The Two Rust Diseases of the Spruce. 
BY 
A. W. BORTHWICK, D.Sc., 
Advisory Officer for Forestry to the Board of Agriculture 
for Scotland, 
AND 
MALCOLM WILSON, D-Sc., F.L.S., 
Lecturer in Mycology in the University of Edinburgh. 
With Plate CXLIX. 
- Chrysomyxa Rhododendri, De Bary. The Spruce Blister 
Rust, Rust of Rhododendrons. 
Chrysomyxa Rhododendri was first recorded in Britain by 
D. A. Boyd in June 1913, who discovered the uredospore and 
teleutospore stages on Rhododendron hirsutum at Douglas 
Castle, Lanarkshire. 
Shortly afterwards, in October 1913, material of the aecidial 
stage of the fungus on Picea excelsa was sent for identification 
to one of the writers from the south-west of Scotland, and its 
discovery was recorded in the Proceedings of the Botanical 
Society of Edinburgh in June 1914.* 
The life-history of this species was first described in 1879 
by De Bary,+ who showed that, the forms previously known as 
Aecidium abietinum and Uredo Rhododendri were stages in the 
development of one species to which he assigned the present 
name. 
This species is found frequently in the Alps wherever the 
Alpine Rose (Rhododendron hirsutum and R. ferrugineum) occurs. 
The yellow clusters of uredospores are developed in September 
on the lower surface of the leaves and also on the bark of the 
Bd. xxxvii, 1879, p- 
* Proc. Bot. Soc. Edinburgh, vol. xxvi, 1913-14, p. xxxiii. 
, ue Bot. Zeit., il 761. 
[Notes, R.B.G., Edin., No. XLI, April 1915.] A 
