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Full text of "Effects of the rays of radium on plants"

'X*-. 



MEMOIRS 



New York Botanical Garden 



Vol. IV 



EFFECTS OF THE 
RAYS OF RADIUM ON PLANTS 



CHARLES STUART GAGER, Ph.D. 




Tsst-ied Dec. '2, 1908 



1-1 

MEMOIRS 

OF THE 

New York Botanical Garden 

Vol. IV 



EFFECTS OF THE. 
RAYS OF RADIUM ON PLANTS 



BY 



CHARLES STUART GAGER, Ph.D. 




Issued Dec. 2, 1908 



EFFECTS 



OF THE 



RAYS OF RADIUM ON PLANTS 



BY 



CHARLES STUART GAGER, Ph.D. 



Published by the aid of the 

David Lydig Fund 

Bequeathed by Charles P. Daly 



NEW YORK 
1908 



7 



» ^ 



5 



Press of 

The new Era printing compan* 

Lancaster Pa 



PREFACE 

The investigations embodied in this Memoir were begun in the 
autumn of 1904, with the intention of making them a minor problem 
during a year's residence at the New York Botanical Garden. On 
account of the scarcity of radium the work progressed slowly, for it 
was seldom that more than one or two experiments could be con- 
ducted simultaneously. When it became certain that the facilities of 
the Garden laboratories would be available for an indefinite period, 
other work was made secondary to the radium problem, for the rela- 
tively large quantities of radium and radium preparations placed at 
my disposal created an opportunity too valuable to let pass unim- 
proved. 

Chapter I. contains, in concise, non-technical language, informa- 
tion that is widely scattered in publications, many of which are not 
easily accessible or familiar to botanists. This information, however, 
is absolutely essential in order to understand the discussions that fol- 
low, and it was deemed advisable to include it. 

The problem was originally suggested by Dr. William J. Gies, 
Consulting Chemist of the New York Botanical Garden, and it is a 
pleasure to acknowledge his helpful suggestions during the earlier 
progress of the work. 

The investigations would not have been possible had it not been 
for the munificent liberality of Mr. Hugo Lieber, of the firm of H. 
Lieber & Co., of New York City. Mr. Lieber has freely placed at 
my disposal some $3,000 to $4,000 worth of standard preparations 
of the purest radium bromide yet obtained, as well as weaker prepara- 
tions of radium, polonium, and radio-tellurium. As stated in detail in 
the pages that follow, he has devised apparatus, and made other 
apparatus at my suggestion, without which many of the experiments 
could not have been performed. It is not possible adequately to ex- 
press in words my sincere gratitude to Mr. Lieber, not only for his 
great liberality, but also for the kindly interest he has maintained in 
the research throughout its entire progress. 

C. Stuart Gager. 

New York Botanical Garden. 



TABLE OF CONTENTS 

Chapter Page 

I. The Discovery AND Nature OF Radioactivity i 

II. Radioactivity A Factor OF Plant Environment 22 

III. Previous Investigations upon Animals 43 

IV. Previous Investigations upon Plants 56 

1 . Effects of Rontgen Rays on Plants 56 

2. Effects of Radium Rays on Plants 59 

3. Effects of Radium Rays on Plant Fibers 68 

V. Bio-Radioactivity, Eobes, Radiobes 74 

1. The Supposed Radioactivity of Plants and Wood 74 

2. The Professed Artificial Creation of Life 76 

VI. Radium Preparations and Methods of Exposure 81 

VII. Effects on Growth of Exposing Seeds to Radium Rays 84 

1. Effects on Growth of Exposure of unsoaked Seeds 84 

2. Effects on Growth of Exposing Seeds while soaking 90 

3. Effects on Growth of Exposing soaked Seeds 102 

4. Effect of Duration of Exposure and Degree of Activity., iii 

VIII. Effects of Radium Rays in the Soil on Germination 

AND Growth 135 

IX. Effects of a Radioactive Atmosphere on Plant 

Growth 146 

X. Effects on Plant Growth of Exposed Water and 

Freshly Fallen Rain 158 

1. Effects of Tap- Water exposed to Radium Rays 15S 

2. The Radioactive Influence of freshly fallen Rain- Water.. 173 
XL Effects on Plant Growth : Miscellaneous Experi- 
ments 1 80 

XII. Effects of Radium Rays on the Synthesis of Carbo- 
hydrates 188 

1. Effect on Photosynthesis 188 

2. Effect on the Conversion of Cane-Sugar to Starch in the 

Dark 191 

3. Effect on Chlorophyll Solution and Chlorophyll Paste... 193 
XIII. Effects of Radium Rays on Plant Respiration 196 

1. Effect on Aerobic Respiration 196 

2. Effect on Anaerobic Respiration 202 



Vlll TABLE OF CONTENTS 

Chapter Page 

XIV. Effects of Radium Rays on Alcoholic Fermentation... 206 

XV. Effects of Radium Rays ox Tropistic Response 216 

1 . Effects of the Rays on Normal Tropisms 219 

2. Can Radium Rays cause Tropistic Response.'* 219 

XVI. Histological Effects OF THE Rays OF Radium 223 

XVII. Effects of Radium Rays on Nuclei and Nuclear Divi- 
sion 230 

XVIII. Effects of Exposing Germ-Cells to the Rays of Radium 235 

XIX. Theoretical Considerations 257 



EFFECTS OF THE RAYS OF RADIUM ON 

PLANTS 



CHAPTER I 
THE DISCOVERY AND NATURE OF RADIOACTIVITY 

The Discovery of Cathode Rays : The discovery of radio- 
activity was dimly foreshadowed as far back as the year 1838, when 
Michael Faraday, ^^ studying the discharge of electricity through rare 
gases, noted the fact that there was always a dark space between the 
glows surrounding the positive and negative poles in the vacuum tube. 
Fourteen years later Grove ^''observed and described the stratified ap- 
pearance of the electric discharge through very rare gases. Gassiot ^* 
further studied the stratification, and found that there were two dis- 
tinct forms of stratified discharge, and that they could be deflected 
and thus separated by a magnet. He *' later described the negative 
discharge in a vacuum tube, and ascertained, not only that it could be 
deflected by a magnet, but that, wherever the charge impinged, " a 
brilliant blue phosphorescent spot is perceivable, which spot is in a 
short time sensibly heated." Gassiot concluded that there is the ap- 
pearance of " a direction of a force emanating from the negative," and 
inferred from his experiments that an electric current cannot pass 
through a perfect vacuum; the intervention, he said, of a certain 
amount of matter is necessary. Four years later he ^^ published the 
results of experiments confirming these conclusions, and stated that 
there was " an actual disruption of particles from the negative termi- 
nal," which indicates force there. 

The idea of cathode rays was more fully and accurately expressed 
by Hittorf,^^ whose paper, *' Ueher die Electricitdts-Leitung der 
Gase,'"\i^2irs the date of October 9, 1868, and was published in 1869, 
six years after Gassiot's announcement. 

Lord Kelvin's*^^ statement* that the " kathode torrent" was dis- 

* Made also by Rutherford, 'i^ p. 73. 
2 I 



2 DISCOVERY AND NATURE OF RADIOACTIVITY 

covered by Varley seems, therefore, rather extreme. Varley^^'" cor- 
rectl}'^ interpreted the cathode rays as " attenuated particles of matter 
projected from the negative pole by electricity in all directions"; he 
also caused these rays to produce motion by deflecting a thin plate of 
talc suspended in the vacuum tube by a silk liber. The rays were 
deflected so as to impinge on the talc by a magnet, and the spot where 
they struck the talc was observed to become luminous. 

In the year 1879, ^^^ William Crookes"^ published the results of his 
wonderful experiments on the passage of electricity through very rare 
gases. These experiments confirmed beyond question * the obser- 
vation of Varley that, when the gas in a glass tube is exhausted to 
about one ten-thousandth of an atmosphere, a stream of material 
particles passes from the negative pole in the tube. It was already 
well known that a moving conductor carrying a charge of electricity 
could be deflected by a magnetic force. The stream of particles ob- 
served by Crookes could be thus deflected, and, furthermore, they 
could impart motion to a movable object placed in their path, f and could 
cast a shadow, as Hittorf had previously shown. Crookes concluded 
that they revealed a fourth state of matter. " The phenomena in 
these exhausted tubes reveal to physical science a new world — a 
world where matter may exist in a fourth state, where the corpuscu- 
lar theory of light may be true, where light does not always move 
in straight lines, but where we can never enter and with which we 
must be content to observe and experiment from the outside."^" It 
was to this stream of negatively charged particles that the name 
cathode rays was given. " We have actually touched the border- 
land," said Crookes, " where Matter and Force seem to merge into 
one another. . . ."^^ 

Perrin,^®' ^'' some years after, showed that the particles composing 
these rays carry charges of negative electricity. Two years later 
Thomson ^^^ verified the work of Perrin, and determined a most im- 
portant figure, viz., the value of the ratio of the charge to the mass 
(e/m) of an individual particle from the cathode, and ascertained the 

*The German school was slow to abandon its position that the phenomena in a 
Crookes tube were a kind of ether-wave. The -work of Varley and Crookes proved that 
hypothesis erroneous, and it is nowhere held at present. 

t Thomson •*" later stated that the rotation of mill-wheels by the bombardment of 
the cathode rays is to be considered, not as due to momentum imparted by their par- 
ticles, but to a secondary effect, due to the rays making the vanes hotter on one side 
than on the other, thus producing a radiometer action. 



DISCOVERY AND NATURE OF RADIOACTIVITY 3 

velocity of the particles. He found the mass to be one one-thou- 
sandth that of a hydrogen atom. 

Lenard Rays : Hertz ^^ discovered that cathode rays will pass 
through thin aluminium foil inside of a Crookes tube. This proved 
that aluminium is transparent to the particles constituting these rays. 
Acting on this suggestion, Lenard ^^ succeeded in producing cathode 
rays in a tube containing a window of aluminium. Some of the ray-s 
passed through the window, and Lenard was thus able to experiment 
with cathode rays outside of the tube, and to demonstrate that they 
carry a charge of negative electricity. Thus the statement of Crooks, 
quoted above, that we must be content to observe and experiment 
with cathode rays " from the outside," no longer held true. Cathode 
rays that have passed outside of a Crookes tube have been called 
Lenard rays. 

The researches above referred to became the foundation stones 
for the new science of radioactivity. 

Divisibility of the Atom : In 1899, Professor J. J. Thomson 
found that carriers of negative electricity are given off from a red 
hotwire in a vacuum, and it was for these carriers that he proposed 
the name corpuscle. In Thomson's paper, also, we find one of the first 
statements, based upon experimental evidence, that the atom is not 
the limit of physical divisibility. "I regard the atom," says Pro- 
fessor Thomson, ^^'' " as containing a larger number of smaller bodies 
which I will call corpuscles. ... In the normal atom this assem- 
blage of corpuscles forms a system which is electrically neutral." 

The term electron * has largely supplanted that of corpuscle. 
The mass of an electron is always the same, no matter from what 
gas, or from what solid produced, or by what means. It has the 
smallest mass of any known body. It will be noted later that an 
electron can be split off from the atom of probably every known sub- 
stance. This fact leads to the immensely important inference that 
unit charges of negative electricity are constituents of the atoms of 
all matter, or, in other words, that the nature of all matter, organic 
or inorganic, is electrical. In fact the work of Professor Thomson 
lends much probability to the conclusion that the entire mass of the 
corpuscle is electrical, that it is a disembodied charge of negative 
electricity, and that matter and electricity are one and the same thing. 

Ionization : When an electron passes through a mass of a gas 

* Coined by Dr. G. Johnstone Stonej. Kelvin wrote it " electrion." 



4 DISCOVERY AND NATURE OF RADIOACTIVITY 

it will collide with some of the molecules of the gas. As a result of 
this collision, a unit charge of negative electricity (electron) may be 
torn from the molecule. The remaining portion of the molecule, by 
virtue of the loss of the electron, is positively charged. Such a sepa- 
ration of molecules into negatively and positively charged units is 
called ionization. Each of the units is a gaseous ion^ and the gas is 
said to be ionized. 

At low pressures, such for example as obtain in a vacuum tube, 
the electron is all there is of the negative ion, and the positively 
charged remainder of the molecule constitutes the positive ion ; * but 
at atmospheric pressure each of these charged bodies becomes the 
center of aggregation of several molecules, and then the central 
charged nucleus, together with the surrounding molecules^ is regarded 
as an ion. Gaseous ions are positive or negative according to their 
charge. 

It is essential not to confuse the free gaseous ions with the ions of 
electrolytes in solution, and the employment of the same term in two 
senses is, in some ways, unfortunate. Negative gaseous ions are frag- 
ments of atoms, while the ions of electrolytes in solution result from 
the splitting up of molecules. The mass of a free negative gaseous 
ion is about t^.^^ the mass of a H ion in solution (Jones), but they both 
carry the same kind of a charge. The free negative ions, or elec- 
trons, are the same as the "satellites" of Kelvin, and the "cor- 
puscles " or " particles " of J. J. Thomson. Electrons do not behave 
as a gas. They cling to positively charged bodies, and, if left quiet, 
settle on the walls of the containing vessel. 

Discovery of X Rays : Three years previous to Thomson's 
proposal of the term corpuscle, Rontgen -"^-^^ read before the Wiirz- 
burg Physico-Medical Society his epoch-making communication on 
the X rays, and later in the same year Perrin^' and Stokes ^^^ showed 
that X rays are probably electro-magnetic pulses in the ether, and 
develop at any place where a body arrests the motion of the elec- 
trons of the cathode rays. This conception was subsequently more 
fully expressed by Thomson. '^^ Thus when the cathode rays are 
stopped b}^ the walls of the Crookes tube, X rays result. Here was 
a new kind of ray that could pass through bodies opaque to ordinary 
light, and darken a photographic negative. f 

*The mass of positive ions varies with the substances from which thej are pro- 
duced. 

t The eftect of X rajs on a photographic negative was in reality a later discovery. 



DISCOVERY AND NATURE OF RADIOACTIVITY 5 

Rays of Niewenglowski : The phenomenon of X rays was 
always associated with phosphorescence, and Henri Poincare'^'' had 
already suggested that the two phenomena might bear a causal rela- 
tion to each other. Experiments with phosphorescent sulfide of zinc, 
by Henry, *^" led to the discovery that a coating of that substance on a 
body, otherwise opaque to the X rays, rendered the body transparent 
to them. Rays that could penetrate matter opaque to ordinary light 
were obtained by Niewenglowski^^ in 1896 with several phosphores- 
cent bodies after exposing them to sunlight. He obtained the image 
of a piece of money on sensitive paper that was protected from light 
rays by rays from phosphorescent sulfide of calcium that had been 
exposed to sunlight. 

Becquerel Rays and the Discovery of Radioactivity ; In 
the same eventful year of 1896 Becquerel ^ confirmed Niewen- 
glowski's results, and experimented with, among other substances, 
various salts of uranium. Finally he ^ demonstrated that exposure 
to sunlight was not necessary, but that salts of uranium that had 
never been exposed to light gave out invisible rays that could pass 
through opaque objects and darken a photographic plate. Further- 
more, while uranic salts are phosphorescent, the uranous salts are 
not, though both possess the property of radioactivity. Thus it was 
shown that the phenomenon is not necessarily connected with phos- 
phorescence. 

It was recognized^ that Becquerel rays were very similar to X rays, 
and since all the salts of uranium, whether they had ever been ex- 
posed to light or not, and whether crystallized or dissolved, gave rise 
to the rays, the latter were thought to be due to uranium. Experi- 
ment showed that metallic uranium was strongly active. "Uranium," 
said Becquerel,'' " is the first example of a metal manifesting a phe- 
nomenon of the nature of an invisible phosphorescence." These in- 
visible rays from uranium that can pass through matter opaque to 
ordinary light and darken a photographic plate, are known as 
Becquerel rays. 

The Discovery of Radium : After Becquerel's discovery. Mon- 
sieur and Madame Curie, of Paris, began to examine different min- 
erals containing uranium in order to see if they gave off Becquerel 

Rontgen's first hint of the rays was their effect on barium platino-cyanide paper (Nov. 
8, 1895). In the following year Troost "* announced that artificial hexagonal blend 
gave off X rays, and could be substituted for the Crookes tube in many experiments. 



6 DISCOVERY AND NATURE OF RADIOACTIVITY 

rays. Some thirteen minerals were found to possess this property, 
and among them pitchblende was the most active.* One of the first 
results of their work was the discovery of foloniitm^ the first 
substance emitting Becquerel rays to be isolated from pitchblende. 
It was named by Madame Curie from Poland, her native country. 
In this paper Madame Curie ^^ also proposed the term radioactive for 
all substances giving rise to rays of this nature. Later in the same 
year M. and Mme. Curie and Bemont''' announced the discovery of 
radium, f and the fact that it was a new element was confirmed spec- 
troscopically by Demarcay.*^ The atomic weight of radium, as 
determined by Mme. Curie, is 225, while Wilde's "* determination 
gives 232. The atomic weight of uranium is 240. The results of 
Mme. Curie's researches up to the year 1904 are embodied in her 
TheseJ'^ 

It remains now to trace very briefly the researches that have led 
to a clear understanding of the nature of radioactivity, and its general 
distribution in nature. 

The Complexity of the Rays : In 1899 Rutherford ^"^ made the 
discovery that the rays of uranium are complex, consisting of at 
least two kinds, to which he gave the names « rays and /5 rays. 

Cathode Rays from Radium ; Beta Rays : In the same year 
Giesel,'^^ Meyer and von Schweidler,"'' and Becquerel^ all discovered 
independently that rays from radium were deflected by a magnet, 
and in the following year (1900) BecquereP showed that their 
behavior in the magnetic field was quite similar to that of cathode 
rays. Evidently, then, here was a type of cathode ray given off by 
certain bodies spontaneously, and at atmospheric pressure. Follow- 
ing up these experiments, M. Curie ^ demonstrated, as Rutherford 
had the year previously for uranium, that the rays given off by 
various radioactive bodies are complex, consisting of at least two 
kinds of rays, one deviable by the magnetic field, and the other not. 
The deviable rays, said M. and Mme. Curie, •^'' are charges of nega- 
tive electricity. In 1902 Rutherford ^"^ announced that the negatively 
charged particles emitted by both uranium and radium are similar 
in all respects to cathode rays. The /9 particles vary considerably in 
velocity between certain limits, thus introducing a complexity into 
the nature of the /9 ray. 

*Afanasjew (1900) has since examined 51 minerals, and found that all containing 
uranium and thorium can blacken the photographic plate. 
t See also citation No. 40. 



DISCOVERY AND NATURE OF RADIOACTIVITY" 7 

Positive Ions from Radium ; Alpha Rays : It was Strult '^^ 
who first suggested that the less deviable, or a rays were streams of 
positively charged particles, and the experimental confirmation of 
this hypothesis was reported by Crookes^^ in the following year. 
One year later Rutherford ""^^ demonstrated that the a. rays could be 
deviated in a magnetic field, and in a direction opposite to that of the 
^ rays, thus further confirming the fact that they carry a positive 
charge.* The a. particles from radium were shown to have twice 
the mass of a hydrogen atom. Further communications by Thom- 
son"^'"^ and by Rutherford"^ established beyond reasonable doubt that 
the a. rays of radium and other radioactive substances, consist of a 
stream of positively charged particles, shot off from radioactive 
bodies, but with a velocity much less than that of the electrons. 
Rutherford ^^'^ has recently calculated that the velocities of expulsion 
of the a particles from various radioactive substances all lie within a 
range of 1.56 X lo** and 2.25 x 10^ cm. per second.! Thomson '^^ 
also showed that bodies struck by the a rays from polonium have a 
positive charge communicated to them. Because of their greater 
size and less velocity, the particles of the a. rays are much less pene- 
trating than are those of the /9 rays. Rutherford and Grier ^^^ have 
shown that a layer of aluminium .09 mm. thick completely absorbs a 
rays. Not all of the a particles have the same velocity, for, since 
their motion is retarded by passing through matter, those coming from 
different depths of a thick layer of radium will have unequal veloci- 
ties, those from the surface moving fastest. For this reason a. rays 
like /9 rays are not simple but complex.:]: The a. particle, losing its 
positive charge, becomes a helium atom.'"^" 

Thomson found, in the course of his experiments, that both 
polonium and radium emit slowly moving cathode rays which cannot 
penetrate aluminium foil easily penetrated by /? rays. Swinton ^^* 
has recently shown that anode rays that have passed through perfora- 
tions in the cathode terminal (" canal rays ") may cause rapid motion 
of mill wheels, just as Crookes demonstrated for cathode rays. 

* Experiments indicate that the a particle acquires its positive charge as the result 
of ionization through collision. See Bibliography, p. 14, Nos. 17, 18, 113, and 77. 

Whether the a particle is a molecule of hydrogen, an atom of helium, or a helium 
molecule carrying twice the ionic charge, is not easily decided (Rutherford"*), but 
the results obtained by Cameron and Ramsay'* seem to indicate that the a particle and 
helium are not identical. 

tBy the photographic method Des Coudres^' found the velocity (V) of the a 
particles from radium to be 1.65 X lo' cms. per second. 

t Cf. citations Nos. »i7, 12, 21, ii6. 



8 DISCOVERY AND NATURE OF RADIOACTIVITY 

X Rays from Radium ; Gamma Rays : It was Villard •^''' ^" who 
discovered that radium, besides emitting a and ^ rays, is the source 
also of a non-deviable ray, analogous to very penetrating or " hard " 
X rays. Becquerel,'" Strutt,^^^ and Eve ^^ also identified the very 
penetrating, non-deviable rays. Now a type of X ray arises whenever 
a ^ particle is either started or stopped, and Strutt considered that 
the non-deviable rays from radium arise secondarily by the self-bom- 
bardment of the radium by the /? particles. Ashworth,^ on the other 
hand, supported the theory that these rays were not of a secondary 
nature, but resulted directly from the disintegration of the radium- 
atom. Finally Rutherford '"^ showed that this " hard " type of X ray 
(a narrow electro-magnetic pulse) arises from radium by atomic dis- 
integration, while a " soft " type of X ray (a broad electro-magnetic 
pulse) arise at the points where the /3 particles strike another body. 
The non-deviable rays were named by Rutherford y rays. 

The Emanation : In addition to the giving off of three types of 
rays as above indicated, it was found by Rutherford '"^ that a radio- 
active gas diffuses from thorium, and in the same year Dorn ^" deter- 
mined the same fact to be true of radium. To this heavy, radio- 
active gas Rutherford gave the term emanation* Its gaseous nature 
was confirmed by Rutherford and Brooks.*^"- ^^^ The emanation was 
found to condense at — 150° C.,^" and in 1904 its spectrum was 
mapped by Ramsay and Collie. ^'^ Ramsay,''^ also, gave further evi- 
dence that the emanation is a gas by showing that it obeys Boyle's 
law. About three fourths of the activity of radium, according to 
Rutherford,^"' is due to the emanation. 

The Nature of Radioactivity: In brief, then, we know that 
certain elements of very high atomic weight are giving rise, spon- 
taneously, to three types of mvisible radiation, as follows : 

I. A stream of positively charged particles, with slight pene- 
trating power, with a mass twice that of an atom of hydrogen, and 
moving with about one tenth the velocity of light. Streams of these 
particles constitute the a. rays. The u. rays consist of " veritable 
atoms of matter projected at a speed, on an average, of 6,000 miles 

* Sir George Stokes proposed to Crookes^^ a systematic nomenclature in radiology 
as follows: "Ray — A disturbance propagated in the ether. Jet — A discharge of 
electrons. Emanation — To include both Rays and Jets." The distinction between 
the first two terms has obvious advantages, and is used by Crookes in the paper above 
cited. The term emanation, however, is now firmly established as referring to the 
radioactive gas. 



DISCOVERY AND NATURE OF RADIOACTIVITY 9 

an hour. They cause most of the ionization observed near an un- 
covered radioactive substance." The a particle travels 3.5 cm. 
through air before it is stopped, breaking up, or ionizing, in this path 
about 100,000 molecules. 

2. A stream of negatively charged electrons, moving with a 
velocity of from \ to -^-^ the velocity of light, having a mass yiro ^^ 
mass of a hydrogen atom, very penetrating to substances opaque to 
ordinary light, and giving rise, when stopped, to a ray analogous to, 
if not identical with, the X ray. Streams of these particles constitute 
the /9 rays. 

3. An electromagnetic pulse in the ether, exceedingly pene- 
trating to opaque bodies, and similar in all respects to the Rontgen or 
Xray. These pulses are called j' rays. Not all radioactive substances 
give off all three kinds of rays. Only a rays, for example, are 
emitted by polonium. 

In October, 1907, Bragg ^^ put forward the hypothesis that, in 
addition to positive and negative particles, atomic disintegration may 
give rise to the emission of neutral particles, " such as, for example, 
a pair consisting of one a. or positive particle and one /? or negative 
particle." It is not impossible, he says, that the y rays, instead of 
being ether pulses, may consist of streams of these neutral pairs, and 
all the known properties of the 7- rays, as well as of X rays, are satis- 
fied on this hypothesis. In a later paper he"" states that ether pulses 
are a component of both X and ^rays, but do not compose the entire 
phenomenon of the ray. Cooksey,"^ from his experiments, was un- 
able to accept Bragg's view, and Kleeman's ''" experiments led him to 
adhere to the older theory that y and X rays are, in general, alike, 
both consisting of electro-magnetic pulses produced by the accelera- 
tion of electric charges. 

4. In addition to the three types of rays, there is given off a very 
dense, chemically inert, radioactive gas, which slowly diffuses from 
radium (and also indirectly from thorium and actinium). The atom 
of the emanation gives off, in its diisntegration, only a particles.* 

* Experiments of Rutherford "' indicate that the emanations of radium, thorium and 
actinium differ from the other inert gases of the argon family in the fact that, in the 
small amounts in which it is available, it is absorbed by charcoal. 

By comparing the rate of diffusion of radium emanation with that of mercury 
vapor, Perkins*^ determined the molecular weight of the emanation to be 235. This 
excess over the atomic weight of radium is explained by Perkins as due to experimental 
errors. On the basis of the disintegration theory of Rutherford, and considering the 
emanation as a monatomic gas, its molecular weight should be nearly that of the 
atomic weie^ht of radium. 



lO DISCOVERY AND NATURE OF RADIOACTIVITY 

Beta rays and alpha rays are both vehicles of energ}-. Owing to 
their high speed and relatively minute size, the particles of the /9 rays 
may penetrate great numbers of atoms, passing through the spaces 
between the electrons that compose them. Under such conditions 
they continue in their path without deflection ; but when a /9 particle 
collides with an electron the latter may be torn from the atom and set 
free (ionization). The ion may not always be torn from the atom by 
the collision, for the impact may serve only to deflect it from its 
path. In either event the [^ particle will lose energy, will therefore 
travel more slowly, and hence be thereafter more easily deflected. 

The particles of the a rays are more effective ionizers than the 
electrons, but, owing to their relatively large size, they are not easily 
deflected by collision. Hence the a particle loses energy chiefly by 
collision. 

It is partly for the reasons just described that both the a and the 
[i rays, as stated above, are complex. They are both composed of 
streams of particles possessing widely varying amounts of energy. 

The Complexity of the Atom : A conception of the atom 
such as the discoveries in radioactivity compel us to adopt, has been 
expressed by Perrin in a very striking figure. He likens the atom 
to a miniature planetary system. If a suitable force acts on an atom 
strongly enough it disengages a negative planet, or electron, produc- 
ing thereby ionization. If the atom is very unwieldly, that is, rela- 
tively very large, and the corpuscle far from the center — the 
Neptune of the system — it will be loosely held by the electrical 
attraction of the remainder of the atom, and so more easily separated 
from it. In a somewhat speculative calculation, based upon the 
energy liberated in radioactive processes, Campbell ^^ has estimated 
that " the number of electrons in a radium atom must be greater, 
and probably very much greater than 1,200." 

Theory of Atomic Disintegration : The researches of Ruth- 
erford and Soddy,^-^ of Thomson, ^^^ and of Rutherford all indi- 
cate that radioactivity is a manifestation of sub-atomic change. "In 
its simplest form," says Rutherford, ^^^ "the theory (of atomic dis- 
integration) supposes that every second a certain fraction (usually 
very small) of the atoms present become unstable and explode * with 

* Sir Oliver Lodge, in a recent discussion of Lord Kelvin's philosophy (Nature 
76: 198. 2 Jl 1908), has called attention to the difference between the static and the 
kinetic conceptions of the atom. " The internal energy of Lord Kelvin's model atom 



DISCOVERY AND NATURE OF RADIOACTIVITY II 

great violence, expelling in many cases a small portion of the disrupted 
atom at a high speed. The residue of the atom forms a new atomic 
system of less atomic weight, and possessing physical and chemical 
properties which markedly distinguish it from the parent atom. The 
atoms composing the new substance formed by the disintegration of the 
parent matter are also unstable, and break up in turn. The process 
of disintegration of the atom, once started, proceeds through a num- 
ber of distinct stages. These new products formed by the succes- 
sive disintegrations of the parent matter are in most cases present in 
such extremely minute quantity that they cannot be investigated by 
ordinary chemical methods. . . . For any simple substance, the aver- 
age number of atoms breaking up per second is proportional at any 
time to the number present. In consequence the amount of radio- 
active matter decreases in a geometrical progression with time." 
Rutherford'"^ illustrates these changes by the following diagram* 
(figure i). The time periods given indicate how long is required 




oo 




RAOIUNl EMAN. FtAD.A RAO.B RADC RAD.D RAD.E RAD F RAD.G 

iOOQifr3. zjSiaAji Smins,. zSmini- iSmina. •'K)j<ri. Sdaj^& 4SAaAfa /4oa<U)-s. 

f^aetio-LeO'i' RaiiO'Tcfluriurry.Thtoniujn J 

-v— ' 

Active Deposit Rapid Change Active Deposit Slow Change 

Fig. I. Theory of Atomic Disintegration. (After Rutherford.) 

forthe given product to become half transformed. Thus, it requires 
2,000 years f for a given quantit}^ of radium to become half trans- 
formed into the next following product. 

Uranium is now generally regarded as the ancestor of radium, 
but there are several intermediate disintegration products of uranium, 
and of these tonmni, discovered by Boltwood,^^ may be the immediate 

is static or potential. The internal energy of the hypothetical atom at which others 
are working is kinetic. 

" The disintegration of radium in the former case is comparable to the explosion 
of an unstable chemical compound, like gun-cotton. In the latter case it must be rep- 
resented by something more akin to the flying to pieces of a single rapidly spinning 
unit, such as a fly wheel." 

*Duane** states that radium 5, formerly held by Rutherford "^ to be non-radio- 
active, emits as much negative electricity as does radium C. 

t Results obtained by Boltwood'^ on the growth of radium in preparations of 
ionium separated from uranium minerals indicate that the half-value period for radium 
is 2,000 years. Rutherford'-^" gives 1,760 years. 



12 DISCOVERY AND NATURE OF RADIOACTIVITY 

parent of radium. All the a rays given off by the same product be- 
have alike, but the particles from the different products are quantita- 
tively unlike, though qualitatively similar. 

Phosphorescence : It was the association of phosphorescence 
with X rays that led to the discovery of radioactivity. As might 
be expected, radium is phosphorescent. The source of this light is 
not definitely known, but experiments of Lord and Lady Huggins^" 
seem to indicate that the luminosity is not due to the /9 rays. 

Measurement of Activity : Eve"^ has shown that the activity 
of radium is a function of the amount present ; therefore the purer 
the radium salt the greater the activity, weight for weight. The de- 
gree of activity is stated in terms of that of uranium as a standard. 
Thus, to indicate that a given preparation is of 10,000 activity 
(10,000 X ), means that it is ten thousand times as active as an equal 
weight of uranium. The purest radium bromide so far obtained has 
an activity of 1,800,000. The activity of a given radium prepara- 
tion enclosed in a sealed glass tube shows no signs of decreasing 
with time. The intensity of activity, according to Rutherford,^"® 
does not vary with the concentration of the salt. In his experi- 
ments, " a distribution of the radiating matter over a thousand times 
its original volume has no appreciable influence on its original 
activity." 

Amount of Energy Evolved : The results of Curie and La- 
borde,'^® confirmed by Runge and Precht,'** indicate that one gram of 
radium emits energy at the rate of 100 gram-calories per hour, or 
2,400 per day. Rutherford"^ has pointed out that this is nearly as 
much energy as is required to dissociate one gram of water (3,900 
gram-calories). Rutherford"^ has calculated that the total energy 
of radiation during the disintegration of one gram of radium is 
1.6 X 10^ gram-calories, and the energy radiated may not represent 
all of the energy involved in the change. The energy of the trans- 
formation is at least twenty thousand times, and may be a million 
times as great as the energy of any molecular change, such, for 
example, as that involved in the union of hydrogen and oxygen to 
form water. Ramsay ^^ states that the emanation given off by one 
gram of radium evolved 75 calories in one hour. 

In replying to expresssions of doubt as to the validity of the 
foundations of the theory of atomic disintegration, Soddy ^^^ empha- 
sized the fact that it is firmly grounded on experimental evidence, 



DISCOVERY AND NATURE OF RADIOACTIVITY 1 3 

that no fact has been adduced that does not conform to it, and adds 
that it is impossible to form " from words or reading the least idea of 
the really startling character of some of the new discoveries." 

Effect of External Conditions : As might be inferred from 
the fact that radioactivity is neither a molecular nor an atomic, but a 
sub-atomic change, external conditions have no effect upon it. It is 
not affected by temperatures ranging from 200" C. to that of liquid 
air, nor by variations in atmospheric pressure. The emanation, of 
course, being a gas, diffuses from the radioactive body more slowly 
under increased pressure and lower temperature, and the rate of 
escape is greater in moist air, and when the radioactive salt is in 
solution, but its radioactivity is not thereby affected in the least.* 

Excited Radioactivity : It has been found that bodies under 
certain conditions of exposure to radioactive substances become 
themselves radioactive. Radioactivity thus produced is called ex- 
cited radioactivity. Rutherford ^"^^ demonstrated that the presence of 
the emanation is necessary in order to produce excited radioactivity, 
and later (1903) showed that the excited radioactivity is due to a 
deposit of radioactive matter (called the "active deposit") from the 
emanation of either thorium or radium. 

Origin of Radium : The observation of Lord and Lady Hug- 
gins ^^ of the gradual appearance of the spectrum lines of helium in 
the spectrum of radium is the first demonstration in the history of 
science of the origin of one chemical element from another. Ramsay 
and Soddy ^^ in the same month (July, 1903) announced their obser- 
vation that gases occluded by 20 mg. of radium bromide contain 
helium, and soon thereafter they ^^ observed the spectrum lines of 
helium gradually appear in the spectrum of the radium emanation 
after it has stood for four days, thus confirming the results of Lord 
and Lady Huggins. Further confirmation of this transformation was 
published by Dewar and Curie, ^■' and by Himstedt and Meyer."- 

The observation of the actual transmutation of one element into 
another suggests the question as to the origin of radium. In 1903 
Rutherford and Soddy ^-^ suggested that radium is a disintegration 
product of one of the other radioactive substances found in pitch- 
blende. Soddy ^^^ in 1904 expressed his belief that uranium is the 
source of radium, and in 1905 obtained'^" experimental evidence that 

♦Makower" states that the activity of the radium emanation measured by the rays 
it gives off can be changed by high temperature, but this has not yet been confirmed. 



14 DISCOVERY AND NATURE OF RADIOACTIVITY 

the radium atom results from the disintegration of the atom of 
uranium. Two years later McCoy ^^ stated that the results of his 
experiments confirm the conclusion that uranium is the parent, not 
only of radium, but also of all other active substances that accompany 
it in uranium compounds.* 

Soddy '-^ also finds experimental evidence that there is a steady 
production of radium from uranium, though the observed amount is 
of a lower order of magnitude than is indicated by the disintegration 
theory. This discrepancy between observation and theory is doubt- 
less due to the fact, discovered by Boltwood^* in 1906, that the 
transformation of uranium into radium is not direct. The interme- 
diate transformation product was later found to be, not actinium as 
at first thought, but a new radioactive element, which " emits both a 
and /9 radiations, which produces no emanation and which resembles 
thorium in its chemical properties." For this new substance Bolt- 
wood ^^ proposed the name ionium^ from ion, because of its ionizing 
properties due to its emission of a radiations. 

Conceptions on this subject obtaining at the time of this writing 
will doubtless be more or less modified by researches now in progress. 

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DISCOVERY AND NATURE OF RADIOACTIVITY 1 5 

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1 6 DISCOVERY AND NATURE OF RADIOACTIVITY 

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DISCOVERY AND NATURE OF RADIOACTIVITY 1 7 

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3 



lb DISCOVERY AND NATURE OF RADIOACTIVITY 

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20 DISCOVERY AND NATURE OF RADIOACTIVITY 

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16 



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DISCOVERY AND NATURE OF RADIOACTIVITY 21 

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146. Villard, P. Sur la reflexion et la refraction des rayons cathodique et 

des rayons deviable du radium. Compt. Rend. Acad. Sci. Paris 
130 : loio. 1900. 

147. . Sur le rayonnement du radium. Compt. Rend. Acad. Sci. 

Paris 130: 1178. 1900. 

14S. Wilde, H. On the atomic weight of radium. Phil. Mag. VL 15: 

280. 1908. 
149. Winkler, C. Radio-activity and matter. Chem. NewsSg : 289. 1904. 



CHAPTER II 
RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

Previous to the present decade it was possible to classify the 
known inorganic factors of the plant's environment as either molar, 
molecular, or undulatory. The discovery of radioactivit}'^ and other 
revelations closely related to it, as briefly outlined in the preceding 
chapter, together with the investigations referred to below, lead to 
the recognition, not onlv of another element of environment, but to 
an entirely new kind of environmental factor, viz., radioactivity. 

It is a matter of considerable interest to ascertain the effects of 
this new kind of energ}^ on the life-processes of plants and animals, 
but when we realize that it forms a part of the natural surroundings 
of all living things, and must be reckoned with as a possible factor 
in all their vital activities, this interest greatly deepens. 

The life-processes of plants are regarded as reactions to stimuli. 
Permanently remove all stimuli and all processes (/'. ^., life itself) 
cease. In last analysis these different stimuli are all different mani- 
festations of energy. We are familiar with some of the effects of 
the more ordinary ones, such as water, air, heat, sunlight, and 
gravity, with the corresponding tropisms (hydrotropism, geotropism, 
etc.), and with the condition of adjustment to the normal for each 
factor, tonus (phototonus, thermotonus, etc.). The discoveries in 
radioactivity show us that the effects of these long-recognized 
factors cannot be completely interpreted unless we take into account 
the newl}^ discovered facts. 

Probably all plants are in a state of radtotonus, or adjustment to 
the radioactive forces of their normal environment, and evidence is 
at hand that we shall be able to add radiotropic response to the other 
and well-known tropisms. Whether we consider water, sunlight, 
air, or soil, radioactivity is a factor involved, and the following para- 
graphs will briefly outline the investigations which compel to this 
conclusion. 

Radioactivity in Water : Thomson ^^®' ^'^' ^^^ was the first to an- 
nounce that air bubbled through Cambridge (England) tap-water 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 23 

vvas decidedly radioactive. Since then a large number of investi- 
gations seem to establish the fact that various waters, widely dis- 
tributed, are sources of radioactivity. This property was present in 
15 out of 18 specimens of water examined later by Thomson,"" and 
in water from Italian springs examined by Pocchettino and Sella. ''^ 
The radioactivity is due to the presence in the water of some radio- 
active substance, usually radium or its emanation. Allen and Blyths- 
wood " obtained a radioactive emanation from the water of the hot 
springs of Bath and Buxton, and, as might have been expected, 
Dewar has found helium in the same waters. Himstedt "' demon- 
strated the evolution of a radioactive emanation from water- and oil- 
springs, and, later in the year, Adams ^ announced that a radioactive 
gas is evolved from the water of deep wells. When the emanation 
was removed by boiling, the water recovered the power of giving it 
off. It is probable that there is a slight amount of radioactive ma- 
terial dissolved in the water. The emanation was very similar to 
that of radium, and probably identical with it. 

Artesian water from several wells, and the town water of Ely, Bir- 
mingham, and Ipswich was found by Thomson ^^^ to give off a radioac- 
tive gas when boiled. Bumstead and Wheeler^'' obtained a radioac- 
tive gas from a well 1,500 feet deep near New Milford, Connecticut 
(U. S. A.), and found that the city water of New Haven, Con- 
necticut, was radioactive, whether taken directly from the reservoir 
or from a faucet after passing through the city mains. The latter 
writers ^^ established the identity of this emanation with that of radium. 

Vichy from Chomel was found to contain a radioactive emana- 
tion,^^- ^^ as was also the water from the hot springs of Baden-Baden,^^ 
from Aix-les-Bains,^^ and from Karlsbad.''" Radioactivity in the 
water from many German springs was detected by Schenck,^"^ from 
Buxton sprmgs by Blythswood and Allen,^* and Strutt."^ and from 
Lavey-les-Bains by Sarazin, Guye, and Micheli.^"^ Strutt found 
traces of the salts of radium in the mud deposited from the hot 
springs of Bath and of Buxton, as well as radium emanation in 
their waters, while Boltwood states that he found radium dissolved 
in the waters of Bath and Baden-Baden under high pressure and 
temperature. Mache^^ tested the water in 17 springs in different 
parts of Germany, Schmidt and Kurz^''^ that of 117 springs, and 
Dienert and Bouquet^* the waters of four springs in France. Radio- 
activity was found associated with them all, and one hot spring con- 



24 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

tained both radium and thorium. Schmidt and Kurz conclude that 
all spring waters contain an emanation, usually that of radium, but 
in some cases that of thorium. Skinner"*' states that Mr. H. Cottam 
did not succeed in finding *' any marked quantity of active gas " 
from samples of clays from various districts near London (Eng.), 
but found a radioactive gas in water of a deep well which goes be- 
low the clay to the green sand. 

The radioactivity of deep well waters, mineral water, and water 
from a cistern in Columbia, Missouri, is attributed by Schlundt and 
Moore ^"'^ to the presence of radium emanation in the water. Waters 
from 123 springs in southwest German}^, Austria, and Italy, and 
from an old Roman spring, the " Queen Isabella," in the island of 
Ischia, bay of Naples, were, in nearly every instance, found to be 
decidedly radioactive by Engler and Sieveking.^^ The sediment 
deposited by the water of the springs was often active, and self- 
luminous radium preparations were prepared from one of the sedi- 
ments. The radium emanation was detected by Sury^^^ in spring 
water of Baden, Switzerland, Leuker Bad, Garasp, and Disentis. 
The water from St. Placidus spring contains a radioactive salt which 
produces the emanation. In 1908 Joly'" measured the activity of a 
sample of ocean water from Valencia, County Kerry, and suggested 
that oceanic radioactivity is due to radioactive materials brought to 
the ocean by streams. Much uranium, he says, is carried in solu- 
tion or in fine suspension, and deposited in the ooze. 

Radioactivity in Mud and Rocks : The following investigators 
have reported radioactivity in deposits from various springs, and in 
mud from other sources: Elster and GeiteP^' ^^ in the " fango," or 
mud from the hot springs of Battaglia, North Italy, and also'^^- ^* in de- 
posits from Baden-Baden, Nauheim and Wiesen baths. The activity 
of fango they attribute to the presence of radium, and state that 1,180 
tons of this mud would yield i gr. of radium chloride. Borgmann^'' 
in mud from Odessa, and from Arensburg, on the island of Oesel ; 
Blanc ^^ in sediment from 9 springs in the region of the Alps; Cas- 
torina^^ in lava from Mt. Aetna. Giesel''^ found radium and radioactive 
rare earths in fango mud, and in earth from the fields of Capri ; Vin- 
centini and Da Zara,^^^' ^^^ radium emanation in the water and sedi- 
ments from a number of hot springs in northern Italy. Sediments 
from 20 springs from different parts of Germany were found radio- 
active by Schmidt and Kurz,^^* and in 1906 Mogri^^ detected the same 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 25 

property in the deposits from the thermal springs at the Institute of 
Bogni di Lucca, in Tuscany. 

Tomassina ^^^ detected radioactivity in the lava thrown out by 
Vesuvius in the eruption of 1904, and, in a study of 28 samples of 
igneous rocks, including granite, basalt, hornblende, and serpentine, 
Strutt ^^"^ found radium present in all. More was found in granite 
than in any other igneous rock studied, while the basic rocks con- 
tained the least amount. Iron meteorites were found to contain very 
little, if any, while stone meteorites contained about as much as the 
terrestrial rocks which they resembled. 

The same author ^^"^ found radium present in sedimentary rocks 
generally, marble, chalk, flint, clay, roofing slate, oil-bearing sand- 
stone, deposits from the hot springs of Bath, sea salt, boiler-rust 
(Cambridge, Eng.), and in the rock-forming minerals, zircon, apatite, 
hornblende, tourmaline, labradorite, white feldspar, white and brown 
mica, white quartz and others. The specimens came from various 
widely separated regions in continental Europe, Africa, India, Asia 
(Ural Mts.), England, and the United States. It was found that 
more than one half of the radium is contained in the heavy minerals, 
though these form only about one eighth of the whole mass of the 
rock. 

The association of radioactivity with the *' ashes" and lava of 
Vesuvius was reported by Becker,^" and a slight radioactivity of 
soils, clays, basaltic tufas, basalts, soft calcium carbonate, etc., 
was detected by Accolla^ in 1907. Sands and mud of the seashore, 
and mud from the sulfur spring of Brucoli also possess a weak 
activity. 

Analyses by Eve and Mcintosh ^ showed in sedimentary Ordo- 
vician rock from .92 x io~^^ to .91 gr. of radium per gram of 
rock; in igneous Devonian .26 to 4.3 gr. per gram of rock, and in 
sedimentary Quaternary .16 to .8 gr. per gram of rock; and the 
probability that the internal heat of the earth is due to radium is 
discussed /ro and contra by H. A. Wilson, ^^^ Strutt,^^^ and others. 

Radioactivity in Air: Elster and Geitel ^^' *'' were the first to 
show that the atmosphere contains a radioactive emanation. They 
suspended a negatively charged wire for some hours in the air, then 
coiled it up and tested it with the electroscope. The wire was found 
to be radioactive, but this result was not obtained if the wire was first 
given a positive charge. Now a negatively charged wire immersed 



26 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

in the emanation of thorium or radium can collect a deposit formed 
by the disintegration of the atoms of the emanation, hence the con- 
clusion from the above experiments, that the air contains a radio- 
active emanation. 

Evidence of the presence of negative ions in the air was known, 
however, long before radioactivit}'^ was discovered. Thus Giese, ^^ in 
1882, observed the electrical conductivity of gases from flames, and in 
1897 Kelvin and MacLean,''^ investigating the flames of a bunsen 
burner, a candle, an alcohol lamp, and a paraffin lamp, found a small 
negative charge in the gases drawn from them. Charcoal and coal 
" both gave negative electrification when there was a flame ; and both 
gave positive electrification when they were glowing without flame." 
These investigations were extended by MacLean and Goto,^" who 
showed that air is electrified by the burning of matches, wood, paper, 
and many other substances. So also McClelland ^^ in 1898. Waves 
of ultra-violet light, and point-discharges of electricity produce nega- 
tive ions in the air.^^* 

The formation of ions by a candle flame was demonstrated by 
Ayrton,* who observed that such a flame can discharge an electro- 
scope in 40 seconds at a distance of 40 cm. " The flame of a match 
had no less power, and an electric arc no more power than an unin- 
sulated candle flame placed at the same distance." 

Traubenberg ^^^ found the atmosphere in the vicinity of the crater 
of Vesuvius strongly ionized, and in 1904 Allan ^ showed that the 
excited radioactivity from the atmosphere behaves like that from 
thorium and radium, and contains both a and /9 rays. In the same 
year Elster and Geitel ^^ pointed out that the electrical conductivity of 
the atmosphere is due largely, if not wholly, to a radioactive emana- 
tion which issues from the earth's crust. These authors are of the 
opinion that the outer layers of the atmosphere doubtless become 
ionized by the sun's rays of short wave-length, and that perhaps ^ 
and '( rays also proceed from the sun and produce a like effect. In 
this connection, it is known, from the investigation of Bacon, ^ that 
an electroscope discharges nearly 18 times as fast in sunlight as in 
ordinary diffuse light in the middle hours of the day. McClelland ^^ 
believed that the ionization of the atmosphere points to the presence 
in it of some radioactive substance, and Blanc ^^ showed experi- 
mentally that transformation products of radio-thorium are, at least 
in the vicinity of Rome (Italy), a most important agent in atmos- 
pheric radioactivity. 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 27 

C. T. R. Wilson '^'^ calculated that the number of ions being pro- 
duced per second in each cubic centimeter of air is about twenty. 
The actual number of ions present per c.c. of air varies with the 
meteorological conditions, being greater in clear, sunny weather. 
The number usually fluctuates between 500 and several thousands, 
and the positive ions are more numerous than the negative.^'' 
Schuster ^"^ found the following numbers of ions per c.c. of air in 
Manchester (Eng.), under the conditions indicated: 2,370 (snowing 
at intervals, with spells of sunshine. East wind. In a field). 3,600 
(cold, bright, gusty. East wind. On a roof). 3,660 (cold, dull. 
East wind, on a roof). In addition to swiftly moving ions, Lange- 
vin '^^ found slowly moving ones also present. The latter are about 
forty times as numerous as the former. Langevin's experiments 
were made on top of the Eiffel tower. 

