44, PUCCINIA GRAMINIS 
origin of outbreaks of rust. It is not inconsistent with this 
that Ward was able to prove that the mycelium of a uredo- 
sorus extends only a little way round the margin of the sorus; 
that may be and is true in certain cases, especially with regard 
to secondary uredo-sori, but in P. Caricis the mycelium extends 
up and down the leaf between the parallel vascular bundles, 
producing uredo-sori all along its course. The practical bearing 
of Pritchard’s discovery is to show that seed from an infected 
crop should never be used for planting. 
About the third possibility, it is difficult to come to any 
definite conclusion. Eriksson’s hypothesis is that the proto- 
plasm of the fungus is present in the grain, mixed with the 
protoplasm of the host, in such a way that’ the two are 
indistinguishable. As the plant grows up, he supposes that 
the two grow together until, at a certain time, the protoplasm 
of the fungus separates itself from that of its host in the form 
of “Nucleoli,” passes into the intercellular spaces through 
“invisible pores,’ then or earlier surrounds itself with a cell- 
wall, forms a mycelium, and begins its ordinary life by producing 
uredo-pustules. An intermediate stage, where the fungus- 
protoplasm has surrounded itself by a cell-wall but is still 
enclosed within the cells of its host, he named “special cor- 
puscles.” 
The difficulty in dealing with this theory lies in its in- 
definiteness ; its author changes it from time to time to meet 
objections, and supports it by hazy microscopical observations, 
many of which are demonstrably the result of incorrect vision. 
His “special corpuscles” have been shown by Ward and Klebahn 
to be ordinary haustoria, Eriksson having completely overlooked 
the intercellular hyphe to which those haustoria were attached. 
It is incredible that the protoplasm of so highly evolved a fungus 
could live outside its cell-walls, as he supposes. Such a state 
of things is, of course, common in the lower fungi, Chytridinge 
and allied groups. In Synchytrium Solani the fungus-protoplasm 
and the host-protoplasm may be seen in the same cell, before 
the latter has been completely devoured by the former, and in 
that state they are even distinguishable by their microscopic 
appearance. But it will need a great deal more “ proof” before 
