CHAPTER V.—COMPARATIVE REVIEW.—UREDINEAE. 279 
Section LXXX. In she second and much most common case the germ-tube 
of the aecidiospores does not become a promycelium, but forces its way by 
acropetal growth through a stoma into the interior of the host, and there developes 
directly into a mycelium. The mycelium ultimately forms gonid:a on distinct 
hymenia and always by acrogenous abjunction ; and the gonidia, which can germinate 
either directly or after a period of rest, develope a promycelium with sporidia like 
that of Endophyllum. The sporidia are usually obliquely ovoid like’ those of 
Endophyllum, but in some species are round. The germ-tube of the sporidia when 
it has penetrated into the host gives rise to a new mycelium producing spermogonia 
and aecidia. These gonidia which form promycelia have been named /eeutospores 
(Fig. 124 II, III, Fig. 128 A, and Fig. 129). 
The species which produce aecidiospores and teleutospores are again dis- 
tinguished into two subordinate groups according to the stages in the course of the 
development. In some the stages of the development in the order of their 
appearance are mycelium, aecidium, teleutospore, promycelium, sporidium, and there 
are no others. This is the case in Gymnosporangium, Puccinia section Hemi- 
puccinia, as for instance in P. Falcariae. 
In other species the mycelium formed from the 
aecidiospore produces other gonidia besides the teleuto- 
spores, which are called uredospores (Tulasne’s stylospores). 
These too arise by acrogenous abjunction (Fig. 124 //J, ur), 
and as regards the time of their development they may be 
said to be always the precursors of the associated teleuto- 
spores. They are formed according to the species either 
in the same hymenia as the teleutospores, or apart from 
them in special ones which are simply styled uredo or 
uredo-layer. Being short-lived they are able to germinate 
immediately after abscision, and put out a germ-tube 
(Fig. 128 D) which penetrates through a stoma into the gic. 12. Endophyllum Sempervivi, 
tissue of the host like the aecidiospore, and developes Kyle and a ondnem almost fully 
mycelium and a sporidium almost fully 
5 er < a. h i ‘ 
directly into a mycelium. The mycelium forms only new Magn scum ost sierigma 
Magn. 200 times. 
uredospores and teleutospores, and since the process of 
germination, the development of the mycelium, and the formation of the uredo on 
it are very rapidly performed, the sowing of an uredospore is followed in from 
six to ten days under favourable circumstances by the ripening of the uredo of 
the next generation; thus they are especially effective organs for the dissemination 
of the species which produce them abundantly, 
To complete our account it must be added that the mycelium which forms 
aecidia may in exceptional cases subsequently produce gonidia, that is teleutospores 
with or without uredospores. Sometimes individuals of a species, as in Uromyces 
appendiculatus, sometimes single species are distinguished from the majority by the 
regular occurrence of this phenomenon, as Uromyces Behenis, U. Scrophulariae, 
U. Cestri, and Puccinia Berberidis. It is moreover not unusual for the germ-tubes of 
sporidia, when they cannot penetrate at once into the host, first to abscise a secondary 
sporidium at their apex, which has the characters of the original sporidium. 
It has been already said that both kinds of gonidia are produced on hymenia on 

