MILDEWS, RUSTS AND SMUTS 
57 
means a very severe attack. This is, broadly speaking, 
the extent of the usefulness of the uredospore stage to the 
fungus, at least, in countries where the host-plant is not 
growing all the year round, in the latter case, the uredospore 
condition may survive all the year round, as the only cause 
of its disappearance for a period of the year in this country 
is due to the absence of the host-plant in a growing condition. 
During certain mild winters, uredospores may frequently 
be found on grass and other plants throughout the season. 
Teletdo spores 
Teleutospores are usually met with on the same host- 
plant as the uredospore stage, which it normally follows in 
the sequence of development of the different forms of fruit, 
when the full series is produced. As already stated, the 
uredospore stage continues to reproduce itself until the host- 
plant is past its prime of growth, when the same mycelium 
that produced uredospores now commences to produce 
teleutospores, which superficially resemble the sori of uredo¬ 
spores, but are darker in colour, or practically black, when a 
sorus is seen under a pocket lens. Teleutospores are pro¬ 
duced singly at the tips of slender hyphae, and may consist 
of one or several cells. The wall is coloured, and frequently 
ornamented with warts, spines, a network of raised ribs, 
etc. Germ-pores are present in every cell composing the 
teleutospore. The one constant feature that readily 
separates teleutospores from every other kind of spore 
is the mode of germination. A thread or tube of limited 
length grows out of a germ-pore, furnished with two or 
three transverse walls or septa (sing, septum), thus dividing 
‘the tube into three or four joints or cells near the tip. 
From each joint or cell, a single minute spore is produced. 
The tube bearing these minute spores is named a promy¬ 
celium and the minute spores it bears are known as promy¬ 
celium spores, or sometimes secondary spores. In aecidio- 
spores and uredospores, the germ-tubes produced on ger¬ 
mination, on entering the host-plant grow on continuously 
and produce a mycelium, whereas in the case of a teleuto¬ 
spore, the product of germination is a tube of limited growth 
(promycelium), which bears promycelium spores, which 
alone can infect a plant, the teleutospore itself being in¬ 
capable of so doing. A further point of importance in 
connexion with teleutospores is the fact that in the majority 
of species a period of rest is necessary before they can’ 
germinate. Most teleutospores remain in an unchanged 
