THE WHITE RUST, ETC. 
471 
cilige show themselves, and by means of these appendages the 
entire globule oscillates, the zoospores disengage themselves 
from each other, the mass is broken up, and each zoospore 
swims off on its own account. 
The free zoospores are of the form of a plano-convex lens, 
obtuse at the edge. Beneath the plane face, out of the centre, 
and towards that point of the margin which during the move- 
ment of the zoospore is foremost, is a disc-shaped vacuole, with 
two cilia3 of unequal length attached to its margin, the shorter 
cilia is directed forwards, and the longer in the opposite direc- 
tion during the evolutions of the zoospores. 
The zoospores are produced within from an hour and a half 
to three hours after the sowing of the conidia in water. They 
are never absent if the conidia are fresh, or even a month old, 
but beyond this period their artificial generation is very un- 
certain. This little experiment is a very simple and interesting 
one, and may be performed by any one who will take the 
trouble to follow out the above instructions. 
From this simple experiment, let us turn for a moment to 
the plant in its natural condition when affected by the white 
rust. If, after rain or dew, when the little drops of moisture 
hang like pearls about the sickly pallid leaves of the shepherds 
purse, bespattered with the white pustules of the rust, we 
collect and examine a drop of water from the immediate neigh- 
bourhood of one of the pustules, we shall commonly find empty 
conidia and zoospores in different stages of development. 
Water alone seems to be essential to them, and for this the 
conidia may remain unchanged for a month, and literally burst 
into activity at the first gentle shower, till the whole surface of 
the plant is swarming with zoospores. We may no longer 
doubt that a true vegetable produces from itself bodies endowed 
with active motion, resembling low forms of animal life, and 
yet in themselves not animalcules, as some would suggest, but 
essentially vegetable, as we shall hereafter demonstrate. To 
scientific men this is not new, except as regards fungi, for in 
algse such bodies have long been recognized. 
A second kind of reproductive organs are described by 
Dr. de Bary; and if future examinations confirm his obser- 
vations, as they doubtless will, this feature is an important 
one. It is true that M. Caspary long since detected similar 
bodies in moulds (allied to that which produces the potato 
disease), but he only knew them in a limited sense compared 
with what De Bary has revealed. These fruits are hidden 
amid the tissues of the plant on which the “ white rust ” is 
parasitic, and only betray their presence by the coloration of 
those tissues. To these bodies it is proposed to give the 
name of “ oogonia ” and “ antlieridia,” on account of their 
