THE UNIVERSITY
OF ILLINOIS

LIBRARY

no.

r

ACHICUlTUPr

WON CIRCULATING

CHECK FOR UNBOUND
CIRCUU JPY

UNIVERSITY OF ILLINOIS,

Agricultural Experiment Station,

CHAMPAIGN, DECEMBER, 189?.

BULLETIN NO. 29.

CONTENTS — ORANGE RUST IN RASPBERRIES AND BLACKBERRIES.
A NEW FACTOR IN SCIENTIFIC AGRICULTURE.

*ORANGE RUST OF RASPBERRY AND BLACKBERRY.

For the past twenty-five years notes have appeared in various agri-
cultural and horticultural publications of this country of a fungus occur-
ring on raspberries and blackberries, which, on account of the bright
orange colored spores produced on the leaves, has been uniformly known
as " orange rust." So marked and so persistent is the action upon these
berry plants, its "hosts, " of this lowly organized parasitic plant that it is
recognized as one of the most destructive of what are known as parasitic
fungi.

To botanists this fungus has been known since the earlier part of
the present century, when it was first mentioned as occurring in Kam-
tchatka, and soon after, in Carolina of this country. A glance at "Distri-
bution " in the Appendix shows that it is quite widely spread over the
eastern part of the United States. In some localities, however, it is
much more abundant than in others. Mention of it has not been found as
occurring further west than Nebraska, and Dr. Harkness, in a letter,

*The writer wishes to acknowledge his indebtedness to Professor Burrill, who
first suggested the possible relationship of Caeoma nitens and Puccinia Peckiana, and at
whose suggestion the investigation of their life histories was undertaken. To various
botanists who have responded to our letters of inquiry, thanks are also due. Refer-
ence to articles is made in the text by giving author's name and date of pub-
lication; but such references may be found more fully given under " Literature," in
the Appendix. After the above paper had been written for publication, an arti-
cle by Tranzschel, published in Hedwigia, was received. By artificial infection, this
writer so completely verifies the results that we have obtained that his experiments
have been added to the paper, and proper credit has been given.

273

274 BULLETIN NO. 29. [ December,

states that he has never collected it in California. It is not at all im-
probable, however, that it may be found further west. Reports give it
as occurring in our most southern states, and from them it extends be-
yond our northern limits into Canada. In Europe and Asia, while not
so numerously reported, it has been found over a large range of territory
and is said to be quite common in some of the northern stations.

So far as known this fungus has limited its ravages to the genus
Rubus. Both cultivated and wild species are freely attacked, and of the
former quite a number of varieties have been reported as more or less
injured, of which the Kittatinny is perhaps one of the worst affected.
In this region the Snyder seems usually to be quite exempt from at-
tack, although elsewhere reported as more or less infected. In
the Appendix is given a list of species so far found to be attacked.

The fungus shows its first signs of appearance in early spring,
varying slightly in time as the weather is favorable or not to the growth
of its host. In this locality it can first be detected during the latter part
of April or the first of May. As soon as the leaves are fairly started in
their development, and before they are unfolded, what is known as the
spermagonial stage can be seen. The spermagonia resemble small
stalked glands thickly covering both sides of the leaf, and at first are so
deceiving in their appearance as to be mistaken for glands naturally be-
longing to the leaf. As the leaves mature, the spermagonia become
more distinct, and while usually found covering the leaves of the affected
plant, are sometimes variously limited in their distribution. Some leaves,
usually the upper, may be affected, and others entirely free; even some
of the leaflets of a single leaf may show this stage while others do not.
Nor is it an uncommon occurrence to find definitely affected patches of
an individual leaflet sharply marked off from the remaining apparently
healthy parts. About two or three weeks after the first appearance of
the spermagonia, the second, or aecidium stage becomes noticeable,
showing as concealed, slightly elevated spots thickly covering the under
surface of the leaf. The rapid growth of these soon ruptures the epi-
dermis above each bed of spores, and they then show as bright orange
colored masses. About this time the spermagonia have reached their
maximum development. So far as observed the aecidium stage is lim-
ited to those leaves or parts of the leaf that were affected by the sperma-
gonia, although all parts affected with spermagonia do not necessarily
produce the former. The aecidium stage is confined almost entirely to
the lower surface of the leaf, rarely slightly affecting the margin on
the upper side. It is also found, in rare cases, on the stems. It reaches
its maximum development here during the first part of June, and during
the latter part of the month gradually disappears until only isolated
cases can rarely be found during the first of July. Some writers men-
tion it as occurring again during the autumn months. Brunk (1890)
claims to have found it in Maryland as late as the middle of October,
and writes that in the extreme southern states he has found specimens in

1893- J ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 275

December. It has been found by the writer during the spring and early
summer only.

The fungus is found on the leaves of old and new shoots, and is
usually so vigorous in its spore development that it utterly destroys the
usefulness of the affected leaves. These fall off in time, and if the
fungus has not so far impaired the vitality of the plant as to prevent
further development, the subsequent growth of branches with unaffected
leaves may help repair the damage. Frequently, however, especially in
young shoots, the canes, stripped of their leaves, hindered in growth,
fail to overcome the damage, and so die. Since it is also a fact that a
plant once infected is quite certain of attack each succeeding year, it is
usually only a matter of time before the most vigorous of plants are
rendered worthless. Sometimes the presence of only the spermagonial
stage is sufficient seriously to affect the efficiency of young shoots.
Horticultural papers sometimes contain notices of localities in which
blackberries and raspberries in general are so seriously affected by this
disease as to render their cultivation unprofitable, if not impossible.
The same plants or patches being annually subject to attack early led
many to suppose that the fungus must be perennial in its host, a fact
which was first publicly demonstrated by Newcombe (1891), who
found mycelium in microscopical sections taken from different parts of
affected plants.

This perennial nature of the fungus makes successful prevention of
the disease exceedingly difficult. Various methods of treatment have
been made, of which probably only one has given any uniformly good
results, that of digging up and destroying all affected plants as soon as
signs of disease were manifested. Spraying has been tried to see if any
good could be accomplished. With the mycelium perennial in the host,
the good in this case must be in preventing the spread of the disease to
unaffected plants, and then only under conditions depending upon the
life history of the fungus. If the aecidiospores germinate upon the
leaves of Rubus to produce another stage of development, then spray-
ing at the proper season should be beneficial in this direction. As the
indications are that the above supposition is correct, spraying with Bor-
deaux mixture as soon as the aecidiospores begin to show, preceded
by a thorough cutting out of plants as soon as signs of the disease are
manifested, should, in a few seasons, eradicate this disease. As the
spores in germination seem to gain entrance on the under side of the
leaf, it would be especially necessary in spraying to wet that side. The
fungus has also some natural enemies that are of slight use in destroying
its spores. Among these may be mentioned the larvae of certain insects,
which feed quite greedily on the spores, and Tuberculina persicina, a
fungus which occurs frequently as a parasite on the sori.

Having stated that a plant once attacked by this disease is perennially
subject to it, let us see why this is so. This will lead us to consider the

276 BULLETIN NO. 29. [December,

vegetative stage of the fungus, or what is technically known as the
mycelium.

MYCELIUM.

The bright, orange colored patches on the under side of the leaves
are made up entirely of spores, or the reproductive part of the fungus.
To produce these there must be a vegetative system ; just as to produce
the fruit of the blackberry there must be the root, the stem, and the leaf.
This vegetative, or mycelial stage is concealed entirely within the plant,
and in this fungus, contrary to the usual rule of its family, is quite
extensively developed. To show this, microscopical sections of the
affected plants are necessary. From those made of variously affected parts
the following facts have been learned concerning this stage of the
fungus: Such sections reveal mycelial threads present from the upper
parts of the roots running through the stem up into the uppermost
leaves showing signs of affection. That is, we may take any affected
leaf, make sections of its blade, its petiole, the junction of petiole to
branch or main shoot, and so down the stem to the perennial part, and
«ven somewhat into the root itself, and in all the sections find the my-
celium. Frequently plants are found in which the new shoots are
affected but the old ones ar,e free. In such cases the mycelium is found
in the former only. The canes of raspberries and blackberries are bi-
ennial, and, so far as personal inspection goes, unless these are infected
during their first year they can not be the second ; and if they are
affected the first year, they are quite sure to be the next. This is easily
explained by the fact that the mycelium follows young growing cells,
and cannot penetrate tissue to any extent after it has matured. Sections
of very young canes of the diseased plants show that they contain my-
celium, and that in such it follows quite closely the point of growth. In
such sections, fungus threads have been traced from the stem into the
scale-like leaves protecting it, and into the ordinary leaves before they
have become differentiated into blade and petiole. Sections of roots,
except in the neighborhood of the merging of root and stem, do not
show the mycelium. Now, from the above, one can see how a single
plant can have both new and old stems affected and free, illustrations of
which are sometimes met. In such a case the unaffected canes come
from underground parts into which the mycelium failed to pene-
trate when they were young, and so was shut out; and the affected ones
come from where the mycelium had gained entrance. The above facts
also prove that the first infection of a plant must be through the shoots
when very young and easy of penetration. The plants present this
condition during late fall and early spring. As illustrating the perennial
nature of the fungus, and method of infection, the following
experiment is given: In 1892 eighteen plants were marked, of which
ten were affected with this Caeoma and eight were free. In 1893 these
were examined again, and the ten diseased in 1892 were found to be in

1893'] ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 277

the same condition, and the eight healthy ones of the year before were
so still, except in one case. This plant was affected only on the new,
very young canes, showing that through them the fungus gained
entrance.

The structure of this vegetative stage, when examined, is found to
consist of two parts — mycelial threads and haustoria. The function of
the former is, evidently, to carry the fungus to different parts of the
plant; and so the threads are found between the cell walls, quite often
in the spaces where three or more cells come together. In transverse
sections of the plant these show as cut ends, while in longitudinal sec-
tions they can frequently be traced for quite a distance. In such cases
they appear as hyaline filaments of varying diameter, having definite
cell walls, and, according to age, more or less protoplasm. From these
spring the haustoria, similar but very short threads. The haustorium
pierces the cell wall by a narrow neck and inside the cell enlarges into
a body with a more or less knobbed end, the function of an haustorium
being to supply nourishment necessary for the growth of the mycelium.
The fungus filaments are not found distributed irregularly through the
plant, but are limited to certain localities. In the root and root-like part
they are found between the parenchyma cells of the cortex in the vicinity
of the cambium. The abundance of starch in these cells makes it neces-
sary that very thin sections be made, which show best when stained with
an alcoholic solution of potassium iodide and iodine, thereby coloring the
starch grains blue and the fungus a yellowish green. In cells contain-
ing haustoria their effect upon the amount of starch in very evident
{Plate j>, fig. 12). As a rule, in this part of the plant, the largest and
most knobbed of the haustoria have been found. In the stems the my-
celium is found in the pith, mostly between the smaller cells near the
fibre-vascular bundles. The leaves have the mycelium entering them
when quite young, and the interstices of the parenchyma cells afford its
abode. In young shoots the mycelium is not so limited to particular
localities, occurring occasionally among the parenchyma cells of the
bark, and even among the outermost cells of the bundles not yet fully
developed.

The appearance of the mycelium depends somewhat on its age.
When young it is more conspicuous, but when old it loses its proto-
plasm and acquires an occasional septum. The haustoria are at first
simple threads extending half way or more across the cell. They soon
begin, by coiling or wisting, to form an enlarged, knotted end. This
possibly may be due to the effort of the haustorium to come into more
intimate contact with its food particles. Sometimes two haustoria are
found in the same cell, and not infrequently have there been seen signs
of union of these {Plate j, fig. j>, ^, 7). This, however, is to be
interpreted as nothing more than an accidental occurrence.

Late in April a more conspicuous gathering of mycelium in special
places just beneath the epidermis of the leaves is noticeable, and then

278 BULLETIN NO. 29. [December,

begins the formation of the first fruiting stage of the fungus, or the
spermagonia.

SPERMAGONIA.

Transverse sections through one of these mycelial groups at this
time show the threads as an indefinite mass chiefly in cross section. The
threads begin to grow upward between the lateral union of contiguous
epidermal cells, forcing the cells apart and upward as a slight papilla.
Sections now show the mycelium in these papillae more in longitudinal
view as closely packed, septate threads, and the epidermis above the
infected spot is seen as two large cells, forced above the level of the sur-
rounding cells at their juncture with each other, and separated from each
other at their bases by the intervening mass of mycelium {Plate 2, fig.
J, 2). According to Richards ( 1893) further growth so pushes against
the interior walls of these elevated cells as to cause them to collapse,
and the cells become filled with mycelium. The upright threads, so
closely crowded together as to form a sort of false tissue, having
reached their growth, begin to cut off from their upper free ends numer-
ous small oval bodies. These are known as spermatia, and when
entirely formed occupy about the upper third of the spermagonium.
When they have been formed in sufficient numbers, the epidermal
covering becomes punctured, and they ooze out on the exterior of the
leaf as a small viscid drop.

