the plant, in the form of globose oogonia, or resting
spores, which, when mature, also enclose great numbers of zoospores.
Similar oogonia are produced amongst the _Mucedines_ in the genus
_Peronospora_, to which De Bary considers _Cystopus_ to be closely
allied. At all events, this is a peculiarity of structure and
development not as yet met with in any other of the _Caeomacei_. In
_Uromyces_ is the nearest approach to the _Pucciniaei_; in fact, it is
_Puccinia_ reduced to a single cell. The form of spore is usually
more angular and irregular than in _Trichobasis_, and the pedicel is
permanent. It may be remarked here, that of the foregoing genera,
many of the species are not autonomous that have hitherto been
included amongst them. This is especially true of _Lecythea_,
_Trichobasis_, and, as it now appears, of _Uromyces_.[e]

[Illustration: FIG. 19.--_Cystopus candidus._]

[Illustration: FIG. 20.--_Xenodochus carbonarius._]

[Illustration: FIG. 21.--_Phragmidium bulbosum._]

PUCCINIAEI.--This group differs from the foregoing chiefly in having
septate spores. The pustules, or sori, break through the cuticle in a
similar manner, and here also no true peridium is present. In
_Xenodochus_, the highest development of joints is reached, each
spore being composed of an indefinite number, from ten to twenty
cells. With it is associated an unicellular yellow Uredine, of which
it is a condition. Probably, in every species of the _Pucciniaei_, it
may hereafter be proved, as it is now suspected, that an unicellular
Uredine precedes or is associated with it, forming a condition, or
secondary form of fruit of that species. Many instances of that kind
have already been traced by De Bary,[f] Tulasne, and others, and some
have been a little too rashly surmised by their followers. In
_Phragmidium_, the pedicel is much more elongated than in _Xenodochus_,
and the spore is shorter, with fewer and a more definite number of
cells for each species; Mr. Currey is of opinion that each cell of
the spore in _Phragmidium_ has an inner globose cell, which he caused
to escape by rupture of the outer cell wall as a sphaeroid nucleus,[g]
leading to the inference that each cell has its own individual power
of germination and reproduction. In _Triphragmium_, there are three
cells for each spore, two being placed side by side, and one
superimposed. In one species, however, _Triphragmium deglubens_
(North American), the cells are arranged as in _P