68 BoRTHWICK AND WILSON—Two Rust DISEASES OF SPRUCE. 
Professor Trail has kindly forwarded the following informa- 
tion :— 
“It is not more than six or seven years ago that I first 
observed Chrysomyxa abietis in Aberdeenshire, and it is probable 
that the fungus has only recently made its appearance in the 
north of Scotland. I have seen trees attacked by the disease 
in the Monymusk and Farland districts. The disease is now 
also very common in the spruce woods on the banks of the 
Findhorn, where it was first noted some three or four years ago 
by Mr. William Watt, Assistant Forester on the Moray estates. 
When the infected trees in this locality are standing singly and 
foliaged to the ground, only the leaves on the lower branches 
are as yet attacked.”’ 
Mr. P. Leslie, Lecturer in Forestry at the North of Scotland 
College of Agriculture, informs us that Chrysomyxa abietis is 
stated to be quite common on the Novar estate, Ross-shire. 
It is evident, therefore, that the disease is spreading to a con- 
siderable extent. 
Chrysomyxa abietis, which is widely spread in Switzerland 
and Germany, is an autoecious species completing its life-history 
on the spruce. It differs from C. Rhododendyi in producing 
only one kind of spore, the teleutospore. The hibernating 
teleutospores germinate about May and produce sporidia which | 
infect the young leaves of the spruce. An abundant intercellular 
mycelium is developed in the tissue of the leaf which sends 
haustoria into the cell cavities. The hyphae contain numerous 
yellow oil-drops, and in consequence yellow bands appear on 
the leaf. Soon afterwards teleuto-sori are produced which 
take the form of elongated yellow cushions on both the under 
surfaces of the leaf (fig. 6). During the winter the sori are 
covered, but in the following spring the epidermis is ruptured 
and the teleutospores project as an orange-yellow mass (fig. 7). 
Each teleutospore is cylindrical and consists of 8-12 superposed 
cells of which only the terminal one produces a promycelium 
(fig. 8). At about the middle of May the sorus becomes brighter 
yellow and the promycelia grow out. Each produces four small 
spherical sporidia, which become easily detached and are 
distributed by the wind. When the sporidia have been shed, 
the sorus loses its bright colour and shortly afterwards the 
diseased leaf falls. On coming into contact with the young 
needles of the spruce the sporidium produces a germ tube which 
bores through the epidermis and so brings about infection. 
It frequently happens that certain spruces in a wood remain © 
free from the disease, while others are badly attacked. This 
may be explained by the fact that infection of the young leaves 
only takes place at a certain stage in their development ; trees 
