MU. W. H. BURRELL ON THE iECIDIUM ELATINUM IN NORFOLK. 257 
both great and small, from the humble daisy to the forest tree, 
that are attacked by them. The mycelium may be shortdived or 
perennial, and may be limited to a small spot on a leaf or to one of 
the reproductive organs, or it may permeate the whole plant, root, 
stem, and leaves. Its effect on the host may vary from a slight 
and transient disfigurement to the total destruction of the plant 
The Uredines are notable for two characteristics, (a) the variety 
of their reproductive cells, and (/>) the hetercecism of some of 
their members. 
(a) The most fully equipped species produce three distinct 
kinds of spores, secidiospores and uredospores, each giving rise to 
a mycelium on germination ; and teleutospores, first producing 
a promycelium, from which conidia are abstracted, and these conidia 
givo rise to true mycelia. 
( I ) ) The Uredines are the only known plants in which an enforced 
change of host occurs (metcecism). A number of species are unable 
to complete their life cycle without migrating at definite periods 
from one host plant to another of a different genus. 
Both these peculiarities appear in the historic Puccinia gram inis. 
The secidiospores occur on the leaves of Barberry ; these spores 
will not develop on Barberry, but can produce a mycelium only in 
the tissues of the grasses, on the leaves of which uredospores and 
teleutospores appear later. The teleutospores in their turn cannot 
develop in the tissues of grasses, but have to migrate to Barberry. 
Although the devastation caused by these parasites has troubled 
agriculturists for ages, the true cause of rusts and smuts has only 
been discovered in comparatively recent times. Since 1864, when 
l)e Bary first recognised the dual existence of Puccinia graminis , 
a number of workers have given attention to the subject, and much 
progress has been made in the study, but there are at the present 
time between thirty and forty members of the family (Uredinea?) 
whose life history is not completely known. 
Amongst these imperfectly known forms is JEkulium elatinum. 
The secidium stage only is known. Whether under favourable 
conditions uredo and teleuto spores are formed, and whether it is 
autcecious or hetercecious, are botanical problems which remain to be 
solved. Its mycelium is perennial in the cortical and bast tissues 
of the Silver Fir ; its mode of entrance is unknown. Weise believes 
