AMERICAN AGRICULTURIST. 
301 
1879. J 
are experts in the timber business that “powder 
post ” or the destruction by larvse of wood-eating 
beetles, never occurs in hickory or oak cut in 
August; and that pine saw-logs, cut in the sum¬ 
mer, will be sound after being left several years in 
the woods, when those cut in the winter will often 
be seriously rotted. Many farmers aver, as their 
experience, that fence posts cut in August will out¬ 
last by many years, others, that are cut in the win¬ 
ter or in the spring. While we may not be able to 
explain the reason from any difference in the 
character of the sap, or the condition of the wood 
itself at the two seasons, it may be well to accept 
the fact as 6hown by experience, and get out the 
fence posts, if possible, in the month of August, 
The Wheat Rust. 
By the time this number of the American Agricul¬ 
turist reaches its readers, many will have had their 
to what is generally known as 
“ Wheat Rust.” As the skin 
and clothing of the harvester 
are covered with the fine, bright, 
orange-colored powder which he 
brushes from the leaves and stems 
of the wheat plant, he will natur¬ 
ally ask : “ What is this rust ? ” 
“ What causes it ? ” etc. But to 
the farmer who sees his hard 
earned grain almost ready for the 
harvest, shrink to worthlessness 
at the withering touch of this 
destroyer, there will occur the 
more important question : “ How 
to prevent it?” At the outset, 
we may say that the Wheat Rust 
is a minute fungus known to 
botanists as Puccinia graminis. 
Those who would learn some¬ 
thing of the manner of growth 
of these plants are referred to an 
article in the July number, en¬ 
titled : “ Fungus— Fungi— What 
are Fungi?” With the statement 
that the Rust is due to a minute 
parasitic vegetable, let us en¬ 
deavor, with the aid of the micro¬ 
scope, to more fully understand 
its real nature and its habits of life. 
To begin at the proper place in the life history of 
this fungus, we must observe that grain stubble, in 
autumn, is often covered with small, black, or 
dark-brown streaks, which might be easily mistaken 
for weather stains. If the whole plant had re¬ 
mained upon the ground, the leaves and stalks 
would have had these same dark patches and lines 
upon them as are shown in figure 1, where a small 
portion of an affected stem, and the base of a leaf 
are represented. A small part of the leaf is shown, 
somewhat magnified, in figure 2, and the dark spots 
are seen to be due to a vast multitude of dark 
colored spores, which have developed from the in¬ 
terior and ruptured the epidermis, or skin, of the 
leaf. If, with a sharp knife, or better, the keen 
razor, we used in this case, we make a thin cross- 
section of the leaf through one of these dark spots, 
Fig. 2.— PORTION OF WHEAT LEAF. 
we have what is shown in figure 3. The lower por¬ 
tion of the engraving, c, represents the interior of the 
leaf; a, «, the epidermis which has been ruptured 
and pressed back by the spores, b, b, as they formed 
Fig. 3.— CROSS-SECTION OF SPOT. 
and increased in size. These spores are always 
double, that is, there are two, end to end, at the 
extremity of each slender thread. Figure 4, a, shows 
one of these double spores separated from its 
neighbors and highly magnified. The germination 
of these spores is shown in 6, which consists of the 
bursting of the thick outer coat of the spore, and 
the contents elongating into an irregular filament, 
c, upon which in a few hours a number of very 
minute ovate bodies are formed, d, d, which soon 
become detached. We have, in fact, had five or 
more small spores formed out of the old one ; this 
takes place in the spring whenever the winter spore , 
as we will call the one with which we started, is 
provided with heat and moisture. From the winter 
spore we have the small spores, (d, d), formed 
directly, one of which is much magnified at /. 
