Iviii Proceedings of the Botanical Society of 



generation on tree members of the rose order. On the com- 

 mon red cedar is found G. penicillatmn, whose alternating 

 stage is RocstcHa penicillafa, found on Sorbns aiicuparia. 

 On the red cedar occurs also G. trcmelloides and G. clavaricB- 

 forme. The species specially dealt with by the speaker as 

 occurring on white cedar were Gymnosporangium bisepta- 

 tum, whose alternating generation is found on the shad bush, 

 also G. Ellisii, whose alternating generation is on the choke- 

 cherry. By aid of the micro-lantern, he then demonstrated 

 from slide preparations the mode of attack of the two last 

 named Gymnosporangia. In one case the younger branches 

 become so affected that they swell up to form enlargements 

 whose wood internally is permeated hf mycelium. This may 

 so fill up the cavities of the wood elements as to cause "plug 

 formations." In the other species the fungus causes a devel- 

 opment of many small, twig-like branches — the so-called 

 "witches broom" growth. The destruction of trees by these 

 fungi seems to be very gradual, and in many cases no marked 

 change other than those noted above may occur for years. 

 Professor Macfarlane then spoke on "The Comparative 

 Study of the Two Species of Alpine Rose, and of their 

 Hybrid." He stated that he had excellent opportunities for 

 watching and comparing the two species of Alpine Rose 

 (RhodoJcndron hirsiitum and R. fcrrugineiim) and of their 

 hybrid which had been named R. intermedium, while resid- 

 ing duringthe past summer in the High Alps behind Sachseln 

 in Central Switzerland. He showed that while the peltate 

 scale hairs of the leaf were common to both parents, though 

 differing in their relative rustiness, the long fine hairs of 

 R. hirsiitum were inherited by the hybrid, but to a reduced 

 degree, since R. fernigineum did not possess these. In 

 period of blooming, the hybrid was very nearly between 

 the two parents since on August 6th, R. fernigineum was 

 already in fruit with only an occasional flower; R. inter- 

 medium was rapidly passing from the blooming into the 

 early fruiting stage, while R. hirsutum was in bloom or in 

 bud. 