The function of these spore-like bodies is not definitely known.
Some botanists consider such as male elements concerned in the fertiliza-
tion of the aecidium stage of fungi. The function of somewhat
similar bodies found in lichens has led to this view, and, while rather
generally accepted, there seems to be no direct evidence that these so-
called spermatia are really such. Some have thought that these bodies
effect fertilization of the mycelium, while others have held that each
aecidiospore may be fertilized by a spermatium, as spermatia are fre-
quently seen adhering to-the spores. The fact that spermagonia are gen-
erally produced with the aecidium stage, and that both are borne on the
same mycelium suggests, at least, intimate relationship. Other botanists
have discarded the idea that these were at all sexual elements, and declare
that they are merely conidial stages of the fungus, and that the so-called
spermatia are conidiospores. Plowright, holding this view, claims to
have produced a yeast-like germination of these bodies in sweetened
water. A similar germination was also previously claimed by Cornu.
In culture experiments with the spermatia of this fungus, such a method
of reproduction has been noticed, but satisfaction was not had that such
did not contain yeast fungi. The chief objection to the view that these
are conidial bodies is the special use they could have, since they are gen-
erally produced in connection with the aecidium stage whose spores
have an almost similar function. Winter merely says that the physi-
ological significance of the spermatia is not yet surely made out. Be

1893-] ' ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 279

their use what it may, about the time of their maximum development
the signs of a second spore stage become visible to the naked eye.

CAEOMA, OR AECIDIUM STAGE.

This, known as "orange rust," is the most conspicuous stage, on
account of being seen externally and because of the bright color of the
spores. Like the spermagonia, it has its origin in the mycelium of the
leaf, only this time the mycelium begins to form in masses on the lower
side of the leaf. Here is produced a more extended development of
filaments. From these arises a compact mass of threads divided with
septa, in a basipetal manner, into distinct cells. The distal cells gradually
become rounded at their septal unions, and are less securely fastened
together. Their walls also become minutely verruculose, and, though
hyaline, are given an apparent color by the endochrome which with the
protoplasm fills the cell. The aecidiospores thus mature, and separate
into distinct bodies. These being formed now just beneath the epidermis,
the strain on it becomes too great and a rupture takes place. The
epidermis above the sorus soon wears away and the golden spot, until
now seen indefinitely through the epidermis, shows as bright orange.
The spores when fully matured vary from elliptical or oblong to sub-
globose, and usually measure 12 to 24 by 18 to 32 microns. Their thin,
hyaline exospore is finely covered with minute tubercules. Their orange
color is due to the presence of a considerable amount of endochrome.

If, soon after these spores are mature, they are put in a moist place
germination takes place. In watching this under the microscope, the fol-
lowing has been found most useful: A glass ring, the diameter of the
cover glass and about a quarter of an inch high, is fastened to the glass
slip by means of vaseline. In a drop of sterilized water on the cover glass
are dusted a few of the mature spores. This is inverted and fastened
on the top of the ring by means of vaseline previously placed on its
edges. If for any reason one finds the water drop too deep for focusing
on its free surface, this can be prevented by washing the cover before
use with caustic potash. Cultures thus made can be examined through
all stages of spore germination without fear of evaporation. Mature,
fresh spores often show signs of germination within three hours after
being placed in water. The first sign is a small swelling appearing on
the side of the spore. The contents of the spore, surrounded by the
endospore, have pierced the exospore through a small opening, and
have swollen into a small hyaline body. This gradually lengthens by
apical growth into filamentous form, and then the endochrome appears
in the tube as small colored globules. The growth of the tube is about
the same for eight or ten hours, when it has reached a length three or
four times the diameter of the spore. All this time the protoplasm has
been disappearing from the spore and entering the germ tube. The
protoplasm of the spore at first becomes less dense, then vacuoles appear,
and the contents are gradually limited to the region of the germ pore.

280 BULLETIN NO. 29. [December,

The spore is thus emptied in about eight hours, but the germ tube keeps
on growing, and gradually becomes empty at its base. As the proto-
plasm recedes from the lower part of the tube, an occasional septum
may be formed. Growth is practically stopped only by the exhaustion
of the protoplasm, and usually lasts for two or three days after the first
signs of germination, the length of the tubes at this period frequently
being eight or more times the diameter of the spore. The germ tubes
are mostly of a uniform diameter, with the tips sometimes slightly nar-
rowed. They usually present a slightly flexuous, rather than a rigid,
straight growth. Upon some occasions movement of the protoplasmic
granules can be seen in the germ tubes. Occasionally germination pre-
sents anomalies in the shape of suddenly enlarged or of flexuous tips,
and in a single case branching has been seen, but never more than a
single developed germ tube has been found to a spore.

Such being the characters presented in artificial germination, in what
manner should we expect these spores to act when infecting their hosts?
Botanists have proved that such summer spores gain entrance into
plants by the growth of the germ tubes into the stomates of the epider-
mis and so into the parenchyma tissue of the leaves. This being the case
it is left for decision whether with these germinating spores the black-
berry and raspberry leaves are used for further development, or whether,
as i* so often the case, some other entirely different plants have been
chosen. The indications being that the former was the case, artificial
growth on the leaves was undertaken. In both raspberry and black-
berry, the stomates are almost entirely confined to the under side of the
leaf, some few being found on the margins of the upper side. In the
former, too, the lower surface is so covered by hairs as to afford consid-
erable difficulty in examining the epidermis. So blackberry leaves on a
small shoot were moistened on their lower surface and then dusted
with spores. The shoot was then placed in a moist chamber and left
for twenty-four hours. Examination of the leaves was then made under
the microscope. The epidermis of these leaves sticks so closely to the
parenchyma cells that it cannot be satisfactorily removed. The leaf
itself is too opaque for examination under high powers. It was neces-
sary, therefore, carefully to soak pieces of the leaf in hot caustic potash,
wash, and squeeze slightly under the cover glass before the surface of
the epidermis could be examined. Such a process, however, is likely
to wash off any spores that may be on the surface of the leaf. Under such
circumstances were found, on one occasion, spores that showed signs of
entering the stomates {Plate 4, Jig. 22). These spores presented char-
acters never seen in mere water cultures; for, after they had sent out an
ordinary tube about three times the diameter of the spore, it suddenly
became considerably narrowed ; and in several cases this narrowed part
was found between the guard cells of the stomates, showing, at least,
that the fungus could gain entrance in this way. No germ tubes were
ever found piercing through the epidermis itself. The experiment of

1893-] ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 28l

inoculating a healthy plant, kept indoors, was also tried ; but as about
the time results from this could be expected the plant died, evidence in
either direction was wanting.

Since these spores germinate readily as soon as mature, and prob-
ably infect blackberries and raspberries through their leaves, it might
seem that they were means of spreading the aecidium stage from plant
to plant. But when we consider that this stage is limited to spring and
that no plant or parts of a plant become diseased except those early
showing its signs, such an inference becomes impossible, and we are led
to inquire to what does this stage give rise? This brings to our consid-
eration what is known as alternation of spore forms.

ALTERNATION OF SPORE FORMS.

The fact that the aecidiospores soon lose their power of germina-
tion, coupled with the knowledge that such spores have been proved in
numerous cases to be merely summer stages of more advanced forms,
has suggested, with almost certainty, that this fungus has other spore
stages in its life history not now recognized as belonging to it. Botanists
have, therefore, suggested different forms as the mature stage, basing
their opinions on more or less superficial observations. Let us see what
evidence there is that such are advanced stages of this fungus.

Melampsora. Dietel gives the following species of Melampsora and
Caeoma that different investigators have connected with each other by
culture experiments.
Melampsora Salicis capreae, (Pers.) and Caeoma Euonymi, (Gmel.)

— Rostrup.

Melampsora Hartigii, (Thiim.) and Caeoma Ribesii, Lk. — Rostrup.
Melampsora aecidioides, (DC.) and Caeoma Mercurialis, (Pers.)

— Plowright.

,, , rr, , ( Caeoma Mercurialis* (Pers.) )

Melampsora Tremulae, Tul. and \ ^ *• •* ADT

( Caeoma pimtorquum, A. Br. \

— Rostrup.

Melampsora Tremulae, Tul. and Caeoma Laricis, (Westd.) — Hartig.
Melampsora Populina, Jacq. and Caeoma Laricis, (Westd.) — Hartig.
Plowright also made cultures to duplicate the above results, but was
successful in only the case attributed to him. These results indicate a
close relationship between Melampsora and Caeoma, and suggest that
the mature form of the Caeoma we are considering might be found
among the species of Melampsora. So far as is known no culture ex-
periments have been made along this line. The fact that this Caeoma
is so common would indicate that the teleutoform was not rare, and this
again would suggest the Melampsora on Populus or Salix as
the most probable one; but, apparently, the above investigators have
found both of these species connected with entirely different species of
Caeoma. Rathay also claims to have found Melampsora populina as
connected with Aecidium clematidis, and this, taken with other conflict-

282 BULLETIN NO. 29. . [December,

ing results in the above list, makes it quite improbable that all species of
Caeoma will be found connected with Melampsora as the mature stage.

Phragmidium. Another genus with which some botanists have
suggested connection with this Caeoma is Phragmidium, especially with
the species Ph. Rubi. The facts that in this genus all three spore forms
may occur on the same host species, and that in some, Ph. mucronatum,
the aecidium stage has gross resemblance to C. nitens, together with the
further facts that Ph. Rubi and C. nitens are found on the same hosts
and frequently in the same localities, seem to be the chief points in
favor of considering them as forms of the same thing. Perhaps, too,
the fact that the aecidium form of Ph. Rubi is wanting or little known
in some localities has had much to do with suggesting the connection.
These, however, are too general points to be of definite value in proving
connection of the forms. Let us see what more specific points will
indicate. As to structure, we find some difference between the
ordinary aecidium stage of Phragmidium and this Caeoma, for in the
former paraphyses surrounding the sori are characteristic, while in the
latter there is no evidence of them. We find no recorded cases of both
forms occurring commonly on the same individual host, as one might
expect if they were related. Then, in this locality at least, the failure
to find this Caeoma after the first of July, while the collections of Ph.
Rubi have not been made earlier than September, is also against their
connection, as two months between the disappearance of an aecidium and
the appearance of an uredo form is too long a time for which to account.
Lastly, most European botanists have considered this Caeoma as distinct
from the Phragmidium, especially since Krieger has found and described
an aecidium form that corresponds to the normal type of such stages of
Phragmidium, and which is now accepted as the first stage of Ph.
Rubi. Since the aecidium and uredo forms of Phragmidium are fre-
quently so similar, it is not at all unlikely that in this country the earlier
stages of Ph. Rubi have occasionally been classed indefinitely under
the uredo form.

Puccinia. Still another genus, Puccinia, has been named as hav-
ing connection with C. nitens. In 1885 Burrill suggested that a rela-
tionship might exist between Caeoma nitens and Puccinia Peckiana,
as both were found in Illinois on the same hosts. Our study of these
fungi has led to the belief that this is the most probable explanation.
Let us see what is the life history of the latter fungus, and then deter-
mine what evidence there is to offer it as the mature form of the
Caeoma.

In this vicinity the fungus, P. Peckiana, makes its appearance on
leaves of raspberry and blackberry about the first of July, and has been
collected on them as late as September. While the fungus usually occurs
on the under side of the leaf, an occasional sorus is found on the margin of
the upper surface. The sori are so small as generally to escape atten-
tion when the leaf is not badly affected, and sometimes are to be recog-

1893*] ORANGE RUST IX RASPBERRIES AND BLACKBERRIES. 283

nized only by aid of a magnifier. They frequently occur in small,
isolated clusters, but often the leaf is abundantly covered with them,
and then the peculiar mottled green and yellow appearance of the upper
surface serves as a ready aid of detection to the trained eye. Cross
sections of affected leaves show mycelium in different parts running
between the parenchyma cells, but much more abundant toward the
lower surface. Plants known, never to have been affected with the Cae-
oma show mycelium confined to the leaf. The mycelium gives rise
directly to the teleutospores; and, so far, these only have been found.
They are formed in the usual method: by accumulation of mycelium
near the under surface; formation of erect, fertile branches; differentia-
tion into spores; and eventual rupture by these of the epidermis. The
mature spores are quite characteristic in their appearance. They reach
an average size of 22 to 27 by 36 to 45 microns. The cell walls are of
a reddish brown color, and of nearly uniform thickness. The spores
vary considerably as to shape, especially as the front and side views of
the same spore are not exactly the same. Usually, however, the apical
cell is somewhat triangular, with apex covered with several hyaline
papillae. Occasionally these papillae have been seen sparsely covering
the whole cell. The basal cell is frequently quadrangular, with the
short, hyaline, fugacious pedicle at one corner and the other formed by
a few hyaline papillae.

