lviii Proceedings of the Botanical Society of 
generation on tree members of the rose order. On the com- 
mon red cedar is found G. penicillatum, whose alternating 
stage is Roestelia penicillata, found on Sorbus aucuparia. 
On the red cedar occurs also G. tremelloides and G. clavarie- 
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. Ellisti, 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 by 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 
(Rhododendron hirsutum and R. ferrugineum) and of their 
hybrid which had been named R. intermedium, while resid- 
ing during the 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. hirsutum were inherited by the hybrid, but to a reduced 
degree, since R. ferrugineum did not possess these. In 
period of blooming, the hybrid was very nearly between 
the two parents since on August 6th, R. ferrugineum was 
already in fruit with only an occasional flower; R. imter- 
medium was rapidly passing from the blooming into the 
early fruiting stage, while R. irsutum was in bloom or in 
bud. 
ee 
