50 
NOMAD FUNGI 
the liyphae turn upwards towards tbs surface, forming an hymenium 
or layer of basidia. Each basidium, by constriction from its extremity, 
forms a uredo-spore, which assumes a deep yellow or orange colour. 
As the mycelium continues branching, and each branch produces a 
spore, the increasing mass at last ruptures the epidermis, and the 
spores escape. Now these spores, like those of the (Ecidium, have 
only a thin cellulose coat; they are evidently adapted for germinating 
immediately. This is in fact what they do; each uredo-spore, if it 
falls upon a leaf of the wheat-plant, germinates at once, throws out a 
germ-tube, which searches as before for a stomate by which it enters, 
and forms a new mycelium, which produces again uredo-spores. By 
repetition of this process, the fungus spreads itself from plant to plant 
over a large area. The spores are easily dispersed by wind and rain. 
But these spores, though evidently adapted by their vast numbers, 
their ready dispersion, and the ease with which they germinate, for 
effecting their object, namely—the rapid diffusion of the fungus, 
evidently do not furnish the best conditions for prolonging its life 
through the trials of winter, and preserving it to afflict the agricul¬ 
turist in another year. These thin-coated spores lose their power of 
germination in a few weeks. Now see what the fungus does. Know¬ 
ing what is coming, it takes the best means of ensuring its safety by 
producing spores calculated to resist the adverse influences of winter 
weather. Like a wise mother, it clothes its offspring in a warm great¬ 
coat. In fact, it produces resting-spores, as do so many other organ¬ 
isms well known to the microscopists in this room. The same 
mycelium, which has produced uredo-spores all the summer, begins in 
autumn (influenced doubtless by the gradual ripening of the tissues of 
the wheat) to give off the puccinia-spores, which are not only two- 
celled—an unimportant circumstance *—but are distinguished by their 
thick cuticle, that peculiar dense waxy layer which the external 
laminae of the cell-wall have the power of secreting if they wish to 
protect themselves against heat or cold. It is this layer which gives 
to a sorus of puccinia-spores its strikingly shiny aspect. Clothed in 
this extra garment, they lie snugly ensconced in the half-decayed 
tissues of their host, unchilled by wintry blasts, until the warmth of 
returning spring calls forth again the leaves upon which they are fitted 
to grow. In the case which we are considering the leaves for wfflich 
they wait are those of the common barberry. 
Here, however, is another difficulty. The puccinia spores are large 
and heavy—the hoplites of the fungal army; moreover, they are firmly 
attached to the basidia from which they spring, and not readily 
detached, as in the two other kinds. The wind and the rain can do 
but little to effect the transference of such a heavy brigade of spores as 
these from the surface of the ground to the young barberry leaves, 
which alone can furnish the requisite nidus. If the fungus had not 
still another resource in store, if it were now at its wit’s end, the 
*■ This is shown by the fact that in the genus Uroinyces, which is in every 
respect analogous to Puccinia, these spores are one-celled, 