A negatively charged conductor placed in the open air becomes 
temporarily radioactive,^' and this radioactivity can be removed by 
solution in an acid. This experiment was repeated in Canada by 
Rutherford and Allan, ^'^ who found that the greatest amount of ex- 
cited radioactivity on a negatively charged wire was obtained during a 
strong wind. Allan^ thinks the activity of the air is " probably due 
to an emanation of positive electrons in the air, ever present though 
in varying quantities."* Elster and Geitel ^^ found that the radioac- 
tivity of the air of any given place varies with the nature of the soil 
of the locality, and later in the same year '^'* found that sea air is only 
about one third as active as air over the land at Wolfenbiittel. Soon 
after this Himstedt*^^ showed that air through which water is blown, 
or air that has passed through or over surfaces moistened with water 
has its electrical conductivity increased (by ionization) more than 100 
times. This, he thinks, is the origin of the conductivity of the air 
from cellars and soil, observed by Elster and Geitel, as well as of the 
conductivity constantly present in the free atmosphere. In the fol- 
lowing year Himstedt^^ reported that air sent through the water from 
many springs, and fresh ground water has its conductivity increased, 
and he contends that there is widely (perhaps universally) distributed 
in the earth a radioactive material from which a gaseous emanation 
proceeds which is absorbed by water and oil, is carried by these to 
the surface, and thence distributed to the atmosphere. 

In connection with Elster and Geitel's observation it is interesting 

* Cf . also Stewart, R. M.i" 



28 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

to compare the variations in the penetrating radiation from earth, 
studied by Wright ^^^ in 1908. Measurements of this radiation made 
in different localities on the north and south shores of lake Ontario, 
and at different points on the surface of the lake during the passage 
of a steamer, show that there is greater activity inland and at points 
along the shore than over the lake between Toronto harbor and the 
Niagara river bell-buoy. The activity was measured by the number 
of ions generated per c.c. per second within a lead cylinder.* 

Studies on the effect of altitude enabled Saake ^""^ to state that there 
was a larger amount of emanation in the high altitudes of the valley 
of Arosa, Switzerland, than is normal at lower levels. Eberf*" has 
found that a radioactive emanation can be removed from the atmos- 
phere by condensation in liquid air, while Ramsay and Soddy ^^ have 
demonstrated that the inert gases in the atmosphere (helium, neon, 
argon, krypton, and xenon) have no radioactivity of their own. 
That the atmosphere at New Haven, Connecticut, contains the emana- 
tion of both thorium and radium was announced by Bumstead ^**' *^ in 

1904- 

Antedating these discoveries, was the paper of Elster and Geitel^^ 

on the existence of electrical ions in the atmosphere. The authors 

found that the free atmosphere contains positively electrical masses, 

and considered the existence of these free ions as the most suitable 

basis for a rational theory of atmospheric electricity. This theory 

was further elaborated by Geitel®* in 1901. 

Elster and Geitel did not explain the origin of these ions in the 
free atmosphere, but, in the year following their discovery, Lenard^^ 
found that the rays of ultra-violet light generate cathode rays, and 
two years subsequently he"*^ published the results of further investi- 
gations along the same line, stating that the cathode rays thus gen- 
erated show diffusiveness, and must be largely absorbed by gases. 

In the light of Lenard's experiments C. T. A. Wilson "^concluded 
that the sunlight ionizes the atmosphere through which it passes, espe- 
cially in the upper layers, where the sunlight is still strong in ultra- 
violet rays. 

Certain facts, says Wilson, render it not improbable that pene- 

*It has not been thought necessary, in reviewing the above literature, to explain 
that electrical conductivity', through wires or air, or whatever else, is accomplished by 
the passage of electrons, or other ions. Increase in the conductivity of air and water 
means an increase in the number of the ions they contain. The fundamental ideas 
here involved are clearly set forth bvFournier (Bibliography, p. 17, No. 53), and others. 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 29 

trating cathode rays traverse our atmosphere without being absorbed 
until they encounter the solid mass of the earth which thus becomes 
negatively charged. An excess of negative electricity is also carried 
from the atmosphere to the earth by rain. The positive charge thus 
left behind in the air is carried by convection currents to other 
regions. Thus the negative charge of the earth is maintained. As 
Wilson states, the fact that the earth's surface is negatively charged, 
and that free positive ions exist in the atmosphere, must result in a 
continuous flow of positive electricity from the atmosphere into the 
ground. 

The hypothesis has been proposed by Villard ^^"^ that cathode rays 
giving rise to the aurora borealis have their origin, not in the sun, but 
in the earth itself. Even the spraying of liquids may produce ioni- 
zation, the negative ions, as Eve'^' has shown, being greatly in excess 
of the positive. Strong "-• "'^ thinks that the penetrating radiation that 
causes ionization in closed vessels is probably due to gamma rays 
from radioactive products in the air, rather than in the ground, but it 
is considered probable that these products originate in the ground, as 
the theory of Elster and Geitel indicates. The products vary much 
in quantity according to atmospheric conditions. Eve ^* states that 
the ionization of the air is due to radioactive changes in both the air 
and the soil. Of course the amount of emanation coming into the air 
from the soil would vary with the rise and fall of the water-table in 
the soil, the soil temperature, the entrance into the soil of rain water, 
and the decrease of barometric pressure, all of which would be accom- 
panied by a flow of emanation out of the soil into the lower layers of 
the atmosphere.* According to McLennan's *^ calculation, " approx- 
imately 9 ions per c.c. per second are generated in free air by the 
penetrating radiation from the earth." 

Eve ^^ has called attention to the fact that the radium C in the air 
is carried to the earth not only by falling rain, snow, dust, or smoke, 
but also by the potential difference in the atmosphere. Thus the 
radioactive matter in the air is decreased, that in the soil increased. 
Thorium C has been found in the atmosphere of both hemispheres, 
with an activity about one half that of the radium C present. Since 

* Another paper by Strong "3" has appeared since the above sentence was written. 
He finds a relatively enormous amount ot " external radiation " during the forenoon 
from 8 A. M. until 2 or 3 P. M. " This may be due," he says, " to the expansion of 
the air in the soil and an increase of emanating power due to the heating by sunshine^ 
or it may be due to a change of barometric pressure." 



30 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

the emanation of thorium decays about 6,000 times as fast as that of 
radium, and "has a poor chance of escaping from the soil," the 
amount of thorium C in the ground exceeds the amount of radium C, 
and the thorium C in the ground will be more than 15 times that in 
the air. Eve says that, ♦' in most localities the penetrating radiation 
due to active matter in the air is less than one fifteenth that due to 
active matter in the earth." Recent determinations by Dadourian^* 
indicate that the amount of radium emanation present in the air at 
New Haven, Conn. (U. S. A.), is from 20,000 to 50,000 times as 
great as the amount of thorium emanation. 

Radioactivity in Snow and Rain: In 1902 Professor J. J. 
Thomson observed that water drops falling through air that contains 
ions remove the ions, and in the same year C. T. R. Wilson ^'"' ^" tested 
freshly fallen rain and found it radioactive. By adding barium 
chloride to rain water and precipitating the barium with HgSO^ he 
found the precipitate to be radioactive. Subsequently Allan * ob- 
tained a radioactive residue by evaporating freshly fallen snow to 
dryness. From about one liter of snow that fell during a heavy storm, 
there could be obtained about the same effect as from o.i gr. of 
uranium. The amount of activity varied with the amount of snow 
falling per second, and was constant so long as the fall of snow was 
constant. Later in that year the same writer "^ found that the radioac- 
tive residue could be rubbed off onto a piece of cotton, and when this 
was burned the ashes were still radioactive. Allan supported the 
theory that some process is continually going on in the air pro- 
ducing radioactive carriers which are removed by the snow-flakes. 
C. T. R. Wilson ^" also detected the activity of freshly fallen snow. 
Kaufmann has determined that such snow is, under similar cir- 
cumstances, as active as rain, but snow falling on roofs loses its 
activity sooner than snow that falls on the ground.* The loss of 
activity appears to vary with atmospheric pressure. Righi ^* found 
that, during a snowfall, the electrical conductivity of the air is more 
than doubled. 

Soil air from Wolfenbiittel was found to contain a radioactive 
material by Elster and Geitel,^^ and by Ebert and Ewers *^ at Munich. 
GeiteP" found that the activity of the air from the soil in his garden 
did not apparently diminish in eight months, but the ashes of plants 
which had grown on active earth gave off no appreciable rays. 

* This result was confirmed by Constanzo and Negro, ^^ in 1906. 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 3 1 

Carbon-dioxide from great depths of old volcanic soil was markedly 
radioactive, and Sarasin ^''^' ^''^ demonstrated the same property in air 
from the so-called "breathing wells" in Europe. The radioactive 
gas in the air and soil of New Haven (Connecticut, U. S. A.) was 
determined by Bumstead and Wheeler^^ to be identical with the 
emanation of radium. McLennan^^ also found that natural gas 
from wells in the Welland district, near Niagara Falls, and near 
Brantford, was charged with a radioactive emanation, and in the 
experiments of Dadourian^^ the activity of underground air was found 
to be due to thorium. A radioactive emanation, evolved on heating 
raw petroleum, is considered by Burton ^^ to be due solely to the 
presence of radium in the soil. 

The General Distribution of Radioactivity : Evidence 
from the general distribution of radioactive substances, that radio- 
activity is a factor in the normal environment of plants has been 
shown to be abundant. Numerous other researches give added em- 
phasis to this fact. The discharge of positive electrification by 
metals at a temperature of 270° C, or over, ^^'*^' ^^'"^ the evidence that 
the photosphere of the sun is emitting electrons in large quantities, ^^ 
which travel throughout the solar system, the probable existence of 
electrons in metals at all temperatures moving freely between the 
molecules, ^^ and causing a " soft" X ray when they collide with the 
molecules, are all facts pointing to the same conclusion. 

Drops of spray on striking wet rocks at the foot of water-falls 
communicate a positive charge to the water and a negative charge 
to the air.^*^ A very penetrating radiation has been found to exist 
inside buildings, ^^'^^ and zinc and tinfoil, lead, copper, glass coated 
with phosphoric acid, silver, copper, platinum, aluminium,"^ dried 
earth, polished tin, brick, iron,^" and hydrogen-peroxide,^'' have all 
been found to be radioactive, most of these substances giving off rays 
comparable to the /9 rays of radium. Experiments of McLennan 
and Burton^* indicate that all metals in varying degree are sources 
of marked, though feeble, radioactivity, and that " the ordinary air of 
rooms is traversed by an exceedingly penetrating radiation," such as 
comes from thorium, radium, and the excited radioactivity produced 
by them. Campbell, ^^' -^ after testing nine different metals, all of 
which are included in the lists given above, states that '* the emission 
of ionizing radiation is an inherent property of all the metals investi- 
gated," and adds, *' I see no reason why it should not be extended to 



32 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

all substances." The larger portion of the rays, according to Camp- 
bell, are a rays. 

During the course of experiments at the foot of Niagara Falls, 
McLennan^ found that three stretches of No. 24, insulated copper 
wire, of about 30 meters each, exposed to the spray, immediately be- 
came negatively charged to a potential of about 7'5*^o volts. The 
charge was shown to be caused by the spray, and to vary with its 
density. The spray also excited radioactivity in the air, but when 
evaporated it left no radioactive residue. 

From the fact that air bubbled through distilled water in which 
lead acetate or lead nitrate has been dissolved is more radioactive 
than when bubbled through pure water, Thomson^-' infers that lead 
is radioactive. Brick,'^" metals generally,'^* the minerals samarskite, 
pitchblende, and monazite, from North Carolina, Cornwall, Norway, 
and Brazil,"' and tin, zinc, graphite, platinum, lead, aluminum, and 
carbon, -•'' all manifest radioactivity. Munoz '^ has studied minerals, 
earth, water, and gases of the atmosphere in various parts of Spain, 
and finds radioactivity widely distributed throughout that country. 

" From the kinetic theory of gases," says Lord Kelvin,''^ *' it 
seems certain that every kind of matter has some radioactivity ; that 
is to say, shoots off both vitreously and resinously electrified particles. 
Hence it is only in their extraordinarily great abundance and great 
velocities of shooting, that polonium and radium differ from ordi- 
nary matter." * 

Campbell -" concludes from his experiments that potassium and 
rubidium are radioactive substances. The rubidium is less active 
than potassium, while the activity of the latter is yoVo *^^* ^^ 
uranium. The rays given off by pptassium are /9 rays. Tests with 
sodium gave negative results.! The radioactivity of potassium has 
been confirmed by McLennan.^*"' The fact that potassium is an 
essential constituent of the food of most plants renders its radio- 

* In the same paper Lord Kelvin describes a model of an atom to illustrate the 
mode by which, according to his idea, the a and ,3 particles are given off. 

t In 1907 Professor J. J. Thomson ^^' succeeded in getting electrification from both 
heating and rubbing various salts (phosphates and oxides), and explains the result as 
due to the hypothetical fact that the salts are covered superficially with a double layer 
of electrification, one layer negative, the 'other positive. The heating or rubbing 
removes the outer laver and leaves the inner one unbalanced. He suggests that the 
electrifving of bodies by friction results from the removal of one or both layers of 
electrification by the rubbing. 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 33 

activity a matter of especial interest and importance to the plant 
physiologist.* 

Reasoning from various experiments, Thomson ^'^^ states that, *' a 
radioactive substance, apparently radium, is exceedingly widely dis- 
tributed, occurring in the most unexpected places," e. g:, soil, bricks, 
glass, sea sand from Whitby beach, Yorks ("exceedingly rich"), 
one specimen of wheat flour (others none), all clays, sands, and 
gravels that were examined. Nearly all bodies, he states, emit radi- 
ations which can ionize a gas. Experiments of Wood "^ lead to the 
same conclusion, and Strutt "^' '^'^ has calculated that the amount of 
radioactivity necessary to compensate for the radiation of heat by the 
earth is much exceeded by the activity of ordinary materials. The 
spontaneous ionization of the air in closed glass vessels may possibly 
be partly accounted for by the fact that clay and other silicates are 
known to emit large numbers of ions.^^ | 

In this connection may be recalled the paper by Eve,^® describing 
the infection of the entire physics-building of McGill University with 
radium. The use of the radium had been confined to one portion of 
the building, but, later, objects from all parts were found to be 
strongly radioactive. " Sheets of mica, lead foil, iron, zinc, and tin 
were all active, even when taken from drawers and cupboards." 
About 90 per cent, of the activity could be removed by solution in 
strong hydrochloric acid, and the acid thereby became active. The 
influence has spread from room to room, and from floor to floor in 
the large building. 

Lenard^* has found that when light of short wave-length falls 
on metal surfaces slowly moving ions are shot into space. Their 
initial velocity varies, not with the intensity, but with the quality of 
the light, and they ionize gases through which they pass, thus making 
them conductors of electricity. 

The Effect of Radioactivity on Surroundings : In addition 
to causing excited radioactivity, as noted above, radioactivity may 
affect the plant's surroundings in other ways. Oxygen, for example, 
is changed to ozone by the rays from radiferous barium. Further- 
more a slight rise in temperature may result. Curie and Labord'^'" 
were the first to announce the emission of heat from radium. One 

* Phillips ^1 has recently (28 May, 1908) reported evidence of an emanation from 
sodium that will discharge an electroscope negatively (but not positively) charged. 
Whether this is a true radioactive gas, or not, has not yet been demonstrated. 

tCf. also Wood, A.'*^ 

4 



34 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

gram of " pure" radium emits a quantity of heat equal to lOO gram 
calories per hour, or 2,400 gram calories in one day — nearly enough 
to dissociate one gram of water (3,900 gram calories).* 

Relative Importance of the Emanation : A large part of 
the radioactivity to which the sub-aerial portions of plants are exposed 
is due to the emanation diffused in the atmosphere. Rutherford 
states that about three fourths of the activity of radium is due to the 
emanation, and he has calculated that, if we could get i c.c. of 
radium emanation, it would raise to a red heat the glass tube con- 
taining it, and light up an X ray screen brilliantly through one foot 
of solid iron. This evolution of energy would continue for several 
days without much change, and would be appreciable after one 
month. 

This chapter contains a portion of the evidence, accumulated 
during the past ten years or more, that radioactivity and free electrons 
are ecological factors, a part of the normal environment of probably 
every plant. Undoubtedly there will be considerable modification of 
detail as the science progresses, but the main fact of the wide distri- 
bution of radioactivity in nature seems now to be firmly established. 
In what way, and to what extent it influences physiological processes 
and morphological expression remains largely to be determined. 

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* Though Paschen ^'^ finds reasons for thinking that 50 per cent, of the heating 
effect is due to the gamma rajs, the experiments of Rutherford and Barnes ^^" indicate 
that this effect is due mainly to the bombardment bj the a rays. 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 35 

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36 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

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RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 37 

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63. Giesel, F. The occurrence of radium and radio-active rare earths in 

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64. Geitel, H. Ueber die Anwendung der Lehre von den Gasionen auf 

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38 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

65. Geitel, H. Recherches sur la radioactivite de I'atmosphere et du sol. 

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69. . Ueber die radioaktive Emanation der Wassei-- und Olquellen. 

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70. Joly, J. The radioactivity of sea water. Phil. Mag. VI. 15 : 3S4. 

1 90S. 

71. Kaufmann, J. Meteorologische Zeits. March, 1905. (Not seen.) 

72. Kelvin, Lord. Plan of a combination of atoms having the properties 

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73. & Maclean, M. On electrical properties of fumes proceeding from 

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74. Koeningsberger, J. Ueber die Temperaturgradienten der Erde bei An- 

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75. Langevin, P. Sur les ions de I'atmosphere. Compt. Rend. Acad. 

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46: 584. 1892. 

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79. Mache, H. Ueber die Radioaktivitat der Gasteiner Thermen. Sitz- 

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80. Maclean, M., & Goto, M. Some electrical properties of flames. Phil. 

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81. McClelland, J. A. On the conductivity of the hot gases from flames. 

Phil. Mag. V. 46: 29. 1 898. 

82. . Ionization in atmospheric air. Trans. Roy. Dublin Soc. 8: 

57- 1905- 

83. McLennan, J. C. Induced radioactivity excited in air at the foot of 

waterfalls. Phil. Mag. VI. 5: 419. 1903. Phys. Rev. 16: 238. 
1903. 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 39 

84. McLennan, J. C. On the radio-activity of natural gas. Nature 70 : 

151. 1904. 

85. . On the radio-activity of lead and other metals. Phil. Mag. VI. 

14: 760. 1907. 

86. . Some experiments on the radioactivity of potassium salts. 

Science, N. S. 27: 616. 1908. 

87. & Burton. Some experiments on the electrical conductivity of 

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8S. . On the radio-activity of metals generally. Phil. Mag. VI, 

8: 343- 1904- 

89. Mogri, G. Radio-activity of the deposits from the thermal springs at the 

institutes of Bogni di Lucca, Tuscany. Atti Reale Accad. dei Lincei 
15: III. 1906. 

90. Munoz del Castillo, J. Yacimientos y manantiales radioactivos de 

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91. Phillips, C. E. S. An emanation from sodium. Nature 78 179. 1908. 

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93. Ramsay, W., & Soddy, F. Experiments in radio-activity and the 

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95. Rutherford, E. Discharge of electricity from glowing platinum. 

Proc. & Trans. Roy. Soc. Canada II. Trans. 7^: 27. 1901. 

96. . Excited radioactivity and ionization of atmospheric air. Bull, 

Am. Phys. Soc. 2: 59. 1902. 

97. . Radio-activity of ordinary materials. Nature 67: 511. 1903. 

98. & Allan, S. J. Excited radioactivity and ionization of the atmos- 
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98a. & Barnes, H. T. Heating effect of the y rays from radium. 

Nature 71 : 151. 1904. Phil. Mag. VI. 9 : 621. 1905. 

99. & Cook. A penetratiag radiation from the earth's surface. Phys. 

Rev. 16 : 183. 1903. 

100. Saake, W. Messungen des elektrischen Potentialgefalles der Elek- 

trizitatszerstreuung und der Radioaktivitiit der Luft im Hochthal von 
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Brunnen entstromt. Physikal. Zeits. 6 : 708. 1905. 



40 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

02. Sarasin, E. [La radioactivite de I'air qui s'echappe des puits souf- 

fleurs.] Arch. Sci. Phys. Nat. 20: 425, 603. 1905. 

03. , Guye, C. E., & Micheli, J. Sur la radioactivite des eaux de 

Lavey-les-Bains. Arch. Sci. Pliys. Nat. 25: 36. 1908. 

04. Schenck, R. Theorie der radioactiven Erscheinungen. Thesis, 

Univ. Halle. 1904. 

05. Schlundt, H., & Moore, R. B. Radio-activity of some deep well and 

mineral waters. Jour. Phys. Chem. 9: 320. 1905. 

06. Schmauss, A. Aufnahme negativer Elektricitjit aus der Luft durch 

fallende Wassertropfen. Ann. Phys. Chem. 9: 224. 1902. 

07. Schmidt, A. Ueber die Radioaktivitiit einiger Siisswasserquellen des 

Taunus. Physikal. Zeits. 6: 34, 402. 1905. 8: 107. 1907. 

08. Schmidt & Kurz. Ueber die Radioaktivitat von Qiiellen in Gross- 

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1906. 

09. Schuster, A. On the rate at which ions are generated in the atmos- 

phere. Mem. Manchester Lit. Phil. Soc. 48'^: 1-6. 1904. 

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12. Strong, W. W. The penetrating radiation. Terrest. Magnet. & At- 

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Phil. Mag. VL 4: 98. 1902. 
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1903. Nature 67 : 369. 1903. 

The preparation and properties of an intensely radio-active gas 



from metallic mercury. Phil. Mag. VI. 6 : 113. 1903. 
. A study of the radioactivity of certain minerals and mineral 



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London, 1904. 
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21. . Radium and geology. Nature 74 : 610. 1906. 

22. . Radium and the earth's heat. Nature 77 : 365. 1908. 



RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 4I 

123. Sury, J. von. Ueber die Radioaktivitiit einiger Schweizerischer 

Mineralquellen. Chem. Centrlb. V. 11': 12S2. 1907. Mitteil. 
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Pliys. Nat. 24: loi. 1907. 

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126. . Experiments on induced radioactivity in air, and on electrical 

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Proc. Roy. Soc. London 65: 289. 1899. 



42 RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 

140. Wilson, C. T. R. On the ionization of atmospheric air. Proc. Roy. 

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144. . On radio-activity from snow^. Proc. Cambridge Phil. Soc. 

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146. Wilson, H. A. Radium and the earth's heat. Nature 77 : 365. 1908. 

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148. . Spontaneous ionization of air in closed vessels and its causes. 

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149. Wright, C. S. On variations in the penetrating radiation from the 

earth. Science, N. S. 27: 617. 1908. 



CHAPTER III 

PREVIOUS INVESTIGATIONS UPON ANIMALS 

The recent development of the science of the electron has so 
unified physical and chemical phenomena that only artificial boun- 
daries now exist between the physics of heat waves, electro-magnetic 
waves, light waves, ultra-violet light, X rays, and the x rays of 
radium. They differ only in degree, not in kind, and so their 
physiological roles are unified, and effects caused by any one of 
them throw light on the results produced by all the others. Like- 
wise, as is well known, it is becoming increasingly difficult to draw 
the line between physiological investigations in botany and those in 
zoology. They both center in the common field of cell-physiology, 
so that very often results obtained with plants can be adequately 
interpreted only in the light of investigations made with animals, 
and vice versa. 

For these reasons it has seemed best to include, in the following 
historical review, the literature dealing with the effects, not only of 
radium rays, but of X rays and of ultra-violet rays as well on both 
animals and plants. The results of the studies of the physiological 
and therapeutic effects of X rays were brought together by Schiff '"^^ 
in 1901, and no attempt is here made to compass the voluminous 
literature bearing on X ray therapy and radium therapy. 

In 1899 Schaudinn^*^' announced that the various protozoa react 
differently to the stimulus of Rontgen rays ; certain species do not 
react at all, some only slightl}', and still others very strongly. The 
dissimilarity in reaction appears to be connected with differences in 
the structure of the protoplasm. Those which react quickly possess 
a looser plasm than those which react slowly or not at all. 

The now familiar fact that radium rays will cause a painful 
" burning " of the skin was first recorded by Walkhoff,*' in October, 
1900. This effect was noted in the same year by Giesel,^^ who laid 
a double walled celluloid capsule containing 0.27 gr. of radium- 
barium bromide for 24 hrs. on the inner surface of his arm. The 
first effect noticed was a slight reddening of the exposed region, and, 

43 



44 PREVIOUS INVESTIGATIONS UPON ANIMALS 

after two or three weeks, a strong irritation with pigmentation, and 
finally a peeling off of the skin, followed soon thereafter by healing. 
Rutherford *" describes an inflammation that lasts from lo to 20 days, 
after which the skin peels off, while the pain endures for two months. 
He states that these results are due mainly to the a and /9 rays. 
Becquerel and Curie ^ obtained the burns with a preparation of only 
800,000 activity, and found that the effect varied with the intensity 
of the active rays and the duration of the exposure. Personally I 
have never experienced any inconvenience in handling sealed glass 
tubes of radium bromide of activity as high as 1,800,000, though I 
have never taken any special care to avoid injury, I have carried 
a wooden, velvet-lined case containing the preparation in my vest 
pocket for several hours, and in my ungloved hand for as long as 
half an hour, without ever having experienced any " burning " or 
other unpleasant effects. 

Joseph and Prowazek,'^^ exposing Paramoecia and Dafhnia to X 
rays, found that those organisms show a negative tropism with refer- 
ence to the ra3^s. The plasm of Parmnoecia and Bryopsis undergoes 
modifications which were interpreted to signify either injury or 
exhaustion. 

In much of the literature, especially the earlier, the amount of 
radium used and its activity are not given. Bohn ^ found that 
embryos of Bujo vulgaris grew more slowly after exposure to the 
rays of radium, and exposed tadpoles of the frog developed into 
monstrosities. He also says that if the rays of radium act upon the 
body of an animal for several hours, the tissues acquire new proper- 
ties, which may remain in the latent state for a long period, but 
manifest themselves as soon as the normal activity of the tissues is 
resumed. The activity of his preparations is not given. 

In a later paper Bohn^" states that if sea-urchins [Strongylocen- 
trotus lividiis) are exposed for from 20 minutes to 2 hours after 
gastrulation, the plutei are small and atrophied. The rays rapidly 
enfeeble or kill spermatozoids, but, on the contrary, eggs submitted 
to their influence seem to become more susceptible of being fecun- 
dated, and are increased in vitality. The rays affect the nuclear 
chromatin especially, increasing its activity or destroying it, accord- 
ing to the duration of exposure. Spermatozoids are more sensitive 
than ova, because they consist of almost naked chromatin, but the 
chromatin of eggs, protected by the cytoplasm, is so stimulated, he 



PREVIOUS INVESTIGATIONS UPON ANIMALS 45 

says, as to produce parthenogenesis. This last result has not been 
confirmed. 

Danysz ^^' ^^ found the tissues in the peritoneal cavities of guinea 
pigs less sensitive than the skin, but the central nervous system in- 
finitely more sensitive. One centigram of radium in a sealed glass 
tube, placed above the backbone and part of the cranium of a mouse 
one month old, produced phenomena of ataxia and paresis in about 
three hours. Tetanus convulsions followed in from seven to eight 
hours, and, if the tube was left in place, death ensued in twelve to 
eighteen hours. The older the mouse, the less sensitive he was to 
such exposure. At the age of three to four months death did not 
result for from three to four days, and at the age of one year not 
until from six to ten days. Danysz attributed the increased resist- 
ance to the transformation of the walls of the neural cavity from 
cartilage to bone. Caterpillars of Ephertta are paralyzed by the ema- 
nation, and anthrax germs cease developing after an exposure of 24 
hours in an atmosphere charged with the emanation. The microbes 
which produce the proteolytic enzymes of autodigestion are specially 
sensitive. In his later paper he ^^ states that the epithelial tissues 
of young animals are more sensitive than those of adults. 

A. Exner^^ found that blood, hair, nails, and muscle fiber, and 
especially the crystalline lens, are made phosphorescent by the rays, 
and Hardy and Anderson ^^ concluded that the sense organs of higher 
animals are not at all affected by them. The sensation of diffused 
light, caused by bringing a few milligrams of a radium salt near the 
head is purely of retinal origin, and not due to a response of the 
optic nerve or brain. The tissues of the eyeball give out this diffused 
light under the influence of the/9 and y rays. Fresh lenses of sheep, 
ox, and rabbit, and also skin, fat, and muscle are made to glow when 
exposed to the rays. The eyelids are extremely opaque to radium 
rays, and this possesses added interest in view of the fact that a 
penetrating radiation exists in the air (p. 25). Exner's observations 
were confirmed in 1904 by Bouchard, Curie and Balthazard.^^ In the 
same year S. Exner,^^ exposing the tails of mice, determined that 
the /? and y rays are both physiologically active, the former less so 
than the latter. 

According to Perthes, ^^ an intensity of X rays not sufficient to kill 
the cells of man and the chick, greatly retard cell-division. The 
rays similarly affected the cells of Ascaris. 



46 PREVIOUS INVESTIGATIONS UPON ANIMALS 

Radium rays were found by Schwartz ^* to affect the yolk of eggs 
more than the albumin. He considered that the rays decomposed 
the lecithin of the yolk, and that they affect all^tissues in the same 
way, for cells rich in lecithin, he says, are the most sensitive to the 
rays. On the contrary Neuberg *^ concluded from his experiments 
that the rays can decompose neither pure lecithin nor proteins, and 
probably do not decompose them within the cell. 

In 1904 von Baeyer^ found that both the alpha and the more 
penetrating rays from radioactive lead, polonium, and induced sil- 
ver and palladium cause the death of bacteria, but that the alpha rays 
do not affect the skin. He holds the opinion of Scholtz that the 
effect on the skin is to be ascribed to the penetrating rays. 

The effect of Rontgen rays on regeneration in planarians was in- 
vestigated by Bardeen and Baetjer.'' Their experiments showed 
that cell-division may be retarded and entirely stopped by a sufficient 
exposure to the rays. They also noted that the effects did not appear 
for some days after the first exposure, and that the rays have an 
effect, not so much upon tissue differentiation, as upon cell reproduc- 
tion. The rays were found to affect primarily cells possessing repro- 
ductive capacity, and the authors suggest that "death in exposed 
specimens may possibly be due to a necessity on the part of the 
organism for a certain amount of cell-reproduction." 

The physiological effects of the radium emanation were studied 
by Bouchard, Curie, and Balthazard,^^ and it was found to kill guinea 
pigs and mice within one or two hours, according to the quantity of 
the emanation used. The effect was shown not to be due to ozone 
produced by the radioactivity of the emanation. 

In 1904 Caspari ^^ reviewed the physiological investigations with 
the rays of radioactive substances since Becquerel announced the 
discovery of Becquerel rays, and in the same year Danysz ^^ observed 
that the epithelial tissues of young animals were more sensitive to 
these rays than those of adults. 

According to Dorn and Wallstabe,^^ rabbits were not affected by 
drinking tap-water which had absorbed the emanation, but were 
poisoned by an exposure of one and one half weeks to air which con- 
tained it. Their lungs Avere found to be hyperemic. 

Dunham "^ observed that Chilomonas and two species of Para- 
tnoecmm were killed by six exposures of three minutes each to X rays 
on three successive days, while rotifers, Arcella, and Cryptomonas 
were not affected by that treatment. 



PREVIOUS INVESTIGATIONS UPON ANIMALS 47 

The first recorded attempt I have found to ascertain the inde- 
pendent effect of the different kinds of radium rays was made by 
A. Exner^^ in 1904. He separated the ^ from the y rays by means of 
the magnet, and found that they both produced the same kind of 
result on the tails of mice, but the /9 rays were less active than the y 
rays. In the same year Gillman and Baetjer^^ found that the eggs 
of Amblystoma^ exposed to X rays, developed faster than normally 
for a few days, though eventually their development was markedly 
altered and checked. These authors announce that similar results 
were obtained by Bardeen with the hen's egg. 

When invertin, emulsin, and trypsin were exposed to the radia- 
tions from radium, Henri and Mayer ^^ found that their activity gradu- 
ally diminished and was finally entirely lost after several days 
exposure. 

Perthes*^'** found that eggs of Ascaris megalocephala, exposed 
in drop cultures to radium and to Rontgen rays, had their first division 
delayed, and their further development made irregular and slower 
than normally. Eggs in the resting or in the dividing condition 
served equally well for the experiments. Centrosomes and spindle 
fibers were unaffected, but in Ascaris megaloce^hala univalens the 
characteristic number of chromosomes was doubled. In the course 
of the chromatin loops there appeared knotty swellings instead of the 
normal, club-shaped enlargements. In a few eggs, instead of the 
usual two chromosomes on the equatorial plate, there were observed 
numerous, unequal pieces, though Perthes suggests that this may 
have resulted from the mode of sectioning, and says, " I cannot con- 
sider that a disintegration of the chromosomes by Rontgen rays has 
been demonstrated." The eggs exposed to X rays" gave rise to ab- 
normally developed worms. 

Phisalix*^ exposed the venom of a viper for periods of 6, 20, and 
58 hours to radium rays. Its toxicity was decreased by the shorter 
exposures and finally destroyed by the longer. By means of radium 
rays Tizzoni and Bongiovanni^'^^ and Novi*^" obtained an attenuated 
virus of rabies {in vitd). The length of exposure necessary to render 
the virus inoffensive varied with the organ in which the injection was 
made. JVassula and Trypanosoma Brucei, studied by Salomonson 
and Dryer,*'' were killed in from two to three hours by rays from ra- 
dium, and cyst-forming amoebae were injured. The contractile 
vacuoles of ciliates were distended, and their period of contraction 



48 PREVIOUS INVESTIGATIONS UPON ANIMALS 

prolonged. In 1905 Bongiovanni " also announced to the Bologna 
Academy that radium rays rapidly destroy the virus of rabies, both in 
tubes and when applied to animals, within an hour of their infection. 
"Animals already suffering could be cured with certain results." 
Danysz * was unable to reproduce the results of Tizzoni and Bon- 
giovanni. 

According to Schaper,*^ an exposure to radium rays retarded and 
modified the regeneration of the tail in Triton larvae, and regener- 
ation of Planaria luguhris was similarly affected by an exposure of 
three and one half hours to the rays, and of 5 mm. -larvae of Rana 
esculenta by the emanation. Cell-division, embryonal differentia- 
tion, and growth were inhibited after a longer or shorter latent period. 
Eggs of Rana esculenta^ exposed at various stages of segmentation 
or early differentiation of the embryo, were retarded in development, 
and the embryos were small and deformed. 

The destruction of the activity of chymosin by radium rays was 
attributed by Schmidt-Nillsen ^^' ^^ to the ultra-violet rays caused by the 
phosphorus in his preparations. When Venenziani^^ placed speci- 
mens of Opalina ranarnni (a ciliated parasite, living in the intestinal 
fluid of frogs) in a 5 per cent, sodium chloride solution, and then ex- 
posed them to rays from o. i gm. of radium salt of 10,000 activity, they 
lived longer than control specimens, similarly placed, but not exposed 
to the rays. In water the exposed organisms survived still longer. 

Willcock^' found that Etiglena vh-tdis manifested no tendency to 
avoid or to accumulate in the path of rays from barium, but Jen- 
nings'^' had already found it almost impossible to obtain any directive 
response to other stimuli from Etiglena. The barium rays seemed 
to hasten spore formation in small encysted forms, and encysted forms 
of the larger variety were made active by 24 hours' exposure to the 
rays from 5 mg. of radium bromide. Stentor viridis contracts 
when the rays fall upon it. Repeated exposure results in a marked 
decrease in irritability and in the capacity for contraction and exten- 
sion. Hydra Jtisca^ which contains no chlorophyll, gave no tropostic 
response, even during exposures that resulted in death, but Hydra 
viridis, which contains a green algal symbiont, does manifest a nega- 
tive radiotaxis which decreases with fatigue, as with Stentor. The 
response takes place both in full daylight and in absolute darkness. 
An exposure of two hours to «, /9, and /rays acting together caused 
Hydra fusca to disintegrate, and the result was attributed to the effect 

*Ann. Inst. Pasteur 20: 206. 1906. 



PREVIOUS INVESTIGATIONS UPON ANIMALS 49 

on the nervous system of the oral disc, for this was the region first 
affected, and no response at all was obtained when the foot was ex- 
posed. Opalina, JVyctothet'us, and Balantidium^ organisms without 
chlorophyll, suffered no obvious harm, and manifested no response 
when exposed for 24 hours to rays from 50 mg. of radium bromide, 
though these organisms are very sensitive to ordinary stimuli. Nega- 
tive results were also obtained with Actinosphaerimn and rotifers. 
Thus, only forms containing chlorophyll appeared to be sufficiently 
sensitive to the rays to react, and the author suggests that the green 
algae, living symbiotically with Hydra viridis and Stcntor, act as 
sense organs for the beta rays, possibly through a modification of the 
metabolism of the alga by the rays, and a consequent disturbance 
of the balance between the two organisms. This author's brief note 
on experiments with plants is referred to on page 62. 

In harmony with an inference of Willcock with reference \o Hydra, 
is the result of Beck,^ who found that radium rays either deaden or 
destroy the sensibilities of the peripheral nerves. In the same year 
(1905) Salomonson and Dryer ^^ stated that rays from 5 mg. of 
"pure" radium bromide, passing through a sheet of mica, had little 
effect on the protozoan JVassula, even after six days. Some speci- 
mens of amoebae were killed in twelve hours, while others survived 
for four days. Trypanosoma Brucei wdLS killed in from two to three 
hours, and on red blood corpuscles the rays exerted a haemolytic 
power. 

Hewlett-^ has suggested that the inhibition of cancerous growth 
by radium and X rays may be because the rays cause proliferation of 
the connective tissue elements of the growth, and thus interfere with 
its nutrition. ♦' It is possible," he further says, " that the stimulus of 
these rays may also act like fertilization, and cause the gametoid 
once more to revert to the somatic cells." No experimental evi- 
dence, however, is adduced in support of either of these hypotheses. 

A thorough study of the effects of radium rays on chlorophyllous 
and non-chlorophyllous organisms was made in 1905 by Dr. Margaret 
Zuelzer."- She exposed large numbers of Spirostemum ambigiium 
and the chlorophyll-containing Paramoecium barsaria to the rays, and 
found that, after 24 hours' exposure, from four to seven out of ten 
Paramoecia had divided, but not so in the case of the Spirostema. 
Cell-division of the chlorophyll-containing Paramoecia had ceased 
after 30 hours of exposure. The animals which had not been notice- 
5 



50 PREVIOUS INVESTIGATIONS UPON ANIMALS 

ably altered bj^ a radiation of 36 hours then moved more slowly, and, 
after four to seven days of exposure, gradually swelled up and dis- 
integrated. In preserved specimens the macro-nucleus appeared 
swollen, and deeply staining, and Dr. Zuelzer suggests that the 
greater resistance of the chlorophyll-containing organism is possibly 
due to an inhibition of the injurious effects of the rays by the oxygen 
given off by the chlorophyll in the presence of light. 

The source of this suggestion of Dr. Zuelzer's was the work of 
Hertel,-** who studied the effect of waves of ultra-violet light on 
organisms. He found that organisms that contain chlorophyll are 
more resistant to the injurious effects of the ultra-violet rays of a 
wave-length of 280 /in than the chlorophylless organisms. The pro- 
toplasmic streaming in cells of Elodea {Philotria) was retarded more 
promptly in the dark than in light, though darkness in itself, at least 
within one hour, does not affect the process. Illuminated leaves 
were not affected as readily as those not illuminated, and Paramoe- 
ciiim hursa7-ia Ehrenberg, which contains chlorophyll, was less sen- 
sitive in light than species without chlorophyll. Hertel thinks that 
the oxygen given off in the light by photosynthetic processes inhibits 
the injurious effects of the ultra-violet rays. He further found that 
the rays accelerate and favor the decomposition of hydrogen peroxide 
when that process has been started by a catalyzing body, and finally 
concludes that the effects of the rays on the living cell are due to this 
influence on the proportion and distribution of oxygen in the cell. 
Hertel's results with hydrogen peroxide possess added interest in 
light of the studies of Neilson and Brown ^^ on the effects of ions on 
the decomposition of hydrogen peroxide by platinum black. The 
cation has an inhibiting or depressing effect, the anion an acceler- 
ating influence. In these experiments solutions of 22 different salts 
of sodium, and of nine different chlorides were used, with concentra- 
tions of from w/8 to n/<,i2. 

If it shall be determined, says Dr. Zuelzer, after referring to 
Hertel's work, that ultra-violet rays, as well as those of radium, can 
influence the metabolism of the cell by depriving it of oxygen, then the 
results of Venenziani^^ may find here their explanation, ior the Opalina 
ranariun with which he experimented, lives normally in a medium 
(the intestine) poor in oxygen. Continuing, she says that the dis- 
turbance of spermatogenesis and the killing of the spermatozoa in 
healthy tissue, the quick destruction of the skin and of malign tumors 



PREVIOUS INVESTIGATIONS UPON ANIMALS 5 1 

with their rapidly dividing cells, may possibly depend upon the same 
property of the rays. If the exposure of the animals was not too 
prolonged they recovered. Thus, rapidly creeping specimens of 
Amoeba Umax and Pelomyxa palustris came to rest and contracted 
after an exposure of three to four hours. In this condition they lay 
unchanged for 24 hours, but if the radium influence was then with- 
drawn they revived completely, and crawled about normally after 
two hours. Dr. Zuelzer's results were confirmed the following year 
by Hussakof,^" who states that from one to two hours exposure pro- 
duced no effect upon amoeba and paramecium. 

The experiments of Berg and Welker^ on the metabolism of 
young dogs led them to the conclusion that: "Radium preparations 
of low activity (240, 1,000, 10,000) containing barium bromide in 
preponderating proportions were without special influence on metab- 
olism when administered per os or subcutaneously in relatively large 
quantities. Equal or larger doses of pure radium bromide also failed 
to show any decisive effects before fatal results were inaugurated." 

The effect of prolonged exposure to radium of weak activity was 
studied by London. ^^-^^ He does not give the activity of his prepara- 
tion, but rabbits were exposed to 260 mg. of it for 14 months with 
injurious effects both to external and internal organs. The electric 
organ of the torpedo was exposed by Mendelssohn^^ to rays from 3 
mg. of radium bromide of 1,800,000 activity in a glass tube. No 
effect was observed until the end of the first hour of exposure. 
Then, after a period of 20-30 minutes of stronger activity, there took 
place a gradual weakening of the discharge, which fell to a minimum 
in five to six hours. This enfeebled discharge continued for six to 
eight days, but no complete suppression of the function of the elec- 
tric organ of the torpedo, due to the radium rays, has been observed. 

In 1906 Meyer ^^' ^^ ascertained that, " By whatever channel radium 
is introduced (into the animal body) it seems to find its way into prac- 
tically all the fluids of the body," and in 1907 Bardeen^ demon- 
strated that, when the ova of toads were fertilized by spermatozoa 
that had been previously exposed to the X rays, the ova developed 
abnormally. Similar results were obtained later in the same year ^ 
with Rana piptens, and the least abnormal and longest survivor out 
of 250 larvae, died one week after the eggs were^fertilized. 

The coagulation of albumins by the actions of ultra-violet light 
and of radium was studied by Dreyer and Hanssen.^^-^^ They found 



52 PREVIOUS INVESTIGATIONS UPON ANIMALS 

that both serous and egg albumin are coagulated under the action of 
an intense light; the serum of the horse only slightly. A solution 
of peptone remains clear, though becoming yellow, and the same 
effect was noted with casein. These results are all attributed to the 
ultra-violet portion of the light. Radium rays were found to coagu- 
late vitellin, but not other albumins. 

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Arch. Protistenkunde 5 : 358. 1905-. 



CHAPTER IV 

• PREVIOUS INVESTIGATIONS UPON PLANTS 
I. Effects of Rontgen Rays on Plants 

In the year 1892 Leo Errera, ^- * by a series of painstaking ex- 
periments with Phycomyces nitens and other plants, demonstrated the 
fallacy of the notion of " physiological-action-at-a-distance," which 
had been put forward in 1890 by Elfving/' ^* It is not surprising, 
then, to find him one of the first investigators to study the physiolog- 
ical action of the then new kind of rays, the X rays, on living plants, 
for Rontgen's discovery belonged to a series of brilliant investigations 
which have resulted in the almost, if not wholly, complete abandon- 
ment of the idea of action-at-a-distance of any kind. Errera, ^^ how- 
ever, was unable to determine the slightest response of Phycomyces 
niteiis when it was exposed to these rays. 

Soon after the discovery that Rontgen rays are a component of 
sunbeams, Miiller^" raised the question as to whether or not the ra3's 
thus occurring exerted any influence upon plants. He placed speci- 
mens of garden cress in a dark chamber, protected from sunlight, 
and found that their stems turned towards the rays as in phototro- 
pism. By this means, and also by using phosphorescent substances, 
Muller reached the conclusion that the X rays present in sunbeams 
do act upon plants. 

Contrary to these results, Schober^'^ failed to observe in oats any 
tropistic response with reference to X rays, but found that an expo- 
sure of one hour to the rays did not cause the seedlings to lose their 
phototropic sensitiveness. 

Studies of the action of X rays on bacteria also began in the year 
1896. The literature on this subject alone has become so volumi- 
nous that it would not be desirable nor profitable to review it here in 
detail, and no attempt is made even to cite all of the published papers. 
Practically all investigators have obtained one or the other of two 
kinds of results ; either negative results, or an injurious effect on the 
bacteria. Among those who have obtained negative results are Mink *^ 

*Errera's interpretation of " pliysiological-action-at-a-distance " as merely a special 
case of hydrotropism, was confirmed by Stryer '' in 1901. 

56 



PREVIOUS INVESTIGATIONS UPON PLANTS 57 

with the typhus bacillus, Wittlin ""'^ with Bacillus coli-comtmmis, B. 
typhi, diphtheria bacilli, Staphylococcus aureus, Spirochaeta cholerae, 
and Tyrothryx tenuis Duclaux ; Beck and Schultz" with various 
bacilli ; Atkinson ^ with bacteria ; and Freund,^ who exposed bac- 
teria to both X rays and the rays from uranium. 

Rontgen rays were found either to inhibit growth or to kill by 
Rieder^-'^^ with B. prodigiosus, the cholera bacillus, and other forms ; 
by Tolomei'^^ with B. anthracis; by Strebel'^" with bacteria exposed 
to Becquerel rays; and by Aschkinass and Caspari^with bacteria 
exposed to Becquerel rays and to cathode and X rays. Rieder's 
results disagree with those of Kriiger and Friedenthal, who, he says, 
state that bacteria could be killed only when electricit}^ is conducted 
through the culture, thus by electrolysis, forming anti-bacterial sub- 
stances. He states that he carefully excluded from his cultures any 
possible influence from heat rays, rays from fluorescent light, and 
electric currents. 

In 1897 Atkinson * reported that etiolated plants recovered their 
green color less rapidly than normally after exposure to the rays, 
and interpreted this as suggesting some injury to the chloroplasts. 
No other influence was observed, and studies on the absorption of 
the rays by species of Mucor, bacteria, and Oscillatoria gave nega- 
tive results. On the question of the absorption of the rays by the parts 
of plants, however, Hinterberger ^^ had already shown that fruits 
containing little sap, and large cavities, such as beans and pea pods 
are most easily penetrated by the rays, while thick buds and fleshy 
fruits, such as pears and cucumbers, are very impenetrable. 

Lopriore " studied the action of X rays on the protoplasm of the 
living vegetable cell. With an exposure of not more than half an 
hour the protoplasmic streaming of Vallisneria spif-alis was accel- 
erated. After this time, if the influence of the rays is removed, the 
motion again becomes normal. An exposure for one hour is dele- 
terious ; the protoplasm continues to stream, but takes on a yellow 
tint, and becomes vacuolated and granular. After an exposure of 
two hours the streaming had not ceased, but the chloroplastids had 
begun to fade. Pollen-grains of Genista and of Darlingtonia did not 
germinate while exposed to the rays, but began to do so after the 
influence of the latter was removed. 

In 1898 Atkinson^ reported negative results from experiments 
with germinating seeds, seedlings, and mature seed plants, Mucor^ 



58 PREVIOUS INVESTIGATIONS UPON PLANTS 

and Mimosa fiidica. He found that the various plant tissues ab- 
sorbed the rays differently, so that X ray photographs may be taken 
which disclose certain details of internal structure, such as vascular 
bundles. 

Maldiney and Thouvenin"*' succeeded in accelerating the germi- 
nation of seeds of Convolvulus aj'vensis, Lepidiuni sativum^ and 
Panicum rniUaceum by exposing them to the action of X rays. From 
the fact that these seedlings as they came from the seeds were yellow 
as usual, the authors conclude that the rays are without influence on 
the formation of chlorophyll. 

Tolomei'^^ states that Rontgen rays act upon plants like light. 
Under their influence the leaves of Philotria canadensis^ in water 
containing COj, give off bubbles of gas as in sunlight. Like light 
also, the rays retard the absorption of oxygen by Mycodernia aceti, 
and also the production of COj by beer-yeast. 

