58 
MILDEWS, RUSTS AND SMUTS 
condition throughout the winter, and germinate the fol¬ 
lowing spring, when their promycelium spores infect the 
proper host-plant, and give origin to the aecidium stage. 
For this reason teleutspores are often termed winter- 
spores or resting-spores. Their special function is to tide 
the fungus over that period of the year, when the host- 
plant is absent, in the case of annuals, or not in active 
growth, in the case of perennials. To the above general 
statements, there are, as might be expected, some excep¬ 
tions, these will be dealt with in a later chapter. One such 
exception, however, may be dealt with at present. It 
has been stated that the teleutospores are borne singly at 
the tips of slender stalks or pedicels. To this there is an 
exception. One of the Uredinaceae not uncommon on 
living leaves of the houseleek and allied plants, presents 
all the usual features of an aecidium: there .is present the 
outer protective envelope or peridium, enclosing spores 
produced in chains, and for ages this fungus was considered 
as an aecidium, the other stages of which had not been 
discovered. Fortunately some one germinated the spores 
of this supposed aecidium, and was much surprised to find 
that they gave origin to a promycelium, bearing pro¬ 
mycelium-spores. Hence we have an example of teleuto¬ 
spores produced in chains. Other species belonging to this 
exceptional genus, called Endophyllum, have recently been 
described from Africa. 
M esospores 
In addition to the foregoing spore forms, certain others 
called mesospores are met with in the same sorus as the 
teleutospores. These spores are one-celled, ovate or egg- 
shaped, and have the wall thickest at the tip or apex, as 
in most teleutospores. The cell-wall is coloured, and often 
warted. Such spores are considered by some as imperfect 
teleutospores, and are sometimes incapable of germination 
some, however, do germinate, and produce a promycelium 
which gives origin to promycelium-spores. Mesospores 
are present in Pnccinia pruni. 
Amphispores 
In addition to normal uredospores, a second form super¬ 
ficially resembling uredospores, and called amphispores, 
occurs in some species. These agree with ordinary uredo¬ 
spores in being one-celled, in having more than one germ- 
pore, and in giving origin on germination to a germ-tube 
