CHAPTER V.—-COMPARATIVE REVIEW.—-UREDINEAE. 281 
in the same way as the uredospores, only there are no intervening cells (Figs. 129, 
130); but in Triphragmium three spores are formed on the same plane by simul- 
taneous (?) division in the solitary acrogenetic mother-cell, and in Melampsora the 
mother-cell is divided by longitudinal walls into several (four) spores placed side by 
side. The teleutospores are generally distinguished from the uredospores by two 
peculiarities as well as by their mode of germination. In the first place they do not 
separate from the sterigma, but in most species remain with it at their place of origin 
until they germinate; more rarely, as in some species of Uromyces and Puccinia 
(Uromyces Phaseolorum, Puccinia fusca, and some others), they become disengaged, 
though not from the sterigma, since they carry with them a portion of the sterigma, which 
is severed from the hymenium by a transverse rupture. Secondly, all teleutospores are 
filled when they are mature with a finely granular protoplasm which is either 
colourless or coloured by a very finely comminuted reddish yellow fatty matter 
surrounding a comparatively small spherical cavity, the cavity itself being filled 
with a weakly refringent substance. Whether this is a nucleus or a space containing 
a nucleus or something of another kind is not yet certainly ascertained. In other 
respects, such as their special mode of formation, their connection with each other 
and with the hymenium, their configuration and the structure of their walls, there is 
considerable variety among the teleutospores, and the distribution of the Uredineae 
into genera has been founded chiefly on these differences. The mode of germination 
is very similar in them all; Coleosporium only differs from other genera in the 
circumstance that the teleutospores, which are placed one above the other in rows, 
generally four together, each put out one sterigma only in germination, and the 
sterigma abscises a sporidium, so that a row of germinating spores resembles in 
outward appearance the promycelium of other genera. 
It appears from the foregoing review that the simplest known course of development 
among the Uredineae which form aecidia is found in the Endophylleae. But even here 
between the aecidiospore and the next generation which forms aecidia there is always 
an intervening alternating generation which forms gonidia, the promycelium with its 
sporidia, though it is only a transitory state. In the two known species, Endophyllum 
Sempervivi and E. Euphorbiae, a year elapses between the formation of two successive 
aecidium-generations, and this time is employed in the complete development of the 
mycelium in the tissue of the perennial host. There may possibly be species in which 
the course of development is still further simplified by the absence of sporidia, the 
germ-tube from the aecidiospore developing directly into the mycelium with aecidia ; 
but these the simplest conceivable species are not known. The simple tubes which 
may develope from the spores of Endophyllum when they are placed under water 
do not become promycelia, and are, as far at least as we at present know, incapable 
of further development. 
The intercalation of teleutogonidia and uredogonidia in the course of development in 
the other species, either as necessary or at least as regular members of it, makes it more 
complicated, and there are various degrees of complication in different species according 
to the greater or less abundance or the entire absence of the uredo. Besides 
these purely morphological gradations there are biological differences also, which give 
an extraordinary variety to the actual living forms in the plants by frequent change of 
combinations from species to species. The chief difference here is that the teuleuto- 
spores of some species germinate as soon as they are ripe, those of others are obliged to 
pass through a period of rest; the former mature in the period of vegetation, the 
latter mature at the end of one period and germinate at the beginning of the next. 