By exposing seeds for about an hour daily for several days to X 
rays, Wolfenden and Forbes^* induced an acceleration of germi- 
nation, and two years later (1902) Seckt^® published the results of 
his studies on the influence of X rays on the plant organism. He 
found, as did Lopriore, that the rays have a decided accelerating 
influence upon the protoplasmic streaming in hairs of Cucurhita 
Pepo, Tradescantia virginiana, and 7 . Sclloi. Seckt remarks that 
this effect may be similar to that called forth by poison or by wound 
stimulus, by which the organism is stimulated to an abnormally 
aggravated vital activity. Spirogyra-ceWs were plasmolyzed at a 
distance of 10-12 cm. from the X ray tube, but were indifferent to 
the rays at greater distances. Increased turgor could also be called 
forth by the rays. The guard cells of the stomata of Tradescantia 
Selloi, and the pulvini of Mimosa and of Oxalis, under the influence 
of the rays undergo an increase of cell-pressure which may have its 
cause in a peculiar influence upon the protoplasm of the cells. 

The latest studies of the effects of Rontgen rays on plants are 
those of Koernicke ^^' ^'^' ^^ In his first paper (1904) he announced that 
the immediate effect of exposure is an acceleration of growth, an 
effect similar to that which Townsend ^" found to occur in plants 
after a slight wounding. Finally, however, growth was retarded. 
The time intervening between exposure and the decrease in the rate 
of growth varies with the plant and its physiological condition at the 
time it was exposed. Brassica napus, for example, is especially 



PREVIOUS INVESTIGATIONS UPON PLANTS 59 

resistant to the rays, not being at all affected by an intensity of ray 
that calls forth a strong reaction in Vicia Faba. If the rays are not 
sufficiently strong no retardation occurs at all. Roots whose growth 
is inhibited by the rays for a certain period will resume their growth. 
The centgener power of seeds was not affected by two exposures to 
rays of the intensity employed (20 Holzknecht units), and the author 
suggests that perhaps Rontgen rays of a certain intensity may act as 
a stimulus to germination, but such experimental effects were not 
recorded. Further results obtained by Kornicke by treatment with 
X rays are mentioned in connection with his experiments with 
radium. ^^' *^ 



2. Effects of Radium Rays on Plants. 

The first recorded observations of the effects of radium rays on 
plant tissues were made by Giesel,^^ two years after Madam Curie's 
discovery. He announced that the rays produced a bleaching of the 
chlorophyll in leaves, causing them to assume an autumnal yellow 
throughout, with a brown coloring on the side exposed to the radium. 
Paper in which radium preparations have lain for a long time becomes 
brown and brittle, and celluloid loses its firmness. These effects of 
intense radium rays, said Giesel, hint at a molecular rearrangement, 
whereby their physiological effects upon plant and animal cells may 
be explained. 

Aschkinass and Caspari^ reported that Becquerel rays "of the 
second type" (/3 rays), as well as X rays, are injurious to bacteria, 
and a few weeks before this Becquerel ^^ announced that an exposure of 
a week or more to radium rays destroyed the germinating power of 
seeds of cress and white mustard. Negative results followed an 
exposure of only 24 hours. These experiments were made in Bec- 
querel's laboratory by Louis Matout. 

Danysz '* studied the pathogenic action of the rays and " emana- 
tions " * given off by radium on different tissues and organisms, and 
found that all species of bacteria are hindered in their development 
by radium rays, but that certain kinds, notably those which produce 
proteolytic enzymes, are more sensitive than others, and are killed 
under certain conditions of exposure. 

* As explained in Chapter I, there is but one " emanation " given oft" by radioac- 
tive substances. It is difficult to know to just what Danysz refers bj "emanations." 



6o PREVIOUS INVESTIGATIONS UPON PLANTS 

In November, 1903, Dixon ^^ reported that the growth of cress 
seedlings was retarded by the rays from 5 mg. of '*pure" radium 
bromide in a sealed glass tube supported at a distance of i cm. over 
seeds sown uniformly on moist sand in the dark. The retardation 
was apparent only in those plants situated within a radius of about 
2 cm. from the tube, and on these seedlings the root-hairs were fewer 
and shorter than on the others. No curvatures were evoked by the 
rays, and when the tube was placed in a vessel of water containing 
Volvox globator in the dark, the Volvox showed no signs of attrac- 
tion or repulsion, or other response. Later in the same year Dixon 
and Wigham ^^ announced that ,5 rays from radium bromide exercise 
an inhibitory action upon the growth of Bacillus pyocyaneus^ B. 
typhosus, B. prodigiosus, and B. anthracis in agar cultures. An 
exposure for four days at a distance of 4.5 mm. to rays from 5 mg. 
of radium bromide did not kill all of the bacilli, for a tube of broth, 
inoculated from a patch thus exposed, developed organisms. 

Hoffmann'^'' found Staphylococcus pyogenes aureus, and milk 
bacteria more resistant than B. prodigiosus. The latter on an agar 
plate was killed by an exposure of three hours to rays from 5 mg. 
of the bromide, passing through a mica plate at a distance of 3.5 
mm. Pfeiffer and Friedberger^' also found the spores more resistant 
than the bacteria of typhus and cholera, the latter being killed by an 
exposure of 48 hours to rays from radium bromide. 

On the contrary. Van Beuren and Zinsser"^ obtained negative 
results in every experiment with B. typhosus, B. pyocyancus, and 
Staphylococcus pyogenes aureus. They employed 12 mg. of radium 
of 300,000 activity, with exposures varying from 8-14 hours, and at 
distances of from i cm. to 0.5 cm. Negative results also followed 
the exposure of the fore arm for one and a half hours with one thick- 
ness of a linen handkerchief intervening. 

Abbe*^ stated that the germination and growth of rape were 
retarded in proportion to the duration of the exposure to rays from 
*' a grain or two of radium salt," of activity not given. The seeds 
were exposed before planting in soil, and exposure of the same kind 
of seeds to X rays was followed by similar results. Later in the 
same year (1904) Abbe ^ reported that the power of seed-germination 
was weakened and finally inhibited by exposure of from two to ten 
days, but he does not mention the kind of seed nor the amount nor 
. tivity of the radium salt used. 



PREVIOUS INVESTIGATIONS UPON PLANTS 6l 

Experiments on the physiological effect of a rays were made by 
Baeyer.*" He employed radioactive lead and " induced " silver, pal- 
ladium, and polonium. The a rays from these preparations killed 
bacteria, but did not affect the skin. 

Dauphin ^^' ^^ was the first to investigate the effect of radium rays 
on the lower fungi. He found that growth was retarded in cultures 
oi Alortierellay Mucor^ Piptocephalis, and Thamnidmm. Spores of 
Mortierella would not germinate in the neighborhood of the radium 
tube, but germinated as soon as the tube was removed. The growth 
of hyphae was arrested, and outgrowths were formed on the filaments. 
The plasma withdraws from the influence of the rays, and septation 
of the hyphae takes place, followed by encystment. On the removal 
of the radium, growth recommences. 

The most extensive paper, up to the date of its publication, was 
that of Dixon and Wigham,^*^- ^^ which appeared in March, 1904. In 
all of their experiments these authors used 5 mg. of radium bromide 
in a sealed glass tube, but the activity (presumably 1,500,000) is not 
given. They found that the seedlings of Lepidium sativum were 
not radiotropic, but grew less rapidly, and had fewer and smaller 
root-hairs when exposed to the rays. Volvox glohator (" positively 
photoscopic ") gave no reaction to the rays. The failure of Bacillus 
^yocyaneus, B.^rodigiosus^ B. typhosus, and B. anthracis to develop 
under the influence of the rays is attributed, not to the direct effect of 
the rays on the organisms, but to a probable change in the agar. 
The effects are thought to be due more to the /9 than to the y rays, for 
the latter are too penetrating to be absorbed by 30 mm. of air, and 
beyond this distance the radiations were apparently without effect. 
It is suggested that the electrons, emitted directly by the radium, or 
produced indirectly by it, were partly absorbed by the bacterial cul- 
tures. They possibly attach themselves to the positive ions of the 
cultures, among which are the hydrogen ions of the water. Thus 
OH ions would be set free, and the water in the protoplasm would 
become alkaline. This would check the action of the enzymes on 
which the metabolism of the cells depends, for most enzymes, except 
trypsin, are inhibited in an alkaline solution. In support of this 
hypothesis it was found that colorless phenolphthaline, diffused 
through an agar culture, acquired a feeble pink color when the 
preparation was exposed for a day or two to the radium rays. This 
the authors explain as being due to the liberation of negative OH 



62 PREVIOUS INVESTIGATIONS UPON PLANTS 

ions through neutralization of the H ions by the electrons from the 
radium. It is recognized that the coloration may be due to direct 
ionization of the phenolphthaline as well as of the water. Further 
experimentation, however, showed that the detection of electrons by 
means of this indicator is very uncertain. The same agar prepara- 
tion became pink when supported over a solution of caustic potash * in 
a closed chamber. 

In a note on the action of radium on microorganisms, A. B. 
Green ^* states that the specific germ of vaccine is killed after 22 hrs. 
exposure to radium rays from i eg. of <' practically pure radium 
bromide," contained in a vulcanite and brass capsule, fronted with 
thin talc. Only the [-i and y rays were thus available. Staphylo- 
coccus pyogenes aureus, S. pyogenes albus, S. cereus jlavus, and S. 
cereus albus were less resistant than the specific vaccine organism, 
and spore-forming bacteria were most resistant, requiring 72 hrs. to 
kill. It is further stated that, after an exposure of from 24-120 hrs., 
the microorganisms themselves ma}'^ exhibit radioactivity. It is con- 
sidered uncertain as to whether or not living organisms can acquire 
this power, but those killed by the rays can do so. It is impossible 
to conceive how the organisms, dead or alive, could become radio- 
active as a result of their exposure to a radium salt in a sealed con- 
tainer. If the container was not perfectly sealed, however, then 
traces of the emanation might diffuse out and thus cause induced 
activity of the organisms. 

Willcock ''^ stated that an attempt by Mr. Hardy to secure photo- 
synthesis in liverworts by the energy of radium rays was unsuccess- 
ful, and that Dr. Anderson had shown that the tissues of leaves may 
be killed by the rays. 

Koernicke's ^^ paper on the influence of radium rays on germina- 
tion and growth appeared twelve days after that of Dixon and Wig- 
ham. He found that the growth of the roots of Vicia Faha in 
sawdust was inhibited when a sealed glass tube of radium bromide 
was placed close by the elongating tip. The radium was removed 
at the end of four days, but growth was not resumed, though the 
roots remained alive for over a month after they had ceased to grow. 
When dry seeds of Vicia Faha were exposed for 24 hrs. the subse- 
quent growth of the root was retarded, but the shoot did not appear 

\' * The radioactivity of potassium, discovered by Campbell (p.'sz), was not known 
at the time of publication of Dixon and Wigham's experiments. 



PREVIOUS INVESTIGATIONS UPON PLANTS 63 

affected. Adventitious roots sprang from the epicotyl, and three 
days after this the main root died. The intervention of three days 
between exposure of seeds and planting seemed to make no difference 
in the result. The effect of the rays decreased with the distance, 
and apparently ceased at a distance of four centimeters. When roots 
of Vtcta Faha seedlings 3-11 cm. long were exposed to rays from 5 
mg. of radium bromide for five days, the roots near the radium tube 
grew longer at night, and the portions lying back of the tip grew a 
little to one side in the region of the radium influence. Growth 
ceased on the fourth day. 

Seeds of Brasstca napus seemed specially resistant both to radium 
and to X rays. Five days exposure with 10 mg. of the bromide 
did not interfere with germination and further development. Swollen 
seeds irradiated with the same mass of radium salt showed an accel- 
eration of germination, but subsequently the rate of growth became 
normal. Removal of the seed-coats of Brasstca did not make them 
any more sensitive, for development of these seeds was normal after 
they were exposed. Ten days' exposure to rays from 10 mg. re- 
tarded germination and growth, and exposure for a longer time com- 
pletely destroyed the power to germinate. 

Growth of both root and shoot of Vict'a was retarded by exposing 
the vegetative points to the rays, and in this respect etiolated and 
non-etiolated specimens behaved alike. The growth of callus on 
wounds of Poftilus alba was retarded by the rays. 

Germination of the spores of Aspergillus niger was inhibited by 
two days' exposure under the radium tube, and the mycelia that 
developed near the tube did not fruit. Kornicke considered these 
non-fruiting hyphae in a condition of " latent Hfe," an interpretation 
which Dauphin had applied to spores of Mortierella which failed to 
germinate while exposed, but did so after the radium was removed. 
Dry conidia of Asfergilhis niger, irradiated for 1-4 days with 10 
mg. of the bromide, did not lose their power to germinate, though 
the germination was more or less delayed according to the length of 
exposure. 

London's*^ experiments indicate that the vitality of bacterial 
cultures was destroyed after an exposure of two days to the 
" emanations."* 

* See footnote, p. 8. This word is doubtless not used here in the sense of 
emattatton, as defined bj Rutherford, but as a collective term, referring to all the influ- 
ences from the radium, especially the rays. 



6/\. PREVIOUS INVESTIGATIONS UPON PLANTS 

Dorn, Baumann, and Valentiner,^^ experimented with the gase- 
ous emanation, and found that Bacillus typhosus, cholera germs, and 
bacilli of diphtheria, exposed to its influence, were killed. The 
effects were attributed to the /9 rays * given off by the emanation, 
and not to the gas itself, apart from its radioactivity. 

In August, 1905, were published Koernicke's*'' further researches 
concerning the effect of Rontgen and radium rays on plants. His 
earlier results were confirmed by these experiments, in which he used 
0.75 gm. of about 4 per cent, radium-barium chloride in a thin 
aluminium and glass capsule. Brassica was found very resistant, 
and no difference was noticed in the effect of rays from the large 
quantity of radium preparation passing through thin aluminium, and 
of those from the smaller amount in the thicker glass capsule. The 
growth of roots of Vicia Faba was inhibited, and, in some instances, 
was resumed after the radium was removed, in other cases not. The 
shoot, once inhibited, never resumed growth, but luxuriant adventive 
sprouts developed in the axils of the cotyledons. Tissues were made 
brown by the exposures, and marked individual variations were found 
in the behavior of the seeds of Vicia. The growth of Pisum seed- 
lings was retarded in proportion to the length of exposure of the seed 
before germination. 

These experiments indicate that roots are more sensitive than 
shoots, and, in the light of Willcock's and of Hertel's work, this was 
explained by the presence of chlorophyll in the shoots. All attempts 
to affect the geotropic sensitiveness of roots and shoots were unsuc- 
cessful, except in those cases where growth had been completely in- 
hibited by the rays. Starch was not found in roots or shoots of 
seedlings grown from the seeds exposed for two days before planting. 
Exposure to X rays gave similar results. Exposed seedlings also 
responded phototropically to light so long as they were growing, but, 
says Koernicke, " at the conclusion of growth they were in a condi- 
tion which I may designate as ' radium-rigor and Rontgen-rigor.' " 
The light waves coming from the preparation induced phototropic 
curvatures in sporangiophores of Phycomyces nitens after an expo- 
sure of about 15 hours, at a distance of more than 3 cm. This re- 
sponse failed when the light rays were cut off by wrapping the 
radium tube in black paper, and Kornicke feels sure that the result 

* So the authors. The emanation, however, does not give off /3 rays, but only a 
rajs. See p. 9. 



PREVIOUS INVESTIGATIONS UPON PLANTS 65 

was not caused by the moisture that gathered on the tube, as was 
shown by Errera and Steyer with reference to the experiments of 
Elfving. Positive phototropic response to the phosphorescent light 
of the radium is also claimed for Vicia Faba seedlings if the activity 
of the preparation is sufficiently strong. 

In November of the same year (1905) appeared Koernicke's*^ 
paper on the effect of Rontgen and radium rays on plant tissues and 
cells. In plants developing from seeds exposed to either radium or 
X rays, the epidermis of the roots was wrinkled over the entire sur- 
face. Direct exposure of growing roots produced the same result. 
The undulatory curvatures of the vascular bundles, present in nor- 
mally contractile roots, was not observed. Multiplication of nuclei 
was also observed in cells of the periblem and plerome of exposed 
roots. 

Cell-studies were made of roots of Vicia Faba and of Pisum 
sativum, after exposure of i, 2, and 3 days to the radium, and also 
of roots that developed from exposed seeds. No results followed 
exposure of the roots for one day, but after an irradiation of two days 
cell-divisions appeared normal, but less numerous* while treatment 
for three days sufficed to practically inhibit mitosis. Resting nuclei 
appeared unaffected. Not until after the roots had ceased growing 
did peculiar forms appear which could be attributed to the influence 
of the rays on the chromatin. Here spindles occurred in which the 
daughter chromosomes were separated from each other with diffi- 
culty, so that their progress toward the poles was delayed. Forma- 
tion of the cell-wall occurred normally in exposed tissues, and for this 
and other reasons it is held that the polynucleate cells resulted from 
amitosis. 

Flower buds of Liliiim mariagon of various ages, from the 
youngest to the oldest, were exposed to the rays for varying lengths 
of time, and fixed at different periods following the exposure. 
Mitosis was retarded and inhibited, and the reproductive cells were 
more sensitive than the vegetative cells to the influence of the rays. 
Numerous irregularities in mitosis were observed. For example, 
anthers fixed 20 hrs. after irradiation for 5 hrs., showed the nuclear 
thread of the pollen-mother-cell separated into smaller and more 
numerous double segments than is normal in the species. The small 
segments were later drawn together on a normally formed spindle, 
and, in one instance, on a multipolar spindle. In the subsequent 

6 



66 PREVIOUS INVESTIGATIONS UPON PLANTS 

longitudinal splitting and distribution to the daughter-nuclei these 
segments moved irregularly, some lagging behind on the equator, 
or appearing distributed along the spindle between the equator and 
the poles. Several cases were observed where two and three 
daughter-nuclei were formed on each side of the cell-plate. In 
some cases an increased number of tetrads resulted from the division 
of the pollen-mother-cell. Following the exposure to the rays, there 
was observed a tendency to a stronger formation of kinoplasm than 
formerly. 

The first recorded experiments of the effect of radium rays on 
plant respiration are those of Micheels and de Heen,*^ who found that 
the respiratory energy of germinating pea seeds was diminished by 
exposure to the rays from 0.5 mg. of a radium preparation of 240 
activity. The authors describe this result as being in good agree- 
ment with other physiological phenomena due to radium. 

Molisch^^ was not successful in any attempts to produce a tropistic 
curvature by the direct influence of the rays of radium, but found 
that the phosphorescent light produced by mixing radium bromide of 
3,000 activity with zinc blend in a sealed glass tube, caused positive 
phototropism of stems in Vic/a sa/i'va, and £rvum I^ens, but called 
forth no curvatures in Helianthus anniius. In the case of Phy- 
comycesnitens^ sporangiophores were positively, and mycelium nega- 
tively phototropic. The phototropic sensibility of the seedlings above 
mentioned was greatly intensified by exposure to the rays. As Molish 
indicates in the title of his paper, these curvatures may be attributed 
only indirectly to the radium ; they are responses only to the phos- 
phorescent light caused in the zinc-blend by the rays. 

The ability of Bacillus pyocyaneiis to secrete its characteristic 
pigments was found by Bouchard and Balthazard ''^ to be diminished 
by exposure to radium emanation, and the power of reproduction 
and division was diminished and finally destroyed, Rays from 
"the radioactive residues from the treatment of pitchblend from 
Joachimsthal " affected various species of Aspergillus in a similar 
manner (Dauwitz ''). Sensitiveness to the rays varies according to 
the species, A. niger and A. Juinigalus being most sensitive, and A. 
ochraceus, A. clavatus, and A. varians less so, in the order named. 
Spores formed while the plant was under the influence of the radio- 
active bodies germinated poorly, and produced a meager mycelium 
that bore no spores. Analogous effects followed the treatment of 



PREVIOUS INVESTIGATIONS UPON PLANTS 67 

different species of Penicilliwn . Experiments with B. prodigiosus 
and B.pyocyancus confirmed the results of Bouchard and Bahhazard. 

Dorn, Baumann, and Valentiner ^^ caused the emanation from 30 
mg. of radium bromide (activity not given) to be bubbled through 
sterilized bouillon for five minutes, and then added i oz. of a typhus- 
bouillon culture. Then daily, for 10-12 days, two or three times a 
day for ten minutes at a time, the emanation was bubbled through 
the mixture. On the tenth and thirteenth days the cultures were 
platted out, and in three days thereafter the exposed culture was 
only a tenth as much developed as the control. Beta and gamma 
rays from 5 mg. of " pure " radium bromide inhibited the growth of 
germs of typhoid, cholera, and diphtheria. The authors hold that 
the emanation itself, behaving as a heavy gas, has no physiological 
effect, and their results are, therefore, to be attributed to the radio- 
activity of the emanation. 

Guilleminot's ^ study of the comparative effects of X rays and those 
of radium on the plant-cell were first published in November, 1907. 
This author had previously * indicated a process for determining the 
effectual strength of X rays, and defined a unit M, obtained by 
a comparison of the fluorescence of barium platynocyanide and that 
of a standard of radium. Using seeds, of Mahon's gilliflower, he 
obtained the following results: i. The true characteristic action of 
the rays is a retardation of growth when the strengths are rather 
great. 2. The strength that slightly retards appears to be 3,000 M, 
radium, and 15,000 M, X rays. 3. The fatal strength is in the 
neighborhood of 10,000 M, radium, while 20,000 M, X rays per- 
mits of a feeble development. 4. The accelerating action, if such 
exists, is apparently reached at about 250-500 M, radium, and 5,000- 
7,500 M, X rays. The differences (in result), he says, are too feeble 
to warrant the unqualified assertion of an acceleration, and, in his 
longer paper, he^^ states that an "exciting" dosage probably does 
not exist. 

* Guilleminot *"' 31 adopts as a unit of intensity (M) of the field of irradiation the 
quadruple of the intensity producing the same luminescence as a standard of 0.02 gm. 
of radium bromide of 500,000 activity, spread over a circular surface of I cm. in diame- 
ter, and placed at a distance of 2 cm. from the phosphorescent surface. Then the unit 
of quantity of irradiation will be the quantity acting for one minute when the field has 
unit of intensity. 



68 previous investigations upon plants 

3. Effects of Radium Rays on Plant Fibers 

In addition to the physiological results reviewed above, the action 
of radium ra3's on vegetable fibers is both interesting and pertinent in 
this connection. This effect was first noticed by Giesel,"* and after- 
ward accidentally by Lord Blythswood,^^ in 1904. "I happened," 
says the latter, " to replace the usual mica plates, used to keep in the 
small quantity of radium in its ebonite box, with a piece of cambric, so 
as to permit the whole of the emanations to pass out, mica stopping 
the a. rays. In four days the cambric was rotted away. I have 
replaced it now several times with the same result." 

In the following year Martin and Morton ^^ experimented on the 
effect of the rays on unspun silk fibers and ordinary unbleached cot- 
ton thread. The threads were exposed to " bare radium," at a dis- 
tance of about one half centimeter. After a certain period of expo- 
sure the average breaking strength of the threads was taken and 
plotted against time. The points obtained lay closely on a smoothly 
descending curve. In the case of the silk the loss of strength went 
on at a practically uniform rate from the beginning up to the end of 
the longest exposure given (seven days). The initial strength of 78 
gm. decreased by about 4 gm. per day. The cotton threads gave 
a curve which fell more rapidly in the early than in the later stages. 
The strength began at 370 gm., and decreased at first by about 60 
gm. per day. After ten days the rate of weakening was about half 
this. At the end of 17 days the strength was reduced to 17 gm. 
The difference in behavior of the two kinds of fibers is attributed to 
the greater thickness of the cotton threads. The effect is due en- 
tirely to the a rays, for only negative results were obtained when 
those rays were screened out. 

Wet threads, with the same length of exposure, were less weak- 
ened, and this, the authors state, was plainly due to the decreased 
emission of rays on account of the solution of the radium salt, and 
the consequent removal of the emanation.* 

In a subsequent paper, McKee and Morton"^ state that the con- 
stant removal of the emanation does not affect the result. It was 
further found that when threads or a piece of filter paper, after 
exposure to the rays are dyed with methylene blue, the exposed part 
takes a deeper color than the rest, thus indicating the presence of 

* " The rate of escape of emanation is much increased by solution of the com- 
pound." Rutherford, p. 255 (see Bibliography, p. 20, No. 115). 



PREVIOUS INVESTIGATIONS UPON PLANTS 69 

oxycellulose. The weakening effect became inappreciable at a 
distance of i8 mm. Under the microscope the broken ends of the 
fibers of exposed threads were straight at their ends, those not 
exposed curled, indicating a loss of elasticity through exposure to the 
rays. 

In July, 1907, Hussakof'^' published a review of the more impor- 
tant papers bearing on the physiological effects of the rays of 
radium. Previous announcements of my own results have appeared, 
with one exception, as abstracts of papers presented before various 
scientific societies ; citations to them will be found in the Bibliography 
appended to this chapter, and further reference to them here is 
unnecessary. 

The details of the investigations reviewed above are numerous, 
but the results may be briefly summarized. There is very general 
agreement on the following points : 

1. Radium rays have the power to modify the life-processes of 
both plants and animals. 

2. Rontgen rays and radium rays produce similar physiological 
results. 

3. Sensitiveness to these rays varies with the species of either 
plant or animal. 

4. Younger, and especially embryonic tissues, are more sensitive 
than those more mature. 

5. With only one or two exceptions, exposure to radium rays has 
been found to either retard or completely inhibit all cell-activities. 
The rays may cause irregularities in mitosis. 

6. Experimental evidence for or against the existence of a radio- 
tropic response is conflicting. 

7. Whatever the immediate, internal change produced in the pro- 
toplast may be, the result, with animals as well as with plants, 
appears to be more or less profoundly modified by the presence of 
chlorophyll in the cell. 

8. Radium rays appear to retard the activity of enzymes. 



yo previous investigations upon plants 

Bibliography 
Physiologial Action-at-a-Distance 

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mentat, Variae Universit. Helsingfors, 1890. 

2. . Sur un action directrice qu'exercent certains corps sur les tubes 

sporangiferes de '•'• Phycomyces niteiis." Ann. de I'lnst. Pasteur 5: 
loi. 1891. 

3. Errera, L. On the cause of physiological action at a distance. Ann. 

Bot. 6 : 373. 1892. 

4. . Sur I'hygroscopicite comme cause de Taction physiologique a 

distance decouverte par Elfving. Recueil de I'lnst. Bot. de I'Univ. 
Bruxelles6: 305. 1906. 

5. Steyer, K. Reizkriimmungen \i€\Phycoi)icyes 7iite7is. Inaug. Dissert. 

Pegau, 1901. 

Effects on Plants 

6. Abbe, R. Radium and radio-activity. Yale Med. Jour. 10 : 433. 1904. 

7. . The subtle power of radium. Med. Record 66 : 321. 1904. 

8. Aschkinass, E., & Caspari, W. Ueber den Einfluss dissocierender 

Strahlen auf organisirte Substanzen, inbesondere iiber die Bakteri- 
enschadigende Wirkung der Becquerelstrahlen. Arch. Ges. Physiol. 
86 : 603. 1 90 1. 

9. Atkinson, G. F. Report upon some preliminary experiments with the 

Rontgen rays on plants. [Xature 56: 600. 1897.] Science, 
N. S. 7:7. 1898. 

10. Baeyer, H. von. Ueber die physiologische Wirkung der Becquerel- 

strahlen. Zeits. Allgem. Physiol. 4: 79. 1904. 

1 1 . Beck, M., & Schultz, P. Ueber die Einwirkung der sogennanten mono- 

chromatisches Lichtes auf die Bakterienentwickelung. Versuche der 
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12. Becquerel, H. Sur quelques effets chimiques produits par le rayonne- 

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13. Bouchard & Balthazard. Action de I'emanation du radium sur les 

bacteries chromogenes. Compt. Rend. Acad. Sci. Paris 142 : 819. 
1906. 

14. Danysz, J. De Taction pathogene des rayons et des emanations emis 

par le radium sur differents tissus et differents organismes. La 
Semaine Med. 23: 64. 1903. Compt. Rend. Acad. Sci. Paris 
136: 461. 1903. 

15. Dauphin, J. Influence des rayons du radium sur le developpment et la 

croissance des champignons inf^rieurs. Compt. Rend. Acad. Sci. 
Paris 138: 154. 1904. Ann. Mycol. 2: 472. 1904. Jour. Roy. 
Mic. Soc. 1905^ : 69. 1905. 



PREVIOUS INVESTIGATIONS UPON PLANTS 7 1 

i6. Dauphin, J. Influence of radium rays on the development and growth 

of the lower fungi. Nature 69 : 311. 1904. 
17. Dauwitz, F. Action biologique des residus radioactifs du traitment de 

la pechblende de Joachimsthal (Boheme). Zeits. Heilkunde 27: 

87. 1906. Le Radium 3 : 157. 1906. 
iS. Dixon, H. H. Radium and plants. Nature 69: 5. 1903. 
19. & Wighman, J. T. Action of radium on bacteria. Nature 69 : 

Si. 1903. 
20. . Preliminary note on the action of the radiation from 

radium bromide on some organisms. Proc. Roy. Dublin Soc. Sci., 

N. S. 10": 178. 1904. Notes Bot. School, Trinity Coll., Dublin 

l: 235. 1905. 

21. Dorn,E.,Baumann,E.,&Valentiner, S. UeberdieEinwirkungderRadi- 

umemanation auf pathogene Bakterien. Physikal. Zeits. 6 : 497. 1906. 

22. Errera, L. Experience relative a Taction des rayons X sur un Phy- 

comyces. Compt. Rend. Acad. Sci. Paris 122 : 7S7. 1S96. 

23. Freund, L. Die phj'siologischen Wirkungen der Polentladungen hoch- 

gespannter Inductionsstrome und einiger unsichtbarer Strahlungen. 
Sitz. Kais. Akad. Wiss. Wien. Math.-Naturw. Kl. 109: 583. 1900. 

24. Gager, C. S. Preliminary note on the effects of radium-rays on plants. 

Amer. Med. 9 : 1026. 1905. 

25. . Preliminary notes on the effects of radio-activity on plants. 

Science, N. S. 22 : iiS. 1905. Torreya 5 : 150. 1905. 

26. . The effect of the rays of radium on plants. Proc. Am. Assoc. 

Adv. Sci. 55: 326. 1906. 

27. . Some effects of radioactivity on plants. Science, N. S. 25: 

264. 1907. 

28. Giesel, F. Ueber radioaktive Substanzen und deren Strahlen. Samm- 

lung Chem. u. Chem.-Teck. Vortrage. (Herausgeg. v. Prof. F. B. 
Ahrens, Stuttgart.) 7: i. 1902. 

29. Green, A. B. A note on the action of radium on microorganisms. 

Nature 70: 69, 117. 1904. Proc. Roy. Soc. London 73: 375. 
1904. Bot. Cent. 37: 269. 1904. 

30. Guilleminot, H. Nouveau quantitometre pour rayons X. Compt. 

Rend. Acad. Sci. Paris 145: 711. 1907. 

31. , Mesure de la quantite de rayonnement (preliminaire a I'etude de 

Taction des radiations sur la germination des plantes). Assoc. 
Fran9aise Adv. Sci. 1907^: 389. 1907. 

33. . De Taction des i-ayons du radium et des rayons X sur la germi- 
nation. Assoc. Fran9aise Adv. Sci. 1907^: 1344. 1908. 

33, . Effets compares des rayons X et du radium sur la cellule vege- 

tale. Valeur de Tunite M en physiologic vegetale. Compt. Rend. 
Acad. Sci. Paris 145: 798. 1907. 



72 PREVIOUS INVESTIGATIONS UPON PLANTS 

34. Hardy. See Willcock, 1904. No. 62. 

35. Hinterberger, H. Rontgenogramme von Pflanzentheilen. Verhandl. 

Zool.-Bot. Ges.Wien46 : 365. 1896. Photographischen Correspon- 
denz 1S96. (Not seen.) 

36. Ho^mann, W. Ueber die Wirkung der Radiiimstrahlen auf Bakterien. 

Hygien. Rundschau 13: 913. 1903. 

37. Hussakof, L. Recent investigations of the action of radium on plants 

and animals. Med. Record 72: Jy 3o, 1907. (Separate reprint. ) 

38. Koernicke, M. Ueber die Wirkung von Rontgenstrahlen auf dieKeim- 

ung und das Wachstum. Ber. Deut. Bot. Ges. 22: 148. 1904. 

39. . Die Wirkung der Radiumstrahlen auf die Keimung und das 

Wachstum. Ber. Deut. Bot. Ges. 22: 155. 1904. Nature 71 : 

373- 1905- 

40. . Weitere Untersuchungen iiber die Wirkung von Rontgen- und 

Radiumstrahlen auf die Pflanzen. Ber. Deut. Bot. Ges. 23 -.324. 1905. 

41. . Ueber die Wirkung von Rontgen- und Radiumstrahlen auf 

pflanzliche Gevvebe und Zellen. Ber. Deut. Bot. Ges. 23 : 404. 1905. 

43. . Die Wirkung der Radiumstrahlen auf dem pflanzlichen Organ- 

ismus. Sitzber. Niederheim. Ges. Nat. u. Heilk. Bonn, 1905, A: 
64. 1906. 

43. London, E. S. [Note on the physiological action of radium bromide in 

solution.] Nature 70: 331. 1904. From Arch. d'Elect. M^d. 
No. 142. 1904. 

44. Lopriore, G. Azione del raggi X sul protoplasma della cellula vegetale 

vivente. Nuova Rassegna, Catania, 1S97. (Not seen.) Abstr. in 
Bot. Cent. 73: 451. 1898. 

45. Maldiney & Thouvenin. De I'influence rayons X sur la germina- 

tion. Rev. Gen. Bot. 10 : Si. 1898. Compt. Rend. Acad. Sci. 
Paris 126: 548. 1898. 

46. Micheels, H., & Heen, P. de. Influence du radium sur I'energie respira- 

torie de graines en germination. Bull. Acad. Roy. de Belgique 
Class, des Sci., p. 29. 1905. Bot. Cent. 98 : 646. 1905. 

47. Mink, F. Zur Frage den Einfiuss der Rontgen'schen Strahlen auf 

Bakterien, und ihre eventuelle therapeutische Verwendbarkeit. 
Miinchener Med. W^ochens. 43: loi, 202. 1896. 

48. Molisch, H. Ueber Heliotropismus indirekt hervorgerufen durch Ra- 

dium. Ber. Deut. Bot. Ges. 23: 2. 1905. 

49. Montemartini, L. Intorno all' influenza dei raggi ultra violetti sullo 

sviluppo degli oi'gani di riproduzione delle piante. Atti Inst. Bot. 
Pavia, N. S. 9. (Not seen.) Bot. Jahrb. 31^: 564. 1903. 

50. Miiller, N. J. C. Kommen die Rontgenstrahlen im Sonnenstrahl fiir 

die Pflanzen zur Wirkung. Ber. Deut. Bot. Ges. 14: (66). 1896. 



PREVIOUS INVESTIGATIONS UPON PLANTS 73 

51. Pfeiffer, R., & Friedberger, E. Ueber die Bakterientodtente Wirkung 

der Radiumstrahlen. Berliner Klinische Wochens. 40 : 640. 1903. 

52. Rieder, H. Wirkung der Rontgenstrahlen auf Bakterien. Miinch. 

Med. Wochens. 45^ : loi. 1S98. 

53. . Weitere Alittheilungen iiber die Wirkung der Rontgenstrahlen 

auf Bakterien, sowie auf die menschliche Haut. Miinch. Med. 
Wochens. 45': 773. 1S9S. Bot. Cent. Beiheft. 8 : 250. 1898. 

54. . Nochmals die bakterientodtende Wirkung der Rontgenstrahlen. 

Miinch. Med. Wochens. 49^ : 402. 1902. 

55. Shober, A. Ein Versuch mit Rontgen'schen Strahlen auf Keim- 

pflanzen. Ber. Deut. Bot. Ges. 14: 108. 1896. 

56. Seckt, H. Ueber den Einfluss der X-Strahlen auf den pflanzlichen 

Oi'ganismus. Ber. Deut. Bot. Ges. 20: 87. 1902. Naturwiss. 
Wochens. 18: 49. 1902. (Not seen.) 

57. Strebel, H. Zur Frage der Lichttherapeutischen Leitungsfahigkeit des 

induktionsfunkenlichtes nebst Angabe einiger Versuche iiber die Bak- 
terienfeindliche Wirkung der Becquerlstrahlen. Fortschritte auf dem 
Gebiete der Rontgenstrahlen 4: 125. 1900. 

58. Tolomei, G. Rayons Roentgen et vegetation. Rev. Sci. IV. 9: 217. 

1898. 

59. . Studi sopra I'azione dei raggi Rontgen sui vegetali. Atti 

della Reale Accad. dei Lincei Rendiconti. V. 7: 31. 1898. Re- 
sume in Nature 57 : 323. 1898. 

60. Townsend, C. 0. The correlation of growth under the influence of 

injuries. Ann. Bot. II: 509. 1897. 

61. Van Beuren & Zinsser. Some experiments with radium on bacteria. 

Am. Med. 6: 1021. 1903. 

62. Willcock, E. G. The action of the rays from barium upon some simple 

forms of animal life. Jour. Physiol. 30: 449. 1904. 

63. Wittlin, J. Haben die Rontgen'schen Strahlen irgend welche Ein- 

wirkung auf Bakterien? Cent. Bakt. Parasitenkunde, etc. 2: 676. 
1896. 

64. Wolfenden & Forbes, R. [Effects of Rontgen rays on germination of 

seeds.] Arch. Rontgen Rays 5 : 1900. (Not seen.) 

Effects on Plant Fibers 

65. Blythswood, Lord. Destructive action of radium. Nature 69: 317. 

1904. 

66. Giesel, F. See No. 28 above. 

67. Martin, H. P., & Morton, W. B. The effect of radium on the strength 

of threads. Nature 72 : 365. 1905. 

68. McKee, J. L., & Morton, W. B. The effect of radium on the strength 

of threads. Nature 75 : 224. 1907. 



CHAPTER V 
BIO-RADIOACTIVITY, EOBES, RADIOBES 

I. The Supposed Radioactivity of Plants and of Wood 

Soon after the discoveries of "contact" electricity and "animal" 
electricity by Volta and Galvani, plant physiologists began to look 
for electric currents in plants, and to find therein the explanation of 
" vital" activity. In a similar manner the announcement of the dis- 
covery of radioactivity has been followed by numerous supposed 
observations of a natural or acquired radioactivity of plants and 
plant tissues. 

Professor A. B. Green" was among the first to report that micro- 
organisms, especially species of Staphylococcus^ after an exposure 
of from 24-120 hrs. to radium rays at a distance of 0.5 mm., them- 
selves exhibit phenomena of radioactivity. He considers it uncertain 
as to whether living organisms can acquire this property, but states 
that those killed by the action of radium rays can do so. In his ex- 
periments the radium salt was enclosed in a vulcanite and brass cap- 
sule, and the radioactivity acquired by the organisms, lasted for 
three minutes after the termination of the exposure, and enabled 
them to photograph themselves on a sensitive plate. Their spores 
were found to be best for this purpose. I have already discussed 
these results on page 62. 

Lambert'^ stated in 1904 that ferments that digest albuminous 
matter emit Blondlot rays, and that the emission of these rays is the 
cause of the action of the soluble ferments. 

The experimental demonstration of the emission of the so-called 
N rays by plants of the garden cress was reported by Meyer. Their 
emission, he said, varies with the activity of the protoplasm, and is 
diminished when the plants are exposed to the vapor of chloroform, 
and is modified by mere compression of the tissues. 

In 1904 Russel ' described before the Ro3^al Society the rather 
startling discovery of the action of wood on a photographic plate in 
the dark. This property, he said, belongs probably to all woods. 
Conifers are especially active, and the spring wood most of all, but 
the dark autumn wood produced no such effect. Oak, beech, acacia 

74 



BIO-RADIOACTIVITY, EOBES, RADIOBES 75 

{Robmid), Spanish chestnut, and sycamore possess this property, but 
ash, elm, the horse-chestnut, and the plane tree only to a slight 
degree. Most resins manifest it, but not so the true gums, such as 
gum Senegal and gum tragacanth. Exposure to sunlight, especially 
to the blue rays of the spectrum, increases the activity. Cork, 
printer's ink, leather, pure India rubber, fur, feathers, and turpen- 
tine are reported to have their activity increased in the same way. 
Since bodies such as slate, porcelain, flour and sugar, in which there 
is no resinous or allied body, do not react in this way, nor affect the 
plate at all, the activity of the various kinds of wood is attributed to 
the resinous substances in them. Tommasina's* paper was also pub- 
lished in 1904. He reported that all freshl}^ gathered plants, fruits, 
flowers, and leaves possess a radioactivity which is stronger in the 
young and in individuals in action than in those at rest, being appar- 
ently proportional to the vital energy. For this phenomenon he pro- 
posed the term hto-radioactivity . Buds of lilac, and leaves of Thuja 
and of laurel were found by him to be bio-radioactive. 

In the following year Tarchanoff and Moldenhauer '^ published 
their preliminary note on the induced and natural radioactivity of 
plants, and on its probable role in their growth. When seeds of 
various grains, and of the pea were exposed to the radium emana- 
tion, the seedlings, growing from such seeds showed induced radio- 
activity in their roots, but the stem and small leaves remained inactive. 
Also when a mature plant was exposed to the emanation the roots 
became strongly radioactive, the stem somewhat less so, the leaves 
only slightly, and the flowers not at all.* 

This distribution of the radioactivity in the plant body is constant, 
and the authors consider that there is in the plant a special substance, 
sensible to the emanation, and capable of becoming radioactive under 
its influence. This substance occurs in the roots, but gradually 
diminishes up the stem. It is found also in seeds. According to 
this same paper plants possess a natural radioactivity, which is dis- 
tributed throughout the plant similarly to the induced radioactivity. 
This natural radioctivity is strong enough to affect a photographic 
plate, and plays an important role in the development of the plant. 

In a second paper Russel*^ gives a list of 33 native and 22 foreign 
woods that are active, and says that the activity of resins and gums 
is increased by exposure, not only to sunlight, but to the arc-light as 

* Results not confirmed by Acqua, Rend. Accad. Lincei V. 6 : 357. 1907. 



76 BIO-RADIOACTIVITY, EOBES, RADIOBES 

well. Photographic plates often contain a negative of the plate- 
holder. That this is not a case of radioactivity appears to be proved, 
says the author, for a glass or a mica screen of one thousandth of an 
inch in thickness entirely protects the plate from being acted on. 

Finally Paul Becquerel ^ undertook a careful study of "plant 
radioactivity." He tested pea seeds, moss {Hypnum), and branches 
of boxwood for radioactivity, but found not a trace of it manifest 
when the electroscope was carefully guarded from water-vapor. 
This explains the condition found necessary by Tommasina, that the 
parts of plants must be freshl}' picked in order to manifest bio-radio- 
activity. According to Becquerel, the discharge of the electroscope 
in Tommasina's experiments was due to the water in the plants. 

From all the investigations noted above, the general conclusion 
seems to be warranted that radioactivity is not a property of proto- 
plasm nor of living tissues. A clear understanding of the nature of 
radioactivity would lead, a priori, to the same inference. 

2. The Professed Artificial Crf:ation of Life 

Radioactivity and vital activity are in two respects very roughly, 
but only very superficially analogous. Both radioactive bodies and 
living organisms are undergoing a destructive process ; atomic disin- 
tegration in the one, molecular transformation in the other ; both, with 
exceptions, maintain themselves constantly at a higher temperature 
than their surroundings. These analogies have in two or three 
instances proven dangerously attractive. 

A consideration of radioactivity led Dubois, ^^ in 1904, to the view 
that the distinction between " matter of life" and "living matter" is 
superficial. He proposed the term bioproteon, meaning the partic- 
ular state of the " proteon " in living beings, and suggested the desira- 
bility of determining the radioactivity proper of the bioproteon. In a 
subsequent paper ^^ he says : " The unique principle of everything, of 
both force and matter, I have called ' proteon,' and when it pertains 
to a living being, 'bioproteon.'" Pr.oteon and bioproteon are only 
two different states of the same thing. When the bioproteon is dead 
it has only ceased to be radioactive and becomes simply proteon. He 
claimed also to have discovered the emission, from the lamellibranch 
mollusc, Phalade daciyle, of rays that could penetrate paper and 
opaque substances, and darken a sensitive plate. 

Early in the year 1905 appeared his paper ^^ on " La creation de 
Vetre vivant et les lois natiirelles''' in which he announced the forma- 



BIO-RADIOACTIVITY, EOBES, RADIOBES 77 

tion of living organisms in bouillon gelatine by placing on it crystals 
of the bromide of both barium and radium. Later in the same year^*' 
he claimed to have secured a kind of spontaneous generation by 
radium. By the contact of certain crystalloids with organic colloids, 
there are obtained, he says, granulations, or vacuolides, possessing 
the optical and morphological characters of simple life, more rudi- 
mentary than bioproteon, or living matter. These bodies arise, grow, 
divide, grow old, and die, returning to the crystalline state like all liv- 
ing things, and Dubois applied to them the generic term eobe (dawn of 
life). Eobes are held to form the transition between the organic and 
the inorganic world. In his essay "^ on " La radioactivite ei la vie," he 
elaborates the hypothesis that the energy irradiated by living beings 
has two distinct origins — one from the environment, and one ances- 
tral or hereditary. By their " ancestral energy " living beings are 
similar to radioactive bodies. They both give off heat rays, light, 
chemical rays, electricity, and possess molecular motion, and atomic 
and other movements. 

Leduc's ^*'' ^^ profession to have created life was controverted by 
Bonnier,^" Charrin and Gaupil,^'' and by Kunstler,^'^ in 1907. 

The most extravagant claims made in this direction are those of 
Burke '^"^'', whose observations on the spontaneous action of radio- 
active bodies on gelatine media form the basis of a voluminous work 
entitled *' The Origin of Life." While these experiments have little 
of the scientific importance they have been held to possess in the 
popular mind, it is desirable to state, in Burke's own words, what he 
did, and his own interpretation of the results. 

" An extract of meat of i lb. of beef to i liter of water, together 
with I per cent, of Witter peptone, i per cent, of sodium chloride, 
and 10 per cent, of gold labelled gelatine was slowly heated in the 
usual way, sterilized, and then cooled. The gelatine culture medium 
thus prepared, and commonly known as bouillon, is acted upon by 
radium salts and some other slightly radioactive bodies in a most 
remarkable manner." ^^ 

When the mixture above described was placed in a test-tube and 
sterilized, and the surface sprinkled with 2.5 gr. of radium bromide 
(activity not given), after 24 hours (three to four days when radium 
chloride was used), " a peculiar culture-like growth appeared on the 
surface, and gradually made its way downwards, until after a fort- 
night, in some cases, it had grown nearly a centimeter beneath the 
surface." From this growth Burke was not able to make sub- 



78 BIO-RADIOACTIVITY, EOBES, RADIOBES 

cultures. He considers them not bacteria, and not contaminations, 
but "highly organized bodies." They have "nuclei," subdivide 
when a certain size is reached, and " the larger ones appear to have 
sprung from the smaller ones, and they have all probably arisen -in 
some way from the invisible particles of radium." He regards them 
as colloidal, rather than crystalling, "of the nature of 'dynamical 
aggregates' rather than of * static aggregates,' " and coins for them 
a new name, radiohes. This forms the experimental basis for a 
volume of 351 pages. 

With reference to these discoveries, Dubois ^^ claims priority over 
Burke, and rejects his term radiobe in favor of eobe, because these 
bodies may be obtained with non-radioactive substances. 

A few months after Burke's announcement Rudge ^^' -^ showed 
that the alleged growths were " nothing more than finely divided 
precipitates of insoluble barium salts." He was unable, in a prep- 
aration similar to the one described by Burke, to observe anything 
like cell-division, and believes that an occasional grouping of the 
particles in pairs must be purely fortuitous. The appearance of 
growth of the radiobes is explained as due to a diffusion of the pre- 
cipitate through the gelatine from a point of concentration where the 
radium salt was in contact with the gelatine. Salts of barium, lead, 
and strontium produced ejects exactly similar to those caused by 
radium preparations. 

Again repeating Burke's experiments, Rudge'^'' was unable to 
secure the radiobes when agar-agar was substituted for gelatine and 
distilled water was used. If tap-water was employed a slight growth 
resulted, while the addition of a soluble sulfate resulted in a very 
dense growth. An examination of 30-40 samples of gelatine showed 
that they all contained enough H^SO^ to give a distinct, sometimes a 
dense precipitate with barium chloride in the presence of HNO3. 
This precipitate was found, on analysis, to be BaSO^. Gelatine was 
then prepared free from sulfates and gave no growth. Negative 
results were obtained with salts of uranium, thorium, pitchblende, 
and metallic uranium, thus clearly indicating that there is not the 
slightest connection between the formation of the radiobes and radio- 
activity. 

A sample of gelatine from which HgSO^ had been removed was 
sealed with a radium salt from June until September. At the end of 
that time no growth appeared, but when a soluble sulfate was added 
to a portion of this gelatine the growth began at once. 



BIO-RADIOACTIVITY, EOBES, RADIOBES 79 

♦' The cellular form of these precipitates," said Rudge, '• is prob- 
ably due to the circumstance that the gelatine is liquefied by the 
action of the salt, and each particle of precipitate is formed about a 
core of gelatine, so that the layer of barium sulfate forms a kind of 
sac or cell which is surrounded by the solutions of the salt in the 
liquefied gelatine. This ' cell ' may be permeable to the liquefied 
gelatine containing a salt in solution, which, passing through the 
cell-wall, causes an expansion to take place, the limit of growth 
being controlled by some surface tension effect." No trace of a 
nucleus or of mitosis was observed under the very highest magnifi- 
cation, and " cells " under a cover-glass sealed down with cement 
were observed to suffer no alteration during four months. 

