ry, which are rather smaller, and these
occasionally give rise to a third generation.

In _Urocystis (pompholygodes)_ the germinating tubes spring
exclusively from the darker central cells of the clusters. From these
are developed at their extremity three or four linear bodies, as in
_Tilletia_, but after this no further development has as yet been
traced. It may be remarked here that Waldheim observed similar
conjugation of the sporules in some species of _Ustilago_ as have
been remarked in the sporules of the first generation in _Tilletia_.

[Illustration: FIG. 90.--Pseudospore of _Ustilago receptaculorum_ in
germination, and secondary spores in conjugation. (Tul.)]

[Illustration: FIG. 91.--Conidia and zoospores of _Cystopus candidus_;
_a._ conidium with the plasma divided; _b._ zoospores escaping; _c._
zoospores escaped from the conidium; _d._ active zoospores; _e._
zoospores, having lost their cilia, commencing to germinate.]

Returning to _Cystopus_, as the last of the Uredines, we must briefly
recapitulate the observations made by Professor de Bary,[K] who, by
the bye, claims for them an affinity with _Peronospora_ (Mucedines but
too well known in connection with the potato disease), and _not_ with
the Uredines and their allies. In this genus there are two kinds of
reproductive organs, those produced on the surface of the plant
bursting through the cuticle in white pustules, and which De Bary
terms _conidia_, which are generated in chains, and certain globose
bodies termed _oogonia_, which are developed on the mycelium in the
internal tissues of the foster plant. When the conidia are sown on
water they rapidly absorb the moisture, and swell; the centre of one
of the extremities soon becomes a large obtuse papilla resembling the
neck of a bottle. This is filled with a granular protoplasm, in which
vacuoles are formed. Soon, however, these vacuoles disappear, and very
fine lines of demarcation separate the protoplasm into from five to
eight polyhedric portions, each presenting a little faintly-coloured
vacuole in the centre (_a_). Soon after this division the papilla at
the extremity swells, opens itself, and at the same time the five to
eight bodies which had formed in the interior are expelled one by one
(_b_). These are zoospores, which at first take a lenticular form,
and group themselves before the mouth of the parent cell in a globose
mass (_c._) Very soon, however, they begin to move, and then vibratile