PUCCINIA MALVACEARUM 49 
way (Fig. 29). The accumulated basidia and spores give a 
greyish tinge to the red-brown sorus. These spores can cause 
fresh infection and so the disease spreads rapidly. It is most 
active about the end of summer, and has often been the cause 
of a serious epidemic on the more susceptible kinds of Holly- 
hock. The sori are found on every green part of the plant, 
stems, leaves, petioles, bracts, sepals, carpels and fruits, and are 
even reported on the petals. There are no uredospores. 
The chief biological interest of this fungus concerns the 
way in which it passes the winter, a point about which there 
has been much dispute. There are two possibilities, (1) by 
perennial mycelium, (2) by over-wintering teleutospores. The 
first has been strongly advocated, and it is very likely (though 
one can hardly say it has been proved) that the mycelium does 
winter in the young leaf-rudiments that are formed on shoots 
at the base of last year’s stems. Freshly formed sori have also 
been found on the cotyledons of seedlings which grow up in 
late autumn round the parent plants and which in certain 
cases can survive the dead season. But there seems to be 
absolutely’ no justification for the claim that the mycelium 
winters in the embryo of the seed. The disease can undoubt- 
edly be carried with the seed, in sori either on the bracts 
(portions of which are often mixed with the “seeds,” ie. fruits) 
or on the outside of the carpels themselves. 
Eriksson has lately (Ueber den Malvenrost, 1911) published 
a theory, similar to his well-known theory about the Rust of- 
Corn, and standing or falling with it: he says that P. Malvace- 
arum perennates in the form of “mycoplasm” in the cells of 
the autumn buds at the base of the shoots, as well as in the 
embryos of the seeds of the infected plants. With these he 
says it grows up in an imperceptible form, mingled with the 
protoplasm of the host, permeating the newly-formed leaves 
and at last suddenly breaking out in the form of pustules of. 
primary teleutospores, which afterwards spread in the acknow- 
ledged way. He explains the presence of this mycoplasm. by 
stating that certain teleutospores of the previous autumn 
germinated by sending out “ germ-tubes” which cut otf “ end- 
conidia.” (This mode of germination of the late-formed spores 
G. U. 4 