Reference to the extreme claims noted in the literature above 
cited may be fittingly concluded by the following quotation from 
Lord Kelvin : ^' 

" But let not youthful minds be dazzled by the imaginings of the 
daily newspapers that because Berthelot and others have . . . made 
foodstuffs they can make living things, or that there is any prospect 
of a process being found in any laboratory for making a living thing, 
whether the minutest germ of bacteriology or anything smaller or 
greater." 

Bibliography 
The Supposed Radioactivity of Plants and Wood 

1. Becquerel, P. Recherche sur la radioactivite vegetale. Compt. Rend. 

Acad. Sci. Paris 140 : 54. 1905. 

2. Greene, A. B. A note on the action of radium on microorganisms. 

Proc. Roy. Soc. London 73: 375. 1904. 

3. Lambert. Emission des rayons de Blondlot au cours de Taction des 

ferments soluble. Compt. Rend. Acad. Sci. Paris 138 : 196, 1904. 

4. Meyer, E. Emission de rayons N par les vegetaux. Compt. Rend. 

Acad. Sci. Paris 138: loi. 1904. 

5. Russell, W. J. The action of wood on a photographic plate in the dark. 

Nature 70: 531. 1904. Proc. Roy. Soc. London 74: 131. 1904. 

6. . On the action of wood on a photographic plate. Nature 73 : 

152. 1905. 

6a. . The action of resin and allied bodies on a photographic plate 

in the dark. Proc. Roy. Soc. London, 80 B : 376. 1908. 

7. Tarchanoff, I., & Moldenhauer, T. Sur la radio-activite induite et 

naturelle des plantes et sur son role probable dans la croissance 
des plantes. Note preliminaire. Bull. Internat. Acad. Sci. Cracovie 
No. 9, 728. 1905. 



8o BIO-RADIOACTIVITY, EOBES, RADIOBES 

8. Tommasina, T. Constatation d'une radioactivite propreauxetresvivant, 

vegetauxetanimaux. Compt. Rend. Acad. Sci. Paris 139 : 730. 1904. 

9. Tommasina, T. Sur un dispositif pour mesurer la radioactivite des 

vegetaux. Compt. Rend. Acad. Sci. Paris 139: 730. 1904. 

The Professed Artificial Creation of Life 
10. Bonnier, G. Sur les pretendues plantes artificielles. Compt. Rend. 
Acad. Sci. Paris 144: 55. 1907. 
Burke, J. B. Month, Rev. November, 1903. (Not seen.) 

. On the spontaneous action of radio-active bodies on gelatin 

media. Nature 72 : 78. 1905. 
. On the spotaneous action of radium on gelatin media. Nature 



13 
H 

16 
17 

18 

20 
21 



72 : 294. 1905. 

— . Action of radium on gelatin media. Nature 73 : 5. 1905. 
— . Jour. Rontgen Soc. December, 1905. (Not seen.) 
The origin of life. London, 1906. 



Charrin & Goupie. Absence de nutrition dans la formation des plantes 
artificielles de Leduc. Compt. Rend. Acad. Sci. Paris 14 : 136. 1907. 

Dubois, R. Radio-activite et la vie. La Rev. des Idees I : 33S. 1904. 

. La creation de I'etre vivant et les lois naturelles. La Rev. des 

Idees 2 : 198. 1905. 

. La generation spontanee par le radium. La Rev. des Idees 2 : 



489. 1905. 
— . La radioactivite et la vie. I Congres Internal, pour I'etude de 



la radiologie et de I'ionisation, Liege, 1905. Sect. Biol., p. 49. Paris, 
1906. 

22. . Cultures minerales : Eobes et radiobes. I Congres Internat. 

pour I'etude de la radiologie et de I'ionisation, Liege, 1905. Sect. 
Biol., p. 59. Paris, 1906. 

23. Hardy, W. B. Action of salts of radium upon globulins. Chem. 

News 88 : 73. 1903. 

24. Kelvin, Lord. [The living cell.] Nature 71 : 13. 1904. 

25. Kunstler, J. La genese experimentale des processus vitaux. Compt. 

Rend. Acad. Sci. Paris 144: 863. 1907. 

26. Leduc, S. Les bases physiques de la vie et la biogenese. Paris, 

December, 1906. 

27. . Miracles : Comment un savant cree des etres vivants. Le Matin, 

Paris, Dec. 21, 1906. 

28. Rudge, W. A. D. Action of radium salts on gelatin. Nature 73 : 78. 

1905- 

29. . [Note of a paper before the Cambridge Phil. Soc. on the action 

of salts of barium, lead, and strontium on gelatin.] Nature 73: 
119. 1905. 

30. . The action of radium and certain other salts on gelatin. Proc. 

Roy. Soc. London 78: 380. 1906. 



CHAPTER VI 

RADIUM PREPARATIONS AND METHODS OF EXPOSURE 

The radium preparations used in physical and ph3'siological 
experiments are sahs of that element. The one most commonly em- 
ployed is radium bromide, though the more expensive chloride is 
sometimes used. The salt may be obtained in at least three different 
kinds of containers, (i) Thin glass tubes, usually about 30 mm. 
long, and, in the newer preparations, protected by being placed in 
metallic holders with openings extending nearly the length of the 
tube. (2) Aluminium tubes, devised by Mr. Hugo Lieber. (3) Hard 
rubber cells with brass caps having a mica window. By all of the 
above containers the o. rays are practically cut off, as they cannot 
penetrate the walls. 

In addition to these preparations, a radium coating has been 
invented by Lieber, ^"^ by the use of which, not only the a rays, but 
also the radium emanation becomes available for experimentation. 
The process of preparing this coating is thus described by Lieber : 

"Radium coatings are made in the following manner: Radium 
is dissolved in a suitable solvent and into this solution a suitable ma- 
terial is dipped. This material is then withdrawn, with radium solu- 
tion adhering to it. The solvent quickly evaporates, leaving the ma- 
terial covered with an exceedingly thin film of radium. The kind 
of solvent to be used is determined by the nature of the material to 
be coated. Such solvents are employed as have a tendency to soften 
the material which is to be coated. Thus, if celluloid rods, discs, or 
similar instruments are to receive a radium coating, in order to be 
used for therapeutic purposes, solvents such as alcohol, amyl acetate, 
etc., may be employed. These solvents have a tendency to soften 
the celluloid temporarily. When the solvent evaporates, the radium 
has been uniformly distributed over the celluloid, and has also been 
incorporated in its surface. In order to prevent accidental removal 
of the radium in such coatings, the celluloid instruments produced in 
this way are dipped for a short time in a collodion solution. By this 
process the whole radium coating is covered by a very thin film of 
7 81 



82 RADIUM PREPARATIONS AND METHODS OF EXPOSURE 

collodion. In the course of a few days this film of collodion becomes 
so tough that it will strongly resist destruction, thus affording ample 
protection for the underlying radium. . . ." 

" In the preparation of these coatings both the radium and the 
collodion solutions are colored with an analine dye. This is done to 
show the part that has been coated. Besides, if the radium happens 
to be removed by accident or otherwise, as by scraping, etc., the dis- 
appearance of the color makes such removal evident. 

"The great difference between radium used in containers, com- 
posed even of exceedingly thin aluminium, and radium used in the 
form of the coatings here described, is shown by their relative influ- 
ences on the electroscope ; a delicate rod coated at its tip with radium 




Fig. 2. Sealed Glass Tubes of Radium Bromide and a Rod Coated with Lieber's 

Radium Coating. 

bromide of 10,000 activity and holding, therefore, very little radium, 
compared very favorably in its effects with i grm. of radium bromide 
of 10,000 activity in a glass tube, or with 10 mgrms. of radium 
bromide of 1,000,000 activity in a very thin aluminium tube." 

That these coatings permit of the escape of the gaseous emana- 
tion is shown by the fact that the presence of the emanation may be 
demonstrated in a current of air passed over a coating. That the a 
rays penetrate through the thin collodion film is proved by the fact 
that the scintillations produced on a zinc sulphide screen by alpha 
rays may be caused by the use of a coated rod or disc. The activity 
of the radium is not affected by this treatment, for Rutherford ^ has 



RADIUM PREPARATIONS AND METHODS OF EXPOSURE 83 

shown that, " a distribution of the radiating matter over a thousand 
times its original volume has no appreciable influence on its radio- 
activity." 

An illustration of some of the radium preparations used in the 
following experiments is given in figure 2. See also Experiment 
40, p. 147, and Experiment 42, p. 149. 

For the purpose of observing under the microscope the effect of 
radium rays on individual living protoplasts, the writer ^ has devised a 
radioactive microscopic slide, the preparation of which has been per- 
fected by Mr. Lieber. This slide has been described as follows : 

"A solution of any desired concentration of radium bromide of 
known activity is made in a suitable solvent, and applied to the sur- 
face of the slide near the center. When the solvent evaporates a 
film of the salt remains on the slide. The film is protected by a 
coating of a specially prepared substance. Living cells may now 
be mounted as on an ordinary slide, and their response, if any, to 
the stimulus of the rays observed. The coating has the advantage, 
not only of being sufficiently transparent to light, but easily trans- 
parent to the /? and y rays, and in less degree to the a rays also." ^ 

The methods of applying to living plants the various preparations 
here described are explained in detail in connection with the experi- 
ments. It may be mentioned here, however, that in no case has the 
radium salt been permitted to come into contact with the plant, nor 
with any portion of it. The effects produced are due solely to the 
action of the rays coming from either the radium bromide direct, or 
from the radioactive emanation. 

Bibliography 

1. Gager, C. Stuart. Radium in biological research. Science, N. S. 25: 

589. 1907. 

2. Lieber, Hugo. Radium and some methods for its therapeutic appli- 

cation. Am. Med. 9: 72. 1905. 

3. . Improved methods for applying radium. Jour. Soc. Chem. 

Indust. 24. 15 Mr 1905. 

4. . A new and possibly improved method of using radium. Arch. 

Rontgen Ray 9 : 253. 1905. 

5. . Radium and its use in therapy. Homoeop. Eye, Ear, & Throat 

Jour. July, 1907. (Separate reprint. ) 

6. Rutherford, E. Does the radio-activity of radium depend upon its con- 

centration.'' Nature 69 : 222. 1904. 



CHAPTER VII 

EFFECTS ON GROWTH OF EXPOSING SEEDS TO 
RADIUM RAYS 

I. Effects on Growth of Exposure of Unsoaked Seeds 
The object of the following experiments was to ascertain the 
effect on germination and growth of exposing unsoaked seeds to the 
rays of radium. 

Experiment i 
January 28, 5 : 15 P. M. 

Six seeds of Lupinus albtis, unsoaked, were placed under the 
radium tube (10 mg., 1,500,000 x), with the tube resting on the 
hilum edges of the seeds. Six control seeds were similarly placed 
under an empty glass tube. 

February 2, 4 P. M. 

After five days radiation the seeds were planted in soil in separate 
pots, and transferred to the propagating-house. 

February 9, 9 A. M. 

Radiufn Control 

The cotyledons of five seeds are The cotyledons of three seeds are 

just emerging; the sixth is just arch- raised about 5 mm. above the surface 

ing the soil. of the soil, the cotyledons of two seeds 

have just emerged, and the cotyledon 
of one seed is just breaking the soil. 

February 11,3 130 P. M. 

Only four seedlings have the coty- Five seedlings have the cotyledons 

ledons clear of the soil, one of which entirely clear of the soil, and well 

has the cotyledons spread showing spread apart, showing the plumules. 

the plumule. The cotyledons of the other seedling 

are just emerged. This culture is 
more vigorous, and further advanced 
in every way than the radiated one. 

The lengths of the hypocotyls above the surface of the soil are as 
follows : 

84 



EFFECTS OF EXPOSING SEEDS 



85 



Radui7n 
lo.oo mm. 
7.00 
8.50 
9.00 
6.00 
5.00 



Control 
10.00 mm. 
21.00 
12.00 
18.00 
24.00 
00.00 



45.50 mm. Total. 
Average height, 7.58 + mm. 



85. 00 mm. Total. 
Average height, 14.16 + mm. 



February 16, 12 M. 

Radiujn 
12.50 mm. 

4-50 

7-50 
12.50 
12.50 

7.00 

56.50 mm. Total. 

Average height, 9.41 mm. 

The cotyledons are not reflexed, 
and the epicotyl has begun to elongate 
in only one seedling. 



Length of Hypocotyls 



Control 
26.00 mm. 
29.00 
24.50 

23-50 
20.50 
20.50 

144.00 mm. Total. 

Average height, 24.00 mm. 

The cotyledons are well reflexed, 
and the epicotyls are elongating w^ith 
leaves well expanded. 



February 22. 

The plants were carefully removed from the pots and the soil 
washed from the roots. The roots of the radiated plants are very 
short, and secondary roots are only slightly, and in two specimens 
not at all, developed. 

The roots of the control plants are several times as long as those 
of the radiated specimens, and with secondary roots well developed. 

The radiated plants did not lose the nyctitropic movements of 
the leaves, and measurements of the length of the stomata in the two 
showed no difference between the normal and the radiated plants. 



Experiment 2 
February 2, 4 P. M. 

Four seeds of Lupimis albtis^ after having lain for four days in a 
cylinder lined with Lieber's " radium coating," were planted in soil 



86 EFFECTS OF EXPOSING SEEDS 

in the propagating-house. Control culture same as in Experiment i. 

February 9, 9 A. M. 

The cotyledons of all four seeds are emerging, but they are not 
yet raised above the surface of the soil. 
February 11, 3 : 30 P. M. 

The cotyledons are all clear of the ground, all spreading and 
showing the plumule. In height the plants are intermediate between 
the radiated and the control in Experiment i. Length of hypo- 
cotyls above the surface of the soil as follows : 

Radium 

7.00 mm. 

13.00 

15.00 

15.00 

50.00 mm. Total. 

85.00 mm. Total. 
Average height, 12.50 mm. Average height, 14.16 -|- mm. 

February 16, 12 M. 

Length of Hypocotyls Above the Surface of the Soil 




Radium 








Control 


24.50 


mm. 








26.00 mm 


19.00 










29.00 


23-50 










24.50 


14.00 










23-50 


Si. 00 


mm. 


Total. 






20.50 
20.50 




144.00 mm 


Average length, 20, 


,25 mm 


1. 


Average 


length, 24.00 






Experiment 


3 





Total. 



April 15, 6: 20 P. M. 

Twenty seeds of " Lincoln" oats, with the glumes removed, were 
placed in two parallel rows with the radicle ends touching and the 
embryo side upermost. Over them was laid the tube of RaBrg 
(1,500,000 X ), resting on the radicle ends of the seeds. 

Control with empty tube, and both sets placed in the dark room. 
April 22, II : 30 A. M. 

After an exposure of 6 days and 15 hours, both sets of seeds 



EFFECTS OF EXPOSING SEEDS 



87 



were planted in separate jars and placed in the propagating-house to 

germinate. 

April 25. 

(Record taken by the gardener.) 

All the seeds in the control culture have broken the soil, save one 
that decayed. 

None of the radiated seeds have yet come up. 
April 27. 

Two of the radiated seeds have come up. 
April 28. 

Seventeen more of the radiated seeds are just breaking through, 
the surface of the soil. The average height of the control seedlings 
from the surface of the soil to the tip of the first leaf, is 60.40 mm. 

On April 29 the cultures were photographed (figure 3), and up 
to May 5 there had been no appreciable growth of the radiated seeds 
since they were photographed, and the experiment was closed. 



R^^^^ ^^^^^c 



Fig. 3. Experiment 3. Germination of Oats Retarded by Exposure, while Dry, to 

Radium Rajs. 



Experiment 4 
May 6, 9:35 A. M. 

Eight dry seeds of Phaseolus (Henderson's " Long Yellow Six 
Weeks ") were placed with their hilum-edges touching the radium- 
coated rod (25,000 X ) four seeds on each side of the rod. 
May 12, 5 P. M. 

After an exposure of 145 hours the rod was removed from the 
seeds, and six hours after its removal the seeds were planted in soil 
(pot R), with the control seeds (pot C) in an adjacent pot in the 
propagating house. 



88 EFFECTS OF EXPOSING SEEDS 

May 19, 5 P. M. 

The gardener reported that the seedlings in R broke through the 
soil before those in C, but he did not have the exact data. 

The radiated culture has four seedlings with the arch of the 
hypocotyl not yet straighted, while the control culture has only one 
such seedling. The heights of the hypocotyls above the surface 
of the soil are as follows : 



Radium 
25.00 mm. To top of arch. 
103.00 



Control 



56.00 










(( 


34.00 

62.00 










(( 

(( 


^15-50 

So.oo 












71.00 












546.50 
Average 


mm. 
leng 


th, 


68 


3 


I + mm 



1 14.00 mm. 

99-50 
112.50 

91.50 
1 12.00 

30.00 

89. 00 
1 14.00 



To top of arch. 



762.50 mm. 
Average length, 95.31 + mm. 




Fig. 4. Experiment 5. Acceleration of Growth of Wheat Following Exposure to 

a Rays from Polonium. 



EFFECTS OF EXPOSING SEEDS 



89 



Experiment 5 

Object : To ascertain the effect of a rays only (from polonium), 
on the germination and growth of wheat. 

Sixteen grains of wheat {Triticiim vulgar e^ Henderson's "Well- 
man Fife ") were exposed to « rays by being placed in contact with 
a metallic rod coated with polonium. 

June 7, 9 :30 A. M. 

After 10 days' exposure the exposed grains and 16 unexposed 
grains were planted in soil. 

The heights of the seedlings above the surface of the soil were 
measured as follows : 





June ii, 


10 A. M. 


June iS, 


10 A. M. 




Polonium 


Control 


Polonium 


Control 


I 


5.50 mm. 


29.50 mm. 


125.00 mm. 


76.50 mm. 


2 


31.00 


27.50 


116.00 


86.00 


3 


25.00 


31.00 


91.50 


107.00 


4 


9.00 


20.50 


132.00 


83-50 


5 


10.00 


4.00 


60.00 


66.50 


6 


19.00 


18.50 


143.00 


59.00 


7 


16.50 


10.00 


118.00 


50.00 


8 


24.00 


7.00 


134.00 


27.00 


9 


4.00 


30.00 


121.00 


91 .00 


10 


23.00 


30.00 


124.50 


100.00 


1 1 


19.50 


33-50 


145.00 


S8.00 


12 


2S.00 


24.00 


118.50 


83.00 


13 


32-50 


24.50 


134.00 


68.00 


14 


24.00 


21.50 


144.00 


71.00 


15 


19.00 


30.00 


123.00 


96.50 


16 


31-50 
321.50 mm. 


15.00 
356.50 mm. 


144.00 


56.00 




1,973.50 mm. 


1,209.00 mm, 


A 


w. 20.00 mm. 


22.20 mm. 


123.34 mm. 


75.56 mm 



While at first there was no significant difference in the heights of 
the exposed and the control seedlings, the exposed plants later grew 
much more rapidly than the control. See figures 4 and 5. 

Summary 
From the above experiments it is seen that both germination and 
growth of Lupnus albus, Phaseolus, and Avena saliva are retarded 



90 



EFFECTS OF EXPOSING SEEDS 



120 
110 
100 

90 

80 
70 
6o 
1 50 
40 
30 
20 
10 






















X 




Ex 


penmen t 5. 










^>*' 


>i^ 
















rf*' 


,/' 


^^^^>^ 


-^ 












..--::. 




















^^ 














^^ 


="*^ 


^" 

















10 



11 



12 



13 



14 



15 



16 



17 18 



/ 8 9 

Fig. 5. Acceleration of Growth of Wheat Following Exposure to a Rajs from 

Polonium. 

by exposure to the rays. A five days' exposure of Ltcfimis to radium 
of 1,500,000 X retarded germination and growth, but did not appre- 
ciably affect irritability, as shown by the fact that the plants still per- 
formed their nyctitropic movements. Exposure in the radium-lined 
cylinder (of much weaker activity, but permitting the a rays to act) 
retarded germination and growth less than exposure to a stronger 
preparation. The effect of the radium-coated rod of 25,000 x was 
also less than that of the preparation of 1,500,000 x . Oats exposed 
to this last preparation for a little over six and one half days were 
greatly retarded in germination, and had their subsequent growth 
completely inhibited. In the rod- and cylinder-exposures the a rays 
were in large part available, as well as the /3 and y rays, but the 
added effect of the a rays was not sufficient to compensate for the 
weaker activity of the preparations. 

An exposure of dry wheat grains ( Triticum vulgar e) for ten days 
to a rays by placing them in contact with a metallic rod coated with 
polonium was followed at first by a slightly less rapid growth, and 
then, eleven days after planting, by a more vigorous and rapid 
growth than that of seeds similarly grown but not exposed. 

2. Effects on Growth of Exposing Seeds while Soaking 
The object of the following experiments is to ascertain the effect 
on germination and growth of exposing seeds during imbibition of 
water to the rays of radium. 



EFFECTS OF EXPOSING SEEDS 



91 



Experiment 6 
February 2, 6 P. M. 

Numerous seeds of timothy grass were scattered evenly over the 
bottom of an earthenware germinator, and the glass tube of RaBrg 
(10 mg., 1,500,000 x) was supported over the center of the dish with 
the end containing the radium resting on the bottom among the seeds. 

A control was similarly arranged with an empty tube, and both 
cultures were placed in the dark room. 



February 9, 10 A. M. 
Radium 
No seeds directly under the tube 
have germinated. Germination has 
begun about 2 mm. from the tube, 
and plumules and radicles are short- 
est near the tube, and increase in 
length toward the edge of the dish. 
There is a slight (in some cases, 
marked) tendency for the plumules 
to bend in toward the center. This 
suggests a positive radiotropism^ but 
is probably a hydrotropic response to 
the more humid conditions at the 
center of the germinator. 

February 11, 9 A. M. 
Radiu7n 

The seeds at the center are be- 
ginning to germinate, but slowly. 
The following measurements of the 
height of the shoots from the cir- 
cumference to the center of the ger- 
minating dish is typical : 10 mm., 9 
mm., 6 mm., 2 mm., i mm. 

All the seedlings are decidedly 
pale and those within a radius of 
7.50 mm. are entirely etiolated. 

All the hypocotyls are excessively 
elongated beyond the radius of ^ -$0 
mm. from the center, making the 
average height of the seedlings be-^ 
yond this radius much taller than 
those not radiated. 



Control 
The seeds have germinated evenly 
over the bottom of the dish, at the 
center as well as elsewhere. No 
tendency to bend toward the center 
or in any other direction was ob- 
served. 



Control 

All of the seedlings are of about 
the same height and average much 
taller than the radiated set. 

The seedliijgs are uniformly of a 
dark green color, in striking contrast 
to those of the radiated set. 

The heights of the shoots average 
much less than those of the radiated 
plants outside of the 7.50 mm. ra- 
dius. 



92 



EFFECTS OF EXPOSING SEEDS 



February 12, ii A. M. 

The relative condition of the radiated and control sets remains as 
yesterday. Measurements of the heights of the seedlings gave the 
following averages at the distances indicated : 

Distance Height 

Radiujn Control 

o mm. 2.00 mm. 10.00 mm. 

5 5-00 10.00 

10 7.50 13.00 

15 11.00 14.00 

20 17.00 9.00 

25 23.00 10.00 

February 16, 3 : 30 P. M. 

All the seedlings in both cultures have apparently grown, but the 
relative condition and size remains as on the 12th. 

Experiment 7 
February 10, 9 : 30 x\. M. 

Experiment arranged as in No. 6, using seeds of alfalfa. 
Februarj'^ 15, 5 : 30 P. M, 

Seeds have germinated in both cultures. In the center of the 
radiated set germination is greatly retarded, but in the control dish 
germination is generally uniform. 

Both cultures were placed near a window in the laboratory. 
February 18, 11 130 A. M. 

The seedlings within a radius of 5 mm. of the radium tube have 
not developed further than the protrusion of the radicle. All the 
seedlings in the control culture have grown, and are taller than those 
exposed. 

Rhizopus nigricans attacked both cultures, but while growing 
vigorous and rank in the control culture, it grew weakly and poorly 
in the radium culture. 
February 22, 10 A. M. 

The leaves of the radiated seedlings are much lighter green than 
those of the control. 

Experiment 8 
February 26, 12 : 30 P. M. 

Unsoaked seeds of timothy grass were arranged in 8 rows, radiat- 
ing from the center of a circular piece of blotter, which was placed 



EFFECTS OF EXPOSING SEEDS 



93 



on the bottom of the germinating dish. Over the center was placed 
the radium-tube (lo mg., 1,500,000 x), with all the radium in the 
lower end, and the tube in contact with the underljnng seeds. 

Control similarly arranged with empt}^ tube. 
March i, 5 : 30 P. M. 

No seeds have germinated in either culture. 
March 9, 9 A. M. 

The control seedlings are all of about the same height and color, 
being normally green. Average height (estimated), 30 mm. 

The radiated plants are entirel}^ etiolated under the radium-tube, 
and for a radius of 4 mm. on all sides. The height of the seedlings 




Fig. 6. Experiment 8. Retardation of Germination and Growth of Timothy Grass 
by Radium Rays. Activity, 1,500,000. 

gradually increases from 3 mm. at the center to about 30 mm. at the 

circumference. 

March 10, 12 M. 

The exposed culture was photographed (figure 6). 
March 11, 3 130 P. M. 

Microscopic examination of the control plants shows in the cells 
of the leaves normal chloroplastids, with healthy, green color. 

In the non-green radiated seedlings, the plastids in man}' cells 
were apparently of normal size and shape, but destitute of green, 
while in other cells the plastids, although green, had largely lost their 
shape and individuality, and were aggregated in a disorganized mass 
against the vertical cell-walls, and often massed in one end of the cell. 

A similar result, though less marked, was obtained by exposure 
made through eight layers of sheet tin, a total thickness of 9 mm. 



Qzj. EFFECTS OF EXPOSING SEEDS 

Experiment 9 
March 19, 6 P. M. 

Seeds of timothy grass were arranged along 8 radii of a circular 
piece of blotter in a Zurich germinator and a tube of RaBrg (7,000 x ) 
was placed vertically over the center with the end containing the 
radium resting on the seeds. 

Control with empty tube, and both cultures placed to germinate 
in the dark-room. 

March 23, 10:30 A. M. 

The seeds have germinated quite uniformly in the control culture, 
averaging about 3-6 mm. high. 

In the radium culture the germination is similar to that in the con- 
trol, except under the radium-tube, where germination, though not 
entirely inhibited, has been greatly retarded, the seedlings not averag- 
ing more' than 1-2 mm. high for a radius of about 5 mm. from the 
center of the tube in all directions. 

The glass tubes were removed and both cultures were placed in 
the laboratory in front of a window. Cylinders of blotter were 
placed around the culture dishes to prevent phototropic curvature. 

March 26, 11 A. M. 

The plants in both cultures are of about the same height, except 
in the radium culture, where those in the center, directly under the 
radium, are noticeably shorter than the others, and the height in- 
creases rather abruptly from the center toward the circumference. 

The tubes were removed and the cultures left to develop further. 

March 30, 3 P. M. 

The retarded seedlings in the center of the radiated culture have 
reached about the average height of the others, and the difference 
in the average height of the seedlings in the two cultures is very 
slight. The balance, if any, is in favor of the radiated set being 
slightly taller. 

March 31, 5 P. M. 

The radiated seedlings average decidedly taller than the con- 
trol set. Thus, following exposure to the radium, there has been 
at first a retardation of germination and growth, then, after the 
removal of the radium, an apparent recovery and subsequent 
acceleration. 



effects of exposing seeds 95 

Experiment io 
March 23, 4:30 P. M. 

The experiment was set up as in No. 9, only a sealed glass tube 
containing radio-tellurium was used instead of the radium tube. 
Timothy seed was employed. 
March 30, 3 145 P. M. 

The seedlings in both cultures have an average height of about 
25 mm., except those immediately under the tube of radio-tellurium, 
which are only about one half as tall as the others, but the influence 
has not extended to any appreciable distance from the tube in any 
direction. The tube was in contact with the underlying seeds. 

Experiment ii 
May 12, 6 P. M. 

Eight seeds of the bean {Phaseolus) were placed, four in a row, on 
moist sphagnum, with the hilum-edges adjacent. Over them, rest- 
ing on the adjacent edges, was placed the coated rod (10,000 x). 
Eight dry seeds were similarly exposed. 
May 14, 12 : 30 P. M. 

After 42 hrs. exposure, the seeds, together with eight unexposed 
seeds, were planted in soil. 
May 26, 9 A. M. 

The seeds in all three cultures germinated poorly, but of those 
exposed while imbibing water, only one has come up, of those ex- 
posed dry, five have come up with an average length of hypocotyl 
above the surface of the soil of 39.60 + mm. Four, only, of the 
control seeds came up, but the average length of their hypocotyls 
above the soil surface is 59.25 mm. The hypocotyls of those ex- 
posed dry, and of the control seeds were preserved for histological 
study. (See p. 226.) 

Experiment 12 
May 14, /| P. M. 

On damp cotton in a moist chamber were placed 8 seeds of the 
bean {Phaseolus), in two rows of 4 seeds each, with the hilum edges 
of opposite seeds adjacent. The radium-coated rod (25,000 x) was 
placed in contact with the adjacent edges. 

Control of 8 seeds in the same chamber, but with no radium. 
May 19, 9 A. M. 

All the seeds have germinated in both cultures. The lengths of 
the radicles are as follows : 



o6 EFFECTS OF EXPOSING SEEDS 

Radium Control 

6.00 mm. 18.50 mm. 

24.00 25.00 

9.00 30.00 

13.00 22.00 



21.00 



9.00 

8.00 30.00 

17.00 14.00 

12.00 25.00 



98.00 mm. 185.50 mm. 

Average of 8, 12.25 "'"^- Average of 8, 23.18 + mm. 

The amount of grow^th following exposure to the radium rays 
during imbibition was only about one half the normal. 

Experiment 13 
May 14, 4 P. M. 

Eight seeds of Liifimis albiis were placed on damp cotton in a 
moist chamber in two rows of four seeds each, with the hilum-edges 
of opposite seeds adjacent. Over the seeds was placed a radium- 
coated rod (10,000 X ), in contact with the adjacent edges. 

Control of eight seeds in the same chamber with no rod. 

May 19, 9 A. M. 

All the seeds have germinated in both cultures, but the radicles 
of the radiated seeds are shorter than those of the control seeds. The 
exposed radicals are also noticeably more yellowish than are those 
of the control. 

The lengths of the radicles are as follows : 

Radium Control 

41.00 mm. 41.00 mm. 

19.00 44.00 

12.00 22.00 

16.00 41.00 

17.00 41-50 

22.00 37-00 

30.00 26.00 

16.00 35 -oo 



173.00 mm. 287.50 mm. 

Average, 21.62 + mm. Average, 35.93 + mm. 

* Caught in seed-coat. 



EFFECTS OF EXPOSING SEEDS 



97 



Experiment 14 
May 25, 12 M. 

Eight dry seeds of the bean {Phaseolus. Henderson's " Long 
Yellow, Six Weeks") were placed in moist sphagnum with their 
hilum-edges touching a rod coated with RaBrg (10,000 x ). Con- 
trol, similarly placed, but with no radium. Rod continued through- 
out the experiment. 




t "^ ^ ^ ^ *|r -^ # 



Fig. 7. Experiments 14 (Bean) and 17 (Lupine). Germination Retarded by Ravs 
from Coated Rods of 10,000 X (Bean), and 25,000 X (Lupine). 

May 27, 3 P. M. 

The radicles have protruded in one radiated seed, and in seven 
of the control seeds. 

May 28, 10 A. M. 

The seeds were photographed with those of Experiment 17 (fig- 
ure 7). 



98 



EFFECTS OF EXPOSING SEEDS 



The lengths of the radicles are as follows 



Radium 






Control 


11.50 mm. 






20.00 mm. 


9-50 






20.00 


13-50 






12.00 


15.00 






20.00 


16.00 






18.00 


1 1.50 






23.00 


16.50 






20.00 


12.00 






18.00 


105.50 mm. 


151.00 mm, 


Average, 13.18 + mm. 




Average, 


18.87 + ''""^* 


Experiment 15 




May 28, II A. M. 








Repetition of Experiment 


14. 






May 30, II A. M. 








Lengths of the radicles as 


foll( 


3WS : 




Radium 






Control 


5.00 mm. 






8.00 mm, 


0.00 






17.00 


0.00 






6.00 


11.00 






13.00 


3.00 






12.00 


7.00 






11.00 


5 'Oo 






15.00 


8.00 






10.50 


39.00 mm. 






92.50 mm 


Average, 4.87 -f mm. 




Average, 


11.56 4- mm. 


June I, 9: 30 A. M. 








Radium 






Control 


38.50 mm. 






43.00 mm 


39.00 






54.00 


38.00 






49.00 


49.00 






42.00 


34.00 






56.00 


47-50 






47.00 


39-50 






59.00 


51.00 






45.00 


336.50 mm. 






395.00 mm. 


Average, 42.06 + mm. 




Average, 49.37 + mm. 



EFFECTS OF EXPOSING SEEDS 



99 



June 3, 2 : 30 P. M. 

Portions of the hypocotyls were placed in formalin for section- 
ing. See page 226. 

Experiment 16 
May 28, II A. M. 

Repetition of Experiment 14, using Lu-pinus albiis. Experiment 
started as there indicated. Rod, 25,000 x. 
May 30, 10 A. M. 

The lengths of the radicles are as follows : 



Radium 


Control 


0.00 mm. 


15.00 mm. 


0.00 


12.00 


0.00 


12.00 


0.00 


11.00 


0.00 


0.00 


0.00 


0.00 


0.00 


7-50 


0.00 


9.00 


7.00* 


1. 00 


13.00* 


0.00 


20.00 mm. 


67.50 mm. 


Average of 10, 2.00 mm. 


Average of 10, 6.75 mm 


June I, 2 : 30 P. M. 




Radium 


Control 


44.00 mm. 


62.00 mm. 


36.00 


75.00 


20.50 


61.50 


55 -oo 


66.00 


53 -oo 


27.00 


52.00 


54.00 


28. 00 


59.00 


57.00 


44.00 


63.00 


54.00 


73 -oo 


26.50 



481.50 mm. 
Average, 48.15 mm. 

* Very poorly exposed. 



529.00 mm. 
Average, 52.90 mm. 



lOO EFFECTS OF EXPOSING SEEDS 



J 


une 3, 


, 12 M. 








Radium 






83 


.00 mm 






63 


.00 






58, 


.00 






94, 


.00 






97' 


,00 






91, 


,00 






70. 


.00 






112. 


00 






108. 


.00 






135- 


00 






911. 


00 mm, 




Average, 91. 


10 mm. 




978.50 mm. 
Average, 97.85 mm. 

Experiment 17 
May 25, 12 M. 

Ten dry seeds of Lufinus albus were placed in moist sphagnum, 
with the hilum-edges in contact with a rod coated with RaBrg 
(25,000 x). Control of ten seeds, similarly placed, but with no 
radium. 
May 27, 3 P. M. 

The radicles have protruded from none of the radiated seeds. 

The radicles have protruded from 9 of the control seeds. 

Two of the radiated seeds were poor, and have not absorbed water. 
May 28, 10 130 A. M. 

The lengths of the radicles are as follows : 

Radiuyn Control 

13.00 mm. 15-00 mm. 

0.00 18.00 

0.00 23.50 

6.50 10.50 

6.50 26.00 

4.50 22.00 

0.00 27.50 

0.00 Injured. 26.50 

26. ICO 

30.50 mm. -" 

A " c I 22. ICO 

Average, 3.01 + mm. ^ 

2 1 8. 00 mm. 
Average, 21.80 mm. 



EFFECTS OF EXPOSING SEEDS lOI 

September 19. 

The plants were photographed together with those of Experiment 
14, and portions of the hypocotyls and roots were preserved for sec- 
tioning (figure 7). The radium rod was continued throughout 
the experiment. 

Experiment 18 

Object : To ascertain the effect of the rays from a radium-coated 
rod on the germination and growth of Lu^inus albus. 

June 16, 3 P. M. 

Eight seeds of Ltipinus albus were placed in two parallel rows in 
moist sphagnum, with a rod coated with Lieber's "radium-coating" 
(about 10,000 X , and one year old) placed in contact with the hilum- 
edges of the seeds. 

Eight control seeds similarly placed, but with no radium. 

June 20, 3 P. M. 

The lengths, of the hypocotyls from the cotyledons measured as 
follows : 





Radiutn 






Control 


I 


50.00 mm. 






54.00 mm, 


2 


61,50 






46.00 


3 


63.00 






69.50 


4 


70.00 






50.00 


5 


83.00 






44.00 


6 


59-50 






63.00 


7 


33-00 






55 -oo 


8 


81.50 
501.50 mm. 






49.00 
430.50 mm 


rage, 


62.68 mm. 


Average, 


53 


.81 -f mm. 



Acceleration of growth has followed exposure to the rays. 

Experiment 19 

Five seeds of Henderson's "Long Yellow Six Weeks" bean 
{Phaseolus) were exposed for five days (120 hours), during imbibition 
from the dry condition, to a radium-coated rod (10,000 x). 

At the end of the 120 hours the hypocotyls of the exposed seeds 
averaged 50.80 mm. in length, those of the control seeds 56.00mm. 
Portions of the root and hypocotyl of the exposed seeds and of con- 
trol specimens were preserved for sectioning (p. 226). 



i02 effects of exposing seeds 

Summary 

Seeds were exposed to radium preparations in sealed glass tubes, 
and of activities of 7,000, 10,000, and 1,500,000. Under the con- 
ditions imposed, exposure to rays from all of these preparations was 
followed by a retardation of growth, the amount of retardation vary- 
ing directly with the activity of the preparation. 

When seeds of timothy grass {Poa -pratense) and alfalfa were 
exposed to /9 and y rays during imbibition and subsequent stages of 
germination, both germination and growth were retarded and the 
plants were etiolated. Microscopic examination of the etiolated 
plants showed that in some cases the plastids had apparently failed 
to form chlorophyll, while in others the green chloroplastids 
seemed to have been disorganized. Bean seeds placed in contact 
with the coated rod («, /? and x '"^ys) during germination were also 
retarded. When timothy grass seeds were exposed to radium of 
weak activity (7,000 x) an initial retardation was followed by appar- 
ent recovery after an interval of five days." At the end of this period 
the exposed seeds averaged even taller than those of the control cul- 
ture, though other conditions of growth had been practically identical. 

A similar recovery of growth vigor followed exposure of bean 
seeds to the coated rod of 10,000 x , and of lupine seeds to the 
coated rod of 25,000 x . These results suggest the establishment of 
a condition of radium tonus^ in which the organism becomes ad- 
justed to a certain intensity of radioactivity in its environment, and 
th(? rays of preparations of this strength cease to act as a stimulus. 

Exposure of seeds to a preparation of radio-tellurium in a sealed 
glass tube was followed by results similar in kind to those following 
exposure to radium rays. The germination of fungus spores (Exp. 
7) was also apparently less vigorous in radium cultures than 
normally. 

In one case (Exp. 18) the germination of seeds of Lufinus albus 
and the subsequent growth of the radicle was apparently accelerated 
16 per cent, by placing a radium-coated rod of about 10,000 x in con- 
tact with the seeds as they germinated in moist sphagnum. 

3. Effect on Growth of Exposing Soaked Seeds 
The aim of the following experiments was to ascertain the effect 
on germination and growth of exposing soaked seeds to the rays of 
radium. 



effects of exposing seeds io3 

Experiment 20 

Six seeds of Liifintis albus were soaked in water for 17 hours, 
and the seed-coats were removed from over the hypocotyls. The 
seeds were then placed in a Zurich germinator in two rows, with the 
hypocotyls facing each other, and the glass tube of RaBrg (5 mg., 
1,500,000 X ) was placed over the seeds in contact with the hypocotyls. 

Control of six seeds similarly treated except that an empty glass 
tube was used instead of the radium-tube. 

November 26, 8 : 30 A. M. 

All seeds have begun to germinate, and an ink mark was placed 
on each radicle as a reference mark in measuring. 

November 27, 4 : 30 P. M. 

Increase in length of the radicles in the past 32 hours as follows : 

Control 

3.00 mm. 

8.00 

8.00 

10.00 

5-50 
11.00 

25.00 mm. 
Average, 4.16 mm. 

November 28, 3 : 30 P. M. 
Radium 
7.00 mm. 



I. 


.00 


mm. 


5' 


,00 




5 


.00 




2, 


.00 




6 


.00 




6, 


.00 






45.50 mm. 


Average, 7.58 mm. 


Control 


15.00 mm 


broken 


12.50 


17.00 


13.00 


20.00 



54.50 mm. 77-50 "1"^- 

Average, 9.08 mm. Average, 15.50 mm. 

The radicles of the control seeds have elongated almost twice as 
rapidly as those exposed to the radium. 

Experiment 21 
November 28, 4 : 30 P. M. 

Twenty-four seeds of hnc\!.vfhQ2ii{Fagopyrum esculenttcm), soaked 
in water for 24 hours, were divided into two groups, R and C, of 12 



I04 EFFECTS OF EXPOSING SEEDS 

seeds each, and placed to germinate in the Zurich germinators ; 7? 
with the radium-tube (1,500,000 x) lying over and in contact with 
the seeds, C with a short glass rod lying over the seeds. 

December i, 8 130 A. M. 

In R three radicles have protruded, in C four. The seeds were 
placed to develop further in two pots of earth of equal size. 

December 18, 12 M. 

In the radiated culture four arched hypocotyls are above the sur- 
face of the soil ; in the control culture, six. 

January 2, 9 : 30 A. M. 

Radium Control 

Onlv 5 seeds have germinated. Seven seeds have germinated. 

Lengths of hypocotyls above surface Lengths of hypocotyls above surface 

of soil as follows : of soil as follows : 

35.00 mm. 7S.00 mm. 

23.00 90.00 

14.00 90.00 

9.00 69.00 

5.00 65.00 

86.00 mm. 392.00 mm. 

Average, 17.20 mm. Average, 78.40 mm. 

The petioles of the cotyledons in C were longer than those in 7?, 
and the seedlings were in ever}^ way more vigorous and healthy. 

Experiment 22 
January 5, 9 A. M. 

Six flax seeds {Lmum)^ soaked in water over night, were placed 
in Zurich germinators, and the glass tube of RaBr2 (1,500,000 x) 
was laid over them, with the radium evenly distributed along the 
bottom of the tube. 

Control, similarly arranged with an empty glass tube, and both 
cultures placed in the dark room. 

January 6, 2 P. M. 

None of the seeds have germinated. 
January 7, 9 A. M. 

All of the seeds under the radium have germinated ; all but one 
of the control seeds. 

An exposure of 48 hrs. to the RaBr2 of 1,500,000 activity has 
not been sufficient appreciably to affect germination. 



effects of exposing seeds io5 

Experiment 23 
Januar}^ 11, 9 A. M. 

Eight seeds of white ijiustard {Brassica alba), soaked in water 
for 15 hrs., were placed in Zurich germinators in the dark-room with 
the glass tube of RaBrg (5 mg., 1,500,000 x) resting on the seeds, 
the radium evenly distributed along the bottom of the tube. 

Control of 8 seeds similarly treated and placed under an empty 
glass tube. 

January 12, 9 A. M. 

One radiated seed has begun to germinate ; two control seeds. 
The seeds were planted in the same pot of soil, the exposed seeds 
on one side, the control seeds on the other side of the pot. 

January 14, 9 A. M. 

Of the radiated seeds, two hypocotyls have pierced the soil ; of 
the control seeds, five. 

January 16, 4 : 30 P. M. 

Radium Control 
Lengths of hypocotyls of six seed- Lengths of hypocotyls of six seed- 
lings above soil surface as follows : lings above soil surface as follows : 
33.50 mm. 30-50 mm. 
23.00 37'00 
22.00 14.00 
18.00 39'00 
20.00 14.00 
30.00 38.00 

146.50 mm. 172.50 mm. 

Average, 24.41 mm. Average, 28.75 mm. 

January 17, 3 : 45 P. M. 

One seedling was injured in each culture and discarded. 

Radium Control 

46.00 mm. 49-50 mm. 

36.00 45.50 

35-50 30.00 

41.50 53.00 

38.00 25.00 

27.00 49.00 

224.00 mm. 252.00 mm. 

Average of 6, 37.33 mm. Average of 6, 42.00 mm. 



io6 



EFFECTS OF EXPOSING SEEDS 



January 19, 9 A. M. 

Radiutn 
67.00 mm. 
60.50 
36.00 
70.00 
57.00 

54-50 



Control 
69.50 mm, 
76.50 

30.50 
64.50 

73-50 
45.00 



345.00 mm. 


7^-50 




431.00 mm. 


Average of 6, 57.50 mm. 


Average of 7, 61.57 4" "i"^- 


January 22, 11 : 30 A. M. 




Radium 


Control 


So. 50 mm. 


80.50 mm. 


91.50 


61.50 


91.50 


79.00 


49-50 


100.00 


83.00 


65.00 


S7.50 


89.00 



4S3.50 mm. 



Average of 6, 80.58 4- mm. 



79.00 

554.00 mm. 
Average of 7, 79.14 4- nim. 



Germination and growth were at first retarded, following exposure 
to the radium, but after ten days (January 21-22) the exposed and 
the control seedlings are of practically the same length. 

Experiment 24 
February 26, i P. M. 

Six seeds of Ltifimis albus were soaked in water for 18 hrs. and 
after the removal of the seed coats, were placed to germinate in a 
Zurich germinator in two rows, with the hilum-edges in contact, 
and a sealed glass tube of RaBrj (10,000 x ), with the radium salt 
evenly distributed over the bottom of the tube was placed lengthwise 
over the hypocotyls, and in contact with them. 

Five control seeds were similarly placed with an empty tube. 

March i, 5 : 30 P. M. 

The seeds have all germinated in both cultures, with hypocotyls 



EFFECTS OF EXPOSING SEEDS IO7 

from 15-35 mm. long. The relative lengths of the radiated and 
control seed hypocotyls were not recorded. 

Both sets of seeds were placed to develop further in moist 
sphagnum. 

March 17, 9 : 30 A. M. 

The tap-roots of the radiated plants have failed to develop 
normally, being not more than one half to one sixth as long as those 
not exposed to the radium rays. Correlated with the failure of the 
tap-root to develop, the secondary roots are more fully developed in 
the radiated seedlings, but there was no difference ii^ growth of sec- 
ondary roots on the side of the hypocotyl that was next to the radium- 
tube during exposure and those on the opposite side. 

Experiment 25 
March 22, 4 P. M. 

Ten soaked seeds of " Lincoln " oats (^Avena), with the glumes 
removed, were placed in a Zurich germinator, in parallel rows of 5 
each, in contact with the glass tube of RaBrg (10,000 x ) with the 
radium evenly distributed over the bottom of the tube. The radicle 
ends of the oats were all touching the glass tube. 

Control of 5 seeds with empty tube, similarly placed, and both 
sets placed in the dark room to germinate. 

March 23, 11 A. M. 

All the grains have germinated in both cultures, but those under 
the radium are only about one half as far developed as the control 
grains. 

March 26, 11 A. M. 

All the grains have grown since the last observation, but the 
control grains have grown more than those radiated. Two secondary 
roots have developed on each control grain, no secondary roots on 
the radiated grains. The grains of both sets were planted in soil 
and placed in the propagating house to develop. The total length 
of exposure to the radium has been 67 hrs. 35 min. 

March 31, 9 : 30 A. M. 

The experiment was photographed. The control plants are 
several times taller than those from exposed seeds (figure 8). 



io8 



EFFECTS OF EXPOSING SEEDS 




Fig. 8. Experiment 2-^. Retardation of Germination and Growth of Oats Exposed to 
Radium Rajs During Early Stages of Germination. Cf. figures 9 and 24. 

April I, 3 P. M. 

After removing the plants and carefully washing the soil from 
the roots, the following observations were made : 



Roots 
Number. 

Length. 



Secondary 
roots. 



Diameter.] 

Root-hairs. 

Root-tips. 



Radium 
3.5 (av. for 10 plants). 



Control 
5.7 (av. for 7 plants). 



Average (estimated) about Estimated twice the length of 
]/2 as long as the control. the radiated. 

None, except a few very Numerous on all plants save 
short ones on the most vig- one, which had only 3-3 small 
orous plant. ones. 

Decidedly club-shaped in 
five of the specimens. 

Appear to be slightly more 
numerous, and about twice as 
long as in the control plants. 
(See R, FIGURE 9.) 

Much darker colored than in Of normal appearance. De- 
the control plants, cidedly lighter than those of the 

radiated plants. 



Normal appearance : not en- 
larged near the root-tip. 

Normal. 



EFFECTS OF EXPOSING SEEDS 



109 



Summary 
The exposure to radium rays of seeds previously soaked was fol- 
lowed, in all instances by a retardation of growth. When seeds of 
Lupinus a/dus were exposed for 17 hrs. to rays from radium bromide 
of 1,500,000 X the seedlings produced by them grew only one half 
as rapidly as normally. Exposure of soaked seeds of buckwheat for 




Fig. 9. Experiment 25. Roots and Root-Hairs of Seedlings from the Exposed Culture 
{J^j, and from the Unexposed. Slightly Enlarged. Cf. figure S. 