These spores, (d, d), find their way to the leaves 
of the Barberry, and if there are no Barberry bushes, 
probably to some other plant, where they germi¬ 
nate, sending their filament into the tissue of the 
leaf, and in the course of a few days a yellow spot 
is formed on the Barberry leaf, figure 5, a, and 
shortly after a number of cups are formed from the 
bursting open of the epidermis of the leaf. As 
these cups are close together they are often spoken 
of as “ Cluster Cups,” which is shown somewhat 
magnified at b, and a single one more highly at c, 
with a side view of the same at d. The lower por¬ 
tion of figure 5 represents a still more highly mag- 
Fig. 4.— SPORE GERMINATING. 
nified view of a cross section through one of these 
cups, showing the ruptured epidermis of the leaf 
at e and/, between which the cup, A, extends down 
into the interior of the leaf, g. The cup is packed 
with spores which are formed in rows and break 
away from their attachment, h, and are carried 
away by the wind. Owing to pressure, they are 
more or less angular in outline, as seen at i, which 
shows one of these spores enlarged. These spores 
soon find their way to the growing wheat, upon the 
leaves and stems of which they germinate and send 
their absorbing threads through the plant tissue. 
After a short time these threads congregate at 
certain places near the surface of the wheat leaf, 
and, in enlarging, rapture the epidermis, a , a, rapid¬ 
ly ripen the myriads of yellow spores which gives 
the rusty color to the parts affected, and the com¬ 
mon name to the fungus. This stage of the fungus 
is known to botanists as TJredo. Figure 6 shows a 
cross section through one of these Uredo spots, 
with the rough orange-colored spores, b, crowded 
together, each on a slender stalk, which attaches it 
to the filaments in the tissue of the leaf, c. From 
these same filaments, and in these same spots, the 
brown spores appear later in the season and close 
the cycle of changes of this polymorphic fungus. 
The Clover Crop. 
Many farmers look to a crop of clover, to restore the 
fertility of their land, and in so doing, they look in 
the right direction. Why is it that this plant is so 
potent in bringing up exhausted soils, as it cannot 
of itself create any plant food ? In the first place, 
we have in the clover a plant which exposes a large 
expanse of leaf surface to the air and sunshine, and 
is able to transpire a large amount of moisture. 
An average acre of clover will send off from its 
leaves, over 8 tons of water in 24 hours, in the state of 
vapor, while underthesame circumstances, an acre 
Fig. 5.— BARBERRY LEAF AND CLUSTER CUPS. 
of wheat will transpire only one-fourth as much. 
Such being the case, a much weaker solution of 
plant food will suffice for the clover plant. It is on 
this account that clover is known as a close feeder, 
because is can thrive on a soil that is poor in plant 
food. But this is only one factor in the success of 
clover on a soil where a cereal would fail. The clover 
plant is a deep feeder, sending its fine roots far 
down into the soil, and filling all the sub-soil as 
well as the top-soil with its multitude of absorbing 
rootlets. If it is a close feeder, it must follow that 
it must have abundant provision for the absorption 
of a large amount of the weak solutions of plant 
food, which it concentrates in the leaves by evap¬ 
oration. One man may be able to profitably man¬ 
ufacture salt from sea water, while another would 
starve when engaged in the same industry, owing 
to inferior facilities for using the weak solution. 
So with the clover,as cont rasted with wheat, or many 
other crops. Having shown why the clover plant 
can succeed where others will not do well, let us see 
why a crop of clover can benefit the land by making 
it more productive. There are many instances 
on record, where a heavy crop of clover has been 
removed, and the following year, a much larger 
crop of wheat has been obtained, than on like soil 
where wheat had succeeded wheat. We must also 
remember that in removing a crop of clover, we 
take off much more of the essential food elements, 
than in the case of the wheat. The explanation is 
something like this : The stubble and the part be¬ 
low ground, is to be remembered as making up no 
small part of a clover plant, and here we have a 
large quantity of plant food, especially nitrogen, 
in a concentrated and available form. The clover 
plant has pumped up and accumulated a quantity 
of food which the wheat plant cannot of itself reach, 
but gladly accepts when thus prepared. If the 
