MILDEWS, RUSTS AND SMUTS 
59 
which continues, to grow indefinitely into ordinary myce¬ 
lium. They differ in having a thicker wall than in uredo- 
spores, and in germinating only after a period of rest, in 
this respect agreeing with teleutospores. According to 
Arthur, an American mycologist, amphispores are mostly 
present in species inhabiting somewhat dry regions, and 
represent a resting form of uredospore. In Puccinia 
vexans, which is not, however, a British species, teleuto¬ 
spores and mesospores, and uredospores and amphispores 
are present. 
Paraphyses 
Certain hair-like, or club-shaped structures are met with 
surrounding the sori of some species, and are usually best 
developed in the sori of uredospores. Such are termed 
paraphyses. Their function is considered to be protective, 
by preventing desication, etc., of the spores after the epi¬ 
dermis of the host-pl-ant has been ruptured. 
Taking the teleutospore stage as the most perfect and 
highest form of spore production met with in the Uredina- 
ceae, if we commence with the immediate product of in¬ 
fection set up by it through its promycelium-spores, and 
granting that all the stages are present, as in Puccinia 
graminis, the rust of wheat and other cereals, we have the 
following sequence of spore formations in the life-cycle : 
I, pycnidia ; 2, aecidium ; 3, uredospore ; 4, teleutospore ; 
the spores of the last stage remaining passive during the 
winter, and germinating the following spring to commence 
the cycle anew. But in reality, comparatively few of the 
uredines possess the four forms of spore mentioned, any 
one stage or more may be omitted, without in any way 
interfering with the continuance of a species. For example 
in many parts of the world, where Puccinia graminis is 
rampant, the pycnidium and aecidium stages are left out 
of its cycle of development, without in any way interfering 
with its continuance as a scourge to agriculturalists. In 
many instances only the teleutospore stage remains, as in 
Puccinia malvacearum. 
The following arrangement, adopted by Saccardo, of 
the species included in the genus Puccinia, where spore 
forms are most numerous, gives some idea as to the various 
stages that have dropped out during the gradual changes 
that have taken place since the time when presumably 
all the spore forms were present. 
A. Eu-Puccinia. Pycnidia, aecidia, uredospores and 
teleutospores produced on a living host-plant ; teleutospores 
