden more or less on the upper 

 side and bear on the whole under side the scurfy or felty 

 fructification but are not notably thickened or deformed. 

 This gall differs from the leaf spot gall of Woronin 's fig. 1 

 merely in having the whole of the leaf infected. 



(b) Shoot gall with all the leaves toward the tip of the 