Attempts at germination of these spores have been made at various
times of the year, except in spring, but were successful only on one
occasion. About the middle of September lately gathered spores were
placed in water, and, failing to show signs of germination at the end of
the third day, the slide was laid aside and not examined until the spores
had been a week in the water. It was then found that a few spores
had sent out germ tubes {Plate 4, Jig. 24-29). The endospore pierced
the exospore through a small opening, and immediately enlarged into
the natural diameter of the promycelium. Apical growth of this took
place until it had reached a length two or three times the diameter of
the spore. This was about sufficient to empty the cell of its contents.
Both apical and basal cells were found to germinate, though but a
single tube was produced from a cell, and no example was found of
both cells of the same spore germinating. The germination ceased
before there was any evidence of the formation of promycelial spores.
The germination of the spores at this time of the year suggests that
they infect their host through some other place than the leaves.

So much for the life history of this fungus, but how may the
phenomena it presents, together with those of the Caeoma, be inter-
preted? These will be considered in the following paragraphs on Dis-
tribution, Hosts, Life Histories, and Artificial Infection.

Distribution. While the distribution of this Puccinia has not
been apparently so widespread, or so frequently reported as in the case
of the Caeoma, still it has been found in the same regions only with the

284 BULLETIN NO. 29. [December,

latter. Under "Hosts" of the Appendix are given the localities in which
these have been found. The effect of the former on its hosts is so incon-
spicuous, especially when compared with that of the latter, that there is
no doubt that its range will be more widely extended when a careful
search is made for it. This conclusion is based on experience in this
locality; for, while here the Caeoma had always been considered com-
mon, the Puccinia was not, until a careful search revealed it to be at
least as common, if not more so, than the former fungus. In five
localities watched during the past three years both forms have appeared
abundantly.

Hosts. Naturally enough, the Puccinia having been less frequently
seen, the number of host species it occupies will be found to be less, as
is shown in the Appendix; but such as it does attack are the same as
those upon which the Caeoma occurs. Until recently only one was re-
ported from Europe, but it is the same as that upon which the Caeoma
was first reported over seventy years ago. In this vicinity they
leave the same host species exactly, and on the cultivated plants both
have been found on the variety known as the Kittatiny. In a patch of
these affected with both forms, neither was seen on an occasional Snyder
growing there. Not only are they found occurring in the same locality
and on the same species, but the writer has recorded hundreds of exam-
ples where they occurred on the same individual. This is forcibly
shown by an experiment, given in detail in the Appendix, to determine
if they were common on the same individual. In early May, as soon
as the spermagonia began to show, all the affected plants were marked
in a place about two rods wide and twenty long. Later, in June, when
the aecidium form began to appear, these thirty-four plants were again
examined and it was found that all had developed the aecidium stage.
In July, they were examined a third time, and Puccinia Peckiana
was found on all except two or three plants; that is, about 90 per cent
were affected. In these exceptions the lower leaves, those most likely
to become affected, had all dropped off. As some might think that the
occurrence of the Caeoma and the Puccinia on the same plant was acci-
dental, a check was had by examining for the Puccinia plants not affected
by the Caeoma. Such plants of course would not be so likely to
become infected unless they were close to those affected by the Caeoma.
These twenty plants were chosen at random from those near and away
from the marked plants. Of these, thirteen were free, and seven affected,
or 65 per cent free. The seven having the Puccinia were all within
three feet of plants affected with the Caeoma; while of those free, ten
were from one to several rods from the nearest marked plant. Cases
have also been found in which the same leaf had sori of both not the
twentieth of an inch apart (Plate i,fig. 2). The fact that the Puc-
cinia is not uniformly found with the Caeoma is easily explained. The
two forms are produced from entirely different myceliums, and as the
aecidium form is so destructive to the leaves it attacks, they are fre-

1893-] ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 285

quently destroyed and have fallen off before the time of ' appearance of
the teleutoform.

Life Histories. Another thing that forcibly strikes one as to the
connection of these fungi is their time occurrence. The Caeoma, abund-
antly producing spores during June, gradually disappears just as the
Puccinia begins to appear on the same hosts in early July. As the
aecidiospores, though germinating abundantly, do not produce the
aecidium stage, what could be more natural than that mature spore
forms, occurring on the same hosts and at the proper interval of time,
should be connected with them? Again, what other influence can be
had when the Puccinia spores are found mostly on the lower leaves,
where the aecidiospores can best fall from the affected leaves above?
We have found several cases of a leaf unusually affected by Puccinia
that was just beneath a Caeoma infected leaf. Again, these aecidiospores
gain entrance into their host through the stomates, and, as our
culture experiments indicate, through those of Rubus; the stomates of
our raspberries and blackberries are found on the under side and mar-
gins of the upper side of the leaves; the Puccinia sori are found only in
these places. But if the germ tubes of the aecidiospores enter through
the stomates and these are on the under side, what avail is it even if the
Caeoma affected leaves are above? The Caeoma affects the earliest
leaves. Many leaves on lower, unaffected branches are beginning to
unfold when these aecidiospores are mature. These young leaves
are folded together conduplicately, usually with the margins upward.
The lower surface is thus exposed and is not yet well protected by
hairs. This is undoubtedly the time when most of the leaves are enter-
ed by the Puccinia producing agent, a fact that is further emphasized
when we find that leaves of the raspberry affected by the Puccinia are
not usually so hairy beneath as those that are free. The production of
these hairs has been lessened by the presence of the fungus in the leaf
tissues, and to effect this the leaf must have become infected before
the hairs were fully developed. In examining the epidermis of leaves
at about the time the Puccinia began to appear, threads of mycelium could
frequently be seen beneath the stomates, and in a few cases what looked
like the broken end of an upright thread seemed to be coming up
between the guard cells (Plate 4, fig. jo). We have, however, never been
able to trace this to an aecidiospore. Lastly, the Puccinia spores germ-
inating in fall, possibly in spring also, when infection of mature leaves
would be useless and when the young underground sprouts are in con-
dition for infection, seems to indicate that the Puccinia enters the plant
through these underground parts. Since the spores of the Puccinia fall
off from the leaf very easily, it being impossible to find them on old
leaves in spring, the spores might very easily be washed down against
the young shoots. But if the sporidia of the Puccinia stage enter these
young shoots or their parts they do not give rise to the Puccinia pro-
ducing mycelium, for this is limited to the leaves. Why not, then, give
rise to the mycelium of this Caeoma?

286 BULLETIN NO. 29. [December,

Artificial Infection. But after all, the chief proof of connection of
two forms is by artificially producing the one from the other. Our ex-
periments along this line have been fewer and unsatisfactory. The
plants to be experimented with were transplanted in spring and died
before inoculation could be made, or before time for judging of its
effects. It is hoped to continue experiments in this direction. What
one might call natural infection seems to be furnished by those examples
where badly Puccinia affected leaves appeared just beneath a Caeoma
infected leaf. However, this weak point in our evidence is strengthened
by the experiments of Tranzschel (1893), whose article came to hand
after this paper had been written, but the results of whose experiments
are appended to this paragraph. In 1892 and 1893 he undertook infec-
tion of plants of Rubus Saxatilis with the aecidiospores of Caeoma nitens.
His experiments were carried on at the botanical gardens of the Univer-
sity of St. Petersburg. June 18, 1893, plants both in and out of doors had
the spores placed on the leaves of their young shoots, and the izth of
July the first teleutospores of Puccinia Peckiana were found on the
plant kept indoors. The next day they were found on one of the two
plants placed outdoors, and by the 24th the plants experimented with had
a number of leaves badly affected. He also reports that in one locality
especially examined the Puccinia was common on plants previously
affected with the aecidium stage of the Caeoma.

CONCLUSIONS.

From what has been presented, the following conclusions may be
given:

1. The so called Caeoma nitens, a widespread and very destruct-
ive fungus of raspberries and blackberries, has been proved to possess a
perennial mycelium, which probably first gains entrance into its hosts
through very young underground shoots.

2. This mycelium, following the growing parts of the plant, in
early spring, gives rise to spermagonial, and soon after to aecidium
stages, the function of the former being as yet unproved.

3. The aecidiospores, by immediate germination, give rise to a
more mature spore form, which is in no way connected with the original
mycelium.

4. These aecidiospores produce this form by infecting the host
through the stomates of the leaves, and evidence now proves Rubus as
the host infected, and Puccinia Peckiana as the teleutoform thus produced.

5. Puccinia Peckiana, produced on the under side of leaves of
raspberry and blackberry, germinates its spores in the fall, and possibly
in early spring, and probably enters its hosts through young under-
ground shoots.

6. The two facts that the mycelium of the Puccinia is limited to
the leaves, and that the mycelium of the Caeoma is found throughout the
plant suggest that the mycelium of the aecidium stage has its origin
from the germinating Puccinia spores.

1893-] ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 287

APPENDIX.

NOMENCLATURE.
*iS2O, Caeoma interstitiale, Schlechtendal. Horae physicae Berolinenses,

p. 96.

1822, Aecidium nit ens, Schweinitz. Synop. Fungi Car., p. 69, n. 458.
1825, Caeoma (Aecidiitm) luminatum, Link. In Species Plantarum, T.

VI, P. II, p. 61, n. 166.
1825, Caeoma interstitiale. Link in Species Plantarum, T. VI, P. II,

p. 32, n. 89.
1827, Uredo interstitialis, Schl. Sprengel in Systema vegetabilium,

V. IV, p. 574.
1831, Caeoma (Aecidium) luminatum, Schweinitz. North American Fungi,

p. 293, n. 2887. Printed in 1834.
^1859, Uredo lucida, Dietrich. Blicke in die Cryptogamenwelt der Ost-

seeprovinzen, Abth. II, p. 492.

1869, Puccinia Peckiana, Howe. 23 Rep. Bot., N. Y. State Museum,
p. 57. Printed in 1872.

1870, Puccinia tripustulata, Peck. 24 Rep. Bot, N. Y. State Museum,
p»9i. Printed in 1872.

1893, Puccinia interstitiale (Schlechd.), Tranzschel. Hedwigia, Heft.

5» P- 257-

So far as can be made out from the above and other references, the
the history of the fungus is as follows:

In 1817, Ehrenberg, while on a journey, made some collections of
fungi in Kamtchatka. Schlechtendal, in 1820, while working over the
Caeoma of this collection, came across one on Rubus arcticus, which he
described as a new species under the title of Caeoma interstitiale. Two
years later, Schweinitz, of America, in publishing the fungi collected in
Carolina, also described as new a fungus on Rubus strigosus, to which he
gave the name, Aecidium nit ens. In 1825, Link, writing up descriptions
of known fungi, gave both Schlechtendal's fungus and Schweinitz5 fungus,
in the latter case, however, placing the fungus in the genus Caeoma and
retaining Aecidium as a subgenus. Then, without authority as recognized
to-day, he rejected the specific term applied by Schweinitz and substi-
tuted "luminatum" for the same. When Sprengel published the Systema
Vegetabilium, in 1827, he recognized the Asiatic and American forms as
the same, for he gave Aecidium nitens Schw. as a synonym for Uredo
interstitialis, Schl. Schweinitz, in his second publication, in 1831, accepted
the specific name as exchanged by Link, but added his own name as the
authority. According to Tranzschel the fungus was again described

* References marked thus (*) I have not been able to examine personally.

288 BULLETIN NO. 29. \December,

as new in 1859 by Dietrich, who used the name Uredo
lucida. Streinz (1862), in his Nomenclator fungorum, placed
the forms of Schweinitz and Schlechtendal together, recognizing "inter-
stitialis" as the specific term; and Oudemans (1891), in a note in Hed-
ijuigia, again called attention to their identity. Some considerable con-
fusion has been caused by Karsten (1879), who described this Caeoma
as the Aecidium form of Phragmidium Rubi. Winter (1884), used this
description of Karsten's, but stated that he had never seen this stage of
Phragmidium, but in 1885 he evidently recognized the Caeoma as dis-
tinct. Krieger, however, by finding and describing the real aecidium
form of Phragmidium Rubi has cleared up this difficulty. It seems
from the references to be found that Trelease first called the fungus
Caeoma nitens, and that Curtis is responsible for Uredo nitens and Uredo
luminata. The above terminalogy not being sufficient for the botanists of
to-day, various combinations have been made and Schweinitz has been
burdened as the authority in most cases. Such are Uredo luminata, Caeoma
{Uredo) luminatum, Uredo {Caeoma) nitens, Uredo caeoma-nitens, Caeoma
nitens, Caeoma luminatum, Uredo luminatum, Uredo nitens, Aecidium
luminatum.

The history of the mature stage is briefer, perhaps on account of
its late discovery. In 1869 Howe described a new Puccinia found on
the raspberry as P. Peckiana; while the next year, Peck, finding it on
the blackberry, and thinking it different, described it as P. tripustulata.
Burrill, in 1885, called attention to these as identical, adding that they
were now so considered by Peck. Lately, Tranzschel, by culture ex-
periments connecting the Caeoma and the Puccinia, has taken the first
specific name given to the Aecidium form and called the fungus Puc-
cinia interstitiale (Schlechd). We believe, however, with Farlow,* and
and it seems to be the usual method, that when such forms are found to
be connected the specific name of the mature stage should be retained,
in which case Puccinia Peckiana, Howe, is still proper and should be
retained.