24 hrs. to rays of the same strength retarded growth, and impaired 
the general vigor of the plants. One experiment was tried with flax 
seed, but an exposure of 48 hrs. (1,500,000 x) was followed by no 
appreciable effect on the germination of the seeds. 

An initial retardation of the growth of white mustard after the 



no 



EFFECTS OF EXPOSING SEEDS 



soaked seeds were exposed for 15 hrs. (1,500,000 x ), was followed 
by a recovery and apparent acceleration of growth, for the plants 
from exposed seeds, within ten days after planting, had caught up 
with and even slightly surpassed the control plants in height. The 
effect of this exposure of the white mustard was slight, and in har- 
mony with results obtained by Koernicke,* who found Brassica nafiis 
especially resistant. He reported that swollen seeds were accelerated 
in growth by exposure to 10 mg. of radium bromide, but does not 
state the activity of the preparation he used. 

When seeds of Ltcpinus albus were first soaked in water, and then 

12 0. 




11 12 

Day of month 

Fig. 10. Effect on the Growth of Zea Mays of Exposing the Grains, before Plant- 
ing, for 16 Hours, to Raj'S from Radium of Different Degrees of Activity. 

exposed while germinating for 18 hrs. (10,000 x ), and planted in soil, 
the tap-roots grew very abnormally. After 16 days' growth in the 
soil the tap-roots had evidently ceased growing, and, correlated with 
this fact, the secondary roots had developed more vigorously than 
normally. 

Oat grains were exposed for 67 hrs. after being soaked in water, 
and then planted in soil. The subsequent growth of the shoots was 

♦Bibliography, p. 72, No. 39. 



EFFECTS OF EXPOSING SEEDS 



III 



greatly retarded (figure 9), and roots were fewer in number, shorter, 
thick, and club-shaped, with the slightly more numerous root-hairs 
nearly twice the normal length. The root-tips of the exposed plant- 
lets were of a decidedly darker color than those of the control. 

4. Effect of Duration of Exposure and Degree of 

Activity 

In the preceding experiments it has become more and more 

clearly evident that the effect of exposure to radium rays varies, as 

Koernicke also found, with the duration of the exposure and the 

degree of activity of the radium. The purpose of the following six 

experiments was to confirm this fact, and get more accurate data on 

the relation between the duration, the degree of activity, and the 

effect produced. 

Experiment 26 

The object of the following experiment is to ascertain the effect 
on the germination and growth of corn {Zea Mays) of exposure for 



120 




10 



11 12 13 

Day of month 



15 



Fig. II. Effect on the Growth of Zea Mays of Exposing the Grains, before Plant- 
ing, iomU Hours, to Rays from Radium of Different Degrees of Activity. 



112 



EFFECTS OF EXPOSING SEEDS 



the same period of time to rays from radium of different strengths of 
activity. 

May 4, 10 A. M. 

Four sets of four seeds each of Zea Mays were exposed for 16 
hours to radioactive preparations as follows : 

Set A to RaBrg, 1,800,000 x » in sealed glass tube. 

Set B to RaBrg, 1,500,000 x , in sealed glass tube. 

Set C to RaBr2, 10,000 x , in sealed glass tube. 

Set D to radio-tellurium in sealed glass tube. 

Set E, Control — not exposed. 

Similar exposures were made for 24 hours and for 33 hours, and 
the seeds were then planted in soil. 

Exposure for 16 Hours 
May 10, 10 A. M. 

The heights of the seedlings above the surface of the soil are as 
follows : 





A 


B 


C 


D 


E 




1,800,000 X 


1,500,000 X 


10.000 X 


Ra. Tel. 


Control 


I 


0.00 mm. 


0.00 mm. 


just up 


0.00 mm. 


16.50 mm. 


2 


0.00 


just showing 


0.00 mm. 


0.00 


18.00 


3 


0.00 


arching soil 


0.00 


0.00 


11.00 


,4 


0.00 
0.00 mm. 


just showing 
0.00 mm. 


0.00 
0.00 mm. 


just up 
0.00 mm. 


12.00 




57.50 mm 












14.38 mm. 


Ma 


y II, 10 A. 


M. 










A 


B 


C 


D 


E 




1,800,000 X 


1,500,000 X 


10,000 X 


Ra. Tel. 


Control 


I 


4.00 mm. 


7.50 mm. 


9.00 mm. 


0.00 mm. 


29.50 mm. 


2 


0.00 


3.00 


3-50 


4.00 


28.00 


3 


3.00 


6.00 


3.00 


4.00 


23.00 


4 


0.00 
7.00 mm. 


6.00 


3.00 
18.50 mm. 


9.00 
17.00 mm. 


22.50 




22.50 mm. 


103.00 mm. 




3.50 mm. 


5.62 mm. 


4.62 mm. 


5.66 mm. 


25.75 mm. 



EFFECTS OF EXPOSING SEEDS 



"3 



May 12, ID A. M 
A 

i,Soo,ooo X 
7.00 mm. 
0.00 
9.00 
5.00 



B 

i,5cx),ooo X 
1 8. 00 mm. 

7.00 
16.00 
13.00 



C 

io,oooX 
18.00 mm. 
13.00 
10.00 
13-50 



D 

Ra. Tel. 
0.00 mm. 
11.50 
15.00 
20.00 



E 

Control 
44.00 mm. 
37.00 
37.00 
36.00 



21.00 mm. 
7.00 mm. 

120 



54.00 mm. 
13.50 mm. 



54.50 mm. 
13.62 mm. 



46.50 mm. 
15.50 mm. 



154.00 mm. 
38.50 mm. 



110 
100 












/ 


90 

80 


Exj 


)cnine7it S 


r ..._ 




/ 


/ 


70 

1 ^^ 

"53 

1 ^^ 
1 40 

30 
20 
10 



Oi 


# 


k 










/ 








^ 






.0^- 




y 


,-..<='- 


Z^" 




OOP 


.•••••'*'***'^ 



10 



13 



14 



15 



11 12 

Day of month 

Fig. 12. Effect on the Growth of Zea Mays of Exposing the Grains, before Plant- 
ing, for 33 Hours, to Rays from Radium of Different Degrees of Activity. 

Ma}' 14, 10 A. M. 





A 


B 


C 


D 


E 




1,800,000 X 


1,500,000 X 


10,000 X 


Ra. Tel. 


Control 


I 


27.00 mm. 


57.00 mm. 


68.00 mm. 


0.00 mm. 


loS.oo mm. 


2 


10.00 


29.00 


62.00 


50.00 


80.00 


3 


30.00 


52.00 


62.00 


65.00 


95.00 


4 


20.00 
87.00 mm. 


38.00 
176.00 mm. 


51.00 
243.00 mm. 


68.00 


90.00 




183.00 mm. 


373.00 mm. 




21.75 mm. 
9 


44.00 mm. 


60.75 '^'^• 


61.00 mm. 


93.25 mm. 



114 



EFFECTS OF EXPOSING SEEDS 



May 15, 10 A. M. 

A 

1,800,000 X 

1 34.00 mm. 

2 10.00 

3 35-00 

4 20.00 



99.00 mm. 
24.75 mm. 




221.00 mm. 
55.25 mm. 



C 

10,000 X 
86. 00 mm. 
73.00 
75.00 
62.00 



296.00 mm, 
74.00 mm, 



D 

Ra. Tel. 
0.00 mm. 
57.00 
86.00 
93.00 

236.00 mm. 
78.67 mm. 



E 
Control 
135.00 mm. 
1 1 1 .00 
121.00 
115.00 



482.00 mm. 
120.50 mm. 



None of these plants exposed to the radium of 1,800,000 activity 
are erect, but grow parallel with and close to the surface of the soil. 




10 



11 12 13 

Day of month 



Fig. 13. Effect on the Growth of Zea Mays of Various Durations of Exposure of the 
Grains, before Planting, to Radium Ravs. Activity, 10,000. 



Exposure for 24 Hours 
The heights of the seedlings above the surface of the soil are as 
follows : 



EFFECTS OF EXPOSING SEEDS 



May lo, lo A. M. 



115 





A 


B 


c 


D 


E 




1,800,000 X 


1,500,000 X 


10,000 X 


Ra. Tel. 


Control 


I 


just showing 


just showing 


not up 


not up 


16.50 mm. 


2 


0.00 mm. 


a 


(( 


(( 


18.00 


3 


0.00 


i I 


(( 


a 


11.00 


4 


0.00 
0.00 mm. 


It 


K 


u 


12.00 










57.50 mm. 




0.00 mm. 








14,38 mm. 



May II, II A. M. 





A 


B 




C 


D 


E 




1 ,800,000 X 


1,500,000 X 


10,000 X 


Ra. Tel. 


Control 


I 


4.00 mm. 


7.00 


mm. 


1. 00 mm. 


3.00 mm. 


29.50 mm. 


2 


2.00 


7-50 




4-50 


0.00 


28.00 


3 


6.00 


7.00 




0.00 


0.00 


23.00 


4 


0.00 


11.50 
33-00 


mm. 


3.00 
8.50 mm. 


5.00 

8.00 mm. 


22.50 




12.00 mm. 


103.00 mm. 




4.00 mm. 


8.25 


mm. 


2.83 mm. 


4.00 mm. 


25.75 ^^'^' 


May 


12, 10 A. 


M. 












A 


B 




C 


D 


E 




1,800,000 X 


1.500,000 X 


10,000 X 


Ra. Tel. 


Control 


I 


10.00 mm. 


14.00 


mm. 


9.00 mm. 


13.00 mm. 


44.00 mm. 


2 


6.50 


21.00 


• 


14.00 


0.60 


37.00 


3 


14.00 


17.00 




0.00 


0.00 


37.00 


4 


0.00 


26.50 
78.50 


mm. 


12.00 


15.00 
28.00 mm. 


36.00 




30.50 mm. 


35.00 mm. 


154.00 mm, 




10.16 mm. 


19.62 


mm. 


[ 1.66 mm. 


14.00 mm. 


38.50 mm. 


May 


14, 10 A. 


M. 












A 


B 




C 


D 


E 




1,800,000 X 


1,500,000 X 


10,000 X 


Ra. Tel. 


Control 


I 


31.00 mm. 


52.00 


mm. 


42.00 mm. 


53.00 mm. 


108.00 mm 


2 


19.00 


74.00 




61.00 


0.00 


80.00 


3 


20.00 


67.00 




0.00 


29.00 


95.00 


4 


21.00 


70.00 
263.00 


mm. 


61.00 
164.00 mm. 


70.00 
152.00 mm. 


90.00 




91.00 mm. 


373.00 mm 




22.75 ''""^• 


65.75 


mm. 


54.67 mm. 


50.67 mm. 


93.25 mm 



ii6 



EFFECTS OF EXPOSING SEEDS 



May 15, 10 A. 


M. 








A 


B 


c 


D 


E 


1,800,000 X 


1, 500,000 X 


10,000 X 


Ra. Tel. 


Control 


I 45.00 mm. 


62.00 mm. 


53.00 mm. 


71.00 mm. 


135.00 mm. 


2 20.00 


S3. 00 


79.00 


0.00 


1 1 1 .00 


3 19-00 


85.00 


0.00 


41.00 


121.00 


4 22.00 


S3. 00 
313.00 mm. 


77.00 
209.00 mm. 


88. 00 
200.00 mm. 


1 15.00 


106.00 mm. 


4S2.00 mm. 


26.50 mm. 


78. 25 mm. 


69.66 mm. 


66.66 mm. 


120.50 mm. 



All the plants exposed to the radium of 1,500,000 x have failed 
to become erect, and grow horizontally over the surface of the 
ground (figure 14). 





n 




1 




^ 


E 


Wi 


^^^BS^^ 


li 


m 


m 




^ 


& 


■■^■■Li^'^Mtt^&*^^ 



Fig. 14. Experiment 26. Absence of Geotropic Response in Shoots of Zea Mays, 
following a 24 Hours' Exposure of the Grains, before Planting, to Radium of i, 500,000 X- 
From left to right, RaBr^ 1,800,000 X; RaBr2 1,500,000 X i Ra. Tel.; Control. 
Cf. FIGURE 62. 

On June 4, the culture exposed to the radio-tellurium was photo- 
graphed with the control set (figure 15). 

Exposure for 33 Hours 
The heights of the seedlings above the surface of the soil are as 
follows : 



May 


10, 10 A. M. 












A 


B 




D 


E 




1, 800,000 X 


1,500,000 


X 


Ra. Tel. 


Control 


I 


0.00 mm. 


8. 50 mm. 


12.50 mm. 


16.50 mm 


2 


0.00 


just up 




5.00 


18.00 


3 


0.00 


a 




0.00 


11.00 


4 


0.00 
0.00 mm. 


(( 


- 


10.00 
27.50 mm. 


12.00 






57.50 mm 




0.00 mm. 






9.16 mm. 


14.37 mm 



EFFECTS OF EXPOSING SEEDS 



117 




Fig. 15. Experiment 26. Retardation of Growth of Zea Mays by Exposing 
Grains, before Planting, to a Sealed Glass Tube of Radio-Tellurium. Duration of 
Exposure, 24 Hours. 



^a_3 


J II, 10 A.M. 










A 


B 


D 


E 




1, 800,000 X 


1,500,000 X 


Ra. Tel. 


Control 


I 


0.00 mm. 


13.50 mm 


22.50 mm. 


29.50 mm 


2 


6.00 


7.00 


17.00 


28.00 


3 


0.00 


7.00 


0.00 


23.00 


4 


4.00 


3.00 


20.00 


22.50 




10.00 mm. 


30.50 mm. 


59.50 mm. 


103.00 mm 




5.00 mm. 


7.62 mm. 


19,83 mm. 


25.75 mm 



ii8 



EFFECTS OF EXPOSING SEEDS 



May 


12, lo A. M. 










A 


B 


D 


E 




1,800,000 X 


1,500,000 X 


Ra. Tel. 


Control 


I 


0.00 mm. 


19.00 mm. 


34.00 mm. 


44.00 mm, 


2 


8.00 


14.00 


30.00 


37.00 


3 


5.00 


12.00 


0.00 


37.00 


4 


7.00 
20.00 mm. 


6.00 


32.00 
96.00 mm. 


36.00 




51.00 mm. 


154.00 mm 




6.66 mm. 


12.75 mm. 


32.00 mm. 


38.50 mm 


May 


14, 10 A. M. 










A 


B 


D 


E 




1, 800,000 X 


1,500,000 X 


Ra. Tel. 


Control 


I 


0.00 mm. 


29.00 mm. 


76.00 mm. 


108.00 mm 


2 


1 1. 00 


33-00 


85.00 


80.00 


3 


iS.oo 


27.00 


0.00 


95.00 


4 


12.00 
41.00 mm. 


13.00 
102.00 mm. 


80.00 


90.00 




241 .00 mm. 


373.00 mm, 




13.66 mm. 


25.50 mm 


80.33 mm. 


93.25 mm, 


May 


15, 10 A. M. 










A 


B 


D 


E. 




1 ,800,000 X 


1,500,000 X 


Ra. Tel. 


Control 


I 


0.00 mm. 


29.00 mm. 


93.00 mm. 


135.00 mm. 


2 


1 1. 00 


33-00 


107.00 


1 1 1 .00 


3 


19.00 


27.00 


0.00 


121.00 


4 


12.00 


13.00 


90.00 


115.00 




42.00 mm. 


102.00 mm. 


290.00 mm. 


482.00 mm 




14.00 mm. 


25.50 mm. 


96.66 mm. 


120.50 mm. 



The results of this experiment are rather difficult to interpret, and 
do not harmonize in some places with the hypothesis that the effect 
of radium rays on growth varies directly with the activity of the 
radium, and the duration of the exposure. In the first place, the 
results of exposure to the various preparations are not in all points 
strictly comparable. For example, there was 100 times (.52 gm.) 
as much of the radium bromide of 10,000 x and of radio-tellurium 
as of the stronger radium preparations. Again, in laying the tubes 
over the seeds, it is more than probable that the salt was not dis- 
tributed along the tube precisely similarly in any two cases, and doubt- 



EFFECTS OF EXPOSING SEEDS 



119 



less not all of the four seeds of any given set were equally exposed, 
though great care was taken in this regard. The necessity of using 
such a small number of seeds was doubtless here (as in other experi- 
ments) a source of error, by emphasizing individual variations, but 
this could not well be eliminated on account of the scarcity of the 
radium, and the comparatively short period of time that any given 
preparation was at my disposal. 




.10 



11 



12 
Dau of month 



13 



Fig. 16. Effect on the Growth of Zea Mays of Various Durations of Exposure of 
the Grains, before Planting, to Radium Rays. Activity, 1,500,000. 

Interpretation of the results is greatly facilitated by inspection of 
the curves (figures 10-12). In figure 10 it is clearly shown that, 
for an exposure of 16 hrs., the effect of the rays from the preparations 
of 1,500,000 X and 1,800,000 X varied directly as the activity of the 
radium. The same fact is clearly indicated in figures ii and 12, 
where the exposures were respectively for 24 and 33 hours. 

The immediate effect of exposure for 16 hrs. to the radium of 
10,000 X (figure 10) was a greater retardation of growth than that 
produced by the next more active preparation, but from the third day 



I20 



EFFECTS OF EXPOSING SEEDS 



the plants of this culture grew faster, so that, from this time on, the 
rate of growth varied inversely as the strength of the radium. In 
FIGURE II, also, growth following exposure to the larger amount of 
the weaker radium is shown to be less at first than after exposure to 
the radium of 1,800,000 x , but soon becomes greater, though the 
indicated effect of the radium of 1,500,000 x is less than that of 
either the 10,000 x or the 1,800,000 x radium. 



110 
1 no 












/ 


90 
80 


F-i 


cperimefU 


'^(^ 




-7 


/ 


70 
s2 60 






( 

/ 


4/ 




.1 50 
§ *0 








/ 






30 
20 




^ 


^^ 




-.^"^^ 


^^,0^" _ 


10 




^ 


^ 


^.^^ 


^<^ 

•^^•^^•••••* 


'0'\_ 


Ss'v^^^- 



10 



14 



15 



Fig. 17. 



11 12 13 

Day of month 

Effect on the Growth of Zea A/ays of Various Durations of Exposure of 
the Grains, before Planting, to Radium Rays. Activity, 1,800,000. 



If we consider the effect of rays of the same strength allowed to 
act for varying lengths of time (figures 13, 16, 17), we shall not find, 
in this experiment, that the hypothesis is very well verified. With the 
radium of 10,000 x (figure 13) the results are what the hypothesis 
calls for.* 

*The 10,000 X culture of 33 hrs. exposure went bad, and was discarded, but this 
is only partially true in the other three cases (figures i6, 17). These results being 
at variance with the expectation warranted by previous experience, it was impossible 
to avoid the conclusion that some unknown source of error crept into the experiment. 
I think it best, however, to give the results as they were obtained. 



EFFECTS OF EXPOSING SEEDS 



121 



The experiment suggests that the degree of activity of the radium 
is a more important factor than the duration of the exposure. That 
is, that a slight increase in activity is more effective than a relatively 
slight increase in the duration of the exposure. If this is so, the facts 
concerning the effect of varying the length of exposure will be more 
readily ascertained by exposing for longer periods of time. With this 
in view the following experiment was made, and the greatest care 
was exercised in choosing seeds apparently as nearly alike as pos- 
sible in size and vigor, in distributing the radium salt evenly over the 



120 




10 



11 



12 13 

Day of month 

Fig. i8. Effect on the Growth of Zea Mays of Various Durations of Exposure of 
the Grains, before Planting, to Radio-Tellurium in a Sealed Glass Tube. 

bottom of the horizontal tube, in having the tube in contact with all 
the seeds, and at the same region of the seed, and in having the pots 
in which the exposed seeds were planted, and all other conditions of 
growth as nearly uniform as possible for all four cultures. 

Experiment 27 
Object : To ascertain the effect of varying lengths of exposure to 
the rays of radium of the same activity on the germination and 
growth of Lu^inus albus. 



122 



EFFECTS OF EXPOSING SEEDS 



October 22, 10 A. M. 

Three sets of six dry seeds each, A, B, and C, were exposed as 
follows, to the rays from 10 mg. of RaBr^, 1,800,000 activity, in a 
sealed glass tube : 

A. 72 hrs. Planted 4 days after the end of the exposure. 

B. 50 hrs. " 2 " " " " " " 

C. 26 hrs. " 21 hours " " " " " 

D. Control, not exposed. 

The seeds were then planted without soaking, in separate pots in 
soil. 




Fig. 19. Expei-iment 27. Effect of Duration of Exposure to Radium Rays on 
Germination and Growth of Lupinus albus. Length of Exposures, from Left to Right, 
72 Hours, 50 Hours, 26 Hours, Control. Cf. figure 20. 

The lengths of the hypocotyls above the surface of the soil were 
measured as follows : 



Oclob 


er 29, 
A 


10 


A. 


M. 


B 




72 h 


rs. 






50 hrs. 


1 


6.00 


mm 


. 




10.00 mm 


2 


S.oo 








9.00 


3 


5.00 








10.00 


4 


4-50 








lO.OO 


5 


10.00 








just up * 


6 


12.00 








T 1. 00 



45.50 mm. 50.00 mm. 

7.58 mm. 10.00 mm. 

Poor seed. Discarded. 



c 

26 hrs. 
10.00 mm. 
1 1. 00 
9.00 
10.00 
11.00 
12.00 



63.00 mm. 
10.50 mm. 



D 

Control 
12.00 mm. 
17.00 
1 1. 00 
16.00 
12.00 
13.00 



Si .00 mm. 
13.50 mm, 



EFFECTS OF EXPOSING SEEDS 



123 



October 30, 10 A. 


M 










A 




B 


C 


D 




72 hrs. 




50 hrs. 


26 hrs. 


Control 


I 


10.00 mm. 




16.00 mm. 


16.00 mm. 


iS.oo mm 


2 


10.00 




11.00 


17.00 


22.00 


3 


9.00 




15.00 


16.00 


16.00 


4 


5.00 




14.00 


16.00 


20.00 


5 


12.00 




0.00 


15.00 


19.00 


6 


16.00 




15.00 
71.00 mm. 


16.00 


19.00 




62.00 mm. 


96.00 mm. 


1 14.00 mm 




10.33 "^'"• 




14.20 mm. 


16.00 mm. 


19.00 mm 


Octob 


er 31, 9:30 


A. 


M. 








A 




B 


C 


D 




72 hrs. 




50 hrs. 


26 hrs. 


Control 


I 


13.00 mm. 




19.50 mm. 


20.00 mm. 


19.50 mm 


2 


10.00 




12.00 


20.00 


25.00 


3 


9-50 




19.50 


21.00 


20.00 


4 


6.00 




19.00 


20.00 


24.50 


5 


12.00 




0.00 


19.50 


25.00 


6 


19.50 
70.00 mm. 




20.00 


21.00 


19.50 




90.00 mm. 


121.50 mm. 


133.50 mm 




11.66 mm. 




18.00 mm. 


20.25 mm. 


22.25 "^'^^ 



November i, 9 : 30 A. M. 





A 


B 


C 


D 




72 hrs. 


50 hrs. 


26 hrs. 


Control 


I 


14.00 mm. 


19.50 mm. 


20.00 mm. 


21.00 mm 


2 


12.00 


12.00 


20.00 


27.00 


3 


10.50 


20.00 


21.00 


21.50 


4 


8.50 


19.00 


22.00 


24.50 


5 


14.00 


0.00 


20.50 


25.00 


6 


20.50 
79.50 mm. 


21.00 


24.00 
127.50 mm. 


21.00 




91.50 mm. 


140.00 mm 




13.25 mm. 


18.30 mm. 


21.25 11^1''^. 


23.33 iT^m 



124 EFFECTS OF EXPOSING SEEDS 

November 2, 9 : 30 A. M. 

B 

50 hrs. 
19.00 mm. 
12.50 
20.00 
19.00 
0.00 
21.00 





A 




72 hrs. 


I 


15.00 mm 


2 


12.00 


3 


10.50 


4 


10.00 


5 


15.00 


6 


23.00 




85.50 mm 




14.25 mm 



91.50 mm. 
18.30 mm. 



November 3, 9 : 30 A. M. 

B 





A 




72 hrs. 


I 


15.00 mm. 


2 


12.00 


3 


12.00 


4 


10.00 


5 


16.00 


6 


23.00 




88.00 mm. 




14.66 mm. 



50 hrs. 

19.00 mm. 
12.50 
21.00 
21.00 
0.00 
21.50 



c 




D 


26 hrs. 


Control 


20.00 


mm. 


21.00 mm, 


21.00 




29.00 


21.00 




21.50 


22.00 




25.00 


21.00 




26.00 


24.00 


m m . 


21.00 


129.00 


143.50 mm 


21.50 


m m . 


23.92 mm 


c 




D 


26 hrs. 


Control 


21.00 


mm. 


2 1. 00 mm 


21.00 




29.00 


24.00 




22.00 


22.00 




25.00 


21.50 




27.00 


25.00 


mm. 


21.00 


f 34-50 


145.00 mm 


22.41 


mm. 


24.16 mm 



95.00 mm. 
19.00 mm. 

In the 72-hrs. culture the plumule is above the partly opened 
cotyledons in only two seedlings. In the other three cultures the 
plumule is well above the spreading cotyledons. The effect on the 
root-system is shown in figure 20. 

November 5. 

No apparent growth of the hypocotyl has taken place in any of 
the cultures since November 3, but the epicotyl has grown in all the 
plants of all four cultures, except four plants of the 72-hrs. exposure. 

November 14. 

The experiment was photographed (see figures 19 and 20), and 
portions of the hypocotyls were preserved for sectioning (see p. 224). 

The experiment clearly shows that, when the activity of the radium 
is the same, retardation of germination and growth varies directly 
with the duration of the exposure (see figure 21). 



EFFECTS OF EXPOSING SEEDS 



125 



The results are in perfect accord with the hypothesis, and with 
the results of other experiments. The rate of growth is seen to vary- 
inversely with the duration of exposure (figure 21), and to decrease 




Fig. 20. Experiment 27. Root Systems of Seedlings of Lupinus albus from 72- 
Hour and from Control Cultures Shown in figure 19. 

most -rapidly as the activity of the radium increases. The experi- 
ment was continued until all the hypocotyls ceased growing in all 
four cultures. 



126 



EFFECTS OF EXPOSING SEEDS 



Experiment 28 

To ascertain the effect of exposing dry seeds for short periods of 
time to radium of strong activity, the following experiment was made. 

Five sets of eight dry seeds of Lufimis albus each were exposed 
respectively to the rays of radium of 1,500,000 activity by having the 
sealed glass tube of the radium bromide (10 mg.) placed in contact 
with their hilum-edges. The duration of exposures was 2, 3, 4, 6, 
and 14 hrs., respectively. 




Fig. 21. Activity of Radium, 1,800,000. 

April 17, II A. M. 

The exposed seeds, together with eight control seeds, were 
planted in soil, in similar pots. 

April 21, 2 P. M. 

No marked difference could be observed in the six cultures. No 
measurements were taken. 

April 23, 10 : 30 A. M. 

Average lengths of the hypocotyls above the surface of the soil : 

14 hrs. 6 hrs. 4 hrs. 3 hrs. 2 hrs. Control 

14.50 mm. 15.87 mm. 14.70 mm. 18.28 mm. 17.70 mm. 15.12 mm. 



EFFECTS OF EXPOSING SEEDS 



127 



April 26, II A. M. 



14 hrs. 6 hrs. 4 hrs. 3 hrs. 2 hrs. Control 

23.60mm. 25.75 mm. 24.00 mm. 25.62 mm. 26.85 ^^- 23.50 mm. 

At the end of five weeks (May 24) there was no appreciable dif- 
ference in the six cultures that could be attributed to the radium rays. 
An exposure of dry lupine seeds for 14 hrs. to radium of 1,500,000 x 
was not sufficient appreciably to affect germination or growth. 

Experiment 29 

The relation between the degree of activity of the radium and the 
retardation of growth is clearly shown by the following experiment. 

Object: To ascertain the effect on the germination and growth 
of Litpinus albus of exposure for the same period of time to rays of 
radium of different degrees of activity. 

Oct. 30, I : 30 P. M. 

Three sets. A, B, and C, of six dry seeds each of L. albus were 
exposed to the rays of RaBr2 in sealed glass tubes by laying the tubes 







^ 


» 


y 


■^'^.Y ^y> 


9 


«a« 


=^:iiisaaJ^-5=^ -■ -'* 


"1 





Fig. 22. Experiment 29. Effect on the Germination and Growth of Ltipinus albus 
of Exposure for the Same Period of Time to Rays from Radium of Different Activities, 
as Follows (from Left to Right) : 1,800,000; 1,500,000: 10,000; Control. 



against the hilum-edges of the seeds. The time of exposure was 
91.50 hrs., and the strengths of the radium as follows : 

A. 1,800,000 X . 

B. 1,500,000 X . 

C. 10,000 X . 

D. Control — not exposed. 



128 



EFFECTS OF EXPOSING SEEDS 



Nov. 3, 9: 30 A. M. 

The seeds were planted in soil, each set in a separate six-inch pot. 

Nov. 8, 8:30 A. M. 

Seedlings are breaking through the soil in all cultures, but with 
no significant difference in the four sets. 

Nov. 9, 8 : 30 A. M. 

Relative growth the same as yesterday. Only 5 or 6 plants with 
hypocotyls long enough to measure. No measurements were taken. 

Nov. 10, 10 A. M. 

Measurements of the lengths of the hypocotyls were taken as 
follows : 



B 





1.800,000 X 


1,500,000 X 


I 


8.00 mm. 


9.00 mm. 


2 


0.00 




4-50 


3 


7.00 




0.00 


4 


3.00 




5.00 


5 


7.00 




5.00 


6 


12.00 


mm. 


6.00 




37.00 


29.50 mm. 




6.16 


mm. 


4.91 mm. 


Nov. 


12, 9 : 


30 A. M. 






A 




B 




1,800,000 X 


1,500,000 X 


I 


13.00 


mm. 


20.00 mm, 


2 


5.00 




14.00 


3 


12.00 




0.00 


4 


9.00 




17.00 


5 


10.00 




15.00 


6 


18.00 


mm. 


19.00 




67.00 


85.00 mm 




1 1. 16 


mm. 


14.16 mm, 



10.000 X 
5.00 mm. 

4-50 
14.00 

5-50 
9.00 

5-5Q 

43.50 mm. 

7.25 mm. 



D 

Control 
5.50 mm. 

13.00 
5.00 
8. 00 

1 1. 00 

11.00 



53.50 mm. 
8.91 mm. 



c 




D 


10,000 


X 


Control 


15.00 


mm. 


18.00 mm 


18.00 




27.00 


27.00 




16.00 


17.00 




16.00 


17.00 




25.00 


16.00 


mm. 


23.00 


110.00 


125.00 mm 


18.33 


mm. 


20.83 "^™ 



EFFECTS OF EXPOSING SEEDS 



129 



November 13, 


9- 


130 


A. 


M. 












A 








B 




c 




D 




1,800,000 


X 






1,500,000 X 


10,000 


X 


Contror 


I 


14.00 mm. 






22.00 


mm. 


15.00 


m m . 


20.00 mm. 


2 


10.00 








17.00 




19.00 




31.00 


3 


10.50 








6.00 




28.50 




16.50 


4 


10.00 








18.00 




17-50 




iS.oo 


5 


13-50 








16.00 




17.00 




26.00 


6 


18.00 


m. 






20.00 


mm. 


17-50 
114.50 


mm. 


24.00 




76.00 mi 


99.00 


135.50 mm. 




12.66 mm. 






16.50 


mm. 


19. oS 


mm. 


22.58 mm. 



November 14, 9 : 30 A. M. 





A 




B 




C 




D 




1,800,000 X 


1,500,000 X 


10,000 


X 


Control 


I 


14.00 


mm. 


22.50 


mm. 


16.00 


mm. 


21.00 mm. 


2 


10.00 




17.00 




21.00 




33-50 


3 


11.50 




10.00 




30.00 




19.00 


4 


10.50 




20.00 




18.00 




20.50 


5 


14.50 




17.00 




17-50 




27.50 


6 


1S.50 
79.00 


mm. 


21.00 


mm. 


19.00 
121.50 


mm. 


27.00 




107-50 


148.50 mm 




13.16 


mm. 


17.91 


mm. 


20.25 


mm. 


24.75 mm 



November 15, 9 : 30 A. M. 





A 




B 




C 




D 




1,800,000 X 


1,500,000 X 


10,00c 


)X 


Control 


I 


14.00 


mm. 


26.00 


mm. 


^9.00 


mm. 


23.00 mm 


2 


10.00 




17.00 




24.00 




38.50 


3 


11.50 




12.00 




34.00 




21.00 


4 


10.50 




21.00 




20.00 




20.00 


5 


14.50 




18.50 




19.00 




30.00 


6 


19.00 
79-50 


mm. 


23.00 
117.50 


mm. 


20.00 


mm. 


30.00 




136.00 


162.50 mm 




13-25 


mm. 


19.58 


mm 


22.66 


mm. 


27.08 mm 



10 



130 EFFECTS OF EXPOSING SEEDS 

November 16, 9 : 30 A. M. 





A 




B 




C 


D 




1,800,000 X 


1,500,000 X 


10,000 X 


Control 


I 


14.00 


mm. 


2S.00 


mm. 


20.00 mm. 


26.00 mm 


2 


10.00 




18.00 




27.00 


42.00 


3 


1 1.50 




15.00 




34-50 


23-50 . 


4 


10.50 




24.00 




21.00 


23.00 


5 


14.50 




20.00 




19.50 


31.00 


6 


19.00 




24.00 




22.00 


34.00 




79-50 


mm. 


129.00 


mm. 


144.00 mm. 


179.50 mm 




13-25 


mm. 


21.50 


mm. 


24.00 mm. 


29.91 mm 



November 17, 9 : 30 A. M. 

A B C D 





1,800,000 X 


1,500,000 X 


10,000 


X 


Control 


I 


14.00 


mm. 


30.00 


mm. 


22.00 


mm. 


28.00 mm 


2 


10.00 




18.00 




2S.50 




45.00 


3 


1 1.50 




17.00 




35-50 




26.50 


4 


10.50 




25.00 




23-50 




25-50 


5 


14.50 




20.50 




20.00 




31-50 


6 


19.00 




25-50 




24.00 




37-50 




79-50 


mm. 


136.00 


mm. 


153-50 


mm. 


194.00 mm 




13.25mm. 


22.66 


mm. 


25.5S 


mm. 


3 2. 33* mm 



When the duration of the exposure is the same, then the retarda- 
tion of growth varies directly with the strength of the radium em- 
ployed. (See FIGURE 23.) 

The 1,800,000 X curve is made to cross the 1,500,000 x curve 
during the first time interval by the excessive growth of one seedling 
(No. 6) of the 1,800,000 X culture. It is very probable that this seed 
was not as effectively exposed as the others. Likewise the initial 
difference between the average growth of the 10,000 x culture and 
the control on November 10 would have been greater but for the 
exceptional growth of seed No. 3, which was either not well exposed 
to the rays, or else was unusually resistant to their influence. 

In experiments 26, 27, and 28, it was necessary that a longer time 
should intervene between exposure and planting in some cultures 
than in others. The following experiment was made in order to see 
if this variation in time-interval had any effect on the result of 
exposure for the same length of time to radium of the same activity, 
at least within the limits imposed in the preceding experiments. 



EFFECTS OF EXPOSING SEEDS 



131 



Experiment 30 

Object : To see if a variation in the time-interval between the 
exposure of seeds to radium-rays and their germination, alters the 
efficacy of the exposure to affect germination. 

November 19, 10 A. M. 

Three sets of six seeds each of Lit^imis albus, treated as follows, 
were planted without soaking, in soil in flower pots. 




1 2 3 4 5 6 7 

Fig. 23. Lupinus albus. Duration of Exposure, 91-50 Hours. 

A. Exposed for 72 hrs. to RaBr2 1,500,000 x . Interval between 
exposure and planting, 6 days. 

B. Exposed for 72 hrs. to RaBr, 1,500,000 x . Interval between 
exposure and planting, 3 days. 

C. Exposed for 72 hrs. to RaBr, 1,500,000 x . Interval between 
exposure and planting, o days. 

D. Control, not exposed. Planted at same time as A, B, and C. 
Heights of the hypocotyls above the soil-surface as follows : 



132 



EFFECTS OF EXPOSING SEEDS 



November 26, 10 


A. 


M. 








A 




B 


C 


D 




6 days 




3 days 


da^'s 


Control 


I 


7.00 mm. 




6.50 mm. 


4.50 mm. 


9.50 mm, 


2 


6.50 




9-50 


5-50 


11.50 


3 


8.00 




not up 


6.50 


8.50 


4 


8.50 




9-50 


7.50 


10.00 


5 


7.00 




9.00 


5-50 


10.00 


6 


8.00 




5.00 
39.50 mm. 


6.50 
36.00 mm. 


11.50 




45.00 mm. 


61.00 mm, 




7.50 mm. 




7.90 mm. 


6.00 mm. 


10.16 mm 


Nove: 


mber 27, 10 


A. 


M. 








A 




B 


C 


D 




6 days 




3 days 


days 


Control 


I 


7.50 mm. 




7. £50 m:i:. 
13.00 


6.50 mm. 


13.50 mm. 


2 


8.50 




6.00 


15-50 


3 


8.50 




not up 


11.00 


13-50 


4 


1 1.50 




II .00 


11.50 


16.50 


5 


8.50 




10.00 


9.00 


14.00 


6 


8.50 




8.50 


13.00 


19.00 




53.00 mm. 




50.00 mm. 


57.00 mm. 


92.00 mm. 




8. S3 mm. 




10.00 mm. 


9.50 mm. 


15-33 i"m. 


November 28, 10 


A. 


M. 








A 




B 


C 


D 




6 days 




3 days 


days 


Control 


I 


8.00 mm. 




10.00 mm. 


8.50 mm. 


16.00 mm. 


2 


9.50 




15.00 


9-50 


21.50 


3 


12.50 




not up 


13.00 


16.50 


4 


14.00 




13.00 


15.00 


19.50 


5 


9-50 




10.00 


9.00 


iS.oo 


6 


9-50 




10.00 


15.00 


23-50 




63.00 mm. 




58.00 mm. 


70.00 mm. 


115.00 mm. 




10.50 mm. 




1 1.60 mm. 


1 1.66 mm. 


19. 16 mm. 



EFFECTS OF EXPOSING SEEDS I33 



Nove 


mber 29, 10 


A. 


M. 








A 




B 


C 


D 




6 days 




3 days 


days 


Control 


I 


10.00 mm. 




12.00 mm. 


13.00 mm. 


21.00 mm. 


2 


15.00 




21.00 


12.00 


29.00 


3 


16.00 




just up 


13.00 


21.50 


4 


20.00 




13-50 


18.00 


25.00 


5 


13.00 




12.00 


10.00 


24.50 


6 


10.00 




11.00 
69.50 mm. 


19.00 

85 .00 mm. 


30.00 




84.00 mm. 


151.00 mm. 




14.00 mm. 




13.90 mm. 


14. 16 mm. 


25.16 mm. 


November 30, 10 


A. 


M. 








A 




B 


c 


D 




6 days 




3 days 


days 


Control 


I 


10.00 mm. 




13.00 mm. 


14.00 mm. 


21.00 mm. 


2 


15.00 




21.00 


12.00 


29.00 


3 


16.00 






13.00 


21.50 




4 


21.00 




13-50 


18.00 


25.00 


5 


13-50 




12.00 


10.00 


24.50 


6 


10.00 




11.00 


19.00 
86.00 mm. 


30.00 




85.50 mm. 


70.50 mm. 


151.00 mm. 




14.25 mm. 




14.10 mm. 


14.33 mm. 


25.16 mm. 



A time-interval of from three to six days between exposure and 
planting makes only a very slight, if any difference, at first, and any 
early difference, if one really exists, does not persist. 

Experiment 31 

Object : To ascertain the result of varying the distance between 
the radium-tube and the seeds, on the effect of radium ravs on the 
germination and growth of Lu^imis albus. 

Four sets of six seeds each of L. albus were exposed for 72 hours 
to the rays from the same amount of radium bromide of 1,500,000 
activity, contained in a sealed glass tube. The distances from the 
bottom of the radium-tube to the upper surfaces of the seeds were 
respectively 80 mm., 40 mm., 20 mm., and o mm. 

December 7, 10 A. M. 

The seeds, exposed as above, together with a control (unexposed) 
set of six, were all planted without soaking, in soil in pots. 



134 



EFFECTS OF EXPOSING SEEDS 



The lengths of the hypocotyls above the soil-surface are as follows : 
December 17, 10 A. M. 





So mm. 


40 mm. 


20 mm. 


mm. 


Control 


I 


2^.oo mm. 


20.00 mm. 


21.00 


mm. 


16.00 mm. 


not up 


2 


not up 


20.00 


20.00 




S.oo 


24.00 mm 


3 


17.00 


18.00 


21.00 




12.00 


17.00 


4 


27.00 


20.00 


20.00 




10.00 


19.00 


5 


20.00 


17.00 


28.00 




12.00 


23.00 


6 


30.00 
119.00 mm. 


23.00 
1 1 8. 00 mm. 


25.00 
135-00 


m m . 


16.00 


30.00 




74.00 mm. 


1 13.00 mm 




23. So mm. 


19.66 mm. 


22.50 


m m . 


12.33 i^m""' 


22.60 mm 


December 18, 10 


A. M. 












80 mm. 


40 mm. 


20 mm. 


mm. 


Control 


I 


30.00 mm. 


25.00 mm. 


25.00 


mm. 


20.00 mm. 


not up 


2 
3 




28. 00 
22.00 


25-50 
27.00 




12.00 


26.00 mm. 


23.00 




18.00 


22.00 


4 


30.00 


25.00 


24.00 




13.00 


23-50 


5 


24.00 


23.00 


30.00 




15.00 


28.00 


6 


35 -oo 
142.00 mm. 


29.50 
152.50 mm. 


29.00 
160.50 


mm. 


20.00 


35- 00 




98. 00 mm. 


134.50 mm 




28.40 mm. 


25.41 mm. 


26.75 


mm. 


16.33 "''"^• 


26.90 mm 



It is seen that the effect produced when the radium-tube is in 
immediate contact with the seeds is marked, and in agreement with 
the results of preceding experiments. No effect, however, can be 
detected when the exposure is made at distances of 20 mm., 40 mm., 
and 80 mm., and this indicates that the /5 rays are physiologically 
more effective than the y rays, for, while the former are eliminated 
by these distances in air, the latter are not, or npt completely. 



CHAPTER VIII 

EFFECTS OF RADIUM RAYS IN THE SOIL ON GER- 
MINATION AND GROWTH 

It has been ascertained, as previously pointed out, that soil-air is 
radioactive. Therefore it becomes a matter of considerable interest 
to ascertain the effect on germination and growth of passing radium 
rays through soil in which seeds are planted. The object of the fol- 
lowing experiments is to answer this question. 

Experiment 32 
March 4, 4 P. M. 

Unsoaked seeds of " Lincoln" oats (Avena) were sown in soil in 
three concentric circles, at distances of 7 mm., 22 mm., and 45 mm. 




Fig. 24. Experiment 32. Acceleration of Germination and Growth of Oats bj 
Placing a Sealed Glass Tube of Radium ( 1,500, 000 X) '" the Soil. The Glass Tube in 
C is Empty. Cf. figures 8, 25, and 26. 

from the center of the pot. The sealed glass tube of RaBrj (1,500, 
000 x) was inserted in the soil at the center of the pot, with the end 
containing the radium at a depth of about 15 mm. below the surface. 
Control culture similarly arranged, but with empty tube. 

135 



136 



EFFECTS OF RADIUM RAYS IN THE SOIL 



March 10, 2 P. M. 

After an exposure of 106 hours, the seedlings in the pot contain- 
ing the radium are all up, and are most decidedly taller than those 
in the control culture, three of which were not yet up, and all of 
which were less developed in every way than those exposed to the 
radium. 

The plants in the outer circle of the exposed culture average 50 
mm., those in the middle circle 46 mm., and those in the inner circle 
42 mm. taller than those in the corresponding circle of the control. 




Fig. 25. Experiment 32. The Former Control ( C) is now Exposed to the Radium 
(C/?), and the Culture Formerly Exposed (i?) becomes the Control. The Tube in 
CR now Contains the Radium, while the Tube in/? is now the Empty Tube. Cf. 

FIGURE 24 . 

After the plants were photographed (figure 24), one seedling 
was carefully removed from each culture, and the soil washed from 
its roots. The plant from the exposed culture has root-hairs from 2» 
to 3 times as long as those on the control, and they are also more 
numerous. 



EFFECTS OF RADIUM RAYS IN THE SOIL I37 

March lo, 5 P. M. 

I now changed places with the radium-tube and the empty tube, 
placing one end of the radium-tube in the center of the soil of the 
culture that had served as the control. This pot was labeled CR, 
and the other pot R. Five days later the control plants (CR), under 
the influence of the radium, averaged nearly as tall as those first 
radiated. Thus, by changing the radium-tube back and forth from 
time to time, one can accelerate either culture at will (figure 25). 

Experiment 33 
Repetition of Experiment 32, using seeds of Lufinns albus. 

March 19, 11 130 A. M. 

Six unsoaked seeds of L. albus were planted about 5 mm. deep 
around the margin of a 5-inch pot. All the seeds were placed with 
the hypocotyl facing the center of the pot and pointing downward. 
In the center of the soil was inserted one end of the sealed glass tube 
containing RaBr2 of 1,500,000 activity, to a depth of about 10 mm. 

Control pot with six seeds and empty glass tube. 

March 24, 11 : 30 A. M. 

In the radium-culture no seeds are up. Two of them are just 
beginning to lift the soil. 

In the control culture four seeds are up, from 10 to 15 mm. high. 
Two other seeds are just coming through the soil. 

On March 26 only one exposed seed was up, with the hypocotyl 
10 mm. high, while 5 of the control seeds were up with an average 
height for the five of 19.60 mm. The radium and empty tubes were 
removed from the soil. 

Six days later (March 30) only two of the exposed plants had 
come up. Their average height was 30 mm. Five of the control 
seeds were well up, with an average height of 45.60 mm. 

The plants were all removed from the soil. On the two radiated 
plants the primary and secondary 'roots were very slightly developed, 
but on the control plants the secondary roots were long and numerous, 
and the primary root was from three to five times as long as in the 
plants exposed to the radium. 

Experiment 34 
Repetition of Experiment 33, using white mustard {Brassica alba) 
seeds instead of lupine. 



138 EFFECTS OF RADIUM RAYS IN THE SOIL 

March 19, 11 : 30 A. M. 

Exposed and control cultures were arranged as described in Ex- 
periment 33, except that white mustard seeds were used. Twenty- 
one unsoaked seeds were planted in each pot, at distances from the 
center as follows : 

II seeds 40 mm. from the center. 

6 seeds 25 mm. from the center. 

4 seeds 10 mm. from the center. 

March 23, 10 : 30 A. M. 

Eleven of the exposed seeds have germinated, and only six of the 
control seeds. The seedlings from the exposed seeds average at least 
one third taller than the control seedlings, but measurements were 
not taken. The exposed plants seem in every way more vigorous. 

Experiment 35 
April 3, 9 A. M. 

Into each of three pots of soil were planted 12 unsoaked seeds of 
Henderson's " First-of- All " peas {Pisum sativum), m two circles, 
the outer one of 8 seeds 60 mm. from the center of the pan, the inner 
of 4 seeds 30 mm. from the center. 

Into the center of the soil in the first pan was inserted the end of 
a tube of radium bromide (10,000 x ), in the center of the second the 
sealed glass tube of radio-tellurium, into the third an empty glass 
tube. The lower ends of all the tubes were depressed 25 mm. below 
the surface of the soil- 
April 6, to: 30 A. M. 

8 plants exposed to radium rays show the arch of the hypocotyl. 

6 plants exposed to radio-tellurium show the arch of the hypocoytl. 

3 plants of the control culture show the arch of the hypocotyl. 

April 18, 10 A. M. 

The plants grown in the soil with the radium-tube are taller, and 
in every way more vigorous looking than those of the other two pots. 
There is very slight, if an}^, difference between the height of the 
plants grown with the radio-tellurium in the soil and the control 
plants. 

A count of the total number of root tubercles on the roots of the 
plants gave a total of 18 tubercles where the radium-tube was, 19 
with the radio-tellurium, and 22 in the control. These differences 
are not considered significant. 



effects of radium rays in the soil i39 

Experiment 36 
April 15, II : 15 A. M. 

Twenty unsoaked seeds of *' Lincoln " oats were sown in soil in a 
6-inch pot, and a rod coated with a *' Lieber's radium coating" 
(10,000 X ) was thrust vertically into the soil in the center of the pot. 
All the seeds were placed with the radicle vertical, and the embryo- 
side of the seed facing the radium-coated rod. 

Control with no rod, and both cultures placed in a glass frame in 
the propagating house. 

April 28, 5 P. M. 

Heights of the seedlings from soil-surface to tips of second leaf : 

Radium Control 

77.00 mm. 113.00 mm. 

91.50 86.50 

94.50 ' 107.50 

83.50 ■ 90.00 

64.00 0.00 injured 

21.50 39.00 

61.00 20.00 

107.00 32.00 

44.50 109.00 

116.50 63.00 

0.00 injured 94.00 

91.00 37'00 

98.50 67.00 

44.00 0.00 

71.50 93.00 

69.00 170.00 

24.00 160.00 

78.00 148.00 

79.00 67.00 

0.00 injured 108.00 



1,316.00 mm. 1,604.00 mm. 

