VHALLOPHYTA 









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307 
Fig. 376. Urediniospore stage of a rust 
Protobasidit. ‘The most important order of 
the Protobasidi is the Uredinales, or rusts, 
which are fungi parasitic on various green 
plants, and which produce some very de- 
structive plant diseases (Figs. 873, 374). 
The rusts have five different kinds of spores. 
In some species all of these different forms 
are present, but in others some of them 
are lacking. The life history of those fungi 
which contain all the different kinds is as 
follows: 
Eciospores. A_ basidiospore germinates 
and produces a hypha which infects the host 
plant, in which a mycelium is produced. 
Finally the mycelium produces numerous 
zeciospores in cup-shaped structures, the eecia 
(Figs. 374, 875). The spores are formed in 
numerous rows. Associated with the cia 
are flask-shaped structures, the pyenia, in 
which are found large numbers of minute 
pycnospores (Fig. 375). 

Fig. 377. Teliospore 
stages of rusts 
Left, wheat rust (Puc- 
cinia graminis) (x 4) ; 
on the right, Puccinia 
thwaitesii on a dicoty- 
2 
ledon (xX #2) 
The wciospores are capable of germinating at once and pro- 
ducing a mycelium that can infect a susceptible host. In some 