DISTRIBUTION.

From notes printed in various publications, the following distri-
bution of the fungus has been obtained.

The aecidium stage has been reported as follows in the United
States — Carolina, Schweinitz; Connecticut, Thaxter; Georgia, Ravenel;
Illinois, Burrill; Iowa, Arthur; Kansas, Kellerman; Maryland, Brunk;
Massachusetts, Sprague; Minnesota, Sheldon; Mississippi, Earle; Mis-
souri, Demetrio; Nebraska, Webber; New Hampshire, Seymour; New
Jersey, Britton; New York, Peck; Ohio, Detmers; Pennsylvania,
Schweinitz; Texas, Jennings; West Virginia, Millspaugh; Wisconsin,
Trelease. In Canada — Ottawa, Ellis & Everhart. In Europe — Bavaria,

*Proceedings American Academy of Arts and Sciences, 1883, p. 66.

ORANGE RUST IN RASPBERRIES AND BLACKBERRIES.

289

Allescher; Finland, Kihlman; France, Cornu; Scandinavia, Eriksson ;
Russia, Tranzschel. In Asia — Siberia, Thumen ; Kamtchatka,Schlechten-
dal. In European and Asiatic Russia, Tranzschel also gives the following :
Gouv. St. Petersburg, Gouv. Archangelsk, Gouv. Moscow, Gouv. Esth-
land, N. Ural, and Minussinsk, and region of Semipalatinska, and
Enisseisk.

The stations of the teleutostage are more limited and as follows:
In the United States — Illinois, Burrill; New York, Howe; Massachu-
setts, Farlow; Missouri, Galloway. In Europe — Lapland, Lagerheim;
Russia, Tranzschel.

HOSTS.

The hosts of the aecidum stage are as follows: In the United
States — Rubus Canadensis, R. hispidus, R. occidentalis, R. strigosus, R.
triflorus, R. trivialis, R. villosus. In Europe and Asia — R. saxatilis, R.
arcticus.

For the teleutostage hosts have been reported as follows: United
States — Rubus occidentalis, R. strigosus, R. villossus. Europe — R.
arcticus, R. saxatilis.

INDIVIDUAL HOSTS,

The following table proves an intimate relationship existing be--
tween this Caeoma and the Puccinia, as shown by their occupancy of
the same individual plants.

INDIVIDUAL HOSTS OF CAEOMA AND PUCCINIA.

Spermagonia, May lyth.

Caeoma, June gth.

Puccinia, July 6th-i4th.

i. Raspberry. Leaves of
old and new shoots af-
fected.

Affected.

Old with few lower leaves
still present and badly
affected.

2. Rasp. Old and new
affected.

Old affected.

Old nearly all dead, like
lower, new badly affect'd.

3. Rasp. Old affected,
new shoots not yet de-
veloped.

Old affected

Dead, but some dead leaves
slightly affected.

4. Rasp. Old and quite
young new affected.

Old affected.

Dead, and leaves all dried
up.

5. Rasp. Old free The
single new affected.

Old free. New affected.

Failed to find plant.

6. Rasp. No old. The
single new partly affect'd

One new affected.

One lower leaf affected^
near Caeoma affected
leaf.

7. Rasp. Three old free.
Two new affected

Two old free. Two new
affected.

One old, lower leaves bad-
ly affected; single new
affected live leaf.

8. Rasp. Old free. New
affected.

Old free. Four new affect-
ed.

Old, nearly dead, slightly
affected.

9. Rasp. One old free.
Three new affected.

One old free. Three new
affected.

Several new, nearly dead,
free. One old affected.

10. Rasp. Three old free.
Many small new mostly
affected.

Three old, three new, free.
Four new affected.

Old and new affected, some
badly.

290 BULLETIN NO. 29. [December,

INDIVIDUAL HOSTS OF CAEOMA AND PUCCINIA — Continued.

Spermagonia, May lyth.

Caeoma, June gth.

Puccinia, July 6th-i4th.

ii. Rasp. One old free.
Five new affected.

One old free. Three new
affected.

Several new, without low-
er leaves, free. One old,
one new, affected.

12. Rasp. One old free.
Bunch of new affected.

Two old, one new, free.
Two new affected.

Old and new affected.

13. Rasp. One old free.
One new affected.

One old free. One new
affected.

Two new, with few lower
leaves, free. One old
affected.

14. Rasp. One old, one
new affected.

One old affected.

Dead, but plant near bad-
ly affected.

15. Rasp. One new affect-
ed.

Failed to find plant.

Three new, lower leaves
affected.

16. Rasp. Twoold, some
new, slightly affected.

Twoold, two new, affected.

Two old, nearly dead,
slightly affected; new,
lower leaves slightly af-
fected.

17. Rasp. One new affect-
ed.

One new affected.

One new, lower leaves
mostly dead; but with
one affected.

1 8. Rasp. One old free.
Several new affected.

One old free. Two new
affected,

Failed to find plant.

19. Rasp. Several old
free. Several small new
slightly affected.

One old, five new, free.
Two new slightly affect-
ed.

A few lower leaves af-
fected.

20. Rasp. One weak old
free. Bunch of new
affected.

Practically dead.

Practically dead, but with
single live leaf affected.

21. Rasp. Bunch of new
affected.

One new affected.

Slightly affected.

22. Rasp. One old, sev-
eral new, affected.

One old free. One old,
three new, affected.

Affected.

23. Rasp. Two old, one
new, affected.

One new free. One old,
one new, affected.

One new, with lower leaves
affected.

24. Rasp. One old, near-
ly dead; several new,
affected.

One old, five new, affect-
ed.

Practically dead, with two
or three affected leaves.

25. Rasp. Several old
affected. No new of im-
portance.

Failed to find plant.

Dead.

26. Rasp. Two old free.
Three new affected.

One old free. Three new
affected.

One old, two new, affected.

27. Rasp. One old near-
ly dead, some new, af-
fected.

Abundantly affected.

Practically dead, free.

28. Blackberry. Old near-
ly dead, some new, af-
fected.

Abundantly affected.

Lower leaves affected.

29. Blackberry. One old
nearly dead, some new,
affected.

Abundantly affected.

Practically dead, some low-
er leaves affected.

1893-] ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 29 1

INDIVIDUAL HOSTS OF CAEOMA AND PUCCINIA — Continued.

Spermagonia, May lyth.

Caeoma, June gth.

Puccinia, July 6th-i4th.

30. Rasp. Old nearly
dead, some new, affect'd.

Affected.

Old without leaves; new
without lower leaves;
upper free.

31. Rasp. One old free.
One new affected.

Abundantly affected.

A few lower leaves slightly
affected.

32. Rasp. Two old free.
One old, some new, af-
fected.

Abundantly affected.

Failed to find plant.

33. Rasp. Two old, some
new, affected.

Abundantly affected.

Old without leaves; new
free.

34. Rasp. Old free. New,
affected.

Abundantly affected.

Old affected; new, without
lower leaves, free.

A number of the above plants were affected by the spermagonia and
the aecidium stage on the new shoots only. This does not necessarily
mean that those plants were affected for the first time, for the fungus
may have had such a disastrous effect on those shoots infected the pre-
vious year as to have killed all of them, a thing quite apt to occur. It
will also be seen that a number of plants were killed entirely. Of the
living plants there were only three found in June that were not affected
with the Puccinia, and these had their leaves so destroyed by the aecidium
stage as to render subsequent infection unlikely.

The following serves as a sort of check to the above. These plants
were examined at the same time as the above for the Puccinia. They
were in the same locality, and at varying distances from plants affected
by the aecidium stage; but, as none had been affected by this stage, their
chance of being host to the Puccinia depended considerably on their
distance from plants having the Caeoma. There were thirteen plants free
and seven on which the Puccinia was found. All the affected ones were
near plants that had the aecidium form.

a. Raspberry. A healthy plant. Two old, two new shoots, free. Several rods from

plants affected with aecidium stage.

b. Rasp. Rather vigorous. One old, two new, free. Near a.
Rasp. Vigorous. Single new, apparently free. Near a.
Rasp. Sickly. One dead old, one new, free. Near a.

Rasp. Healthy, One old, two new, free. Two or three rods from affected plants.

Rasp. Rather sickly. Free. Near e.

Rasp. Rather sickly. One dead old, one new, free. Near e.

Rasp. One new free. One old with single leaf slightly affected. Three feet

from affected plant 27.

i. Blackberry. Healthy. One old, one new, free. Five feet from affected plant 27 .
j. Rasp. Vigorous. One old, one new, free. Three feet from affected plant 27.
k. Rasp. Two new free. One old, one new, rather abundantly affected. Two feet

from affected plants 22, 23, 24, 25.
1. Rasp. One new free. One old affected. Near k.
m. Rasp. One old, one new, free. One old slightly affected. Near k.
n. Rasp. One old, several new, affected abundantly on lower leaves. Near k.
o. Rasp. One old, two new, rather abundantly affected. Near k.
p. Rasp. Several old and new free. Ten feet from two affected plants.

292 BULLETIN NO. 29. [December,

q. Rasp. Two old, two new, free. Near p.

r. Rasp. One old, one new, free. Near p.

s. Rasp. One old, one new, free. Close to an affected plant.

t. Rasp. Old and new affected. Close to affected plant.

EXSICCATI.

In exsiccati the Caeoma and Puccinia here considered, on the dates
£iven, were distributed under different names as follows:
1852, Aecidium luminatum, Schw., Ravenel's Fungi Caroliniani, V. i, n. 91.
1876, Uredo luminatum, Curtis, on Rubus Canadensis, De Thiimen's Mycotheca Uni-

versalis, C. V., n. 446.

1879, Uredo luminatum, (Schw.), on Rubus, Ravenel's Fungi Americani, C. Ill, n. 276.
1879, Caeoma luminatum, (Schw.), on Rubus Strigosus, Ellis' N. A. F., C. Ill, n. 277.
1885, Caeoma nitens, (S.), on Rubus villosus, K. saxatilis, Rabenhorst's Fungi Europaei,

C. XXXIII, n. 3225, a. b. c.
*i887, Caeoma nitens, (Schw.), Eriksson's Fungi parasitici scandinavici, exsiccati,

F. IV.
*i889, Caeoma nitens •, Schw., on Rubus villosus, Kell. & Swingle's Kans. Fungi, F. II,

n. 31.
*i89o, Caeoma nitens, Schwein, on Rubus saxatilis, Allescher & Schnabl's Fungi Bava-

rici exsiccati, C. I.
1890, Caeoma nitens, (S.), on Rubus Canadensis, R. villosus, Seymour & Earle's Eco.

Fungi. F. I., n. 27, 28.

1879, Puccinia Peckiana, Howe, on Rubus occidentalis, Ellis' N. A. F., C. Ill, n. 261.
1890, Puccinia Peckiana, Howe, on Rubus villosus, Seymour & Earle's Eco. Fungi, F.

I., n. 26.

LITERATURE.

The following references are such as have been used in the prepa-
ration of this paper. Scattered through agricultural and horticultural
papers are notes on the "Orange Rust," which we have not cited, save
in one or two instances. While it has been the intention to include all
articles or notes of scientific importance on this subject, it is quite prob-
able that some may have escaped observation.

Allescher, 1888, Bot. Centralblatt, B. XXXVI, p. 287, notes finding Caeoma nitens on
Rubus saxatilis near Allach in 1878, and mistaking it for a form of Phragmidium
Rubi.

Arthur, 1884, Bull. Iowa Agr. Coll., p. 164, lists C. nitens as occurring on black-
berry in that state.
Bessey, 1885, Rep. Amer. Pom. Soc., p. 43, lists C. luminatum among the injurious

fungi of horticulturists.

Botanisches Centralblatt, 1887, B. XXIX, p. 158, gives C. nitens as one of the fungi
in the IV Fas. Fungi parasitici scandinavici, which appeared about this date.
Brendel, 1887, Flora Peoriana, p. 69, lists C. nitens from Peoria Co., 111.
Britton, 1889, Geol. Surv. New Jersey, V. II, P. I. p. 503, gives Uredo luminata on

R. strigosus from New Jersey.

Brunk, 1890, Ann. Rep. Md. Agr. Coll. and Ex. Sta., p. 115, mentions twenty varie-
ties of blackberries affected by C. nitens, and gives notes on degree of affection.
1891 Rep. same publication, pp. 389 & 416, gives results of spraying and notes
on varieties affected.
Burrill, 1882, Agr. Review, p. 88, gives an account of Caeoma luminatum.

1885, Parasitic Fungi of Illinois, P. I, pp. 178, 220, gives scientific descriptions

of C. nitens and P. Peckiana, and suggests relationship.

1885, Rep. 111. Industrial Univ., p. 115, writes scientific description of P.

1893-] ORAXGE RUST IN RASPBERRIES AND BLACKBERRIES. 293

Peckiana, also p. 138 same, of C. nitens, and suggests a connection between

them.