Average of 18, 73.11 + mm. Average of 19, 84.42 -f- mm. 

April 29. 

Cultures photographed (figure 26), and experiment closed. 

May 12, 5 P. M. Experiment 37 

Into each of three 6-inch pots were planted eight unsoaked 
seeds of the bean [Phaseolits). Into the center of the first pot (R) 



140 



EFFECTS OF RADIUM RAYS IN THE SOIL 




Fig. 26. Experiment 36. Retardation of Germination and Growth of Oats by 
Placing in the Soil a Celluloid Rod Coated with Lieber's Radium Coating. Cf. 
FIGURE 24. 

was placed the sealed glass tube containing the RaBr^ (1,500,000 x ), 
into the second (R') four rods coated with "Lieber's radium-coating" 
25,000 X ), the third served as a control, with no radium. 

May 19, 5 P. M. 

The lengths of the hypocotyls above the surface of the soil were 
as follows : 

C 

Control 
114.00 miti. 

99-50 
112.50 

91,50 
112.00 

30.00 t 

89. 00 
1 14.00 

762.50 mm. 

Average of 8: 86.875 Averageof7: 91.14 -f Average of 8 : 95.31 4- 
mm. mm. mm. 

*To top of arch. tTo top of arch. Went bad. 



R 


R' 


Tube, 1,500,000 X 


Coated Rods 


95.00 mm. 


98. 00 mm. 


53.00* 


84.00 


45.00* 


89.00 


125.00 


96.00 


106.00 


1 13.00 


67.00 


98. 00 


100.00 


60.00 1 


104.00 


0.00 


695.00 mm. 


638.00 mm. 



effects of radium rays in the soil i4i 

Experiment 38 
Object : To ascertain the effect on the germination and growth of 
wheat of the rays from RaBr, and radio-tellurium contained in sealed 
glass tubes placed in the soil. 

June 4, II A. M. 

Twelve grains of wheat {Tri/ /cum vulgar e, Henderson's "Well- 
man Fife ") were planted without soaking in each of four pots, A, B, 
C, and D. Each grain was placed in the soil vertically with the 
embryo-end down, and the embryo-side facing the center of the pot. 
In the center of pots A, B, and C, were placed vertically the tubes of 
RaBr^ and radio-tellurium, as follows : 

A. RaBr, 10 mg. 1,800,000 x. End about 10 mm. below the surface. 

B. " " 1,500,000 X . " " " " 

C. Radio-tellurium. " " " " 

D. Control. No tube. 

June 6. 

The tubes have been removed for 18 hours since planting. The 
average heights of the seedlings that have come up are as follows : 

A B C D 

1,800,000 X 1.500,000 X Radio-tellurium Control 

7 up. Av. ht. 4 up. Av. ht. 3 up. Av. ht. 7 up. Av. ht. 
3.28 mm. 4*^7 rnm. 6.33 mm. 2.58 mm. 

The tubes were replaced. 

June 7, 10 : 30 A. M. • 

A BCD 

1,800,000 X 1)500,000 X Radio-tellurium Control 

12 up. Av. ht. 12 up. Av. ht. 10 up. Av. ht. 10 up. Av. ht. 
23.60 mm. 23.90 mm. 24.35 mm. 15. So mm. 

The tubes were again removed at 11 A. M. for another experi- 
ment. 



142 



EFFECTS OF RADIUM RAYS IN THE SOIL 



June 8. 

Heights of seedlings above the surface of the soil as follows : 



A 

i,Soo,ooo X 

1 41,50 mm. 

2 35.00 

3 44-50 

4 45 -oo 

5 47 -oo 

6 47.00 

7 38-00 

8 53-50 

9 53-50 

10 4500 

11 57.00 

12 37'Oo 



Av 



54.^.00 mm. 
45.30 mm. 



B 




C 


D 


1,500,000 X 


Radio-tellurium 


Control 


51.00 


mm. 


53.00 mm. 


13.00 mm 


40.00 




32.00 


33-50 


41.00 




50.00 


31.00 


40-50 




45-50 


injured 


36.00 




47.00 


39-00 


48.00 




48. 00 


injured 


54-50 




65-50 


23.00 


48. 00 




injured 


injured 


52.50 




27.00 


39-50 


30.00 




50.00 


33-00 


40.00 




injured 


41.50 


38.00 




45-50 


39-50 


519-50 


mm. 


463.50 mm. 


293.00 mm 


43.20 


mm. 


46.35 mm. 


32.55 mm 



Acceleration of growth has followed exposure to all the radio- 
active substances. (See figure 27.) 



44 
40 
36 
32 
i 28 





24 


g 


20 




16 




12 




8 




4 








Expenvieiit 38. 
Acceleration of growth by radium 
rays in the soil. 




5 6 

Day of month 
Fig. 27. Triticum vulgare. 



/ 



"6- 



*' 



effects of radium rays in the soil i43 

Experiment 39 
April I, 4 P. M. 

Unsoaked timothy grass {Phleiim -pratense) seed was sown on the 
surface of the soil in two flower pots. In the center of the soil of 
one pot was inserted the end of the glass tube containing RaBrg of 
7,000 activity, to a depth of 15 mm. ; in the control pan the empty 
glass tube. 

Both pots were watered by being set in a pan of water until the 
top of the soil appeared entirely moistened. They were then cov- 
ered with bell- jars. 

April 10, II 130 A. M. 

The seedlings in the radiated culture are slightly taller than those 
of the control set, but the difference is not marked. 

April II, 5 P. M. 

There is no appreciable difference in the height of the plants in the 
two pots. 

Summary 

When unsoaked oat grains were planted at distances of 7» 22, and 
45 mm. from a sealed glass tube containing 10 mg. of radium bro- 
mide of 1,500,000 X inserted into the soil, germination and subse- 
quent growth were accelerated. The seeds farthest from the radium 
were accelerated most, those nearest least. The root hairs on the 
exposed seedlings appeared to be more numerous, and were 2-3 times 
longer than normally. When seeds of Luptnus albus were exposed 
in a similar way to the same radium preparation the growth of the 
shoot was retarded, but the roots were from three to five times longer 
than normally. This is in agreement with the results of Willcock 
and of Zuelzer which indicate that tissues containing chlorophyll are 
more sensitive to these rays than other tissues. Under similar condi- 
tions the germination of seeds of Brassica alba was accelerated. 
When seeds of Pisuni sativum were similarly exposed, using radium 
of 10,000 X and the sealed glass tube of radio-tellurium, acceleration 
of growth was produced by the radium rays, but none by the radio- 
tellurium. Careful counting disclosed no significant difference in 
the number of root-tubercles on the exposed plants and those of the 
control culture. More careful observation has not confirmed my 
earlier * statement to the contrary. 

* Bibliography, p. 71. No. 24. 



144 EFFECTS OF RADIUM RAYS IN THE SOIL 

The growth of oats exposed in the same way (10,000 x ) was 
accelerated, but bean seeds [Pkaseolus vulgaris) exposed to radium 
(1,500,000 x) in the sealed tube, and also to four coated rods 
(25,000 x) had their germination and the growth of the seedlings 
retarded. Exposure to the rods (low activity) produced less retarda- 
tion than did exposure to the preparation in the glass tube (high ac- 
tivity), though in the former case the a rays escaped for very short 
distances into the soil. 

Exposure of wheat {Triticum vtilgarc) to radium of 1,800,000 x 
and 1,500,000 X , and to radio-tellurium, each in a sealed glass tube in- 
serted into the soil, was followed by acceleration of germination and 
growth. The amount of acceleration was about equal in each of the 
three exposed cultures, though slightl}^ in excess in the culture ex- 
posed to the radio-tellurium, where the amount of the salt was larger 
than in the radium cultures. I am unable to explain how physiolog- 
ical effects can be obtained with radio-tellurium in a sealed glass 
tube, for this substance gives off only a rays, and these are not 
thought to be able to pass through the glass walls of the tube. The 
results, however, were constant and decided, leaving not the slightest 
doubt as to the physiological efficacy of the preparation. 

When seeds of timothy grass were sown on the surface of soil 
into which a sealed glass tube of radium bromide of 7,000 x was in- 
serted to a depth of about 10 mm. below the surface, germination 
and growth were very slightly accelerated. 

Whether the acceleration of growth produced by inserting sealed 
glass tubes of radioactive preparations into the soil is due to the direct 
action of the rays, or to ions which they may possibly form in the 
soil-solution, remains to be demonstrated. If to the former, then the 
result must be attributed largely to the gamma rays, for the alpha 
rays do not leave the glass tube, and the beta rays would be stopped 
by at least one centimeter of moist soil. The gamma rays, however, 
on account of their high penetrability, might be effective through as 
much as one foot of moist soil. 

Fischer ^ has shown that hydrogen ions and hydroxyl ions, 
whether of acids or of strong alkalis, stimulate germination. In his 
experiments the ions acted explosively, as he described it, a marked 
effect being produced by them by an exposure of one half a minute, 
a maximum stimulation on two minutes, while killing began with 
only four minutes' exposure. If the radium rays produce ionization 



EFFECTS OF RADIUM RAYS IN THE SOIL I45 

in the mineral solutions in the soil then these ions would act as a stimu- 
lus to plants growing there, and, under suitable conditions, cause an 
acceleration of growth. It is not improbable that the results recorded 
above are due to a combination of both causes, that is, to the direct 
action of the gamma rays combined with that of ions produced by 
the rays in the soil-solution. 

Bibliography 

I. Fischer, Alfred. Wasserstoff- und Hydro^cylionen als Keimungsreize, 
Ber. Dent. Bot. Ges. 25: 108. 1907. 



II 



CHAPTER TX 



EFFECTS OF A RADIOACTIVE ATMOSPHERE ON 
PLANT GROWTH 

The fact, pointed out in Chapter II, that the earth's atmosphere 
normally contains the emanation of radium and possibly of other 
radioactive substances, makes it desirable to ascertain the effect of this 
factor of environment on plants. Such an experiment was rendered 





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c \ 


n 

) 
^ 


1 




'■ 


fZ. 


P 

f 


"«"SalK 






^#^ 






^VHSiSHil^^^^^^^^^^lHI 


^^^^^w 





Fig. 28. Experiment 40. Apparatus for growing Plants in an Atmosphere con- 
taining the Emanation of Radium. The inner Surface of the Tube ( T) is coated 
with Lieber's Radium Coating. From the lower Tubulures of the Bell-Jars Rubber 
Tubing leads to a Suction Pump. Control Apparatus at the right. Cf . figure 30. \ jj 

comparatively easy by the invention by Mr. Hugo Lieber of a cyl- 
inder lined with a coating of a radium salt, and covered by a protect- 
ing layer of such a nature as to permit of the diffusion of the emana- 
tion into the surrounding space, as described more fully on page 81 

146 



EFFECTS OF RADIOACTIVE AIR ON GROWTH I47 

of this Memoir. The details of the method are given in connection 
with the experiments that follow. 

Experiment 40 
Object : To ascertain the effect of germinating and growing tim- 
othy grass [Phletwi pratense) seeds in an atmosphere containing 
the radium emanation. 

March 12, 11 A. M. 

Unsoaked timothy seeds were sowed in a pot of earth (thinly cov- 
ered with the soil), and placed to germinate and develop under a bell- 
jar. From a hollow cylinder lined with " Lieber's radium-coating" 
there passes a glass tube through the upper tubulure of the bell-jar and 
down into the latter, ending, at the side of the pot of soil, in a dove- 
tail gas tip, at a height of about 20 mm. above the surface of the soil. 
From the opposite side of the pot leads another glass tube through 
the bottom tubulure of the bell-jar to a suction pump. By this means a 
current of air containing the emanation from the radium-lined cylinder 
spreads out over the surface of the soil, and converges to the outlet 
tube, passing thence out of the jar. A control apparatus was sim- 
ilarly arranged, connected with the same suction pump, but with no 
radium tube attached (figure 28). 




Fig. 29. Experiment 41. Retardation of Growth of Timothy Grass bj exposure 
to Air which has passed over Lieber's Radium Coating, and thus contains Radium 
Emanation. 

March 15, 4 : 30 P. M. 

There are no signs of germination in either pot. 

March 16, 9 : 30 A. M. 

The seeds in both pots have begun to germinate, but those 
exposed to the emanation appear to be slightly further advanced 
than the control. 



148 EFFECTS OF RADIOACTIVE AIR ON GROWTH 

March 17, 9 : 30 A. M. 

The seedlings of the exposed culture are decidedly taller than 
those in the control. 

This difference in height of the seedlings of the two cultures con- 
tinued until March 24, when the experiment was discontinued. 

Experiment 41 
The object of this experiment is to ascertaiji the effect of growing 
seeds of timothy grass {Phleum p7'atense) in the apparatus described 
for Experiment 40, /. c, in an atmosphere containing the radium 
emanation, but exposed more directly to the rays resulting from the 
decay of the emanation. 

April I, 2 : 30 P. M. 

The experiment was set up as described in Experiment 40, except 
that the air and the emanation were delivered at a distance of only 
about 5 mm. above the seeds. Special care was taken to have the 
illumination equal on all sides, and both the light and the moisture 
conditions as nearly as practicable the same for both the exposed 
and the control cultures. 

April 6, 8 : 30 A. M. 

Germination has begun in both cultures, but is more advanced in 
the control pan. 

April 10, 10 A. M. 

In the exposed culture the plants are shorter and lighter colored 
on the side nearest the delivery of the emanation, and increase in size 
toward the opposite side of the pan. They manifest a slight photo- 
tropic curvature. 

The plants of the control culture are of uniform height, and also 
have a slight phototropic curvature like those exposed. 

The growth of the seedlings nearest the point of delivery of the 
emanation has been retarded. The cultures were photographed on 
April 12 (figure 29). 

This experiment was repeated with entirely confirmatory results. 

Experiment 42 
In order to test the effect on the germination and growth of the 
timothy seed, when grown in an atmosphere containing the radium 



\ 



EFFECTS OF RADIOACTIVE AIR ON GROWTH 



"49 



emanation, but with the emanation delivered at a greater distance 
from the seeds than was the case in the preceding experiments, the 
following experiment was made. 

May 27, 5 130 P. M. 

Dry seeds of timothy grass were sown on the surface of the soil 




Fig. 30. Experiment 42. Apparatus for growing Plants in an Atmosphere con- 
taining Radium Emanation. The Air, after passing over the Radium Coating on 
the inner Surface of the hollow Cylinder (/?), is delivered over the Cultures through 
a glass Funnel. Control Apparatus at the right. Cf. figure 28. 



I50 



EFFECTS OF RADIOACTIVE AIR ON GROWTH 



in two pots, and the pots placed, one under each of the bell-jars, as 
described in Experiment 41, except that the emanation was delivered 
over the seeds from a small glass funnel, suspended over the center 
of the pot at a distance of 50 mm. The ordinary air in the control 
was similarly delivered over the control seeds (figure 30). 

May 30, 9: 30 A. M. 

The exposed seeds have germinated except directly under the 
funnel, where germination has not yet begun. 

The control seeds have germinated uniformly, under the funnel 
as well as elsewhere. 

June I, 9 A. M. 

The exposed seeds have practically all failed to germinate under 
the funnel, but are quite evenly germinated elsewhere. Numerous 
decidedly undersized seedlings are scattered throughout the culture. 




Fig. 31. Experiment 42. Inhibition of Germination of Timothy Grass Seed hy 
direct exposure to Air that has passed over a surface coated with Lieber's Radium 
Coating, and thus contains Radium Emanation. Cf. figure 30. 

The control seeds are all evenly germinated, and there is no 
appreciable difference in their height under the funnel and elsewhere. 
There are also very few undersized seedlings — much fewer than 
in the exposed culture. 

Complete inhibition of germination has followed exposure under 
the conditions described. On June i the cultures were photographed 
(figure 31), and the experiment closed. 



effects of radioactive air on growth i5i 

Experiment 43 
Repetition of Experiment 42, only with the air and emanation 
delivered at a distance of 190 mm. above the seeds, planted on the 
surface of the soil. 

June I, 4 : 30 P. M. 

Dry seeds of timothy grass were sown evenly over a blotter, kept 
moist by being placed on damp cotton, and placed under the bell-jar 
into which the radium emanation is to be drawn. The opening of 
the funnel through which the emanation is to be delivered is about 
190 mm. from the surface of the blotter where the seeds lie. 

Control with no radium. 

June 3, 6 P. M. 

No seeds have germinated in either culture. 

June 4, 12 M. 

In the exposed culture only one or two seeds have begun to 
germinate. 




Fig. 32. Experiment 43. Retardation of Germination and Growth of Timothy 
Grass by exposure to Air containing the Emanation of Radium. 

In the control culture the seeds have quite generally germinated, 
with plumules estimated at from i to 2 mm. long. 

June 5, 12 M. 

The seedlings in the control culture are about 5 mm. high, with 
the green color well developed. Growth is uniform throughout the 
culture. 

The exposed seedlings are not more than one half as tall as the 
control, and only very slightly green. Growth seems uniform 
throughout the culture. 

June 8, 3 130 P. M. 

After seven days of exposure the radiated seedlings are still 



152 EFFECTS OF RADIOACTIVE AIR ON GROWTH 

shorter than the control plants, but the difference is not so marked 
as it was 3 days ago, i. e., 4 days after the exposure. 

On June 10 the control seedlings averaged about one fourth taller 
than those exposed. On June 15 the cultures were photographed 
(figure 32). 

Retardation of germination and growth has followed exposure as 
described. 

This experiment was repeated and similar results were obtained. 

Experiment 44 

Object : To ascertain the effect of germinating and growing 
timothy grass seed in an atmosphere containing the radium emanation. 

Seeds of timothy grass {Phleum -pratcnse) were planted on the 
surface of the soil in each of two pots, and each pot was placed un- 
der a bell-jar with a tubulure at the top and bottom. By means of a 
blast bulb the emanation from RaBrj was forced into the bell-jar at 
irregular intervals of from 2 to 24 hours from a cylinder lined with a 
" Lieber's radium-coating." Blasts of ordinary air were similarly 
forced through the control jar. 

The emanation was delivered at a height of about 90 mm. above 
the seeds, and the periodic blasts were continued for ten days. 

On the tenth day the exposed plants were slightly but definitely 
taller, on the average, than the unexposed plants, and on the eleventh 
day they were still taller than the control. On the twentieth day 
after planting the same difference in height was maintained and the 
experiment was discontinued. 

Experiment 45 
Object : To ascertain the effect of growing germinated seeds of 
Lu^inus albus in an atmosphere containing the emanation of radium. 

April 29, 12 M. 

On the radicles of five germinated seeds of Lti^inus albus, ger- 
minated in moist sphagnum until the radicles were over 10 mm. long, 
were placed reference marks in India ink, 10 mm. from the root-tip. 
The seedlings were suspended on glass spits under a bell-jar into 
which the radium emanation was drawn, as described in Experi- 
ment 44. 

Five germinated seedlings were similarly arranged in a control 
jar. 



EFFECTS OF RADIOACTIVE AIR ON GROWTH I53 

Measurements of the growth in length of radicles were made as 
follows : 



Control 
13.00 mm. 
10.00 
14.50 
10.50 
12.50 



April 30, II 


:30 A. M. 




Radium 


I 


18.50 mm. 


2 


17.00 


3 


19.50 


4 


21.50 


5 


18.50 




95.00 mm. 




19.00 mm. 


May I, 9 A 


. M. 




Radium 


I 


22.00 mm. 


2 


21.50 


3 


24.00 


4 


27.00 


5 


22.00 




116.50 mm. 




23.30 mm. 



60. 


50 mm 


12. 


,10 mm 


Con 


'trol 


13 


,00 mm 


10 


.00 


17 


.00 


1 1. 


.00 


12, 


•50 



63.50 mm. 
12.70 mm. 

Exposure to the emanation has been followed by a decided accel- 
eration in growth. 

May I, 12 M. 

A repetition of the above experiment was started, using six seeds 
of Lu^imis albus in each culture. 

May 2, 12 M. 

Measurements of growth were recorded as follows : 

Radium Control 

1 13.50 mm. 10.00 mm. 

2 14.50 10.00 

3 11.50 10.00 

4 17.50 10.00 

5 19.00 10.00 

6 19.00 10.00 

95.00 mm. 60.00 mm. 

15.83 mm. 10.00 mm. 



154 effects of radioactive air on growth 

Experiment 46 
Repetition of Experiment 45. ' 

The experiment was arranged as described in Experiment 45. 
Measurements of growth in length were made as follows : 



May 6, 


10 


A. M. 


(After 12 hours' 


exposure.) 






Radium 


Control 




I 


19.00 


mm. 


13.00 mm. 




2 


16.00 




13.00 




3 


16.00 




16.50 




4 


20.00 




17.50 




5 


22.50 




17.00 




6 


17.00 




15.00 






110.50 


mm. 


92.00 mm 






18.41 


mm. 


15-33 "1™' 


May 7, 


11 


A. M. 










Radium 


Control 




I 


24.50 


mm. 


14.50 mm 




2 


16.00 




14.50 




3 


23.00 




16.00 




4 


25-50 




32.00 




5 


28. 00 




injured 




6 


17-00 




injured 






134.00 


mm. 


77.00 mm 






22.33 


mm. 


19.25 mm 



Growth in the atmosphere containing the emanation is more rapid 
than the normal growth. 

In a fourth repetition of this experiment the 5 exposed seedlings 
averaged 9.60 mm. growth in 20 hours, while the average growth of 
the control seedlings was only 7.30 mm. Again the average amount 
of growth in 24 hours was, for those exposed, 18.41 mm. ; for the 
control, 15.80 mm. 

In a fourth repetition of Experiment 45, the following measure- 
ments were made : 



EFFECTS OF RADIOACTIVE AIR ON GROWTH 



155 



May II, 5 : 30 P. M. (After 23 hours' exposure.) 

Radium Control 

20.00 mm. 14.00 mm. 
25.00 17.00 

25.00 14.00 

21.00 12.00 

25.00 17.00 

20.00 15-00 

136.00 mm. 89.00 mm. 
22.67 mm. i4'^3 ^'""^- 



May 12, 5 : 


30 P. M. 




Radium 


I 


26.00 mm. 


2 


32.00 


3 


32.00 


4 


25.00 


5 


31.00 


6 


25.00 




171.00 mm. 




28.50 mm. 



Control 
14.00 mm. 
20.00 
15.00 
13.00 , . 
19.00 
i5v5o 

96.50 mm. 
16.08 mm. 



The curves of growth given in figure 33 are typical of the results 
obtained in all five experiments, which clearly indicate that the 



on 




/ 

/ 


^^<^- 

r" 


>-'' 




Millimeters 

. c 


• 


/ 

/ 
/ 
/ 
/ > 


^coT^^isl- 


^ 


/ 
/ 


y^ 











/ ^ 


Experiment 0. 





10 



11 

Days 



12 



Fig. 33. Acceleration of Growth of Roots of Lupinus albus in a Radio- 
active Atmosphere. 



156 EFFECTS OF RADIOACTIVE AIR ON GROWTH 

growth of roots in an atmosphere containing the decaying radium 
emanation is more rapid than normally. 

Experiment 47 

In order to see if the emanation given off from about 10 mg. of 
RaBrj of 7,000 activity, contained in a glass tube open at one end, 
would affect germination and growth, timothy seed was sown on the 
surface of the soil in two pots, and each pot was placed under a bell- 
jar. One bell-jar contained the open tube of radium bromide 
throughout the experiment, the other served as a control. The 
radium tube had been open under the first bell-jar for 48 hrs. before 
the seeds were introduced. 

Observations were continued for nine days, but with negative 
results. The seeds germinated and grew in both pots, but no sig- 
nificant difference was detected between the two cultures. 

Summary 

In harmony with results previously obtained under other condi- 
tions, it is seen that the effect of exposure to the radioactive ema- 
nation varies with the conditions of exposure. As in Experiment 32, 
when a layer of moist soil intervened between the radium and the 
seeds, the rays produced an acceleration of growth, so here, when 
unsoaked (and hence less sensitive) timothy seeds were planted 
beneath the soil surface, and the emanation delivered at a distance 
of 20 mm. above the soil, growth was accelerated. Under similar 
conditions of planting, but with the emanation delivered at a distance 
of only 5 mm. above the soil, growth was retarded. Again when the 
distance was 50 mm., but the timothy sown on the surface of the soil, 
retardation resulted. The same effect followed when the distance 
was increased to 190 mm. over timothy seeds sown on moist blotter. 

If, now, the seeds are sown on the surface of the soil, and the 
emanation delivered, not continuously, as before, but by means of 
blasts at irregular intervals of from two to twenty-four hours, germi- 
nation and growth are increased. The growth in length of radicles 
of Liifimis albiis was uniformly accelerated in an atmosphere con- 
taining the emanation (figure 33). This result was repeatedly veri- 
fied and is additional evidence of the greater sensitiveness of tissues 
containing chlorophyll. An exposure which proved to be an over 
stimulus for the chlorophyll-bearing shoot system, causing a retarda- 



EFFECTS OF RADIOACTIVE AIR ON GROWTH I57 

tion of growth, approximated the optimum stimulation for the chloro- 
phylless root, causing acceleration of growth. 

No appreciable effect resulted from exposing germinating timothy- 
seeds in a closed bell-jar to the emanation that diffused from an open 
■ glass tube of about lo mg. of radium bromide of 7,000 activity. 

These experiments with the radioactive atmosphere all point to 
the same general truth, namely, that the rays of radium act as a 
stimulus to protoplasm. Retardation of growth following exposure 
to the rays is an expression of over-stimulation ; acceleration of 
growth indicates stimulation between a minimwn and an optimum 
point. 



CHAPTER X 

EFFECTS ON PLANT GROWTH OF EXPOSED WATER AND 
FRESHLY FALLEN RAIN 

I. Effects of Tap-Water Exposed to Radium Rays 

Because of the fact, now so well known, that penetrating, or 
gamma-like radiations are present in probably all soil, the following 
experiments were made for the purpose of ascertaining the effect on 
germination and growth of water exposed to the penetrating rays of 
radium, for it is evident that the water in the soil is naturally thus 
exposed. 

Experiment 48 

Object : To ascertain the effect on the germination and growth of 
seeds of imbibition of water in which sealed glass tubes of radium 
bromide have been immersed. 

April 9, 2 P. M. 

Three beakers, a, b, and c, were arranged two thirds full of 
water, and containing {a) the tube of radium of 1,500,000 activity; 
{b) the tube of 10,000 activity ; (c) no tube, and serving as the control. 

April 10, 5 : 30 P. M. 

After the water had been exposed to the radium rays [for 26.5 
hrs., seeds were put to soak in each of the beakers as follows : 

12 seeds of lupine {Liifinus albus). 

15 grains of oats {^Avena: Henderson's " Lincoln"). 

8 grains of corn {Zea Mays: " Hickory King"). 

April II, 5 P. M. 

After soaking for 23.5 hrs. the seeds were all planted in soil in pots. 

The records of observations of the different seeds are given sep- 
arately, as follows : 

Corn {Zea Mays) 
On April 14 none of the corn grains had germinated, but on April 
16 four seedlings were up in the 1,500,000 culture, and five in each 

158 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



159 



of the other two. On April 17 measurements of the heights of the 
seedHngs were recorded as follows : 





RaBr, 


RaBr, 




No. 


1,500,000 X 


10,000 X 


Control 


I 


29.50 mm. 


18.00 mm. 


16.50 mm. 


2 


23.00 


12.50 


25.00 


3 


25.00 


18.50 


4-50 


4 


not up 


23.00 


15-50 


5 


25.00 


not up 


10.50 


6 


16.00 


13.00 


7-50 


7 


not up 


13.00 


5.00 


8 


12.00 


20.00 
118.00 mm. 


15-50 




130.50 mm. 


100.00 mm. 




21.75 ^'^^^' 


16.86 mm.. 


12.50 mm. 



The relative heights of the plants in the three cultures remained 
as above until April 24, when observations were discontinued. 

Lupine {Lufinus albus) 

On April 14, none of the control plants were up, but in the other 

two cultures some of the seedlings were just breaking the surface of 

the soil. On April 16 seedlings were up in all of the pots, but there 

was no appreciable difference in their height or in any other character. 








2 



S 4 5 6 T 8 

Days 

Fig. 34. Effect on the Germination and Growth of Oat of soaking the Grains in Water 
exposed for 26.5 Hours, to Rays from Radium of different degrees of activity. 

On April 23 the average height of the seedlings of the 1,500,000 
culture was 26.10 mm., of the 10,000 culture 25.38 mm., and of the 



l60 EXPOSED WATER AND FRESHLY FALLEN RAIN 

control culture 25.00 mm. Thus, in the case of the lupines, no 
appreciable effect resulted from the treatment. 

Oat {Avena) 
On April 14 five seedlings of the 1,500,000 culture were just up, 
six seedlings of the 10,000 culture, and eight seedlings of the control. 

April 16. 

The following measurements of height were recorded : 





RaBr^ 


RaBr^ 




No. 


1,500,000 X 


10,000 X 


Control 


I 


30.00 mm. 


35.50 mm. 


16.00 mm 


2 


15.00 


35-50 


27.50 


3 


23-50 


32.50 


not up 


4 


23-50 


5-50 


37-00 


5 


10.00 


33 -oo 


27.50 


6 


31.00 


27.00 


not up 


7 


38.00 


15.00 


23-50 


8 


34-50 


23.00 


34-50 


9 


27.00 


22.50 


40.00 


10 


35 -oo 


17-50 


36.00 


1 1 


28.50 


6.50 


35-50 


12 


27.00 


32.00 


25.00 


13 


not up 


17.00 


37.00 


H 


28.00 


not up 
302.50 mm. 


not up 




351,00 mm. 


339-50 mm 




27.00 mm. 


23.26 mm. 


30.87 mm 



On April 17 the averages were, for the 1,500,000 culture, 45.34 
mm. ; for the 10,000 culture 35.80 mm. ; and for the control 47.41 
mm. On April 21, the average heights were, respectively, 77.10 
mm. ; 66.20 mm. ; and 71.37 mm., on April 23, 97.60 mm. ; 80.30 
mm.; and 87.80 mm., and on June 4, 311.70 mm.; 290.70 mm.; 
and 283.88 mm. Thus the initial slight retardation is replaced by 
an acceleration. Experiment closed. 

In the bean culture, from a comparison of the measurements, it 
is seen that soaking the seeds in the water exposed to the radium 
rays was followed by a much less rapid growth than the normal, but 
the difference between the 10,000 x and the 1,500,000 x cultures is 
negligible. At the end of six weeks there was no apparent difference 
in the height and vigor of the plants in the three cultures. 



EXPOSED WATER AND FRESHLY FALLEN RAIN l6l 

In the case of the lupines no appreciable effect was produced on 
germination by soaking in the treated water, but subsequent growth 
was slightly accelerated. 

With the corn, acceleration of growth followed the soaking in 
the exposed water, but the rate of germination was apparently, in 
the early stages at least, not affected. 

In the case of the oats, soaking in the treated water was followed, 
for two days after the seeds came up, by a retardation of germina- 
tion and of growth. Then the rate of growth of the exposed plants 
increased. Acceleration was most rapid in the case of the plants 
soaked in the water exposed to the stronger radium, and these plants 
were taller than the control at the end of the fifth day after they 
came up. At the end of 51 days this relatively greater height was 
still marked, and the plants soaked in the water exposed to the 
radium of 10,000 activity were also taller than the control. 

Part of the results of this experiment are shown graphically in 
FIGURE 34. 

Experiment 49 

The following experiment shows the effect on the germination 
and growth of corn grains {Zea Mays), bean seeds {Phaseolus), and 
oats {Avena), of soaking, before planting, in water in which sealed 
glass tubes of radium bromide had been immersed. 

April 23, 4 : 30 P. M. 

Into each of three beakers, a, b, and c, was placed 100 c.c. of 
water, and into the water of each beaker was suspended a sealed 
glass tube of RaBrg, as follows : 

Into a the RaBrg of 1,800,000 x . 

Into b the RaBrg of 1,500,000 x . 

Into c the RaBrg of 10,000 x . 

April 24, 4 : 30 P. M. 

After 24 hrs. exposure to the rays of the radium, the radium- 
tubes were removed from the water, and 8 seeds each of corn, bean, 
and oat were placed to soak in each beaker. Also in a control 
beaker a like number of each kind. 

April 26, 8 : 30 A. M. 

After soaking for 40 hrs., the seeds were removed from the 
water and planted in soil in flower-pots. Observations of germi- 
nation and growth follow. 



l62 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



Bean [Phaseolus) 
For several reasons the 1,800,000 and 10,000 cultures were dis- 
carded. On May 2 in the 1,500,000 culture 4 seeds were partly up, 
while in the control only 3 seeds were just appearing. 



Mays, 


10 A. 


M. 




May 11,9: 


30 A. 


M. 




RaBr, 




RaBr, 






No. 


1,500,000 X 


Control 


1,500,000 


X 


Control 


I 


50.00 


mm. 


35.00 mm. 


114.00 mm. 


85.00 mm, 


2 


41.00 




just up 


106.00 




82.00 


3 


75.00 




25.00 


124.00 




100.00 


4 


7-50 




17.00 


100.00 




128.00 


5 


21.00 




18.50 


85.00 




107.00 


6 


20.00 




36.00 


95.00 




108.00 


7 


45.00 




35-00 


injured 




75.00 


8 


45.00 




8.50 


99.00 




114.00 




304-50 


mm. 


175.00 mm. 


723.00 mm. 


799.00 mm 




3S.06 


mm. 


25.00 mm. 


103. 28 mm. 


99.88 mm 



Germination and growth have been slightly more rapid in the 
seeds soaked in the water exposed to the rays of radium. 

Corn {Zea Mays) 
April 30, 9 : 30 A. M. 

In the 1,800,000 culture one seed is just up, in the 1,500,000, six 
seeds, in the 10,000, eight seeds, and in the control culture four seeds. 



^ay 


I, 9: 30 A. M. 














RaBr, 


RaB 


1-2 


RaBr, 




No. 


1,800,000 X 


1 ,500,000 X 


10,000 X 


Control 


I 


7.50 mm. 


13.00 


mm. 


10.00 


mm. 


18.00 mm 


2 


not up 


25.00 




15.00 




not up 


3 


15.00 


15.00 




16.00 




23-50 


4 


11.00 


7.00 




14.00 




not up 


5 


not up 


18.00 




15.00 




5.00 


6 


17-50 


11.50 




10.00 




20.00 


7 


not up 


12.00 




12.00 




18.00 


8 


not up 
51.00 mm. 


15.00 
116.50 


mm. 


18.00 


mm. 


1 1. 00 




1 10.00 


95.50 mm, 




12.75 iTi'^' 


14.56 


mm. 


13-75 


mm. 


15.91 mm. 



EXPOSED WATER AND FRESHLY FALLEN RAIN 163 

May 2, 9:30 A. M. 





RaBr^ 


RaBr^ 


RaB 


'"2 




No. 


1,800,000 X 


1,500,000 X 


10,000 


X 


Control 


I 


27.00 mm. 


35.00 mm. 


27.00 


mm. 


40.00 mm. 


2 


5.00* 


44.00 


36.00 




5.00* 


3 


39.00 


33 -oo 


40.00 




47.00 


4 


31.00 


24.00 


32.00 




5.00* 


5 


5.00 * 


42.00 


37.00 




18.00 


6 


39.00 


32.00 


33-00 




36.50 


7 


9.00 * 


35 -oo 


34.00 




38-50 


8 


not up * 


39.00 


40.00 




32.00 




136.00 mm. 


284.00 mm. 


279.00 


mm. 


212.00 mm. 




34.00 mm. 


35.50 mm. 


34.88 . 


nm. 


35-33 mm. 


May 3, 


, 9 : 30 A. M. 












RaBr^ 


RaBr, 


RaB 


'•2 




No. 


1,800,000 X 


1,500,000 X 


10,000 


X 


Control 


I 


47.00 mm. 


54.50 mm. 


44.00 mm. 


61.50 mm. 


2 


20.00 * 


64.00 


55-50 




18.00* 


3 


61.00 


50.00 


60.00 




67.00 


4 


54.00 


45-50 


53-00 




7.00 * 


5 


17.00* 


62.00 


56.00 




35-00 


6 


61.00 


52.50 


55-50 




54-50 


7 


25.50* 


58.00 • 


53-50 




53.00 


8 


not up * 
223.00 mm. 


60.00 


57.00 
434.50 mm. 


injured * 




446.50 mm 


271.00 mm. 




55-75 mm- 


55.81 mm. 


54.31 mm. 


54.20 mm. 



On May 4, the average height of the seedlings in the 1,800,000 
culture was 77.00 mm. ; of the 1,500,000 culture, 75.68 mm. ; of 
the 10,000 culture 74.81 mm. ; and of the control, 69.50 mm. On 
May 5 the average heights were as follows : 

92.75 mm. ; 93.81 mm. ; 90.87 mm. ; 85.28 mm. 



* Discarded and not'added in. 



164 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



104 

96 




r> .. 














/ 


88 
80 


Effect on germination and growth , 
of water exposed to radium rays. 








•• 


72 
64 












' 








1 56. 

"53 

■S 48 












// 








=3 

§ 40 

32 










X/ 


,/ 








24 
16 






^^^^ 


^^^^ 


' / 










8 

n' 


^. 


.^^^^t'" 
^^^••** 

















26 27 28 29 30 1 2 3 4 

T>ay oj month 
Fig. 3S. Avena sativa. The Water was exposed to Radium Rajs for 24 Hours. 



Oat [Avena) 

The heights of the seedlings were recorded as follows : 
April 30, 9:30 A. M. 



No. 
I 

2 

3 

4 

5 
6 

7 
8 



RaBr^ 

1,800,000 X 
23.00 mm. 
17.00 
4.00* 
19.00 
20.00 
13.00 
18.00 
20.00 



130.00 mm. 
18.57 i'"'^' 



RaBr, 


RaBr, 




1,500,000 X 


10,000 X 


Control 


20.00 mm. 


26.00 mm. 


22.00 mm 


4.00* 


14.00 


23.00 


S.oo* 


23.00 


25.00 


21.00 


not up * 


24.00 


not up * 


17.00 


18.00 


not up * 


11.00 


25.00 


21.00 


not up * 


22.00 


21.00 


16.00 


not up * 


83.00 mm. 


107.00 mm. 


159.00 mm 


20.75 i^i''*''- 


17.83 mm. 


22.71 mm 



* Discarded. 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



i6s 



^ay 


I, 9:30 A. M. 










RaBr, 


RaBr, 


RaBr, 




No. 


1,800,000 X 


1 ,500,000 X 


10,000 X 


Control 


I 


45.50 mm. 


35.00 mm. 


46.00 mm. 


43.50 mm. 


2 


39-50 


47-50 


19.50 


44-50 


3 


29.00* 


43.50 


32.00 


46.50 


4 


38.00 


35-00 


not up 


47-50 


5 


40.00 


not up 


44.00 


35-00 


6 


35- 00 


11.50 


49.00 


45.00 


7 


40.50 


35-00 


not up 


42.00 


8 


41.00 


41.50 


48.00 


not up 




279.50 mm. 


248.00 mm. 


238.50 mm. 


304.00 mm, 




39.93 mm. 


35.42 mm. 


39.75 mm. 


43-43 mm 



The average heights of the seedlings were as follows on the 
dates indicated : 





Ral 


K 


RaBr, 


RaBrjj 






1,800,000 X 


1,500,000 X 


10,000 X 


Control 


May 2. 


56.93 


mm. 


53.50 mm 


59-75 nim. 


61.21 mm 


May 3. 


72.14 




70.21 


76.66 


78.27 


May 4. 


81.71 




80.85 


90.25 


85.92 


May 5. 


90.50 




98-57 


104.50 


108.64 


See FIGURE 


:35- 











Experiment 50 
Object : To ascertain the effect on the growth in length of the 
radicles of Lupinus albiis of soaking in water in which sealed glass 
tubes of radium bromide have been immersed. 



May 5, 12 :3o P. M. 

Into each of four beakers containing 100 c.c. of tap-water was 
placed a sealed glass tube of radium bromide, as follows: 

A. Activity 1,800,000. 

B. Activity 1,500,000. 

C. Activity 10,000. 

D. Control. 

After the water had been exposed for 24 hours to the radium 
rays, the hypocotyls of germinated seeds of lupine were suspended 

'Discarded. 



i66 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



in it up to an ink mark, placed lo mm. from the root-tip. Observa- 
tions of the length of the hypocotyls were recorded as follows : 



120 




Day of', 



ith 



Fig. 36. Lupinus albiis. Duration of exposure of the Water, 24 Hours. 
Control; , 1,500,000 X; > 1,800,000 X- 



y 6, 10 A. 


M. 








A. RaBr, 




B. RaBr, 


C. RaBr, 


D 


1,800,000 X 




1,500,000 X 


10,000 X 


Control 


24.00 mm. 




27.00 mm. 


29.00 mm. 


28.00 mm 


24.00 




26.00 


27.00 


29.50 


24.50 




27.00 


28.00 


27.00 


26.00 




24.00 


24.00 


27.50 


98.50 mm. 




104.00 mm. 


108.00 mm. 


112,00 mm 


24.62 mm. 




26.00 mm. 


27.00 mm. 


28.00 mm 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



167 



May 7, II A. M. 



A. RaBr^ 


B. RaBr^ 


C. RaBr^ 


D 


i,8oo,cxx) X 


1,500,000 X 


10,000 X 


Control 


40.00 mm. 


47.50 mm. 


49.00 mm. 


44.00 mm, 


42.00 


44.00 


46.00 


52.00 


43-50 


46.00 


48.00 


51-50 


39.00 


42.00 


36.00 


47-50 


164.50 mm. 


179.50 mm. 


179.00 mm. 


195.00 mm, 


41.12 mm. 


44.87 mm. 


44.75 mm. 


48.75 mm 



May 8, 11 130 A. M. 



A. RaBr^ 


B. RaBr^ 


C. RaBr, 


D 


1 ,800,000 X 


1,500,000 X 


10,000 X 


Control 


54.00 mm. 


68.00 mm. 


69.00 mm. 


63.50 mm, 


55.50 


64.00 


64.50 


82.00 


59.00 


62.00 


71.00 


76.00 


54.00 


57.00 


41.00 


76.00 


222.50 mm. 


251.00 mm. 


245.50 mm. 


297.50 mm 


55.62 mm. 


62.75 mm. 


61.37 "^™- 


74.37 mm 


May 9, 3 P. M. 








A. RaBr, 


B. RaBr^ 


C. RaBr, 


D 


1,800,000 X 


1,500,000 X 


io,ooo X 


Control 


69.50 mm. 


87.00 mm. 


88.50 mm. 


83.00 mm 


69.50 


78.00 


81.00 


109.00 


71-50 


74-50 


91.00 


101.00 


66.00 


71.00 


53-50 


101.50 


276.50 mm. 


310.50 mm. 


314.00 mm. 


394.50 mm 


69.12 mm. 


77.62 mm. 


78.50 mm. 


98.62 mm 



May 10, II A. M. 



A. RaBr, 


B. RaBr^ 


C. RaBr, 


D 


1,800,000 X 


1,500,000 X 


10,000 X 


Control 


82.00 mm. 


99.00 mm. 


102.50 mm. 


99.00 mm 


79-50 


81.50 


95.00 


129.00 


81.00 


81.50 


106.00 


1 20.00 


76.00 


80.00 


56.00 


123.00 


318.50 mm. 


342.00 mm. 


359.50 mm. 


471.00 mm 


79.62 mm. 


85.50 mm. 


89.87 mm. 


117.75 mm 



i68 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



The less rapid growth in the water in which the radium-tubes were 
immersed is shown graphically in another figure. The curve for 
the results of exposure to the radium of 10,000 activity is omitted 
for the sake of clearness. 



^ ^"^ 


W^W^^^^^^^M 


SI jsef 


■«5fefc» 



Fig. 37. Experiment 51. Acceleration of Growth of Ltipintis albtis by watering, 
after planting in Soil, with Water exposed to Radium Rays. Cf . figure 38. 



Experiment 51 

Object : To ascertain the effect on germination and growth of 
watering with water in which a sealed glass tube of radium bromide 
has been immersed. 

June 29, 9 : 30 A. M. 

Into each of two pots of soil, thoroughly moist with tap-water, were 
planted four seeds of Lupintis albus, and into each of two other 
similar pots four seeds of Zea Mays. 



June 30, 9 : 30 A. M. 

One pot of each set was watered with 100 c.c. of tap-water, in 
which a glass tube containing 10 mg. of RaBr2 of 1,800,000 ac- 
tivity had been immersed for 8 days. The other pot in each set was 
watered with a like amount of ordinary, unexposed tap-water. 

This method of watering was continued daily until July 25, the 

radium tube being in the water from i to 9 days before each watering. 

Observations of germination and growth were recorded as follows : 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



169 




Fig. 38. Experiment 51. Retardation of Germination and Growth of Zea Mays 
by watering, after planting in Soil, with Water exposed to Radium Rajs. Cf. 
FIGURE 37. 



July 2, 10 : 30 A. M. 





Zea 


Mays 


Radium 




Control 


not up 




15.00 mm. 


not up 




28.00 


10 mm 




23.00 


not up 




22.00 

88.00 mm. 
22.00 mm. 



Lupinus 



Radium 
just up 



Control 
just up 



July 3, 10:30 A. M. 



Zea Mays 
Radium Control 

3.00 mm. 45-00 mm. 

0.00 66.00 

32.00 73-00 

0.00 60.00 



35.00 mm. 
17.50 mm. 



244.00 mm. 
6r.oo mm. 



Lupinus 



Radium 
16.00 mm. 
10.00 

7.00 
15.00 

48.00 mm. 
12.00 mm. 



Control 
10.00 mm. 

2.00 

7.00 
17.00 

36.00 mm. 
9.00 mm. 



lyo 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



July 4, lo A. M. 



Zea Mays 



Lupinus 



Radium 


Control 


Radium 


Control 


iS.oo mm. 


102.00 mm. 


35-00 


mm. 


15.00 mm 


20.00 


107.00 


33- 00 




5.00 


60.00 


116.00 


20.00 




18.00 


just appearing 


102.00 


32.00 
120.00 


mm. 


37.00 


98.00 mm. 


427.00 mm. 


75.00 mm 


32.66 mm. 


106.75 mm. 


30.00 


mm. 


18.75 '"""^ 



Julys, II A. M. 



Zea Mays 



Lupinus 



Radium 


Control 


Radium 


Control 


50.00 


mm. 


148.00 mm. 


55.00 


mm. 


20.00 mm 


55-00 




152.00 


53- 00 




18.00 


65.00 




175.00 


33 -oo 




35-00 


10.00 




157.00 


50.00 




56.00 


180.00 


mm. 


632.00 mm. 


191.00 


mm. 


129.00 mm, 


45.00 


mm. 


158.00 mm 


47-75 


mm. 


32.25 mm, 



July 6, 10: 30 A. M. 

Zea Mays 



Radium 
72.00 mm. 
82.00 
65.00 
30.00 

249.00 mm. 
62.25 ™n^' 



Control 
179.00 mm. 
172.00 
199.00 
185.00 



735.00 mm. 
183.75 "^'^• 



Lupinus 



Radium 
63.00 mm. 
60.00 
45.00 
60.00 



228.00 mm. 
57.00 mm. 



Control 
27.00 mm. 
22.00 
46.00 
65.00 



160.00 mm. 
40.00 mm. 



The plants were kept growing and watered as described above 
until July 25, when the relative differences in height were the same 
as on July 6, and the experiment was closed. On July 4 the cultures 
were photographed (figures 37 and 38 ; also figures 39 and 40). 

On July 8 one plant was removed from each culture, dried, and 
tested with the electroscope to see if the dry substance of the tissues 
was radioactive. Neither plant was radioactive. This was the result 
to be expected under the conditions of the experiment. 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



171 



Experiment 51^ 
In order to ascertain the effect on the growth of roots in water of 
placing a sealed glass tube of radium bromide in the water, two glass 
beakers were partly filled with tap-water. Into the water of each 



5 6 

48 



40 



I 24 
16 



..Experimetit 51. 
Effect on germination atid growth 
of water exposed to radium rays. 

Lupinus albtis. 




-7 



3 4 

Day of month 

Fig. 39. 




3 4 

Day of month 

Fig. 40. 



172 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



beaker were inserted the radicles of four germinated seeds of 
Lu^inus albus to a uniform distance of 10 mm. from the root tip. 
The radicles were arranged in a circle, in the center of which was 
suspended the sealed tube, containing 52 mg. of radium bromide 
of 10,000 activity. The distance from the tube to the radicles 
was about 10 mm., and the radium salt was opposite the zone 
of maximum growth. The experiment was set up at 8 : 35 A. M., 
June 19. Measurements of the amount of growth in length of the 
radicles were recorded as follows : 



June 19, 5 : 30 P. M. 





Radium 


I 


18 mm. 


2 


16 


3 


15 


4 


17 


Total, 


66 mm. 


Average, 


16.50 mm 



C 


ontrol 


I 


16 mm. 


2 


20 


3 


18 


4 


18 


Total, 


72 mm. 


Average, 


18.00 mm 



June 20, 8 A. M. 





Radium 


I 


38 mm. 


2 


34 


3 


32 


4 


32 


Total, 


136 mm. 


^erage, 


34.00 mm. 



Control 

1 35 mm. 