1885, Prairie Farmer, V. LVII. p. 762, gives detailed structure of C. nitens, etc.

1885, Reprint from Amer. Soc. Micr., pp. 3, 8, gives general description and

possible connections of C. nitens.

*Cobb, 1887, List PI. Amherst, p. 39, gives Uredo luminata.
Cooke, 1878, Grevillea, V. VII, p. 46, lists Uredo luminatum from Georgia.
Cornu, 1881, Bull. Soc. Bot. France, p. 145, gives an account of finding Ae. lumi-
natum on Rubus in France, mentioning it as new to Europe.

Cragin, 1885, Bull. Washburn Coll., V. I, n. 2, p. 68, lists C. luminatum from Kansas.
*Curtis, 1867, Bot. N. Car., p. 122, gives Uredo luminata.

Day, 1883, Cat. Plants of Buffalo and vicinity, gives Uredo luminata in the list.
Detmers, 1891, Ohio Ex. Sta., Bull. No. 6, p. 127, makes a general description of C.

nitens with its effect on host.

1892, Same Pub., V. V, No. 7, p. 137, mentions finding what seems to be an
uredo stage of C nitens. etc.

1893, Same Pub., Tech. Series, V. I, No. 3, p. 180, describes further this sup-
posed uredo form of Uredo (Caeoma) nitens, etc.

De Toni, 1888, Saccardo's Sylloge Fungorum, V. VII., P. II, p. 866, gives synonyms,

hosts, and description of Uredo (Caeoma) nitens, also p. 699 treats P. Peckiana

similarly.
Dietel, 1887, Botanisches Centralblatt, B. XXXII, p. 87, makes mere reference of

variability of spores of P. Peckiana, as shown by Lagerheim, 1887.

1892, Bot. Centralblatt, B, XLIX, p. 270, gives reference to two articles on

Russian Uredineae by Gobi and Tranzschel.
^Dietrich, 1859, Blicke in die Cryptogamenwelt der Ostseeprovinzen, abth. II, p.

492, describes, according to Tranzschel, this Caeoma as a new species, Uredo

lucida.
Earle, 1889, U. S. Dept. Agr., Sec. Veg. Pathol., Bull. No. XL, pp 84, 85, 88, gives

results of spraying with Bordeaux mixture blackberries affected with C. nitens.
*Ellis, 1889, Cat. PI. New Jersey, 503, gives Uredo luminata.
Ellis & Everhart, 1885, Journal of Mycology, V. I, p. 86, give C. luminatum on R.

triflorus from Ottawa, Canada.
Ex. Sta. Record, Vol. II, pp. 32, 455, 482; V. Ill, pp. 161, 313, 411, 722, makes

reference to different Ex. Sta. notes on C. nitens.
Evans, 1893, Handbook Ex. Sta. Work, U. S. Dept. Agr., p. 283, gives account of

general appearance of C. nitens.
Farlow, 1876, Bull. Bussey Institution, p. 432, lists P. Peckiana as occurring in

Massachusetts.

1883, Proc. Amer. Academy Arts and Sciences, p. 76, gives a general de-
scription of appearance of Ae. nitens, and suggests that this may prove to be a

heteroecious fungus.
Farlow & Seymour, 1888, Host Index U. S. Fungi, p. 37, give hosts and synonyms

of C. nitens and P. Peckiana.

*Frost, 1875, Cat. PI. Amherst, p. 84, lists Uredo luminata.
Galloway, 1889, U. S. Dept. Agr., Bot. Div., Bull. VIII, pp. 56, 58, lists C. nitens

and P. Peckiana from Missouri.

1889, Rep. U. S. Dept. Agr., p. 416, speaks of spraying experiments made by

Earle. Printed in 1890.
Gardner's Monthly, 1871, pp. 211, 266, correspondents give notes on "orange

rust" of blackberry, treatment, etc.
Hoffman, 1863, Index Fungorum, p. 3, lists Ae. luminatum with "nitens" as the

synonym.
Howe, 1869, (23) Rep. Bot. N. Y. State Museum, p. 57, gives description of a new

fungus, Puccinia Peckiana, on Rubus occidentalis. Printed in 1872.

294 BULLETIN NO. 29. [December,

Humphrey, 1890, Ann. Rep. Mass. Ex. Sta., p. 224, mentions C. nitens as common

there, etc. Printed in 1891.
Jennings, 1890, Texas Ex. Sta., Bull. No. IX, p. 23, mentions C. nitens as quite a

drawback to culture of blackberry, and mentions it as also found on wild plants

of R. trivialis.
Journal of Mycology, 1889, p. 103, gives reference to Lagerheim's 1889 article and

p. 161, lists C. nitens as in Kellermann & Swingle's Kans. Fungi, Fas. II.
Kellerman, 1885, Washburn Coll. Bull., V. I, n. 2, p. 74, gives host of C. nitens in

Kansas.
Karsten, 1879, Mycologia Fennica, P. IV, p. 51, describes what is probably C.

nitens as aecidium form of Phragmidium bulbosum (Ph. Rubi).
Lagerheim, 1887, Botanisker Notiser, p. 60, gives an account of finding P. Peckiana

on R. arcticus in Lapland, discusses forms of this fungus as found in different

localities, and suggests C. nitens as a stage of Ph. Rubi rather than of P.

Peckiana.

1889, Hedwigia, B. XXVIII, H. 2, p. no, treats of distribution, of hosts, and
of the relationship of C. nitens to other forms, and, as Krieger has found the
aecidium stage of Ph. Rubi, now thinks the Caeoma heteroecious.

1890, Hedwigia, p. 173, gives mere reference to variability of position of germ
pore of P. Peckiana.

Link, 1825, Species Plantorum, T. VI, P. II, p. 61, n. 166, describes C. luminatum
and gives its host and locality as taken from Schweinitz, but instead of adopt-
ing the latter's name for the fungus gives it one on his own account.
Same, p. 32, n. 89, gives description, hosts, locality and name of Schlechtendal's
(1820) Caeoma interstitiale,

Ludwig, 1884, Bot. Cent., B. XX, p. 356, reviews Trelease's 1884 article.

1887, Botanisches Centralblatt, B. XXXI, p. 162, makes a short abstract of
Lagerheim's 1887 article.

Magnus, 1890, Separat-Abdruck aus Hedwigia, H. 6, gives C. nitens as one of the
interesting fungi in Cent. I, Fungi Bavarici.

Millspaugh, 1892, West Va. Agr. Ex. Sta. Bull., n. 24, p, 509, gives C. nitens as
found in that state on R. hispidus.

Newcombe, 1891, Jour. Mycology, Vol. IV. p. 106, proves mycelium of C. nitens to
be perennial in its host. Remarks by Galloway on consequent treatment.

New York Agr. Ex. Sta., Bull. n. 36, p. 641, mentions orange rust as a troublesome
disease of raspberry.

Oudemans, 1891, Hedwigia, H. 3, p. 178, refers to Caeoma interstitiale published
by Schlechtendal in 1820, it being collected by Ehrenberg in 1817 in Kam-
tchatka on Rubus arcticus, states that the illustration given of this fungus corre-
sponds exactly with that of C. nitens, which must now be known as C. inter-
stitiale, as this one was published two years earlier.

Peck, 1868, (22nd) Rep. Bot. N. Y. State Museum, p. 92, lists Uredo luminata as
common on Rubus. Printed in 1869.

1870, (24th) Rep. p. 91, gives scientific description of Puccinia tripustulata,
n. s. found on Rubus villosus. Printed in 1872.

1871, (25th) Rep. pp. 113, 114, gives scientific descriptions of P. tripustulata,
Pk. and P. Peckiana, Howe, which at that time he considered distinct. Printed
in 1873.

1873, (27th) Rep. p. 77, notes Uredo luminata as rapidly becoming a serious
drawback to the culture of blackberries and raspberries. Printed in 1875.
1875, (2gth) Rep. p. 72, lists P. Peckiana and P. tripustulata, also p. 75, lists
Uredo luminata as found there on R. villosus, R. Canadensis, R. occidentalis,
R. strigosus. Printed in 1878.

Richards, 1893, Proc. Amer. Acad. Arts and Sciences, p. 31, treats of development of
the spermagonia of C. nitens, and states that they do not originate in one
greatly enlarged epidermal cell.

1893-] ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 295

*Schlechtendal, 1820, Horae physicae Berolinenses, p. 96, t. 20, f. 13., describes and
figures C. interstitiale as new, it being collected by Ehrenberg in Kamtchatka
in 1817 on R. arcticus.

Schroeter, Ein Beitrag zur Kenntniss der nordischen Pilze. p. 7, gives C. nitens as
found in Sweden.

Schweinitz, 1822, Synop. Fungi Carolina, p. 69, n. 458, describes Ae. nitens, n. s.
on Rubus strigosus.

1831, North Amer. Fungi, p. 293, n. 2887, gives his former Ae. nitens as
Caeoma (Aecidium) luminatum, Schw., his specimen this time being from
Pennsylvania. Printed, 1834.

Scribner, 1886, Rep. U. S. Dept. Agr., p. 133, lists C. nitens from Michigan. Printed
1887.

Seymour, 1886, Reprint from Minn. Hort. Rep., V. XIV, gives some facts concern-
ing life history of C. nitens.

1887 Amer. Naturalist, p. 1115, notes a more erect and rigid growth of plants
attacked by C. nitens.

Sprague, 1856, Proc. Boston Nat. Hist. Soc., p. 328, lists Uredo nitens as occurring
in Massachusetts.

Sprengel, 1827, L. Sys. Veg. i6ed., V. IV, p. 574, gives scientific description of
Uredo interstitialis, Schl., which he considers the same as Aecidium nitens,
Schw.

Streinz, 1862, Nomenclator fungorum, p. 644, n. 10757, gives Uredo interstitialis,
Spr., with Ae. nitens,' Schw., C. interstitiale, Lk., and C. luminatum, Lk. as
synonyms.

Thaxter, 1889, Ann. Rep. Conn. Ex. Sta., p. 172, gives C. nitens as common on
cultivated and wild raspberries and blackberries, and suggests method of treat-
ment. Printed in 1890.

*Thumen, 1880, Beitrage zur Pilz-Flora Sibiriens, III, p. 14 gives Uredo lumjnata
as found in Asiatic Siberia.

Tranzschel, 1892, St. Petersburg Naturforscher Gesellschaft (Bot. Section), gives
preliminary report on producing P. Peckiana by means of artificial infection of
R. saxatilis with spores of C. interstitiale (C. nitens).

1893, Hedwigia, H. V., p. 257, gives further successful results of artificial infec-
tion, and concludes that the Caeoma and the Puccinia must hereafter be known
as stages of Puccinia interstitiale (Schl.)

Trelease, 1884, Extract from Trans. Wis. Academy of Science, Arts and Letters,
V. VI, p. 30 gives host of C. nitens in Wisconsin. • Probably the first to call
this fungus Caeoma nitens.

1884. Psyche, V. IV, p. 195, notes insect larvae as eating spores of C. nitens.
Underwood & Cook, 1889, Illustr. Fungi, 51, give C. nitens.

Watt," 1885, Canadian Naturalist and Geologist, Second Series, V. II, p. 391, gives
Ae. laminatum, the specific term probably being "luminatum" misspelled.

Webber, 1889, Extract from Rep. Neb. Slate Board of Agr., p. 73, notes Uredo (C.)
nitens as being very destructive.

1889, Neb. Agr. Ex. Sta., Bull. No. n, lists same on p. 65, and Pond mentions it
on p. 89.

Winter, 1884, Rabenhorst's Kryptogamen Flora I-I, p. 230, gives Karsten's(i879) de-
scription of I stage of Ph. Rubi, although he states that he has never seen the
same for certain.

1885, Hedwigia, B. XXIV, p. 181, gives C. nitens on R. villosus and R. Cana-
densis, as sent from Missouri by Demetrio.

1885, Rabenhorst's Fungi Europaei, C. XXXIII, n. 3225, presents specimens
of C. nitens for America and Fennia, and says that Fennia specimens are C.
nitens rather than a form of Ph. Rubi for which they were sent to him.

G. P. CLINTON, B.S., Assistant Botanist.

296 BULLETIN NO. 29. [December,

EXPLANATION OF PLATES.

Plate i. Fig. i. Under surface of blackberry leaf thickly covered with sori of aecid-

ium stage.

Fig. 2. Under surface of raspberry leaflet, with both aecidio- and teleuto-sori.
Fig. 3. Under surface of blackberry leaflet, with teleutosori in groups.
Fig. 4. Upper surface of raspberry leaflet, with peculiar mottled appearance

frequently caused by teleutostage of fungus.
Fig. 5. Cross section of blackberry leaflet through a sorus of the aecidium

stage.
Plate 2. Fig i. Cross section showing part of blackberry leaflet with a sperma-

gonium beginning to form just beneath the epidermis.
Fig. 2. Slightly more advanced stage.
Fig. 3. Mature spermagonium in cross section.
Plate 3. Fig. 1-4. Haustoria in pith of very young shoot of blackberry, as seen in

cross section. 2 and 3 show the peculiar conjugation sometimes found.
Fig- 5-7. Haustoria in pith of old blackberry stems, in cross section, 5

and 6 being more highly magnified than 7.
Fig. 8-9. Mycelium in longitudinal sections of blackberry pith, 8 being from

a young and 9 from an old cane.
Fig 10. Section with mycelium and a haustorium in parenchyma tissue of

very young leaf.

Fig. 11-13 Cross section of parenchyma cells in cortex of root, with mycel-
ium of fungus, ii showing cross end of mycleium between the cells, 12 and

13 haustoria.
Fig. 14. Tangential section with mycelium and a haustorium in parenchyma

cells of root cortex.
Plate 4. Fig. 1-21. Aecidiospores germinating in water.

Fig. 1-7. Germination of same spore at end of 4, 5, 6, 7, 8, 9, and 24 hours.
Fig. 8-12. Germination of spores during first two days, and 13 during third

day.
Fig. 14-18. Spores from raspberry, having been 48 hours in water, while 19-

20 show quicker germination at end of 24 hours.
Fig. 21. Peculiar tips of germ tubes, two showing suddenly enlarged tips, and

three flexuous tips.
Fig. 22. Aecidiospores that were placed on lower moist surface of blackberry

leaf, showing contracted tip of germ tube, and method of entrance through

stomates.

Fig. 23. Peculiar branch of germ tube of a spore sown on blackberry leaf.
Fig. 24-29. Teleutospores germinated in water, at end of eight days. 24, 26,

28, 29, optical sections of the spores, showing how germ tube penetrates the

exospore.
Fig. 30. Mycelium as seen beneath epidermis, and between guard cells of

stomates. From blackberry leaflet just beginning to show teleutoform.

1893- J ORANGE RUST IN RASPBEKK1ES AXD BLACKBERRIES. 297

PLATC /

298

BULLETIN NO. 29. [December,

PLATLU.

1

1893'] ORANGE RUST IN RASPBERRIES AND BLACKBERRIES. 299

PLATEffl

joo

BULLETIN NO. 29. [December, 1893.]

*A NEW FACTOR IN ECONOMIC AGRICULTURE.

Economic agriculture has in store many problems whose solution
will greatly lessen labor while at the same time increasing the
productiveness of the soil. There is no subject of greater interest and
importance to physiological botany and agriculture than the recently
discovered symbiotic relation between different organisms; a relation
mutually beneficial and in many cases absolutely necessary to existence.
It is the purpose of this paper to discuss a form of symbiosis which may
prove to be of special interest to agriculture. Taking it for granted that
most readers of these bulletins are practically unacquainted with
the subject " Symbiosis," a condensed historical review of it from its
beginning will be first given.

[*It has been well known for many years that clover, especially when plowed
under, made a very marked contribution to the fertility of the soil upon which it
grew, and later scientific investigations have shown that this plant, and some other
allied ones, have the peculiarity of making use of the free nitrogen of the air as an
element in their nutrition. Most other plants cannot do this, though all must have
nitrogen as a food ingredient. It is usually taken from the soil in combination with
other elements; as, for instance, in the lime forming nitrate of lime. Now four-fifths
of the atmosphere is free nitrogen. If by any means plants can make use of it as food,
they have an abundant and constant supply at hand and the combined form in the
soil then becomes less important, or unnecessary. Since the latter is the most expen-
sive of artificial fertilizers and its application is often demanded for full crops, any
substitute for it must be of immense practical value.

It has now been shown that clover, like other agricultural plants, is of itself in-
capable of utilizing free nitrogen, but that it does so through the agency of low organ-
isms (bacteria) found in little knots or tubercles which form like galls upon the roots.
Such tubercles are found on the roots of all plants which are known to gain nutri-
tion from free nitrogen and are not so found upon any other plants. They a/te not
found upon the roots of any of the grasses or cereals. Can the organisms be made to
grow upon these roots by any artificial means?

It must be confessed that it would have been exceedingly hazardous for any one
to have expressed an affirmative opinion upon this question; but the vast importance
of the matter made it desirable to try anything which gave the least promise of success.
In this condition of things it came to the knowledge of officers of this Experiment
Station that Dr. Albert Schneider, then of Minneapolis, Minn., had found from some
preliminary investigations indications of the possibility of adapting the organisms by
artificial cultivation to growth upon the roots of maize or of other cereals. He was
therefore secured to continue these investigations during the latter part of the sum-
mer of 1893, and was given all the facilities at the command of the Station. The
following from his pen gives the results as far as obtained. While little direct evi-
dence has been gained in favor of ultimate success, it is considered desirable to pub-
lish an account of the work so far done with the hope of being able at some future
time to add greatly to the information now obtained. The report is necessarily tech-
nical in form and several terms are employed that may be new to many who read these
pages; but the subject matter is also new to the public and other wording could
scarcely make it easier to comprehend. The term symbiosis is applied to the associa-
tion of two different kinds of living plants or animals in a mutually helpful relation.

THOMAS J. BURRILL, Horticulturist and Botanist.]

301

302 BULLETIN NO. 29. [December,

BRIEF HISTORICAL REVIEW.

The term symbiosis was first used by de Bary in 1879 *n an article
entitled, Die Erscheinung der Symbiose. By it he meant that kind of
commensalism or consortism between different organisms which proved
mutually beneficial. In parasitism the benefit is always one-sided, one
organism flourishing at the expense of the other. The most familiar
form of symbiosis is to be found in the case of lichens. Here we find
an ordinary hyphal fungus living in vital relation with a filamentous or
single-celled alga. The chlorophyll bearing algae make it possible for
the fungus to develop on rocks and tree trunks where it could not exist
alone. In turn the alga absorbs nourishment from the fungus. It is
only a few years since the algae of lichens were looked upon as spores
and hence named gonidia. The dual nature of lichens has been demon-
strated both by analysis and synthesis. The algal and fungal portions
of a given lichen have been separated and each found to be capable of
existing alone. It has been found that by placing a certain fungus and
alga together they form a true lichen.

A form of symbiosis of much greater importance is to be found with
certain forest trees. Often the greater portion of nourishment is
supplied by fungi. These fungi stand in symbiotic relation with the
small rootlets of the tree forming a structure part root and part fungus,
called a Mycorhiza. According to the researches of Frank the sig-
nificance of this root symbiosis is to be explained as follows: The tree
as well as the fungus requires humus; but the humus, before it can be
readily taken up as food by the trees, must first be assimilated by the
fungus. Frank and his pupil Schlicht have found symbiotic fungi
among Ericaceae, Epadridiae, Empetraceae, and Orchidaceae.

Among the Leguminosae we meet still another form of symbiosis.
Here one of the symbionts is a bacterium (Rhizobium) and is always
to be found within the tissue of the host forming swellings called tuber-
cles. The history of Rhizobia tubercles is very interesting and has led
to many controversies.

The tubercles on the roots of Leguminosae had been noted as early
as 1852, though no one understood their meaning. Malpighi considered
them as galls; de Condolle, as pathological growths. Clos looked upon
them as lenticular growths, while Treviranus, considered them undevel-
oped buds. Eriksson gave a more complete description of the tuber-
cles of Faba vulgar is. In 1866 Woronin noticed that the soft paren-
chymatous cells of the interior of the tubercles were entirely filled with
small bodies. He pronounced these bacteria. Most botanists coincided
with Woronin as to the bacterial nature of the tubercle contents. These
bacteria were looked upon as true parasites. In 1879 Frank pointed out
that it was not an ordinary form of parasitism. In 1887 Hellriegel con-
cluded a series of experiments which led him to the conclusion that there
was some close relation between the root tubercles of Leguminosae and

1893-] A NEW FACTOR IN ECONOMIC AGRICULTURE. 303

free nitrogen assimilation. Beginning with 1885 and ending in 1891, a
heated controversy was kept up concerning the contents of the infected
cells of tubercles. Heretofore they had been looked upon as bacteria.
Brunchorst and Tschirch conducted a series of experiments in Frank's
institute which led them to believe that the bacteria, so-called, were not
bacteria but were bacteroid bodies formed by the plants themselves;
that is, the bacteria-like particles were albuminous reserve products
which were finally absorbed by the plant and utilized in maturing the
seed. Frank readily seconded these conclusions. Brunchorst named
these bacteria-like albuminous substances Bakteroiden.

Eriksson had already noted in some tubercles peculiar hyphal
structures penetrating the tubercle. He asserts that these hyphae end
in the meristem of the tubercle and that the Bakteroiden bud off from
them within the vegetable cell. In 1887 Marshall Ward made a special
study of the mode of infection in Vicia Faba. His observations coin-
cided quite closely with those of Eriksson. The above mentioned hyphal
structures Ward looked upon as true hyphae of a fungus belonging to
the Ustilagineae. The Bakteroiden he considered as the spores. Ac-
cording to Vuillemin the Bakteroiden are simply differentiations of the
cell protoplasm and the hyphal structures are to be looked upon as the
tubercle producing organism. He maintains that he succeeded in stain-
ing a cell membrane and hence called it a true hyphal fungus belonging
to the Chytridiaceae, naming it Cladochytrium leguminosarum. Beyer-
inck looked upon these hyphal structures as mere Schleimfaden, produced
by the plant cells themselves. He supposed them to be formed from
the remnants of spindle threads left after nuclear division had taken
place. Relying upon this assumption he also endeavored to explain the
fact that the Schleimfaden pass directly through the cell wall. The
Bakteroiden Beyerinck considered the infecting organisms, formed
from the microsomatic bodies found in the meristem cells of the tuber-
cles. The microsomatic bodies were looked upon as bacteria which
normally live within the soil but which are enabled to enter the plant
root in some unknown way. He also seconded Brunchorst's and Frank's
conclusions that the Bakteroiden are re-absorbed by the plant. Prazmowski
looked upon the hyphal structure as a plasmodium filled with bacilli-
like organisms. As soon as these enter the root parenchyma the plas-
modium surrounds the cell protoplasm so that cell protoplasm, plas-
modium, and the bacilli-like bodies form a thorough mixture. Here the
bacilli-like bodies are converted into the Bakteroiden. Later Prazmowski
changes his opinion, maintaining that the plasmodium is a hyphae-like
tube filled with bacteria. The spores of the bacteria enter the root
hairs in some way and multiply enormously. The bacteria tube pushes
forward as far as the meristem of the tubercle where it dissolves and
liberates the bacteria; the latter become mixed with the cell protoplasm,
and are finally converted into the peculiar Bakteroiden. Schroeter con-
sidered the hyphal structures as true plasmodia of a fungus belonging to

304 BULLETIN NO. 29. \JDecember,

the Myxomycetes. This fungus he named Phytomyxa leguminosarum.
Frank came to the conclusion that the hyphal structures were products
of the plant cells themselves, and served the purpose of assisting the
Rhizobia into the root parenchyma, hence he named them Infek-
tionsfaden.

According to Frank infection takes place as follows: The roots of
Leguminosae secrete a substance which serves as an attraction to the
Rhizobia in the soil. They accumulate and multiply on the surface of
the root, some of them enter the outer cells and are then conducted into
the interior by the Infcktionsfdden. Here the Rhizobium assimilates
the cell protoplasm and becomes much changed in form, finally becom-
ing converted into Bakteroiden. In 1890 he believed with Brunchorst
that the Bakteroiden were albuminoid bodies formed from the cell proto-
plasm, in which the Rhizobia were imbedded. In 1891 he changes his
opinion in regard to Bakteroiden maintaining that they are true bacteria,
as stated above.

So far Frank adheres to the opinion that there is but one species of
Rhizobium, namely: Rhizobium leguminosarum. Investigations by
the writer have led to the belief that there are at least several species.
One and the same species may be found on different plants. For
example, one species, designated Rhizobium curvum, was noticed on
Phaseolus pauciflorisj another, Rhizobium mutabile, was found on
Tri folium pratense and Tri folium repens, on Melilotus alba and
Medicago sativa. The much discussed Infektionsfaden seem to bear
an incidental relation only to the Rhizobia. It is not probable that the
roots of Leguminosae secrete or excrete a substance that is attractive to
Rhizobia. All later experiments, as far as known, verify these state-
ments. Rhizobia in some way gain access to the surface cells of the
roots and multiply and produce their peculiar changes in plant economy.
Elsewhere the writer has described the root tubercle morphology and
hence will not take up space here. It should be said, however, that the
root tubercles are quite permanent in structure; and that it does not
seem to the writer that the contents of Rhizobia and tubercles are at
any time directly reabsorbed by the plant.

It would be impossible to review all the work that has been done
in regard to the root tubercles and the free nitrogen assimilating
Rhizobia they contain. Carefully considered and weighed, the dis-
cussions and controversies up to date may be summarized as follows:

1. Certain bacteria, called Rhizobia, live in symbiotic or mutually
beneficial relations with certain higher plants, especially the Legumi-
nosae.