2 37 

3 37 

4 ^ 
Total, 148 mm. 

Average, 37.00 mm. 



June 20, 6 P. M. 





Radium 


I 


48 mm. 


2 


49 


3 


46 


4 


45 


Total, 


188 mm. 


Average, 


47.00 mm 



Control 

1 50 mm. 

2 57 

3 51 

4 51 



Total, 209 mm. 
Average, 52.25 mm, 



The results are shown plotted in figure 41, 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



173 



2. The Radioactive Influence of Freshly Fallen 
Rain-Water 
The fact that freshly fallen rain-water is radioactive suggested 
the following experiments to ascertain its effect on growth. 

Experiment 52 
May 28, 6 P. M. 

In a glass beaker, washed chemically clean, was caught rain- 
water. The beaker was set in an open place to avoid drippings 
from buildings and trees. It had been raining almost constantly dur- 
ing the preceding day (2.26 in. precipitation), and slightly all the 
morning of the twenty-eighth. Thus the atmosphere was thoroughly 
washed, and the probability of traces of ammonia and COg and any 
atmospheric dust in the rain-water was slight. No electrical disturb- 
ance had accompanied the rain. 




20 
Day of month 

Fig. 41. Effect on Growth of placing a sealed glass Tube of Radium of 10,000 
activity into Water in which Roots of Luptnus albus are growing. 



Into the water thus collected were immersed, to a measured length 
of 15 mm., the tap roots of four germinated seeds of Lufiniis albus. 
Since rain-water is practically distilled, a control was similarly ar- 
ranged with distilled water, also in a chemically clean beaker. 

The following observations were recorded of the amount of 
elongation of the roots : 



174 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



May 29, 12 M. (Eighteen hours' growth.) 

Rain 
10.00 mm. 
11.00 
(7.00) * 
11.00 



33.00 mm. 
10.67 rn"fi' 



Distilled 
15.00 mm. 
10.50 
14.00 
12.00 



51.50 mm. 
12.88 mm. 



The difference of 2.22 mm. in favor of the roots grown in the 
distilled water may have been lessened by the possible toxicity of the 
latter, for it was not prepared in a glass still. Error from this cause 
was eliminated in the next Experiment (No. 53). The figures for 
the second day are omitted. (See figure 42.) 




Days 
Fig. 42. Effect of freshly fallen Rain on the growth of Roots of Luphius albus. 



Experiment 53 

In this experiment, rain-water was caught in chemically clean 
glass dishes in the open, on April 8, after about four hours of rain, 
and again on May 7, after over three hours' precipitation. The ex- 
periment was set up immediately after the last collection, using radi- 
cles of Lu^inus albus, immersed in both the fresh and the stale rain- 
water to a depth of 5 mm. Two parallel cultures, A and B, in both 
the fresh and the stale rain-water were observed. The measured 
lengths of the radicles, in millimeters, are given in the following 
tables : 

* Discarded. 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



175 



May 7, 2 : 30 P. M. 



B 



Fresh 


Stale 




Fresh 


Stale 


5.00 mm. 


5.00 mm. 




5.00 mm. 


5.00 mm. 


May 8, 9 : 30 A. M. 










Fresh 


Stale 




Fresh 


Stale 


13.00 mm. 


14.00 mm. 




12.00 mm. 


11.50 mm. 


12.00 


14.00 




11.50 


13.00 


12.00 


13.00 




13.00 


13.00 


12.50 


13.00 




8.00 


14.00 


49.50 mm. 


54.00 mm. 




44.50 mm. 


51.50 mm. 


Av. 12.38 mm. 


13.50 mm. 


Av. 


. II. 13 mm. 


12.88 mm. 


May 8, 5 P. M. 










Fresh 


Stale 




Fresh 


Stale 


15.00 mm. 


18.00 mm. 




15.50 mm. 


17.00 mm. 


14.00 


17-50 




14.50 


16.00 


15.00 


16.50 




17.00 


15.00 


15.00 


17.00 




10.00 


18.00 


59.00 mm. 


69.00 mm. 




57.00 mm. 


66.00 mm. 


Av. 14.75 mm. 


17.25 mm. 


Av. 


14.25 mm. 


16.50 mm. 


May 9, 9:30 A. M. 










Fresh 


Stale 




Fresh 


Stale 


24.00 mm. 


29.00 mm. 




24.00 mm. 


27.00 mm, 


23-50 


27.00 




24.00 


27.00 


injured 


25.00 




24.50 


25.00 


23.00 


29.00 




17.00 


29.00 


70.50 mm. 


110.00 mm. 




89.50 mm. 


loS.oo mm 


Av. 23.50 mm. 


27.50 mm. 


Av. 


22.38 mm. 


27.00 mm 



Both sets of cultures, A and B, give the same kind of resuh, viz. , 
a slower growth in the fresh rain-water than in that one month old. 

The results are plotted in figures 43 and 44, and are in substantial 
harmony with those obtained in the two preceding experiments. Care 
was taken in this experiment to have the temperature of the stale and of 
the freshly fallen rain-water alike by placing the carefully covered 
dish containing the former out of doors by the side of the latter while 
the fresh water was being collected. The fresh and the stale water 
were then kept side by side throughout the entire experiment. 



176 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



The only known difference between the water in the cultures A 
and B is a difference of radioactivity, that of the water collected one 
month previous to the experiment probably being nearly or quite 



28 
24. 







• 


20 
S It) 




-** 




i§ 12 






4 










Days 

Fig. 43. Relative growth of Roots of Lufinus albtis in fresh Rain-Water and in 
Rain-Water one month old. Culture B, Exp. 53. Cf. figure. 44. 



zero. It therefore seems a conclusion warranted by the conditions 
of the experiment that freshly fallen rain-water tends to retard the 



28 
24 

20 

16 

12 

8 

4 











n^ V^ 


y^ 






.>^ 


.^^ .. 








\^ 


..^-^^ 






^ 


^"•"" 


v^* 




^ 


^■""'*' 




rimenl 53 




K**^^'"" 




■ Exj)i 



















10 



40 



50 



20 30 

Hours 
Fig. 44. Relative growth of Roots of Lnpinus albus in fresh Rain-Water and in 
Rain-Water one month old. Culture A, Exp. 53. Cf. figure 43. 

growth of roots of Ljipinus albiis, and that this effect is due to the 
radioactivity of the water. 



EXPOSED WATER AND FRESHLY FALLEN RAIN 1 77 

In view of the experimental results previously obtained, and indi- 
cating that chlorophyll-bearing tissues respond to radium rays dif- 
ferently from tissues without chlorophyll, it is obvious that no con- 
clusions may be drawn from this experiment as to the effect of the 
radioactivity of freshly fallen rain-water on green leaves and stems. 
Quite possibly these parts may be thus stimulated. 

Experiment 54 

The object of this experiment is to ascertain the effect on ger- 
mination and growth of soaking corn grains {Zea Mays) in freshly 
fallen rain-water. 

May 26, 6 P. M. 

Five corn grains were placed in an empty, chemically clean 
beaker, left out in the open all night while it was constantly raining. 
There had been an almost continuous precipitation during the pre- 
ceding 36 hrs. As a control, the same number of grains were placed 
in a covered, chemically clean beaker, in distilled water, placed 
near the other beaker to secure similar temperature conditions. 

May 30, II : 30 A. M. 

After the grains had soaked for 41 hrs., they were placed in soil 
moistened with ordinary tap-water. The average height of the 
seedlings was recorded as follows : (Two of the control seeds proved 
to be poor, so the growth recorded for the control is the average of 
only three seeds.) 

Rain Distilled 

June 4. 

25.20 mm. 23.30 mm. 

June 6. 

79.60 mm. 86.60 mm. 

June 7. 

136.60 mm. 142.30 mm. 

June 8. 

161.60 mm. 179.00 mm. 

June 9. 

190.60 mm. 207.60 mm. 

Up to 10 days after planting the exposed seeds grew less rapidly 
than the control, and on the tenth day they averaged 17 mm. shorter 
13 



178 EXPOSED WATER AND FRESHLY FALLEN RAIN 

than those not exposed, but from this time on, though the conditions 
in the two cultures were maintained as nearly identical as possible 
as regards light, temperature, and moisture, and though the seeds 
of the two sets were of uniform size, the plants from seeds soaked in 
the rain-water grew much more rapidly, and, on June 18, the relative 
heights of the plants in the two cultures were as represented in the 
photograph (figure 45). 




Fig. 45. Experiment 54. Increased Growth of Zca Mays, following a ten-day 
Retardation, after the Seeds (before planting) were soaked in freshly fallen Rain 
Water. 

Summary 

The experiments show that when corn grains were soaked for 
24 hrs. in water exposed for 26.5 hrs. to radium rays growth was 
accelerated. The water exposed to the stronger radium caused the 
greater acceleration. With seeds of Lupinus albus similarly treated, 
the effects were very slight, but the same in kind as with corn. 
Oats seemed to be slightly retarded at first, but four or five days after 
the planting the oats soaked in the exposed water were much taller 
than the control plants, and tallest after soaking in the water exposed 
to the strongest radium. 

In a similar experiment, after 40 hrs. of soaking in water pre- 
viously exposed for 24 hrs., oats were accelerated from the begin- 



EXPOSED WATER AND FRESHLY FALLEN RAIN 1 79 

ning, and corn slightly. In this experiment the soaking of bean 
seeds in irradiated water was followed by decided acceleration at 
first, but the effect was not lasting, for the control plants eventually 
attained the same height as those soaked in the exposed water. 

After seeds of Lupmus albus had germinated, further growth in 
length of the radicles was retarded in water previously exposed for 
24 hrs. to radium rays of activities of from 10,000 to 1,800,000. 

When dry seeds of corn and lupine were planted in soil, and 
watered with water exposed for from one to nine days to rays from 
radium of 1,800,000 x , the growth of the corn was less and that of 
the lupines greater than of plants watered with fresh tap-water, but 
otherwise similarly treated. 

The rate of growth of roots of Lttpimis albtts is less in freshly 
fallen rain-water than in rain-water one month old or in artificially 
distilled water. This effect is similar to that produced by placing a 
sealed glass tube of radium into water in which roots are growing 
(figure 41), and the retardation is attributed, either directly or in- 
directly, to the radioactivity of the fresh rain. 



CHAPTER XI 

EFFECTS ON PLANT GROWTH: MISCELLANEOUS 
EXPERIMENTS 

It is clearly recognized that in the preceding experiments a rather 
narrow range of plant material was employed. In the following 
miscellaneous experiments a greater variety of material was used. 

Experiment 55 

In order to test the effect of the rays of radium on the germination 
of pollen grains, ten pollinia of Asclepias curassavica were placed 
to germinate in a moist chamber on slices of beet, at varying dis- 
tances from a sealed glass tube of RaBrg of 7,000 activity. Control 
of ten pollinia, similarly arranged, but with no radium. 

Within three hours the three pollinia nearest the radium tube 
had begun to germinate, but there were no signs of germination in 
the control set, and the experiment was closed. 

Experiment 56 
March 10, 10 : 30 A. M. 

In order to test the effect of radium rays on the form and rate of 
growth of yeast {Sacchat'omy ces)^ a small portion of a Fleischmann's 
compressed yeast cake was mixed in a 5 per cent, solution of sucrose. 
The liquid was then divided, and one half placed in a small glass 
dish, the other half in a similar dish. In the former was placed the 
radium tube of 10,000 activity, supported vertically by a cork cover- 
ing the dish, and with the end holding the radium extending to the 
bottom. In the other dish was similarly placed an empty glass tube. 

March 11, 3 : 30 P. M. 

There is no apparent difference in the microscopic appearance 
of the yeast contained in the drops that adhered to the tubes as they 
were withdrawn from the liquid in the two dishes. 

March 12, 11 : 15 A. M. 

The yeast cells seem to be rather more numerous in the radium 

180 



MISCELLANEOUS EXPERIMENTS l8l 

culture, both to naked eye view, and as seen under the microscope, 
but the difference is slight. There is no significant difference in 
the form or size of the cells. 

March i6, ii A. M. 

The odor of the radium culture is decidedly stronger than that 
of the control, and microscopic examination shows the cells to be 
more numerous in the former. 

Exposure of the radium rays was followed by a slightly more 
rapid cell-division, and possibly by more rapid fermentation. On 
this last point see Chapter XIV. 

Experiment 57 
March 26, 12 M. 

In order to ascertain the effect of radium rays on the growth of 
mushroom spawn {Agar/c7is), a half-pound cake of commercial 
mushroom spawn was divided into halves. Into the first half was 
placed two tubes of radium bromide of 1,500,000 activity, 15 mg. 
in all. The second half was used as a control. 

April 3, 9: 30 A. M. 

After an exposure of 190 hrs., both portions of the spawn were 
planted in separate mushroom beds, in boxes, in the propagating 
house. 

June 27. 

The spawn in the control bed is fruiting, but there are no signs of 
growth in the radiated culture. The experiment was continued for 
several weeks, but the spawn exposed to the rays of radium never 
fruited. 

Experiment 58 
April I, 12 M. 

In order to see what effect, if any, the rays of radium would 
have on Spirogy7'a, a bit of the alga, freshly gathered from a stream, 
was placed in two small vials with some of the stream water. In 
one vial was suspended the glass tube containing 10 mg. of RaBrg, 
1,500,000 X, in contact with part of the algal threads. In the 
control vial an empty glass tube was similarly placed. 

April I, 3 : 30 P. M. 

No difference is discernible in the naked eye appearance or in 
the microscopic appearance of the threads or cells. 



l82 MISCELLANEOUS EXPERIMENTS 

April 3, 8 A. M. 

There is no significant difference in the microscopic appearance 
of the cells in the two cultures. 

The experiment was repeated with similar results. 

Experiment 59 
Object : To ascertain the effect of the rays from radium on the 
growth of the gemmae of Limularia. 

December 5, 2 P. M. 

A plant of Lumilaria was placed under a bell-jar in the dark- 
room. Over the cupule, full of gemmae, was placed the sealed glass 
tube containing 10 mg. of RaBr, of i ,500,000 activity, vertically, with 
the end containing the radium at the height of the rim of the cupule. 

A control plant was similarly arranged, but with an empty glass 
tube. 

December 8, 9 A. M. 

After an exposure of 67 hours, gemmae from the radiated cupule 
were sown on the surface of moist sterilized soil, and a control sow- 
ing was made from a plant not exposed. The cultures were placed 
in the propagating house to develop. 

January 11. 

The radiated gemmae have never developed, while those not 
exposed developed thalli of from 4 to 5 sq. mm. in area, and the 
experiment was then discontinued, owing to an accident to the young 
plants. 

Experiment 60 

Repetition of Experiment 59. 

January 17, 11 A. M. 

Gemmae of Lumilaria exposed for 48 hours to the rays from 
RaBrg of 1,500,000 activity, were planted on the surface of soil in a 
pot, and non-exposed gemmae were similarly sown in another pot. 

April 2. 

Both the radiated and control gemmae have developed thalli, but 
those of the exposed culture are only about one half as large as those 
of the control. The plants from the radiated gemmae began to de- 
velop cupules about a month ago. These are now mature, with 



MISCELLANEOUS EXPERIMENTS 183 

abundant gemmae, while as yet there are no signs of cupules on the 
control plants. 

Experiment 6i 

A sealed glass tube of RaBr2 (lo mg. ; 1,500,000 x) was placed 
in contact with the gemmae in a cupule of Lunulart'a for six days. 
The gemmae were then sown on one half the surface of soil in a pot. 
The other half of the surface was sown with unexposed gemmae. 

Fourteen days later the unexposed gemmae are developing thalli, 
but those exposed have not grown at all, and are evidently dead. 

This experiment was repeated, the exposure to the radium-rays 
being for 19 hours. At the close of the experiment, 42 days after 
the exposed and the control gemmae were sown on soil, none of the 
radiated gemmae have grown, but all of the control set have devel- 
oped vigorous thalli. 

Experiment 62 
April 3, 9:45 A. M. 

In order to see if the growth of gemmae of Lunularia would be 
affected by the presence of a tube of radium in the soil, 1^6 gemmae 
were sown on the surface of soil in a flower pot, and a tube containing 
10 mg. of RaBrg of 1,500,000 activity was inserted verticall}^ into 
the soil at the center of the pot, the end containing the radium being 
25 mm. below the surface. 

Control culture with 36 gemmae, but empty glass tube. 

May 5, 2 :30 P. M. 

The gemmae are growing well in both cultures, with no appre- 
ciable difference in the two sets. 

May 12. 

There is no significant difference in the size of the developed 
thalli in the two cultures. The radium tube was removed. Duration 
of exposure 5^ weeks. 

June 2, 10 A. M. 

The thalli in the control culture are much larger and healthier 
in appearance than those exposed, and have well developed cupules 
with genimae, while cupules have scarcely begun to develop at all 
on the radiated plants. 



184 miscellaneous experiments 

Experiment 63 
Object: To ascertain the effect of radium rays on the " sprout- 
ing " of a potato tuber {Solatium tuberosum). 

May 21, 12 130 P. M. 

A glass tube containing RaBrj (1,500,000 x ) was inserted in a 
hole made in a tuber just beneath one of the " eyes," near the prox- 
imal end of the tuber. A portion of the other end was cut off, and 
the tuber was placed with the cut end in a tumbler of water in front 
of a window under a bell jar. 

May 25, 10 A. M. 

Sprouts are growing from all of the eyes, but there is no signifi- 
cant difference in their appearance or size. They all appear equally 
green and healthy. 

Experiment 64 

Object : To ascertain the effect of the rays from polonium on 
the germination and growth of timothy grass seed. 

March 19, 6 P. M. 

Several timothy grass seeds were placed in a narrow glass tube, 
and one end of a metallic rod coated with polonium was placed in 
among the seeds. 

March 26, 11 A. M. 

After 161 hrs. exposure, the seeds were sowed in soil in a flower 
pot, together with a sowing of unexposed seeds in another pot as a 
control. 

March 30, 10:30 A. M. 

The seeds are all growing vigorously, and there is no appreciable 
difference between the exposed and the control seeds. 

Experiment 65 
Object : To ascertain the effect of the thorium rays from a " Wels- 
bach" gas mantle on the germination and growth of timothy grass 
seed. 

June 9, 10 A.. M. 

Unsoaked seeds of timothy grass were sown in a row across the 
surface of the moist soil in a "Zurich" germinator. Lying hori- 



MISCELLANEOUS EXPERIMENTS 



185 



zontally over the seeds at right angles to the row, and about 3 or 4 
mm. above them, was the Welsbach mantle, style "Yusia," No. 
189, purchased in the market (Figure 46). 

Control, with no mantle, and both cultures placed in the dark 
room, in a moist chamber. 




Fig. 46. Experiment 65. Method of exposing germinating Seeds to the Rays of 
Thorium from a Welsbach Gas Mantle. 

June 13, 10 A, M. 

The control seeds are evenly germinated. 

The exposed seeds have germinated about the same amount as 
those of the control, except directly under the mantle, where there is 
only a very slight germination. 

June 14, 10 A. M. 

The seedlings in both cultures have grown since yesterday, but 
the relative conditions remain as then. Both cultures were placed in 
the light and illuminated only from above. 

June 16, 10 A. M. 

Retardation following the exposure is still evident, and the cul- 
tures were photographed (figure 47). 



i86 



MISCELLANEOUS EXPERIMENTS 



This experiment was thrice repeated, with results the same in 
kind as those above. 

Experiment 66 

Object : To ascertain the effect of the rays from a Welsbach gas 
mantle buried in the soil on the germination and growth of timothy 
grass seeds planted in the same soil. 

In a flower pot of earth was buried vertically the Welsbach 
mantle, style " Yusia," No. 189, purchased in the market, and on the 
surface of the soil were sown seeds of timothy grass. Control cul- 




FiG. 47. Experiment 65. Effect of Thorium Rajs from a Welsbach Gas Mantle on 
the growth of Timothy Grass. Cf. Fig. 46. 

ture with no mantle, and both cultures placed in the dark room, and 
watered from below until the water had soaked up to the surface of 
the soil. 

The seeds germinated in both cultures and produced good 
healthy plants, but throughout the duration of the experiment no 
difference could be detected in the height or other characters of the 
plants in the two pots. 

The experiment was repeated, but with similar, /. e., negative, 
results. 

Summary 

The results of the preceding experiments, covering a wide sys- 
tematic range of plants, are in conformity with those previously de- 
scribed. Rays from radium bromide of 7,000 x apparently acceler- 
ate the germination of pollen grains of Ascle-pias curassavica under 
the conditions imposed, while cell-division of commercial yeast was 



MISCELLANEOUS EXPERIMENTS 



187 



accelerated by rays from radium bromide of 10,000 activity. These 
rays produced no apparent morphological change in the yeast under 
the conditions of the exposure. 

Mushroom spawn (^Agartcus ca7npestris L.) was killed by rays 
from 15 mg. of radium bromide of 1,500,000 x, while rays of the 
same activity passing through water produced no apparent morpho- 
logical change in Sptrogyra. 

When the end of the glass tube containing 10 mg. of radium 
bromide of 1,500,000 x was placed a few millimeters above the 
gemmae of Liiniilaria an exposure of 48 hours retarded the growth 
of the gemmae, and one of 67 hours completely inhibited it. The 
reaction of chloroplastids to radium rays is similar to their reaction to 
too intense sunlight (figure \^a). This indicates that the gemmae 
are rather resistant to the rays. Cupules with brood-buds formed 
sooner than normally on thalli grown from the gemmae exposed for 
48 hours. When the same radium tube was placed in contact with 
these gemmae they were killed within at least 19 hours, or possibly 
sooner. Growth of the gemmae was retarded when'they were sown 
on the surface of soil into which the tube was inserted for five and 
one half weeks. 





Fig. 47a. Experiment 60. Response of Chloroplasts to Radium Rajs. 

The sprouting of a potato was evidently not affected by having 
the radium tube (1,500,000 x) inserted into the tissue of the tuber 
about 10 mm. from the " eye." 

No effect on germination followed an exposure of dry timothy 
grass seed for 161 hours to the a rays from a rod coated with 
polonium. 

The thorium rays from a Welsbach gas mantle retarded the 
growth of timothy grass when the mantle was placed over the seeds 
germinating on the surface of soil, but germination and growth did 
not appear to be affected in the least by burying the mantle in the 
soil. 



CHAPTER XII 

EFFECTS OF RADIUM RAYS ON THE SYNTHESIS 
OF CARBOHYDRATES 

I. Effect on Photosynthesis 
A few experiments were made to test the effects of radium rays 
on the photosynthetic activity of the green cell. These experiments 
are qualitative, and in many respects extremely crude. It is hoped, 
however, that they may serve to blaze the way for more accurate 
quantitative work. 

Experiment 67 
Object : To ascertain the effect of the rays from rods coated with 
Lieber's "radium coating" on photosynthesis in the bean leaf 
{Phaseolus). 

June 9, 10 130 A. M. 

A coated rod (25,000 x ) was placed horizontally about three mm. 
above a mature green leaflet of a bean plant, growing in a north 
window. 

A rod of 10,000 activity was similarly placed over a leaflet of an 
adjacent plant. 

Other leaves on the same plants served as controls, and a portion 
of the exposed leaf from each plant was tested and found to contain 
starch at the beginning of the experiment. 

June 9, 5 P. M. 

Nyctitropic movement has lowered both leaves away from the 
rods, and beyond their influence. 

June 10, 10 A. M. 

The rods were readjusted to their former positions. 

June 10, 2 : 30 P. M. 

The leaves were excised, dechlorophyllized, and tested with 
iodine for starch. 

188 



EFFECTS ON THE SYNTHESIS OF CARBOHYDRATES 



189 



The control leaflet stained blue evenly throughout. The leaflet 
exposed to the rod of 10,000 activity showed no effect from the ex- 
posure, staining evenly throughout, but the leaflet exposed to the rod, 
of 25,000 activity, showed only slight starch reaction in the portion that 
was under the rod, but stained deeply in all other parts. Even though 
the rod of 10,000 activity showed no effect, it is possible that the 
effect produced by the more active rod was due either wholly or in 
part to the shading of the leaf by the rod. This source of error was 
eliminated by placing the coated rod under the leaf, as in the fol- 
lowing experiment. 

Experiment 68 
May 29, 10 A. M. 

A nasturtium [Tropaeolum) plant was removed to the light after 
being for 18 hours in the dark-room. Under one of the leaves was 
placed a Lieber's radium-coated rod 
of undetermined activity (probably 
25,000 x). 

May 30, 10 A. M. 

After 24 hours' exposure the leaf 
was tested for starch. ' Abundant 
starch was found in the part of the 
leaf farthest from the rod, but very 
slight traces only in the remainder 
of the leaf, particularly in the part 
that was directly over the coated rod. 




Experiment 69 
May 28, 5 P. M. 

Under a healthy green leaf on a 
nasturtium {Tropaeohim) plant that 
had been in the dark-room for 7 
hours, was placed 10 mg. of RaBr2 
(1,800,000 X ), in a sealed box, por- 
tected from the leaf by only a thin mica window. 

After 19 hours' exposure in the dark-room to the radium rays, 
the radium was removed and the plant placed in the sunlight. 

After an exposure of 30 minutes to sunlight, the leaf exposed to 
the radium rays, and a control leaf were tested for starch, with 



Fig. 48. Experiment 68. Retard- 
ation of Photosynthesis by Radium 
Rays. The print was made by placing 
the leaf itself in contact with velox 
paper in sunlight. Thus the darker 
portions of the print indicate the more 
translucent portions of the leaf-blade, 
due to absence of starch. The darker 
region was directly over the radium- 
coated rod. 



ipO EFFECTS ON THE SYNTHESIS OF CARBOHYDRATES 

iodine. Starch was found in all parts of both leaves, but the iodine 
gave a much darker stain, and more evenly distributed in the control 
leaf, while in the radiated leaf the color was decidedly lighter, and 
lightest in the region that was directly over the radium, growing 
gradually darker toward the margin of the blade. 

Apparently a slight retardation of starch-synthesis has followed 
the exposure to the radium rays. 



Experiment 70 

A nasturtium {Tropaeoltim) plant was removed to the light after 
being in the dark-room for 18 hrs., and under one of the healthy 
leaves was placed the sealed glass tube of RaBrj (1,800,000 x ), the 
tube lightly touching the leaf in places. 

After an exposure to the radium of 24 hours the leaf was tested 
for starch (10 A. M.), but the differences in the staining were not as 
marked as when the coated rod was used. 



Experiment 70a. 

In order to see if an exposure to radium rays for shorter periods 
of time would be followed by an acceleration of photosynthesis, the 
following experiment was tried : 

From a healthy nasturtium plant {Tropaeolum majus) that had 
been in total darkness for 12 hours three vigorous leaves were de- 
tached and exposed to the direct rays of the sun as follows : 

No. I lying on a glass tube of RaBr2 of 1,800,000 activity. 

No. 2 lying on a glass tube of RaBrg of 1,500,000 activity. 

No. 3, Control. Not exposed to radium rays. 

The leaves were all destitute of chlorophyll at the beginning of 
the experiment. Four exposures were made as described, one each 
of 2, 5, 10 and 15 minutes. 

On decolorizing the leaves and staining with iodine no difference 
could be detected in the reaction for starch. No starch was indi- 
cated in any of the leaves. On examination with the microscope, 
also, no starch was found, except, of course, in the guard cells of 
the stomata, as would be expected under normal conditions. 

The results were negative. 

A repetition of this experiment with leaves that had been in the 
dark room for 48 hrs. also gave negative results after exposures of 



EFFECTS ON THE SYNTHESIS OF CARBOHYDRATES I9I 

5, 10, 15 and 30 minutes to the rays from radium of activity 1,800,000 
and 1,500,000, and from a radium-coated rod (activity undetermined). 
In order to give a more thorough test for photosynthetic activity, 
the experiments just described were repeated with the glass tubes 
containing RaBrg of activities 1,800,000 and 1,500,000 respectively. 
Exposures were made of 2, 5, 10 and 15 minutes, and the leaves 
were then tested for both starch and sugar (Fehling's test). Neither 
starch nor sugar was found in any of the exposed or control leaves. 

2. Effect on the Conversion of Cane-Sugar to 
Starch in the Dark 

Experiment 71 

In order to test the effect of the rays of radium on the formation 
of starch by amyloplastids in the dark, two leaves of pumpkin 
[Peppo)^ taken from a healthy plant kept in the dark for 36 hours, 
were floated in separate glass dishes on the surface of a 10 per cent, 
solution of cane sugar, the petioles extending into the solution. 
Over one leaf (^) was placed a glass tube containing RaBrg 
(10,000 x). The other leaf served as the control. 

Tests for starch in both leaves at the end of three days showed 
no effects that could be attributed to the radium. Starch was formed 
irregularly in both leaves, and similar results were obtained in two 
repetitions of this experiment, using pumpkin leaves in each case. 

The experiment was repeated with leaves of nasturtium as 
follows : 

Leaves from a nasturtium plant that had been in the dark-room 
for 12 hours and found devoid of starch when tested, were floated 
on the surface of a 10 per cent, solution of cane sugar, in separate 
glass dishes. Over one of the leaves was suspended the sealed glass 
tube containing 10 mg. of RaBr2 of 1,800,000 activity, about 3 or 4 
mm. from the surface of the leaf. 

After an exposure to the radium rays, as described, for 7^ hours, 
no starch was found in either of the leaves, exposed or control. 
After an exposure of 29 hours the control leaves were found to have 
made starch, but no trace of starch could be detected in the leaf 
exposed to the rays of radium. 

In another repetition of the same experiment, after 20 hours' 
exposure (as above described) to the rays from RaBrg (1,800,000 x ), 



192 EFFECTS ON THE SYNTHESIS OF CARBOHYDRATES 

the result obtained in that experiment was confirmed, i. e., starch 
had been elaborated in the control leaf, but not in the one exposed 
to the rays of radium. 

The exposed leaf was very slightly etiolated. 

The experiment was twice again repeated, once with an exposure 
to rays from RaBrg of 1,800,000 activity for 30 hours, and again for 
20 hours. After the 30-hour exposure an abundance of starch was 
found in the control leaf, but absolutely none in the one exposed to 
the radium. The exposed leaf was greatly bleached. 

After the 20-hour exposure the exposed leaf was only slightly 
bleached, and no trace of starch was found in it, while there was an 
abundance in the control. 

Experiment 72 

To test the effect of exposing the leaf to the radium before feed- 
ing it with the sugar solution, the following experiment was tried : 

Over a nasturtium leaf still attached to a plant that had been in 
total darkness for 30 hours, was placed the sealed glass tube of 
RaBrg (10 mg., 1,500,000 x), just touching the leaf. The plant 
was left in the dark, and after 29 hours' exposure to the radium, the 
leaf was cut off and floated on a 10 per cent, solution of cane sugar, 
in the dark, with two control leaves. 

After 51 hours the three leaves were dechlorophyllized and 
treated with iodine. No trace of starch was indicated in the leaf 
that had been exposed to the radium, but an abundance of it was 
indicated in the control leaves. 

The above experiments show that the rays from RaBr2 of 
1,800,000 and 1,500,000 activity inhibit the activity of plastids in 
converting cane sugar to starch. 

Experiment 73 

Two green nasturtium leaves, devoid of starch, were floated on a 
10 per cent, solution of cane sugar in which the sealed glass tube of 
10 mg. of RaBrg, of 1,800,000 activity has been immersed for 15 
hours, and then the tube of 10 mg. RaBrg, of 1,500,000 activity for 
12 hours. This solution had also stood for two days subsequent to 
its exposure to the radium ra3's, before being employed in this 
experiment. 

Control with two leaves floated on a solution not exposed to the 
rays. 



EFFECTS ON THE SYNTHESIS OF CARBOHYDRATES I93 

After an exposure for 8 hours, the leaves were tested for starch. 
Starch was found in all the leaves, but there was decidedly more 
starch apparent in those floated on the control solution, than in those 
floated on the solution exposed to the rays of radium. 

Whatever effect the rays may have had on the solution per- 
sisted for at least two days, and resulted in a retardation of starch- 
making by the plastids. 

3. Effect on Chlorophyll Solution and Chloro- 
phyll Paste 

Experiment 74 

Object : To ascertain the effect of the rays of radium on an alco- 
holic solution of chlorophyll. 

An alcoholic solution of chlorophyll was prepared by soaking 
filaments of Spirogyra in cold 95 per cent, alcohol. The solution 
was then filtered and divided into two halves. Into one was sus- 
pended a sealed glass tube containing 10 mg. of RaBr2 of 1,500, 
000 activity, with the end containing the radium in about the middle 
of the solution. In the other was placed nothing. Both vials were 
set in the dark-room, at the same temperature. 

Frequent observations during a period of 89 hours disclosed no 
appreciable difference in the appearance of the two solutions. The 
radium-tube was then removed, and the solutions left to stand in the 
dark-room for eight weeks. At the end of that time there was no 
difference in their appearance, and when both vials were then placed 
in the sunlight the solutions behaved precisely alike, so far as could 
be detected, while they were bleaching. 

Repetitions of this experiment were followed by similar (negative) 
results. In the second and third experiments the solutions were 
made respectively from leaves of nasturtium {Tropaeohuii) and bean 
{Phaseolus). 

Experiment 75 

A small box with a mica window, and containing 10 mg. of 
RaBr, of 1,800,000 activity, was placed over a small bit of chloro- 
phyll paste (" Chlorophyll Puriss.,"of supply houses), with only the 
mica between the radium and the paste. The exposure was made 
in the dark-room for 18 hours, but no visible effect from the radium 
resulted to the chlorophyll. 
14 



194 effects on the synthesis of carbohydrates 

Experiment 76 
Into a weak aqueous solution of the chlorophyll paste was placed 
the glass tube of RaBrg (10 mg., 1,500,000 x ), but after an exposure 
of four days the chlorophyll was not bleached, nor could any other 
effect be observed resulting from the influence of the rays of radium. 
The solution bleached in sunlight as normally. 

Summary 

Using the starch-iodine reaction as a test for photosynthesis, it 
was found that when a radium-coated rod of 25,000 x was placed 
over a health}'^ leaf of Phaseolus vulga?'ts for 10 hours in direct sun- 
light, and at a distance of only 2 or 3 mm., no starch was formed in 
the narrow region immediately under the rod, though abundantly in 
the remainder of the leaf. A rod of 10,000 x similarly placed at the 
same time over another leaf of the same plant had no apparent effect 
on starch formation. However, to be more sure that the first effect 
was not due merely to the shading of the leaf by the rod, the experi- 
ment was repeated, using a leaf of nasturtium [Tropaeoltun majus)^ 
and placing the active rod under the leaf, and in contact with the 
under surface. By this method the effect, after an exposure of 24 
hours, was not so marked, but there was a decided retardation of 
starch making. A leaf of a nasturtium plant that had been in the 
dark for 26 hours, and exposed to radium rays (1,800,000 x) that 
had passed through only a thin sheet of mica for 19 hours out of the 
26, was then brought into direct sunlight for 30 minutes. The 
starch-iodine reaction showed less starch in the exposed leaf than an 
unexposed one from the same plant, and the effect was greatest 
directly under the mica window through which the radium rays 
passed. 

An exposure of 24 hours to the rays from radium bromide of 
1,800,000 X in a sealed glass tube placed under a leaf was followed 
by no appreciable effect. 

To see if photosynthesis could be stimulated hy short periods of 
treatment, starch-free leaves of nasturtium were exposed in direct 
sunlight over sealed glass tubes of 1,500,000 x and 1,800,000 x, 
and to a radium-coated rod for periods of 5, 10, 15, and 30 minutes, 
but no effect, of either acceleration or retardation, could be detected 
by the starch-iodine reaction. In a repetition of this experiment, tests 
were made for sugar as well as for starch, but with negative results. 



EFFECTS ON THE SYNTHESIS OF CARBOHYDRATES I95 

It was Boehm,' who, in 1883, first demonstrated the power of 
chloroplasts to form starch in absolute darkness when supplied with 
cane sugar from a 10 to 20 per cent, solution. This process, in 
leaves of nasturtium, was completely inhibited, and the leaves 
bleached by exposures of from 20 to 30 hours to rays from the glass 
tube of 1,800,000 activity. When the leaf was exposed for 29 hours 
(1,500,000 x) before being floated on the starch solution, it made no 
starch in darkness. 

I then reversed the manner of exposure ; that is, I exposed the 
sugar solution instead of the leaf to the rays. The sealed glass tube 
containing 5 mg. of radium bromide of 1,800,000 x was suspended 
in the solution for 15 hours, and then the tube of 1,500,000 x for 12 
hours longer, giving a total exposure of 27 hours. It was then nec- 
essary to wait for two days before placing the leaves in the irradiated 
solution, but, whatever effect the rays had on the solution, it endured 
for at least two days, for, while some starch was found after eight 
hours in leaves floated on this preparation, the amount was very much 
less than that found in similar leaves floated for the same period of 
time on a portion of the same solution that had not been exposed to 
the radium. Undoubtedly the effect would have been much more 
marked had it been possible to use the solution immediately after it 
had been exposed, but I have not been able to repeat this experiment. 

Bibliography 

I. Boehm, J. Ueber Starkebildung aus Zucker. Bot. Zeit. 41 : 33, 49. 
18S3. 



CHAPTER XIII 



EFFECTS OF RADIUM RAYS ON PLANT RESPIRATION 

I. Effect on Aerobic Respiration 

In order to test the effect of the raj^s of radium on plant respira- 
tion, the following experiments were tried : 

Experiment 77 
August 15. 

Into each of three tumblers, i, 2, and C, was placed a saturated 
solution of KOH, and above this, on a moist blotter, supported by a 

24 
22 

20 
18 

16 
.. 14 
12 



bo 



10 



cc 





Experiment 77. 










X 


A 


cceleration c 
rminating 1 


f respiratioi 
jheal. 


^of 




,o,9P>-' 














j^ 


^^^ 










^m^ 


.^"^ 


,-teV^' 
^0^;^ 

C^^"" 
^0*^ 


'^^^ 








::^ 


^ 


i^^^ 





















12 3 4 5 6 7 

Hours 

Fig. 4Q. 

piece of wire gauze, were placed grains of wheat {Triiicumy Hen- 
derson's " Wellman Fife") weighing 2 gr. (dry weight). Over the 
wheat and in contact with the grains were placed the radium-tubes 
as follows : 

196 



EFFECTS ON PLANT RESPIRATION 



197 



1. The sealed glass tube of RaBr^ of 10,000 activity. 

2. The sealed glass tube of radio-tellurium. 
C. Control. No radium preparation. 

Over all was placed, in each tumbler, a piece of moist blotter. 
Leading from each tumbler, through an air-tight rubber stopper into 
a mercury bath, was a glass tube, graduated to i/ioo of a mm. 
The entire tumbler in each case was immersed in water to insure 
similar temperature conditions, and also to make the respiratory 
chamber more surely air-tight. 

The rise of mercury, following the absorption, by the KOH solu- 
tion, of the CO, given off, was taken as the index of both the rate 
and the amount of respiration. The record of readings is given in 
the following table, and in figure 49. 



Readings of the Scale^ Multiplied by lOO 



Time (Aug. 15) RaBr^, 10,000 X 



9:^5 

10: 15 
11:15 
12:30 



15 
15 



74.25 = 0.00 
4.00 
70.25 
67.25 
64.00 
62.25 
59.00 
57.00 

53-50 
Total, 



3.00 
3-25 
1-75 
3-25 
2.00 

3-50 

20.75 



Radio-tellurium 

81.25 = 0.00 

2.00 

79-25 

77-25 
75.00 
74.00 
72.00 
70.00 
67.50 

Total, 



2.00 
2.25 
1. 00 
2.00 
2.00 
2.50 

13-75 



Control 



71.00 = 0.00 
2.00 
69.00 
67.00 
65.00 
64.00 
62.00 
60.00 
57-25 
Total, 



2.00 
2.00 
1. 00 
2.00 
2.00 
2-75 

13-75 



The radio-tellurium produced no effect that could be detected, 
but a decided acceleration in respiration followed the exposure to the 
rays from RaBr2 of 10,000 activity. 



Experiment 78 

This experiment was arranged as in No. 77, using sealed glass 
tubes of RaBrg, of 1,500,000 and of 10,000 activity. In each respi- 
rometer 20 grains of the wheat were used, with a total dry weight in 
each case of .50 gm. 



ipS 



EFFECTS ON PLANT RESPIRATION 



Time 

(Sept. 19) 

9:30 

10:30 

II 130 



Readings of the Scale^ multiplied by 10 

RaBr^ Amt. of RaBr^ Amt. of Amt. of Temp. 

1,500,000 Change 10,000 Change Control Change 



12 
I 

2 
3 



30 
30 
30 
30 



4:30 
5:30 
(Sept. 20) 
8:30 



9-45 

9-05 
S.60 

8.32 

8.10 

7.90 

7.70 

7-50 
7-30 

Total, 3.05 
4-25 



0.40 

0-45 
0.28 
0.22 
0.20 
0.20 
0.20 
0.20 



5-^5 
Total in 23 hrs. = 8.20 



9-35 
8.95 

8.55 
8.22 

8.00 

7.70 

7-45 
7.17 
6.85 

2.60 



0.40 
0.40 

0-33 

0.22 

0.30 
0.25 
0.28 
0.32 

4-25 
6.75 



9-30 
8.95 

S.60 

8.33 
8.15 

7-95 
7.70 

7-50 
7-30 

4.40 



11.00 



0-35 

0-35 
0.27 

0.18 

0.20 

0.25 

0.20 

0.20 

2.90 

4-90 
7.80 



°C. 

25 

25 

25 

25 

25-75 

25-75 

26 

26 
26 

26 



The total amount recorded of CO2 evolved in 8 hours is 3.05 
units, following exposure to the rays from the salt of activity 
1,500,000; 4.25 units following exposure to the rays from the salt 






^ 




1 2 3 4 5 6 7 .& 

Hours 

Fig. 50. Acceleration of Respiration of germinating Wheat by Radium Rays. 



of 10,000 activity, and 2.90 units in the control. During the last 
15 hours of the experiment, 5.15 units were recorded following ex- 
posure to the radium of stronger activity; 6.75 units following ex- 
posure to the radium of weaker activity, and 4.90 units in the control. 
The total amounts evolved during 23 hours were recorded respect- 
ively as follows : 8.20 units; 11.00 units; 7.80 units. 



EFFECTS ON PLANT RESPIRATION 



199 



The greater acceleration following exposure to the radium of 
weaker activity may possibly be attributed to the fact that there was 
much more of the latter salt in the glass tube than of the former, the 
amounts being for the 10,000 x .52 gm., for the 1,500,000 x 10 mg. 
(figure 50). 

Experiment 79 

The following experiment was arranged as in No. 77, using only 
the radium of 1,500,000 activity. Readings of the height of the 
mercury column in the graduated glass tube were taken as follows. 
The scale divisions are multiplied by 10. 





RaBr, 


Amt. of 




Amt. of 


Temp 


Time 


1,500,000 Change 


Control 


I Change 


°C. 


9:30 
10:30 
II : 30 


9.80 

9-50 
9.20 




0.30 
0.30 


9.70 

9-45 
9-25 


0.25 
0.20 


26 
26 
26 


I :30 
3 ' 00 
3:30 
4:30 
5 : 30 


8.65 
8.20 
S.05 

7-73 
7-50 




0-55 
0.45 
0.15 
0.33 
0.23 


8.85 
8.46 

8-35 
8.10 
7.85 


0.40 
0-39 

O.II 

0.25 
0.25 


26 
26 
26 
26 

2^ 


U %J 


Total, 


2.30 


Total, 1.85 










3-55 




3-15 








Total, 


> 5-85 




Total, 5.00 




9 : 00 


3-95 




0.40 
0.23 
0.29 


4.70 


0.30 
0.25 
0.26 


25-5 


10:30 


3-55 




4.40 


25 --s 


II :30 


3-32 




4-25 


25-5 


I :30 


3-03 




0.15 
0.18 


3-99 


0.19 
0.24 


25-5 


2:30 


2.88 




3.80 


26 


3:30 


2.70 




0.17 


3-56 


0.06 


26 


4:30 


2-53 




0.13 


3-50 


O.IO 


26 


5:15 


2.40 






3-40 




26 












2.20 




2.07 




8:30 


0.20 


Total, 


, 9.62 


1-33 


f 

Total, 8.47 


25 



Here also acceleration of respiration has followed exposure to the 
rays from radium of 1,500,000 activity. (See figures 51 and 52.) 



Experiment 80 
In order to ascertain the effect, on the respiration of germinating 
wheat grains, of a previous exposure, in the dry condition, to the 



200 



EFFECTS ON PLANT RESPIRATION 



rays of radium, twenty wheat grains, weighing (dry weight) .50 gm., 
were placed before soaking, in contact with the walls of a sealed 
glass tube containing 10 mg. of RaBr2, of 1,500,000 activity. The 
duration of exposure was 54 hours. 



0.5 _ 



0.4 



tyj 









0^ 



0.2 



0.1 



0.0 



1 1 1 1 1 1 
Experiment 79. 
Kffp.ct of rndium T<nis on Tpspirotton 


«/• 










y' 


germinating wheat. 

S.30 p. m., Sept. 20—5.15 p. m., Sept. 21. 


„.-*'*/ 


■^ 


















y 

^ 


.^^ 


^ 


















■',..-• 


















... 


' ,■' 




















X 



























3.30 5:30 P. M. 



Time 

Fig. 51. 



^M. 9:30 11:30 i;30 3:30 5;30 



These seeds, together with 20 others, also weighing .50 gm., and 
serving as a control, were soaked in water over night, and arranged 
in the respirometer, as described in Experiment 77. 



ccc 



30 



o 1 



26° 

22° 







Experiment 79. 
Effect of radium rays o;t respiration 
of germinating wheat. First 8 hrs. 




9:30 10:30 11:30 12\10 



1:30 
Time 

Fig. 52. 



.oo. 



2:30 



3:30 



4-30 



5:30 



EFFECTS ON PLANT RESPIRATION 



20I 



Observations of the amounts of COg given off were recorded as 
follows : 



Time 



Radium 



Control 





Scale 


Amt. of 


Scale 


Amt. of 




(Oct. 3) 


Reading 


Change 


Reading 


Change 


Temp. ° 


9 : GO 


9-53 


0.13 


9.10 

8.93 
8.92 

8. 90 


0.17 


19 


io:oo 


9.40 


0.03 


O.OI 


19 


II : oo 


9-37 


0.07 


0.02 


19 


12 : oo 


9-30 


o.io 


0.05 


19 


2 : oo 


Q.20 




8.85 


19 


3:00 


9.10 


0. 10 
0.05 


8.80 


0.05 
0.00 


19 


4 : 00 


9-05 


o.io 


8. 80 


0.10 


19 


5:45 


S.95 


1.25 


8. 70 


0.80 


19 


(Oct. 4) 




1.83 




1.20 




9 : 00 


7.70 




7.90 




18 


II : 00 


7.60 


0.10 


7.85 


0.05 


18 


12 : 00 


1'SI 


0.03 


7-S3 


0.02 


18 


(Oct. 5) 




1.42 




0.98 




9:30 


6.15 


0.15 


e.'$>^ 


0.15 


19 


3:30 


6.00 




6.70 




18.5 


(Oct. 6) 




0.60 




0.50 




9 : 00 


5-40 




6.20 




19 


(Oct. 7) 




1.25 




1.30 




10: 00 


4.15 




4.90 




18 


(Oct. 8) 




1.65 




1-37 




9: 00 


2.50 




3-33 




16 



The total amounts of gas evolved during the five days of the 
experiment were, for the exposed seeds, 7.03 units; for the control, 
5.57 units. The results for the first nine hours are shown in figure 
53. There was an apparent initial retardation of respiration during 
the first hour of exposure, but thereafter the rate was more rapid for 
the seeds exposed. At the end of the first nine-hour period the radi- 
ated seeds had evolved a total of 1.83 units of gas, the control seeds 
a total of 1.20 units. 

The effect on respiration of exposing dry seeds before soaking, and 
therefore before germination had begun, differs from that of making 
the exposure only after the seeds were soaked, in that at first there is 
apparently a retardation of respiration, followed by recovery and ac- 
celeration, while in the latter case respiration is accelerated from 
the start. 



202 



EFFECTS ON PLANT RESPIRATION 



o 



Experiment 80. 
Effect of radium rays on respiration 
of germinating wheat grains. 




\^^' 



ooi 



2. Effect on Anaerobic Respiration 

Experiment 8i 

Three seeds of the pea {Pisum sativum)^ soaked in tap-water over 
night, were freed from their seed-coats and then found to weigh 1.41 
gm. They were placed in a test-tube of mercury inverted over a 
mercury bath. In the tube with the peas, and in contact with them, 
was placed a celluloid rod coated with " Lieber's radium coating " of 
10,000 activity. Thus the seeds came under the influence of the a 
rays and the emanation, as well as of the /9 and y rays. 

The control test-tube contained three seeds, also weighing, without 
their seed-coats, 1.41 gm. 

Observations were recorded as follows : 



Volume of Gas Evolved 
Time of Observation 
April 15, 5:00 P. M. 
" 16, 10: 18 A. M. 
" 17, 4: 30 P. M. 
" 18, 9:20 A.M. 
" 18, 6:40 P. M. 
" i9i 9: 30 A. M. 



Radium 


Control 


0.00 c 


.c. 


0.00 c.c. 


•30 




•30 


1.70 




2.10 


.80 




1. 00 


.40 




.90 


•50 




.40 


Total, 3.70c. 


c. 