2. Plants can develop without these Rhizobia, but, as a rule,
thrive much better with them.

3. These Rhizobia have the power of assimilating for the use of
the plant the free nitrogen of the air.

4. There are several species of Rhizobia.

1893*] A NEW FACTOR IN ECONOMIC AGRICULTURE. 305

5. Rhizobium mutabile very likely stands preeminent in the nitro-
gen assimilating function.

6. The Infektionsfaden probably have no essential relation to the
Rhizobia.

7. The tubercles are abnormal growths produced by the presence
of the Rhizobia.

8. The tubercles have a definite structure and form a permanent,
coherent part of the root.

9. The Bakteroiden of Brunchorst (Rhizobia mutabile) are capable
of being cultivated in suitable media.

PLAN OF RESEARCH.

The plan, though in a certain sense original, did not suggest itself
spontaneously, but is the result of careful study.

That the Rhizobia play an important part in the vegetable king-
dom is definitely settled. The results of Hellriegel's, Willf arth's, Lawes
and Gilbert's, and Frank's experiments have opened a new era in
economic agriculture. They have begun a work which will doubtless
result in some great good.

Several interesting problems suggest themselves for solution. One,
to which attention is here directed, is to ascertain if the Rhizobia of
Leguminosae can be induced to live in symbiotic relation with plants of
other families, as, for example, the Gramineae. If, for instance, the
Rhizobium of the Melilotus alba root can be transplanted to the Zea
Mays root and there continue its nitrogen-assimilating function, then our
corn crop can be doubled and trebled with the same amount of labor
now expended on an average crop. Of course it must be left for the
future to decide whether this can be done. So far as known no experi-
ments have as yet been attempted in this line. Knowledge of Rhizobia
and bacteria in general leads to the belief* that satisfactory results may
be obtained. A brief outline of the plan of research which suggests
itself is as follows:

1. To make a suitable culture medium.

2. To develop Rhizobia in this culture medium.

3. To change the culture medium by degrees from a leguminous
nature to a gramineous nature.

4 To modify the Rhizobia by successively transferring from a
highly leguminous medium to a highly gramineous medium.

5. To inoculate Gramineae with modified Rhizobia.

6. Life history of Rhizobia.

First, to make a suitable culture medium. Naturally, in order to
induce the Rhizobia to develop outside of roots, there must be sup-
plied artificially conditions approaching those of nature. Rhizobia, as
they are found in root tubercles, are placed under the following con-
ditions: i. They are in a vegetable medium. 2. The medium is
slightly acid in reaction. 3. They are not exposed to light. Artificially,

306 BULLETIN NO. 29. [December,

these conditions can be supplied as follows: Instead of using the ordin-
ary gelatine-peptone bouillon the purpose is to prepare a special culture
medium from agar-agar and a water extract of certain leguminous roots,
which is then made slightly acid in reaction and placed in the dark after
being inoculated with a given species of Rhizobium. By this means all
the above mentioned essential conditions are met with. Frank's (as
well as those of others) failures to make cultures of the so called
Bakteroiden were probably due to the fact that he did not supply the
required conditions. Frank used gelatine-peptone bouillon. He neither
mentions the reaction nor the light conditions. The writer attempted
cultures in both gelatine-peptone and agar-agar bouillon, slightly alkaline
in reaction and placed in the dark after being inoculated. Bakteroiden
(Rhizobium mutibile) were not thus developed, but there was readily
obtained a culture of Rhizobiam Frankii, var. ma/us. Recently Atkin-
son has succeeded in cultivating the Bakteroiden of vetch in an agar-agar
peptone-vetch culture, which demonstrates conclusively that the
Bakteroiden are true bacteria. The plan of the writer is to modify
somewhat Atkinson's culture medium, and to omit the peptone which is
an animal product. Instead of making an extract of the entire plant,
roots only will be used. Atkinson does not state the reaction of his
culture media, though it is to be supposed that they were acid, as vegetable
cell sap is normally acid. Presumably he kept his cultures in diffused
light, as he does not mention anything to the contrary. There would
seem to be but little difficulty in preparing a suitable culture medium in
which to develop Rhizobia.

The second step is, to develop Rhizobia in this special culture
medium. The desire is to cultivate Rhizobium mutabile {Bakteroiden of
Brunch.), as it is believed to be the one which has, preeminently, the
power to assimilate free nitrogen. Since Atkinson has demonstrated
that it can be cultivated, no doubts need be entertained on that score.
All that is required is to place it in the proper medium under antiseptic
precautions. Being once assured of a pure culture of Rhizobium muta-
bile, considerable progress is made toward the solution of the problem
under consideration.

The third step, to change the culture medium by degrees from a
leguminous nature to a gramineous nature, is of great importance. It is
a well known fact that low organisms, especially bacteria, may become
modified so as to adapt themselves to environments which proved fatal
before they were thus modified. The purpose is to change the culture
media so as to induce the Rhizobia to become modified. The plan is as
follows: To make culture media in which the agar-agar is present in a
constant percentage and the vegetable extracts variable. As already in-
dicated the plan is to modify Rhizobia of a given leguminous plant so
as to be capable of transplanting to the roots of a given gramineous
plant. To begin with a culture medium will be taken which contains the
fixed quantity of agar-agar and 100 per cent of extract of Melilotus

1893-] A NEW FACTOR IN ECONOMIC AGRICULTURE. 307

roots; the culture medium next in the series shall contain 80 per cent
Melilotus root extract and 20 per cent of Zea Mays root extract; the next
in the series shall contain 60 per cent of Melilotus extract and 40 per
cent of Zea extract and so on, each of the series differing by 20 per
cent in the relative amounts of sweet clover and corn root extracts. At
one end of the series is a culture containing 100 per cent of Melilotus
alba root extract; at the other end, a culture containing 100 per cent
Zea Mays root extract.

The fourth step explains itself from what has already been stated.
The Rhizobia are to be transferred from one culture medium to another
until they have passed through the series. By that time they are sup-
posed to have become modified to such an extent as to grow and multi-
ply in roots of corn.

This is to be attempted in the fifth step, to inoculate Gramineae
with modified Rhizobia. The inoculation must be conducted with great
care. Plants to be experimented upon should be placed in special glass
jars. In place of soil, quartz sand will be used with culture solution.
Plants must be grown in a medium which can be made perfectly sterile.
The modified Rhizobia are to be transferred from the culture to the
vessel containing the sterilized corn plants.

Lastly, the behavior of Rhizobia, will be carefully noted and their
life history more carefully studied. Their behavior under normal and
abnormal surroundings will be observed. Though present knowledge
concerning the life history of Rhizobia warrants undertaking the experi-
ments just outlined, yet it is quite essential that their life history
should be more thoroughly studied, especially in regard to the following
conditions:

1. Temperature. — (a) Minimum. (b) Optimum, (f) Maximum.

2. Light. — (a) Darkness, (b) Semi-darkness, (c) Green, (d) Blue. (/) Red.
(/) Yellow, (g) White light (diffused), (h) White light (direct).

3. Moisture. — (a) Very dry. (b) Moderately moist, (c) Very moist.

4. Atmospheric Pressure. — (a) High pressure, (b) Low pressure.

5. Heliotropism. —

6. Hydrotropism. —

7. Geotropism. —

These experiments are not undertaken with any desire to magnify
unduly the importance of bacteria, nor with absolute confidence of suc-
cess. As already stated, the present knowledge of Rhizobia and bac-
teria in general justifies undertaking these experiments.

RESEARCH.

The first thing was to prepare suitable culture media in which to
grow Rhizobia. For this purpose two aqueous extracts were made from
Melilotus alba, one from the roots, rootlets, and tubercles ; the other from
the upper portions of stems and leaves. They were prepared in the
following manner: About one-half a kilogram of roots and rootlets
were weighed, carefully washed, then finely chopped, and put in a jar
with one liter of distilled water. This was allowed to stand in a cool

308 BULLETIN NO. 29. [December,

place for twenty-four hours, being shaken occasionally. The juice was
then squeezed out through cloth into a beaker, and ten grams of agar
were added. After standing for twelve hours the whole was heated to
near the boiling point until the agar was dissolved. It was then filtered
through coarse filter paper in a hot water filter. The agar extract
medium of stems and leaves was prepared in a similar way. To por-
tions of these filtered media were added peptonum, pancreatin, and salt
in various proportions. Some neutral and slightly alkaline media were
made by the addition of sodium carbonate solution. Litmus paper tests
showed that the normal extracts of Melilotus roots and stems were acid
in reaction, the latter more highly than the former. These various cul-
ture media were now ready for use.

Next, plants of Melilotus alba with normal, fully formed root tuber-
cles were secured. The tubercles were removed, washed in distilled
water, and quickly dried with blotting paper which had been
passed through the flame of a Bunsen burner. The tubercle was then
passed through the flame and cut with a sharp, sterilized knife, care
being taken not to allow the knife blade to drag over the cut surface.
Test tubes with culture media were then inoculated from the cut sur-
face by means of a platinum needle. These inoculated test tubes,
numbering about fifty, were set aside in a dark chamber at the normal
summer temperature of the room. In about four or five days a whitish
growth was noticed in most tubes containing agar extract of Melilotus
roots. Examination under a medium power showed that they consisted
of organisms resembling in size and form Rhizobium Frankii, var. majus.
They were somewhat smaller, end spores less distinct, and the majority
were motile during their early life history. They multiplied from
spores as well as by transverse division. Their motility was especially
noticeable in liquid media, often when of quite mature growth. Some-
times two or even more which had just completed division moved about
with great rapidity. Their manner of movement led to the supposition
that they possessed cilia. Staining heavily with Hoffman's violet and
examining under a Zeiss' homogeneous immersion objective demonstrated
the presence of cilia. Each motile organism generally possessed two
cilia, one at either end, sometimes only one. Spores just beginning de-
velopment sometimes had as many as three or four.

Tubes containing culture medium (acid ) of stems and leaves of
Melilotus showed no development of any kind for eight or ten days,
when a small glistening colorless growth was noticed in several of them.
Examination showed the presence of much modified Rhizobiummutabile.
(Plate III, 5.) Cultures renewed from these tubes produced no
further developments. In fact all growth ceased shortly in all tubes
containing the extract of stems and leaves. The medium was no doubt
too acid in reaction. Further efforts with various acid and alkaline
media to secure pure cultures of Rhizobium mutabile were apparently

1893-] A NEW FACTOR IN ECONOMIC AGRICULTURE. 309

unsuccessful. Careful examinations of tubercles and cultures obtained
from them finally led to the following conclusions:

Tubercles of Melilotus alba contain two predominating types of
Rhizobia, namely, Rhizobium Mutabile and the above described motile
forms. These motile forms develop much more readily and by their
great numbers prevent the subsequent development of Rhizobium muta-
bile. In the living plant cells the motile Rhizobia are found in the
Infcktionsfaden of Frank. They develop first and by their irritating
presence cause the development of the Faden which now are a means of
separating the organisms from the other cell contents. This also ex-
plains the predominating presence of Rhizobia of Faden in the meristem
area of the tubercle. The motion of these Rhizobia is in the direction
of their longer axis, hence the tubes {Faderi) are produced in the direc-
tion of the greatest expenditure of energy. As already stated the irri-
tation caused by their motion induces the cell cytoplasm to deposit around
them a coating of cellulose which gives the appearance of Faden. These
are found especially in the meristem area; but since the tubercles grow
and the Faden are as permanent a structure as the cell wall, they remain
as tubes containing spores and mature Rhizobia. The Rhizobia are
always found in a position parallel to the long axis of the Faden, ex-
cept where those peculiar bulgings and swellings occur. Staining the
Faden with chlorzinc-iodine showed the presence of a wall containing
cellulose. Placing them in various culture media produced no growth
or change of any kind ; but the contained Rhizobia rapidly developed
without producing any continuation of the Faden. This demonstrated
that the Rhizobia were not the cause of the development of the Faden
and that the Faden are not living organisms. After the infected cells
of the tubercle had become more mature, the second predominating type
of Rhizobium, namely, Rhiziobiummutabile, began to develop and finally
filled the entire cell. Some tubercles, especially the older ones con-
tain, beside the predominating types, five or six other species. Since
these seem to be the conditions of affairs, it can readily be understood
how difficult it would be to obtain a pure culture.

It not being practicable to secure a pure culture of Rhizobium muta-
bile of Melilotus alba, the next attempt was to secure a pure culture of
Rhizobimn Frankii, var. majus, of Phaseolus vulgaris (garden bean), but
here much the same difficulty was found. Bean tubercles contain also the
above described motile form {Rhizobium Frankit) in small numbers. How-
ever, in order not to lose any more time, and supposing that any species of
Rhizobium would serve much the same purpose for these preliminary
experiments, bean Rhizobia cultures were continued. They readily grew
upon bean-agar extracts and also upon mixtures of corn and bean
extracts. It was supposed that they would also grow in pure corn-
agar extracts. The question for solution was, How long will it be
necessary to allow the Rhizobia to grow in corn-agar extract until they
become sufficiently modified to develop in or upon corn roots? The

310 BULLETIN NO. 29. [December,

purpose in passing the Rhizobia through a series of culture media made
from corn bean-agar extracts was to modify them gradually, else they
might finally die out, if too long continued or suddenly transferred upon
pure corn-agar extract. Though the Rhizobia developed upon pure
corn root-agar extract, yet it was plainly seen that they grew much
better in bean-agar extracts. After the Rhizobia were passed through
the series of cultures they were placed in pure corn root-agar extract,
a transfer being made every sixth day.

In one month from the time cultures were begun upon the
pure corn extract, the first trial inoculations were made upon corn
and oats plants which had been grown under the following conditions:
Lemonade tumblers of heavy glass (large size) were obtained. A small
hole was drilled through the bottom of each for drainage purposes.
These were thoroughly washed and sterilized. In the bottom of each
was placed a plug of cotton followed by one- half a gill of coarse gravel,
then another plug of cotton followed by one-half a kilogram (about
one pound) of carefully washed, tertiary quartz sand. The sand in the
vessels was then moistened with distilled water. The vessels, with con-
tents, were then placed in a hot air sterilizer for two hours at a tempera-
ture of 120° F. After the vessels were sufficiently cool they were
planted with sterilized corn (white dent) and oats and placed on a table
in the laboratory room. All the seed planted came up in about four
days. Some plants were inoculated as soon as they appeared above the
sand. Others eleven days after sprouting. Inoculations were made by
mixing contents of test tubes containing modified Rhizobia with distilled
water and pouring contents over the sand near the stems of the plants,
so as to allow as much of the fluid as possible to drain along roots and
rootlets. About twenty days after inoculation roots were washed and
examined. No tubercles were visible. Inoculated plants of corn looked
slightly more thrifty than those not inoculated and possessed more fine
rootlets. No other differences were visible to the naked eye. Micro-
scopic examination showed, furthermore, that inoculated corn plants
were infected by Rhizobium Frankii, var. majus. (Plate III, i.) Infec-
tion was by no means general. Some of the hair cells were infected,
often causing them to bulge at points of infection. Some of the epiderm-
al cells were infected. The most extensive infection took place in
parenchyma cells near the vicinity of secondary root formations, without,
however, producing any change in the size and form of the cells.
Cells were only partially filled with Rhizobia, as seen in the plate.
Inoculated corn plants also possessed more hair cells than those not inoc-
ulated. No change whatever was noticeable in oat plants.

The reader will please bear in mind that this is a preliminary report
only, and that the results of the experiments are far from being conclu-
sive. The following are, however, the probable conclusions from the
apparent results obtained

A NEW FACTOR IN ECONOMIC AGRICULTURE. 3! I

1. Rhizobia of Leguminosae are capable of being sufficiently
modified to develop to a certain extent in root cells of corn (Zea
Mays).

2. Presence of modified Rhizobia produces increased nutritive
changes in corn.

3. Presence of modified Rhizobia (modified in corn root-agar
extract) has no visible effect upon oats (A vena sativa).

BIBLIOGRAPHY.

Most of the references given in the appended list are to books and
pamphlets in the library of the Agricultural Experiment Station of the
University of Illinois. The list, though not complete, gives the refer-
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reviews. Other references are to original articles.

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* Andre, Exp. Sta. Record, U. S. Dept. Agr., 1892.

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*Bertholet, Bot, Ztg., 1890.

*Bertholet, Exp. Sta. Record, U. S. Dept. Agr., 1891, 1892, 1893.

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312 BULLETIN NO. 29. [December,

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1893-] A NEW FACTOR IN ECONOMIC AGRICULTURE. 313

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*Schneider, Revue Mycologique, 1893.

^Schneider, Bot. Centralbl., 1893.

Schroeter Natiirlichen Pflanzanfamilien, 1890.

Schulze, Landw. Jahrbucher, 1890.

Serno, Landw. Jahrbucher, H. 6, 1889.

Sorauer, Pflanzenkrankheiten, 2te. Aufl., 1886.

*Sorauer, Bot. Centralbl., 1887.

Strecker, Jour. f. Landw., 1886.

Thaer, Jour. f. Landw., 1879, 1884.

1893-] A NEW FACTOR IN ECONOMIC AGRICULTURE. 315

Tollens, Landw. Versuchs-Sta., 1891.

Treviranus, Bot. Ztg., 1853.

Troschke, Landw. Versuchs-Sta., 1884.

Troschke, Biedermann's Centralbl., 1884.

Troschke, Wochenschr. d. Pomra. Ok. Ges., 1884.

Tschirch, Ber. d. deutsch. hot. Ges., H. 2, 5, 1887

Tschirch, Centralbl. f. Bak. u. Parasit'k'de., 1887.

Tschirch, Ges. naturw. Freunde, Berlin, 1887.

*Tschirch, Ann. Agron., 1888.

*Tschirch, Forch. auf. d. Gebiete d. Agr., 1888.

Van Beneden, Archives de Biologic, 1880.

*Van Tiegham, Ann. Agron., 1888.

Van Tiegham, Bull. d. la Soc. Bot., 1888.

Vibranes, Deutsche Landw. Presse, 1893.

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Vogel, Jour. f. Landw., 1890.

Vuillemin, Jour. d. Bot.. 1888.

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Wahrlich, Bot. Ztg., 1886.

Ward, Phil. Transac. Roy. Soc., London, 1887

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*Ward, Ann. Sc. Agron., 1888.

Warington, U. S. Exp. Sta., Bull. No. 8, 1892.

*Warington, Exp. Sta. Record, U. S. Dept. Agr., 1892

Warming, Bot. Jahresber., 1876.

Weber, Bot. Ztg., 1884.

Wigand, Forch. a. d. bot. Gar. z. Marburg, 1887.

Willfarth, Beilageh. z. Riibenz. Indus., Nov., 1888.

Willfarth, Deutsche Landw. Rundschau, Nos. 8, 9, 10, n, 1892.

*Willfarth, Ann. Agron., 1888.

*Willfarth, Bot. Centralbl., 1889.

*Willfarth, Chem. Centralbl., 1893.

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Wolff, Brand des Getreides, 1874.

Woods, StorrsAgr. School, Bull. No. 5, 1889,

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ALBERT SCHNEIDER.

EXPLANATION OF PLATES.

PLATE I.— i. Longitudinal median section of portion of rootlet and developing tubercle
of Trifolium Pratense. (a) Normal hair cells. (£) Hair cell infected by Rhizo-
bia. (c] Dwarfed hair cells on tubercle, (d) Epidermal layer. (e) Infected
area of tubercle. Cells are enlarged containing Rhizobia, Infektionsfiiden,
and abnormally large nuclei, (f) Infektionsfaden containing smaller Rhizo-

316 BULLETIN NO. 29. [December,

bia. (Rhizobium Frankii?}. (Left colorless in this figure), (g) Apical area of
tubercle. Subsequent development of the tubercle is outward from this area.
(h) Area from which the vascular system of the tubercle will arise. (i) Vascu-
lar system of rootlet.

2. Semidiagramatic figures showing probable mode of the growth and extension of

the Infektionsfdden in the infected area of tubercle.

I. Single cell from the apical area of tubercle, (a) The beginning of an Infek-
tionsfdden. It is simply a group of Rhizobia surrounded by a coating of
cellulose secreted by the cell cytoplasm, (b) Another group of Rhizobia differ-
ing from those of (a). They freely mix with the cell cytoplasm and do not have a
coating of cellulose deposited around them. (Example, Rhizobium mutabile.}
(n) Neuclus of cell.

II. Later stage of the same cell. Groups (a) and (&) are enlarged. The nu-
cleus has begun to divide.

III. Later stage than II. The new cell wall (c) has begun to form, passing
through both groups of Rhizobia.

IV. Complete cell division. Two autoinfected daughter cells have developed
from the mother cell. As is seen, the Fdden are not of the same thickness
throughout. Local increase in the development of Rhizobia causes swellings.
This is nearly always the case next to the new cell wall (III and IV).

V. Group of mature cells from infected area, (a) Infektionsfdden filled with
Rhizobia (Rhizobium Frankii?}. (b] Rhizobium mutabile filling remaining portion
of cell and intimately mixed with cell cytoplasm forming the mycoplasm of
of Brunchorst and Frank.

3. Small portion of root of Melilotus alba with tubercles, (a) Developing tuber-
cles, (b) Later stage showing dichotomous mode of branching of tubercle.
(c) Single mature tubercles, (d) Grape bunch-like group of tubercles. Very
common with Melilotus.

[i and 2, highly magnified; 3 is natural size.]

PLATE II. — i. Peculiar Rhizobia sparingly present in infected cells of tubercles of
Petalostemon violaceus. As a rule, each cell contains three or four of these
organisms. •

2. Rhizobium mutabile of Trifolium (clover). (a) Spores. (b} Developing spores.

3. Rhizobium mutabile of Melilotus alba (sweet clover), (a) and (b} as in 2.

4. Rhizobium mutabile of Trifolium, later stage.

5. Rhizobium curvum of Phaseolus (bean).

6. Rhizobium Frankii, var. ma/us, of Phaseolus vulgaris.

7. Rhizobium Frankii of Infektionsfaden of Melilotus, Trifolium, and other genera

of plants.

8. Rhizobium Frankii, var. minus of Pisum (pea) Infektionsfdden. (a) Spores and

young Rhizobia with cilia.

9. Rhizobium spheroides of Pisum sativum. They often contain highly refracti ve

bodies the function of which is undetermined.

10. Rhizobium nodosum of Cassia (partridge pea).

[Highly magnified.]

PLATE III. — i. Longitudinal section of portions of inoculated corn (Zea Mays] rootlet.
(a) Hair cells infected by modified Rhizobia. Cells become somewhat enlarged
at points of infection, (b) Parenchyma cells infected by modified Rhizobia;
cells remain unchanged, (c] Secondary rootlet.

2. Rhizobium mutabile cultivated upon bean and corn root extract.

3. Rhizobittm mutabile cultivated upon corn root extract.

4. Rhizobium mutabile cultivated upon sweet clover root extract.

5. Rhizobium mutabile cultivated upon sweet clover extract prepared from stems

and leaves.

All culture media were solidified by agar-agar.
[Highly magnified.]

1893-] A NEW FACTOR IN ECONOMIC AGRICULTURE.

3'7

PLATE!

3.8

BULLETIN NO. 29.

[ December,

PLATE H.

1893-] A NEW FACTOR IN ECONOMIC AGRICULTURE. 319

Vt-

PLATE I

320 BULLETIN NO. 29. [ December, 1893. ]

ORGANIZATION.

BOARD OF TRUSTEES OF THE UNIVERSITY OF ILLINOIS.

NELSON W. GRAHAM, Carbondale, President.
JOHN P. ALTGELD, Springfield, Governor of Illinois.
DAVID GORE, Springfield, President State Board of Agriculture.
HENRY RAAB, Springfield, Superintendent Public Instruction.
FRANCIS M. McKAY, Chicago. ALEXANDER McLEAN, Macomb.

SAMUEL A. BULLARD, Springfield. RICHARD P. MORGAN, Dwight.

JOHN H. BRYANT, Princeton. NAPOLEON B. MORRISON, Odin.

JAMES. E. ARMSTRONG, Chicago. ISAAC S. RAYMOND, Sidney.

BOARD OF DIRECTION OF THE EXPERIMENT STATION.

GEORGE E. MORROW, A.M., Champaign, Professor of Agriculture, President.
E. E. CHESTER, Champaign, of State Board of Agriculture.

R. T. FRY, Olney, of State Horticultural Society.
H. B. CURLER, DeKalb, of State Dairymen's Association.

N. B. MORRISON, Odin, Trustee of the University.

ISAAC S. RAYMOND, Sidney, Trustee of the University.

THOMAS J. BURRILL, PH.D., Urbana, Professor of Botany and Horticulture.

STEPHEN A. FORBES, PH.D., Urbana, Professor of Zoology.
EDWARD H. FARRINGTON, M.S., Champaign, Chemist of Station.

THE STATION STAFF.

GEORGE E. MORROW, A.M., Agriculturist, President of Board of Direction.

WILLIAM L. PILLSBURY, A.M., Champaign, Secretary.
THOMAS J. BURRILL, PH.D., Horticulturist and Botanist.

EDWARD H. FARRINGTON, M.S., Chemist.
STEPHEN A. FORBES, PH.D., Consulting Entomologist.

DONALD McINTOSH, V.S., Consulting Veterinarian.

GEORGE W. McCLUER, B.S., Assistant Horticulturist.

GEORGE P. CLINTON, B.S., Assistant Botanist.

WILL A. POWERS, B.S., Assistant Chemist.
FRANK D. GARDNER, B.S., Assistant Agriculturist.

UNIVERSITY OF ILLINOIS-URBANA

Q.630.7IL6B C002

BULLETIN. URBANA
17-361891-94

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