4.70 c.c 



effects on plant respiration 203 

Experiment 82 

Five seeds of the pea {Pisum sattvtini), soaked over night and 
then freed of their seed-coats, were placed in a test-tube of mercury, 
inverted in a bath of mercury. The weight of the seeds, minus the 
seed-coats, was 2.29 gm. In the test-tube was first placed a sealed 
glass tube of RaBrj (1,500,000 x ), with a cork over its upper end to 
hold it at any desired level in the test-tube. Thus the seeds, when 
placed into the test-tube, were aggregated about the lower end of 
the radium-tube where the radium was, and so were brought closer 
to the radium salt, and more directly under the influence of the rays. 

Control, with empty tube also supported by a cork, and with 
seeds having a total weight of 2.28 gm. 

Observations of the amounts of gas given off by the seeds were 
recorded as follows (see also figure 54) : 



Time of Observation 


Radium 


Control 


^pril 22, 10: 50 A. M. 


0.00 c.c. 


0.00 c.c, 


" 23, 4 : 00 P. M. 


1.50 


1.60 


" 24, 9:00 A. M. 


1.60 


1.30 


" 25, 9: 10 A. M. 


1.80 


1-75 . 


" 28, 9:45 A. M. 


7-30 


8.05 




12.20 c.c. 


12.70 c.c, 



Experiment 83 
Four test-tubes were arranged as described in Experiment 82, the 
total weight of the seeds (minus the seed-coats) in each case being 
2.22 gm. The first three test-tubes contained radium preparations 
as indicated in the following table. Observations of the volumes of 
gas evolved in the test-tubes were recorded as follows : 

Radium Radium Radio- 

Time of Observation 1,500,000 X io,oooX tellurium Control 
June I, 6 : 00 P. M. 0.00 c.c. 0.00 c.c. 0.00 c.c. 0.00 c.c. 

" 2, 10:00 A.M. .40 .60 .60 .60 

1. 10 



" 3, 1 1 : 00 A. M. .80 1.60 1.30 

" 4, i2:ooM. 1.35 1.30 1.25 1. 00 

" 5,12:15P.M. .97 1.20 1.25 1.20 

" 6, '11: 00 A.M. 1.63 1.65 1.50 1.35 



5.15 c.c. 6.35 c.c. 5.90 c.c. 5.25 c.c. 



204 



EFFECTS ON PLANT RESPIRATION 



These readings indicate, as in the preceding experiments, a re- 
tardation of respiration hy the radium of 1,500,000 activity, but the 
volumes of gas evolved by the seeds exposed to radium of 10,000 
activity and to radio-tellurium exceed the volume given off by the 
control seeds- 



bo 



i 2 



^ 




Summary 

When a sealed glass tube containing .52 gm. of radium bromide 
of 10,000 X is laid over, and in contact with soaked wheat grains 
placed to germinate, an acceleration of respiration results, but no 
effect could be detected when the grains were similarly exposed 
to radio-tellurium in a sealed glass tube. A like exposure to rays 
from 5 mg. of radium bromide of 1,500,000 x also resulted in an 
acceleration of respiration, but not to so great a degree as was caused 
by the preparation of 10,000 activity. 

If the grains were exposed dry, before soaking, for 54 hrs. to rays 
from the radium of 1,500,000 x , their respiration was at first retarded, 
but this was followed by recovery and marked acceleration. 



EFFECTS ON PLANT RESPIRATION 205 

Results obtained by the crude device employed for testing the 
effects of the rays on anaerobic respiration seem to indicate that an 
exposure to a radium-coated rod (a, /9 and j rays, and the emanation) 
caused a retardation of the process in germinating pea seeds, and 
the same kind of result followed exposure to 5 mg. of radium bro- 
mide of 1,500,000 X in the sealed glass tube. In one experiment, 
however, a decided increase in the evolution of gas followed expo- 
sure to radium of 10,000 x in a sealed tube, and also exposure to 
radio-tellurium. 

A comparison of the results seems to indicate^that anaerobic and 
normal aerobic respiration of germinating pea seeds are affected in 
the opposite manner by radium rays, the former being retarded, the 
latter accelerated, but the data are quite too meager to permit of a 
more definite statement. The question needs further experimental 
investicration. 



CHAPTER XIV 

EFFECTS OF RADIUM RAYS ON ALCOHOLIC 
FERMENTATION 

Experiment 84 

To ascertain the effect of radium rays on alcoholic fermentation, 
a small piece of Fleishmann's compressed yeast cake was well mixed 
with 25 c.c. of a 5 per cent, solution of cane sugar. Two saccha- 
rimeters were then filled with 10 c.c. of the mixture. Into one sac- 
charimeter was placed a sealed glass tube containing 10 mg. of 
RaBrg, of activity 1,500,000, with all the radium in the submerged 
end of the tube. 

A control saccharimeter contained an empty sealed glass tube, and 
both cultures were placed side by side at the same temperatures. 

Readings of the saccharimeter-scale during fermentation were 
recorded as follows : 

Time Radium Control 

12 M. 0.00 c.c. 0.00 c.c. 

2 P. M. 2.80 2.40 

3 P. M. 3.50 2.80 

4 P. M. 3.40 3.20 

In a repetition of this experiment, using the sealed glass tube 
containing RaBr2 of 7,000 activity, the following scale-readings 
were recorded : 

Control 
0.00 c.c. 
•30 
•50 
.80 

The results are shown in figure 55. 

Again, using the radium of 1,500,000 activity, the following re- 
sults were recorded : 

206 





Time 


Radium 


2 : 


; 50 P. M. 


0.00 c.c. 


3: 


150 P. M. 


.60 


4: 


; 50 P. M. 


1. 00 


5; 


150 P. M. 


1.60 



EFFECTS ON ALCOHOLIC FERMENTATION 



207 



Time 


Radium 




Control 


12 : 30 P. M. 


0.00 c.c. 


0.00 c.c. 


I : 30 P. M. 


.40 


.40 


2 : 40 P. M. 


.60 


.40 


3 : 34 P. M. 


.70 


•45 


4:28 P. M. 


.70 


•50 


C.C. 

1.6 
1.4 

13, 






Acceleration of 


/ 

/ 
/ 

/ 




§0 1.0 

"i 08 


fennen 


tation. 


/ 
/ 
/ 




-§ 0.6 
0.4 


/ 
/ 








0^ 
0.0 


/ 


Ooy««"^ 






2. 


50 3:50 4:50 


5i 







Hours 






Fig. 55. 


Experiment i 


54. 







The relative effect of the rays from radium and from radio-tellur- 
ium was ascertained from the following experiment. 

Experiment 85 
The experiment was arranged as described for Experiment 84. 
Observations of the volumes of gas evolved in fermentation are 
recorded in the following table : 





RaBr, 


Radio- 




Temp. 


Time 


10,000 X 


tellurium 


Control 


° C. 


9 :20 


0.00 c.c. 


0.00 c.c. 


0.00 c.c. 


31 


10 : 20 


•95 


.60 


•45 


35 


10:53 


2.00 


1.30 


1. 10 


35-5 


II :20 


2^95 


2.10 


1.60 


33 


II 150 


4.00 


3.10 


2.10 


33 


12 : 20 


4-75 


3.S5 


2-55 


33 


12 150 


5-30* 


4.60 


3.00 


33 


I :20 


5-50* 


5-05* 


3-30 


33 


1:50 






3.60 


33-5 



* The last two readings for the radium, and the last reading for the radio-tellurium 
■were estimated, as the surface of yeast mixture passed off the scale of the sacchari meter. 



208 



EFFECTS ON ALCOHOLIC FERMENTATION 



The above results are shown in figure 56. 

After fermentation had ceased in all three tubes they were allowed 
to stand for ten days (April 2-1 1), and as the gaseous products given 



5 
^4 


Experim 


ent 85. 


^' 


,.0^'' 


— 


1 3 
"s 2 








^^-^ 


Co 

1 




-»*fr.*'-- 


y' ..-^ 







01234 

Tiays 

Fig. 56. Effect of the Ravs from Radium and Radio-Tellurium on the Rate of Alcoholic 

Fermentation. 

off during fermentation were dissolved by the yeast mixture in the 
saccharimeters, readings were" taken every 24 hours of the height of 
the liquid. The figures are omitted in tabular form, but the plotted 



So 
P 2 






1 


^ 


. 














-.t:-- -.^ 






"OS;^ 




















^ 


..%:??.'.... 


Cootro/ 


rrrr:r 


^__ 










Experin 


e7it 85. 




10,000 






R 


ate of ah 


sorption i 


if evolvec 


I gases In 


/ the yem 


H mixtur 


e. 





5 6 

Days 
Fig. 57. 



10 



11 



curves are given in figure 57. It is seen, consulting these curves, 
that the rate of absorption of the fermentation-product varied, be ing 
most rapid in the radium preparation, least rapid in the control, and 
intermediate following exposure to the radio-tellurium. 



EFFECTS ON ALCOHOLIC FERMENTATION 2O9 

This result suggests that either the products of fermentation varied 
in the three cases, or else the yeast mixture was modified differently 
by the two radioactive preparations. Possibly the differential result 
is due to a combination of both conditions. Its real meaning must 
await further experimentation. 

In a repetition of Experiment 85 the following readings were 
recorded of the volumes of gas given off in fermentation : 

Radio- 
tellurium Control Temp. ° C. 
0.00 c.c. 0.00 c.c. 

.So .60 

1.80 1.35 

2.85 2.40 

4-30 3-45 

5.00 4.15 

5.60* 4.85 

Experiment 86 
In the following experiment, into each of five saccharimeters, 
filled with 10 c.c. of a 10 per cent, solution of cane sugar, was 
placed .20 gm. of a Fleischmann's compressed yeast cake. Radium 
preparations were inserted into the saccharimeters as indicated in the 
following table, and the following readings of the saccharimeter 
scale were recorded : 





RaBr^ 


Time 


10,000 X 


10:30 


0.00 c.c. 


[ I : 30 


1. 00 


12 : 00 


2.30 


12:30 


3.85 


I : 00 


5-30* 


I : 30 


5.60* 


2 : 00 







RaBr^ 


RaBr, 


Radio 


-tel- 


Coated 




Temp. 


Time 


1,500,000 X 


10,000 X 


lurium 


Rod 


Control 


°C. 


11 : 18 


0.00 c.c. 


0.00 c.c. 


0.00 ( 


:.c. 


0.00 c.c. 


0.00 c.c. 


25 t 


II :48 


.60 


.60 


•50 




•30 


•30 


30 


12: iS 


2.10 


2. 30 


1.40 




.80 


.80 


30 


12 : 48 


3.80 


4.20 


2.50 




1.80 


1.70 


30 


1:18 


5. + * 


5. + * 


-4.00 




3-30 


2.70 


30 


I :48 


» 




5,20 




4.60 


3-50 


29-5 





Bubbles began to rise in the 1,500,000 and 10,000 preparations 
within two minutes after the preparations were placed in the thermostat 
oven, but no bubbles were rising in the control tubes up to four min- 
utes after. The exact time in the latter was not observed, but vig- 
orous fermentation did not begin in the control tubes as soon as in 
the other two tubes just mentioned. 

* Estimated. The surface of the yeast mixture has passed off the scale, 
t At II : 25 A. M. the thermometer registered 35°. 



2IO 



EFFECTS ON ALCOHOLIC FERMENTATION 



In a repetition of Experiment 86, readings of the saccharimeter 
scales were recorded as follows : 



Time 
2:30 
00 

30 
00 

30 



RaBr, RaBr, RaBr.^ 

1,500,000 X 10,000 X 7.000 X 
0.00 

•50 

1.60 
2.60 



0.00 

.60 

2.10 
4.00 

5-50' 



0.00 

.60 

I. So 
4.00 



5-50' 



5:00 



3-85 
4.70 



Radio- 
tellurium 
0.00 
.40 
1.50 
3.00 
5.10* 



Coated 
Rod 
0.00 
.20 
.60 
1.20 
2.50 

3-40 



Control 
0.00 
.10 
.50 
1.20 
2.50 
3-30 



Temp. 
°C. 
29 

22 

31 

31 

30-5 

30 





X. 




di 


^ 








^.^ 




¥ 


^m 


1' 


i ■ 










jtn 


I 






^' I 


• i 




i 




L 


M 


■ ■'' ^^B 




At 


-^•^ 


^bI^ 




jjj 


• J 


li 


^.. ^.JM 






1 ^ 


' It 


1 


W 


* 

.1- — 


1 


Hi 


1 


1 


1 



Fig. 58. Experiment 87. Acceleration of Alcoholic Fermentation hy Rajs from 
Radium and Radio-Tellurium. 



Experiment 87 

Into 250 c.c. of a 5 per cent, solution of cane-sugar was placed 
a piece of a Fleischmann's compressed yeast cake, weighing 2 gm. 
The mixture was thoroughly shaken, so as to distribute the yeast 
cells thoroughly throughout the liquid, and equal quantities were 
then placed in each of five fermentation tubes. Radium preparations 
were inserted into the fermentation tubes in sealed glass tubes as indi- 
cated in the following table, and the following readings of the scale 
were recorded (see also figure 59) : 



* Estimated. The surface of the yeast mixture has passed off the scale. 



EFFECTS ON ALCOHOLIC FERMENTATION 



211 





RaBr, 




RaBr* 


RaBr, 


Control 


s 


Temp 


Time 


1,500,000 


X 


10,000 X 


7,000 X 


a 


b 


°C. 


lo: 07 


0.00 




0.00 


0.00 


0.00 


0.00 


* 


II :30 


.60 




.58 


.40 


.20 


.20 




1 2 : 00 


1.20 




.90 


•50 


.40 


.40 




12:30 


1-55 




1.05 


•50 


.40 


•32 




I : 00 


2.00 




1.25 


.60 


.40 


.40 





2 : 00 



3.20 



2.00 



.70 



.40 



.40 



Between i : 20 and i : 45 P. M., the fermentation tubes were re- 
moved from the thermostat oven and photographed (figure 58). A 
saccharimeter containing the sealed glass tube of radio-tellurium is 
also shown in the photograph. The readings of this preparation are 
not recorded in the above table. 



c. c. 



3S 
2S 

2.4, 






A 


■« 

Experin 
IcohoUc ft 


lent 87. 
'rmentatio 


n. 


^oQ^^ 


/"' 


2J0 
1.1 

1.2 




.SO"" 


•■-•^'?*,. 




■-.._ 


^^^"" 




)^^°'^'."' 


.8 

.4 




._-.=- 


—zzTz:^''^ 


^^^•'•' 





__7,opo , 




Control 


^0 


10 


1 


1 


1 


2 


] 




2 



Time of day 

Fig. 59. Effects of the Rays from Radium of various Activities on the Rate of 

Alcoholic Fermentation. 



Experiment 88 

A yeast mixture was prepared by mixing thoroughly a piece of 
compressed yeast weighing i gm. in 100 c.c. of water, and filling 
the fermentation tubes with equal amounts of the mixture. Into one 
of the tubes was placed the radium bromide (1,800,000 x ) in the 
sealed glass tube, the other served as the control. 

In the following table are recorded the observations of the volumes 
of gas evolved in each tube. 

*The temperature is indicated in figure 59. 



212 



EFFECTS ON ALCOHOLIC FERMENTATION 



Time 


RaBr, 

1,800,000 X 


Control 


Te 


mp. ° C 


2 : oo 


0.00 


0.00 




30 


2:30 


2.00 


1-75 




30 


3:00 


10.00 


7.00 




31 


3:30 


15-50 


12.00 




29 


4: 00 


20.50 


16.00 




31 


5 : 00 


34.00 


23.00 




33 



The acceleration, following exposure to the rays, is shown in 
FIGURE 60. 

°a c.c. 

36 
32 
28 
24 



30' 
26' 



20 



16 
12 



E 


xpenment 8 


5. 




0-/-"" 






Temp- 




^<- 


f%^ 


-^ 






.-^ 




-^^ 















Time 



Fig. 60. Acceleration of Alcoholic Fermentation by Rajs from Radium of 1,800,000 

Activity. 

Experiment 89 

To ascertain the effect of exposing yeast-cells [Saccharomyces)\.o 
the rays of radium before fermentation began, i gm. of a Fleisch- 
mann's compressed yeast-cake was pressed closely around the end of 
three sealed glass tubes containing, respectively, RaBrg of 1,500,000 
activity ; RaBr2 of 10,000 activity ; and an empty glass tube. 

After an exposure of 20 hours to the rays of radium, the yeast 
was removed from the tubes, and each piece was placed in a beaker 
containing 100 c.c. of a 10 per cent, solution of cane-sugar. After 
thoroughly mixing the yeast in the solution, three fermentation tubes 
were filled with the mixture from each beaker respectively, and 
placed in the thermostat oven. Readings of the scale showing the 
evolution of gas due to fermentation were recorded as follows : 



EFFECTS ON ALCOHOLIC FERMENTATION 



213 





RaBr, 


RaBr, 




Temp. 


Time 


1,500,000 X 


10,000 X 


Control 


°C. 


11:55 


0.00 


0.00 


0.00 


30 


2 :oo 


.89 


•55 


.68 


27-5 


2:30 


1.30 


1. 00 


1.00 


32.8 


4:00 


2.30 


I. So 


1-15 


30 


4:45 


2.65 


2.20 


1.20 


30 


5 -"oo 


2.90 


2.50 


1.20 


30 


5:45 


3.20 


2.90 


1.30 


30 


6:15 


3-40 


3.20 


1.30 


30 



A microscopical examination of portions of the mixture ex- 
posed to the radium of 1,500,000 activity, and from the control mix- 
ture, gave the following data concerning reproduction, as indicated by 
the number of yeast-cells having buds in the field of the microscope 
(B & L, 1 obj. and No. i ocular). Five counts were made as follows : 

RaBr^ 

1,500,000 Control 
30 12 

25 12 

25 25 

19 It 

32 14 



131 

, 26,2 



Av, 



74 
14.8 




12 3 

Days 

Fig. 61. Relative Rates of Alcoholic Fermentation in Saccharimeters that have 
been Several Times Exposed, in Previous Experiments, to Radium of 1,500,000 and 
10,000 Activities. 



214 effects on alcoholic fermentation 

Experiment 90 
In order to see if the fermentation tubes had been affected in the 
preceding experiments by the rays of radium, they were filled with 
similar amounts of a yeast mixture, made as already described, and 
placed in the thermostat oven without any radium preparations. 
Observations were recorded as follows of the volumes of gas given 
off in fermentation : 

1, 800,000 X 1,500,000 X 10,000 X Ra.-Tel. Control Temp. 



Time 


Tube 


Tube 


Tube 


Tube 


Tube 


°C. 


8:00 


0.00 


0.00 


0.00 


0.00 


0.00 


30 


9:30 


1.25 


1.30 


1.60 


1. 10 


1.40 


31 


10: 00 


1-95 


2.30 


2.60 


1.90 


2.ro 


30 


10:30 


2.22 


3.10 


3-50 


2.76 


2.60 


28 


II : 00 


2.80 


3-72 


4.16 


3.60 


3.00 


27-3 


11 : 40 


3-48 


4-63 


5.10 


4.66 


3-55 


26.7 


12 : 00 


3-90 


5.10* 


5-50* 


5.10 


390 


27 



15.60 20.15 22.46 19.12 16.55 

Fermentation in the tubes that have been used a number of times 
with the radium preparations is more vigorous than the normal 
(figure 61). The slower acceleration in the tube used with the 
strongest radium preparation (1,800,000 x ) is possibly due to the fact 
that this fermentation tube has only been used twice with the radium, 
while the others have been used 10 or more times. 

Summary 

When sealed glass tubes containing radium bromide of various 
activities, from 7,000 to 1,800,000, and radio-tellurium were inserted 
into fermenting mixtures of commercial yeast, the uniform result, as 
measured by the evolution of gas, was a stimulation of alcoholic fer- 
mentation. The same kind of result was produced by the celluloid 
rod coated with a Lieber's radium coating (10,000 x ). 

Observation of the rate of absorption of the evolved gas by the 
yeast mixture showed different results following exposure to the radium 
preparations of different activities. This is taken to mean, either 
that the products of fermentation varied, or that the yeast mixtures 
were differently affected by the unlike treatment, one or both. No 
definite explanation is attempted at this time. 

* Estimated. The surface of the mixture had moved off the scale. 



EFFECTS ON ALCOHOLIC FERMENTATION 215 

When portions of a Fleischmann's yeast cake of like weight were 
exposed to radium rays before being placed in a sugar solution to 
ferment, the exposure to the preparation of 1,500,000 activity was 
followed by acceleration of fermentation from the start and through- 
out, but, following exposure to the salt of 10,000 activity, there was 
an initial retardation in the rate of fermentation, followed by recovery 
and acceleration. The quantity of the less active salt in this experi- 
ment was about five times that of the more active. 

Microscopic examination showed that the budding of the yeast 
cells was considerably increased by exposure to the rays. 

The fermentation tubes were found to be affected by the rays 
after being used a number of times so as to cause acceleration of 
fermentation, even though no radium was present. Reliable re- 
sults, therefore, may be obtained only by using fresh tubes for each 
experiment. 



CHAPTER XV 

EFFECTS OF RADIUM RAYS ON TROPISTIC RESPONSE 

It has already been shown in Chapter II that radioactivity in air 
and soil is a factor in the normal environment of all plants, and, 
therefore, that both roots and shoots are doubtless in a condition of 
radiotonus. Hence it is probable, a priori, that plants possess a 
radiotropic sensibility, enabling them to detect differences in either 
the direction or the intensity of the rays, and to respond to a uni- 
lateral stimulus of this kind. Moreover, since radioactivity is an 
environmental factor, such responses would be likely to be of an 
adaptive character. For example, the radioactivity of the soil is 
more intense than that in the air ; therefore, within limits of inten- 
sity such that the rays do not become injurious to the tissues and 
produce a traumatropic response, we should expect the root to be 
positively radioti^opic and the shoot negatively so. 

In December, 1907, I very briefly discussed the probability of 
the existence of a true radiotropism, stating* that tropistic curva- 
tures, being reactions to a stimulus felt unilaterally, could be called 
forth by radium rays only with difficult}^ since the rays would 
ordinarily pass entirely through the tissues, and thus fail to be fel^ 
as a unilateral stimulus. In this communication the fact was over- 
looked that the organs of a plant can detect differences in direction 
as well as intensity of stimulus. Thus, as Pfeffer^" has pointed out, 
gravity is felt with equal intensity throughout the diameter of a hori- 
zontally placed root, but its direction is perceived, and responded to. 
In like manner the root or shoot might be able to detect the direction 
of the radium rays, however slight might be the difference in their 
intensity on opposite sides of the organ. 

In this chapter there will be briefly treated, first, the effects of 
the rays upon normal tropisms ; second, a brief experimental investi- 
gation of the existence of a true radiotropism. 

I. Effects of the Rays on Normal Tropisms 
Experiment 91 
To ascertain the effect of the exposure of dry seeds to radium 
rays on the geotropic response of the shoot, 5 grains of " Hickory 

216 



EFFECTS ON TROPISTIC RESPONSE 2l7 

King " corn {Zea Mays) were exposed to the rays from RaBr2 of 
1,500,000 activity for 45 hours, and to the rays from RaBrg of 
1,800,000 activity for periods of 24^ hours and 27 hours, by being 
placed in contact with the sealed glass tube containing the radium salt. 
The grains thus exposed, together with a control set of five 
grains, were planted without soaking in similar pots of soil, and kept 
under similar conditions. The average heights of the seedlings were 
recorded as follows : 

May 29 (4 days after planting). 

4§ Hours 2J Hours 24.^ Hours Control 

3.75 mm. 2.00 mm. S-oo mm. 8.00 mm. 

May 30. 



10.30 mm. 10.00 mm. 9'5o mm. 15*25 "i 



m. 



June 2. 

47.60 mm. 33-00 mm. 18.20 mm. 72.80 mm. 

On this date three of the seedlings from the seeds exposed for 
45 hours (1,500,000 x) had partly ceased to respond normally to 
the stimulus of gravity, and four of the seedlings in each of the cul- 
tures exposed to the radium of 1,800,000 activity had wholly or partly 
ceased to grow erect. On June 7 observations were recorded as 
follows : 

45 Hours 2^ Hours 24. § Hours Cofitrol 

165.00 mm. 133.00 mm. All have ceased 273.00 mm. 

243.00 12.00 (ceased growth) growth since about 2 244.00 

139.00 147.00 (etiolating) days ago, except one; 205.00 

20.90 25.00 (ceased growth) heightofthatoneequals 217.00 

188.00 60.00* 162.00 mm., with par- 163.00 

7^."^ mm. 3^7:^ mm. ^'^^ ^^^^ «^ P«^^^' ^^ 1102.00 mm. 

151.00 mm. 75.40 mm. make chlorophyll. 220.40 mm. 

The radium of 1,500,000 activity, though applied for nearl}' twice 
as long as that of 1,800,000 activity, has retarded germination and 
growth much less than the stronger. In the case of the radium of 
1,800,000 activity, a difference in the length of exposure of 2.5 hours 
was at first followed by no marked difference in results, though sub- 
sequently a decided difference was noticeable. 

* Has ceased to grow erect. 



2l8 



EFFECTS ON TROPISTIC RESPONSE 



Experiment 92 

In order to ascertain the effect on geotropic response of growth 
in an atmosphere containing the radium emanation, 7 germinated 
pea seeds [Piswn sativum), were placed horizontally in conditions 
suitable for further growth, under a glass bell-jar containing the 
radium emanation as described in Experiment 45 (p. 152). In the 
control jar (no radium emanation) were similarly placed 8 seeds. 




Fig. 62. Experiment 91. Absence of Geotropic Response (Pot 27) in Shoots of 
Zea Mays following Exposure of the Grains, before Planting, to Radium Rays: 45 
exposed to Radium of 1,500,000 X ; 27 and 24 to 1,800,000 X- Cf. figure 14. 



After 24 hours 5 of the 7 exposed seeds were found to have curved 
geotropically, and 7 of the 8 control seedlings. 

The experiment was repeated, using 6 germinated pea seeds 
under each bell-jar. After 24 hours all of the seeds showed posi- 
tively geotropic curvatures in both cultures (except one seedling in 
the control jar which became injured), but the radicles exposed to 
the emanation have grown slightly more than those of the control. 

Exposure to radioactivity as described appears to have no influence 
on geotropic sensibility, so far as can be detected by observing the 
growth curvature. The response, however, being a function of 
growth, may be varied according as the rate of growth is modified 
by the rays. 

To further test the effect of the rays on geotropic response, 5 un- 
soaked grains of " Hickory King" corn {Zea Mays) were exposed 
in contact with the sealed glass tube of 10 mg. of radium bromide 
of 1,800,000 activity for 12 hours. Eight days after the exposed 
seeds had been planted in soil, they showed less than one half the 
growth in length of control seedlings, and two of them had failed 
to grow erect, and lay horizontally over the surface of the soil. 
They were perfectly turgid and hence failure to keep erect could 



EFFECTS ON TROPISTIC RESPONSE 219 

not be attributed to loss of turgor.* In two other cases failure of 
corn seedlings to grow erect followed an exposure of the dry grain 
for 27 hours to the same radium-tube. f 

These observations merely show that, under the conditions of ex- 
posure, the irradiated seedlings failed to grow upright as normally 
under the stimulus of gravity, and an examination of the tissues 
showed that, even if the stimulus has been perceived, response would 
have been practically impossible on account of the slight development 
of mechanical tissue, and other histological abnormalities. | 

Czapek^ has proposed a chemical test for the perception of gravi- 
tational or other tropistic stimulus. If the stimulus is perceived, an 
anti-ferment is developed in seedlings of Lupiyius albus and Zea 
Mays, which inhibits the complete action of tyrosinase. This anti- 
ferment is produced whether the organ responds by a curvature or 
not, as when a seedling is rotated horizontally on the clinostat. 
Even such a test would make it difficult to determine whether radium 
rays caused a loss of geotropic sensibility, for the rays might directly 
affect the ability of the protoplast to elaborate the anti-ferment when 
subjected to gravitational stimulus. 

No experiments were performed with the express purpose of 
studying the effect of the rays on phototropism, but observations of 
all exposed plants in other experiments failed to indicate any loss of 
sensitiveness to the unilateral stimulus of light rays. Shoots of seed- 
lings from seeds exposed to radium rays of varying degrees of activity 
and for various durations of exposure, manifested phototropic re- 
sponse. This is in full agreement with observations reported by 
Koernicke,^ who found that both roots and shoots of Via'a Faba, 
Lupinus albus, and Ptsum saiiviun, grown from seeds exposed to 
radium rays, were both geotropically and phototropically sensitive 
so long as growth continued, but not afterward. Radium stimulus, 
therefore, does not seem to interfere with sensitiveness to any other 
stimulus except in so far as it lowers or raises the general vitality of 
the protoplast as a whole. 

2. Can Radium Rays cause Tropistic Response? 

Experiments made for the purpose of detecting the existence of a 

radiotropism, or power to respond tropistically to a unilateral stimu- 

*One of the seedlings, and also one exposed for only 7 hours and a third exposed 
for 27 hours showed a partial loss of chlorophyll from the leaves. 
t See p. 218. 
J For details see Chapter XVI. 



220 EFFECTS ON TROPISTIC RESPONSE 

lation by the radium rays, are referred to in Chapter II. Koernicke's ' 
experiments in this direction led to somewhat contradictory results, 
and he concludes that there is no response to the beta and gamma 
rays, but that, if the activity of the preparation is sufficiently strong, 
plants may bend toward the phosphorescent light of the preparation. 
He used Phycomyces nitens and Vicia sativa. 

I have tried very many experiments with a wide variety of spe- 
cies, but always with negative or indifferent results, so far as con- 
cerns the direct influence of the beta and gamma rays. Neither 
roots nor shoots growing in air have ever shown the slightest ten- 
dency to curve toward or from sealed glass tubes containing radium 
of various activities. 

The tropistic behavior of plants with reference to the electric cur- 
rent is a problem closely related to that of a possible radiotropism. It 
was Elfving^ who, in 1882, first experimentally established the fact 
that roots grown in water or in sawdust may bend toward the posi- 
tive electrode, and he introduced the term " galvanotropic " to desig- 
nate this property. Twenty years later. Plowman^ published a 
paper dealing with the same question, and confirming the correct- 
ness of Elfving's results. In 1904 he ^ proposed the term " electro- 
tropism " as being more appropriate than galvanotropism. He found 
that negative charges of electricity " stimulate" and positive charges 
" paralyze" the embryonic protoplasm of the plants used, and there- 
fore explained the electrotropic curvatures as due to the retarding 
effect of the positive anions on one side of the root, and the acceler- 
ating effect of the negative cations on the opposite side. This inter- 
pretation is in harmony with results obtained by Matthews" with the 
sciatic nerve of the frog. Matthews inferred that, "It is not the 
charge, but its motion and sign, which ultimately determines its 
action," and reached the conclusion that chemical stimulation, light 
stimulation, and electrical stimulation are identical in nature. 

While nothing but failure followed all of my attempts to secure a 
direct tropistic response to radium rays, it was thought that, if these 
rays could be employed as ionizers of salts in solution, like the elec- 
tric current in the experiments of Elfving and Matthews, tropistic 
curvatures could be thus indirectly induced.* In essentials most of 

*The entire question of the effect of radium rays on salts in solution needs further 
experimental investigation. In 1902 M. Curie' stated that the rays act on liquid 
dielectrics as on air, rendering them conductors to a slight degree. Kohlrausch,^ how- 



EFFECTS ON TROPISTIC RESPONSE 



221 



the experiments were arranged on the same plan, except for the 
nature of the Hquid, and the distance of the radium from the roots. 

Experiment 93 

Roots of Lu^inus albus were immersed in a glass dish of tap- 
water to a measured length of 10 mm. On account of the size of the 
seeds and the method of suspending them it was not practicable to 
employ more than two or three seeds at a time. A sealed glass tube 
containing 52 mg. of radium bromide of 10,000 activity was then 





Fig. 63. Fig. 64. 

Experiment 93. Curvatures of Root-Tips of Lupinus albus toward a sealed Glass 
Tube of Radium Bromide in Water (figure 64), and in a nutrient Solution 
(figure 63). 

suspended by threads so as to lie horizontally in the water with 
the salt distributed evenly over the bottom of the tube. The latter 
was placed in numerous trials at distances of from 2-25 mm. from the 
tips of the roots. At a distance of 25 mm. no effects were observed, 
but at distances of from 10 to 2 mm. curvatures took place toward 
the tube. Photographs of two of these trials are shown in figures 
(iT^ and 64. The results in figure 63 are quite similar to the electro- 
tropic curvatures figured by Plowman. In this instance the tap- 
water was replaced by a nutrient solution made according to direc- 
tions given on page 85 of MacDougal's Elementary Plant Physiology. 
No constant differences were observed between the curvatures in 
tap-water and culture solution. 

ever, in the following year, stated that the electrical conductivity of water was not 
altered by exposure for a short period, but was slightly increased by exposure for as 
long as two days. The question is referred to further in Chapter XIX. 



222 EFFECTS ON TROPISTIC RESPONSE 

These curvatures are explained, not as responses to the direct in- 
fluence of the radium rays, but as due to chemical ions produced by 
the rays in the liquid. It is probable that the exciting negative 
cations, travelling faster than the depressing, positive anions from the 
neighborhood of the tube toward the roots produce the curvature 
toward the tube by stimulating growth on one side. By this hypoth- 
esis the results are brought into harmony with those of Elfving and 
Plowman. It also follows that we have not here evidence of a true 
radiotropism. If such a tropism, either positive or negative, is pos- 
sible, it has yet to be demonstrated. Theoretically, as pointed out 
above, we are led to expect its discovery. 

Bibliography 

1. Curie, P. Conductibilite des dielectriques liquides^ous I'influence des 

rayons du radium et des rayons de Rontgen. Comp. Rend. Acad. 
Sci. Paris 134: 420. 1902. 

2. Czapek, F. The anti-ferment reaction in tropistic movements of plants. 

Ann. Bot. 19: 75. 1905. 

3. Elfving, F. Ueber eine Wirkung des galvanischen Stromes auf wach- 

sende Wurzeln. Bot. Zeit. 40: 257, 273. 1SS2. 

4. Gager, C. S. The probability of a radiotropic response. Jour. Biol. 

Chem. 4: xliii. 1908. Proc. Soc. Biol. Chem. i: 137. 190S. 
Science, N. S. 27: 331. 1908. (Title only.) 

5. Koernicke, M. Weitere Untersuchungen iiber die Wirkung von Ront- 

gen- und Radiumstrahlen auf die Pflanzen. Ber. Deut. Bot. Ges. 
23: 324. 1905. 

6. Kohlrausch, F. Beobachtungen an Becquerelstrahlen und Wasser. 

Verhandl. Deut. Physikal. Ges. 5: 261. 1903. 

7. Matthews, A. P. The nature of nerve stimulation and of changes in 

irritability. Science, N. S. 15: 492. 1902. 

8. Plowman, A. B. Certain relations of plant growth to ionization of the 

soil. Am. Jour. Sci. 14: 129. 1902. 

9. . Electrotropism of roots. Am. Jour. Sci. 18 : 145,228. 1904. 

10. Pfeffer, W. The physiology of plants. Eng. Trans, by A. J. Ewart. 

3: 216. Oxford, 1906. 



CHAPTER XVI 

HISTOLOGICAL EFFECTS OF THE RAYS OF RADIUM* 

The discovery of the fact that, following certain conditions of 
exposure to the rays of radium, growth is retarded, raises the question 
as to how the effect is produced. Several alternatives are suggested, 
involving the various factors concerned in the normal growth of an 
organism. If we disregard the numerous attempts at a rigid defini- 
tion of growth, at least four such factors are to be considered: (i) 
increase in the size of the cells ; (2) increase in mass ; (3) cell- 
division;! (4) cell-differentiation. 

Therefore when the growth of a plant or of a plant organ is 
diminished by any agency, the result may theoretically be accom- 
plished by a retardation of any or of all of these four factors. 

As to the effect of radium rays on constructive metabolism and 
resulting increase in mass we have no definite information as yet. 
My own experiments on the subject have so far yielded negative 
results. The same must be said in regard to the effect of these rays 
on osmosis, turgidity, and consequent cell-enlargement. 

With reference to cell-division, however, we have more to say. 
It is known, for example, that karyokinesis may not only be inter- 
fered with, but completely inhibited by exposure to radium rays. 
The experiments demonstrating this are described in Chapters II 
and XVII. The presumption, then, is in favor of the theory that 
retardation or cessation of growth may be due in part to either 
partial or complete inhibition of cell-division. A histological exami- 
nation of the tissues of plants that have suffered retardation of growth 

*The substance of this chapter was given before the bi-weekly Botanical Conven- 
tion of the New York Botanical Garden, April i, 1908. 

t Of course cell-division and cell-differentiation are not a part of growth proper, 
but the discussion of this question need not be taken up here. Growth I would define 
as increase in size, or increase in mass, one or both, with or without an accompanying 
change of form. Cell-division is a factor because the number of the cells present modi- 
fies the amount of growth possible for the given tissue or organ. Cell-differentiation 
is a factor because it may modify the rate of growth. If a tissue rapidly matures (cell- 
differentiation), growth will rapidly cease. The longer the growth period of any given 
tissue or organ the slower the process of cell-differentiation in that tissue. 

223 



2 24 HISTOLOGICAL EFFECTS 

by the rays confirms the correctness of this presumption, and, at the 
same time, discloses the important part played by cell-differentiation. 

In PLATE I are given reproductions of photomicrographs of 
cross-sections of the hypocotyl and roots of seedling lupines {Lupintis 
albus). Figure D shows the normal appearance of a fibro-vascular 
bundle and the adjacent tissues in the hypocotyl ; A and B the 
corresponding region in the hypocotyl of plants grown from seeds 
that were exposed for 72 hours, while dry, to rays from radium 
bromide of 1,800,000 activity. After this exposure the seeds were 
planted in soil. The seedlings were those of Experiment 27 (p. 121). 
On the same plate, C illustrates the appearance of the corresponding 
region of the hypocotyl of one of the exposed plants of Experiment 
29 (p. 127). This plant was grown from seeds exposed for 91.5 
hours, while dry, to rays from radium bromide of 1,800,000 activity. 
The section was taken fourteen days after planting in the soil. 

In D the fascicular and interfascicular cambium is well devel- 
oped, as are also the phloem and xylem regions of the bundle. 
Comparison of A with D discloses profound modifications of these 
tissues. In A the cambium is entirely absent, all of its cells apparently 
having been differentiated into either phloem or xylem. The com- 
plete disappearance of the cambium clearly indicates a total inhibition 
of cell-division in that tissue. No new cells have been formed to 
replace those that have been transformed. 

This effect was to be expected, being in harmony with the results 
of other investigators which show that the tissue most susceptible to 
radium rays is the embryonic. Thus Danysz * found that if i eg. 
of radium (activity not given), in a glass tube, was placed above the 
backbone and part of the cranium of a mouse one month old, phe- 
nomena of paresis and ataxia were produced in about three hours. 
Under a similar exposure a mouse three to four months old died with 
the same symptoms in three to four days, while a one year old mouse 
survived for from six to ten days.f The less mature tissue was 
the most quickly affected. The same author f found the epithelial 
tissues of young animals more sensitive than those of adults. The 

* Danjsz attributed this result to the fact that, in the joung mouse, the rajs had 
to pass through cartilaginous tissue before reaching the cerebellum, whereas, in the 
older specimen, this tissue had become transformed into bone. It is possible also that 
the greater resistance of the older mice was due, in part at least, to the greater maturity 
of the nerve cells. 

t See Chapter II. and the bibliography there given. 



HISTOLOGICAL EFFECTS 2 25 

experiments of Bohn* on various animals, of Schaper * on the frog, 
of Zuelzer* on malign tumors, and of Hewlet * on cancer all indi- 
cate that embryonic tissues are more readily affected by radium rays 
than are mature tissues. 

Now tissue-differentiation is distingruished from cell-division 
(tissue-formation) on the one hand, and from growth on the other. 
It is a function of maturity. The greater the degree of tissue-dif- 
ferentiation in any given species, the greater the maturity of the 
organ. The condition of the tissues in A, therefore, suggests that, 
as it were, the organ had become aged more rapidly following exposure 
to the radium rays. The youthful power of reproduction (cell-divi- 
sion) has been lost earlier than normally. It is also evident that, fol- 
lowing exposure to the radium rays, the cells in the regions of the 
xylem and the phloem are smaller, and in every way less perfectly 
developed than normally. 

In B is shown a cross-section of the hypocotyl of another plant 
of the same Experiment (No. 27, p. 121), exposed precisely as was 
A, and also of the same age as I?. Here the cambium is still 
present, though within the bundle it is being differentiated. Xylem 
and phloem are less perfectly developed than normally. 

Still a third variation in result is seen in C. Here again the cam- 
bium has disappeared, being entirely transformed into xylem and 
phloem. In the phloem-region of the bundle there has been more 
differentiation of tissue than in either A or B. 

Figures ^ and /^illustrate sections of the roots from plants of 
Experiment 29. ^is from a control (normal) plant. In ^ the ex- 
posure of the seed was for 72 hours to rays from radium bromide of 
1,800,000 activity. As in the case of the hypocotyl, the cambium 
has disappeared, the cells are smaller, and the tissues appear in every 
way abnormal. -f 

In PLATE 2, FIGURE A represents a cross-section of the hypo- 
cotyl of a Lufinus albus seedling grown from a seed exposed (Ex- 
periment 16, p. 99) to rays from a Lieber's radium-coated rod of 25,000 
activity during imbibition of water in moist sphagnum. The material 
was collected six days after the seeds were placed to germinate in the 
sphagnum, and the exposure to the rays was continuous during this 
period. The hypocotyls of the control plants {B) were nearly 7 mm. 
longer than those of the exposed specimens. 

* See Chapter II. and the bibliography there given. 
fThe distortion of the cells of the cortex is an artifact. 



2 26 HISTOLOGICAL EFFECTS 

Here, also, it is seen to be the cambium that is most profoundly 
affected. It has nearly, though not entirely, disappeared in the ex- 
posed plant, though some development of xylem and phloem has 
taken place. The cells of the cortex and pith are also smaller in the 
exposed plant than in the control. 

Figures C and D, plate 2, represent, respectively, cross-sec- 
tions of the roots of the same exposed and control plants as those from 
which A and B were taken. They show the same kind of result fol- 
lowing exposure to the radium. The cambium is lacking, and the 
cells of the cortex and pith are much smaller than normally. 

Figures E and E of the same plate (2) show cross-sections of 
the hypocotyl of the bean (^Phaseohis vulgaris)^ F oi 2. control plant, 
E oi 2i plant exposed (Exp. 15, p. 98) during imbibition and germi- 
nation in moist sphagnum, to a Lieber's coated rod of 10,000 activity. 
The section was made after growth under continuous exposure for 
five days. 

The most noticeable difference here is in the size of the various 
tissue elements, especially evident on comparing the cells of the cor- 
tex and pith. The cambium has practically all disappeared from 
both the exposed and the control plant, though traces of it are seen 
in the control, indicating a more tardy tissue-differentiation. The 
same kind of differences appear in figures E and F of pi-ate 3, 
which show cross-sections of the stem of two seedlings of Phaseolus 
vulgaris exposed (Exp. 19, p. loi) as were those of plate 2. In 
figures E and F (plate 2), growth took place entirely in darkness 
and in moist sphagnum, no foliage being developed, and no nour- 
ishment being supplied except tap-water. 

The contrast between figures C and D (plate 3) is most strik- 
ing. These figures represent cross-sections through the hypoctyls of 
seedlings of Phaseolus vulgaris of Experiment 11 (p. 95). The seed 
from which the seedling of C was developed was exposed for 24 
hours while dry, to the rays from a radium-coated rod, the rod being 
in contact with the seed. The activit}' of the rod was 10,000. At the 
close of the exposure the seeds were planted in the soil, and the seed- 
lings developed under the most favorable conditions of heat, light, 
moisture, and nutrition from the soil. The section is from the hypo- 
cotyl twelve days after planting. The average length of the hypocotyl 
above the surface of the soil was, for the plants from exposed seeds 
39.60 mm., for the control seedlings 59.25 mm. 



HISTOLOGICAL EFFECTS 2 27 

Two facts stand out clearly in comparing C with D. First the 
smaller size of the medullary and cortical cells in C, and second the 
greater thickness of the cortex in D. Cambium is present in both, 
but the xylem cells are much smaller in C, and here, also, histolog- 
ical differentiation is slightly more advanced, the cell-walls of the 
xylem being thicker in proportion to the diamater of the cells. These 
differences in details combine to give C the appearance of a more 
mature tissue-complex than D. 

If we compare the histology of the epicotyls, A and B (plate 3), 
of these same two plants, the same kind of differences are apparent. 
Though of precisely the same age (from time of planting to time of 
fixing), the tissue-differentiation of A is that of a more mature organ 
than that of B\ ducts and woody cells are more numerous, and the 
bast fibers are larger. The cells of the cortex are of about the same 
size in the two epicotyls. 

The FIGURES A, B, D and B^ of plate 4, show the structure 
of the leaves of seedlings of Zea Mays grown from grains exposed 
dry to rays from radium of 1,800,000 activity (10 mg.) for 47 
hours. The grains had their embryo-side in contact with the sealed 
glass tube containing the radium salt. These seedlings had almost 
wholly lost their power of responding to gravity by growing upright. 
Whether the capacity of perceiving the gravitational stimulus had 
been lost or not, we have no means of knowing, but a comparison 
of these sections with that of a normal leaf, shown at C, shows a 
profound structural modification. In D, for example, there is an 
almost entire absence of any mechanical tissue. 

Here, doubtless, lies the explanation of the failure to grow upright. 
Even if the gravitational stimulus had been perceived, response would 
have been difficult or impossible. 

In E the wider part of the section is through the midrib, the part 
of the blade to the left being wanting. Both D and B are from the 
same leaf, D being between the midrib and the leaf-margin. In B 
the epidermal layers appear to be hypertrophied, while in A there is 
both hypertrophy of the epidermis and atrophy of the mesophyll 
cells. In B the spongy parenchyma is greatly hypertrophied. 

Summary 
In the above examples, where exposure to the rays of radium was 
followed by retardation of growth, histological examination discloses 



228 HISTOLOGICAL EFFECTS 

a cessation of cell-division, an acceleration of tissue-differentiation, 
a decrease in the size of the cells, a lack of coordination in histo- 
genesis, either one or all in any given case. 

Decrease in the size of the cells may be due, either to diminished 
turgor or to relatively* less vigorous constructive metabolism. It is 
not possible at present definitely to say which, though, since no 
partial loss of tissue-tension, nor any other evidence of a loss of tur- 
gidity, has been detected, following exposure to the rays, a less vig- 
orous constructive metabolism appears to be the more probable cause. 

The first two effects mentioned, viz., cessation of cell-division and 
accelerated tissue-differentiation, have both the same significance, 
that is, early senescence. In such instances as those shown in 
FIGURE B^ PLATE I, and FIGURE D, PLATE 2, where the cambium 
cells have persisted, and retained their characteristic appearance, 
they have evidently ceased to multiply. 

It is true that, in each of these instances, the tissue-differentiation 
has not been vigorous, nor normal in any other respect, but the im- 
portant point to emphasize is that such differentiation has taken place. 
Embryonic tissue has either entirely disappeared or its units have 
lost the peculiar function of such cells, the power of reproduction. 
Every protoplast passes normally from a period of youth through 
maturity and old age to ultimate death. At each stage it manifests 
certain morphological and physiological features peculiar to that 
stage. In general, the period of youth is marked by both structural 
and functional plasticity both of which features gradually diminish 
and finally disappear as old age approaches and advances. 

Whatever picture we may try to form as to just what occurs in 
the protoplast when it is exposed to the rays of radium, the foregoing 
histological effects seem clearly to indicate that one of the ultimate 
results is an acceleration of the period of senescence. If this accel- 
eration proceeds gradually enough, the cells and cell-complexes 
may assume during growth, the various morphological configurations 
characteristic of the successive ages ; but if the acceleration is too 
rapid, physiological senescence is reached quickly, without the 
usually accompanying structural changes, while a sufficiently intense 
over-stimulus by the rays may be quickly followed by complete loss 
of vitality and death. 

In this connection it is interesting to recall the fact that old age 

* Relatively, that is, to either the destructive metabolism, or to normal construc- 
tive metabolism. 



HISTOLOGICAL EFFECTS 229 

finds histological expression in a diminished vitality and relative size 
of the nucleus. Careful measurements with an eye-piece micrometer 
of the size of cells and of their nuclei near root-tips of Zea Mays 
showed, as I have pointed out elsewhere,^ that in roots not exposed to 
radium rays, the cells at a given region near the tips averaged 8.25 
scale divisions, and their nuclei 2.75 divisions in diameter. This is 
the average of a number of cells taken from several different roots. 
Similar measurements of the same number of cells of roots exposed 
to radium rays, and at corresponding regions of the root, gave, for 
the average diameter of the cells, 6.10 divisions of the scale, and of 
the nuclei 2.17 divisions. In other words, the average diameter of 
the nucleus of the normal cells measured was 35.5 per cent, of that 
of the cell, while for roots of the same age, and similarly grown 
except for exposure to radium rays, the diameter of the nucleus is 
33-33 P*^'* cent, of the diameter of the cell. This is a cyto-morpho- 
logical expression of the fact that in tissues of the same " age," 
the period of senescence is reached sooner than normally after ex- 
posure to radium rays. Metchnikoff's" view, expressed by his state- 
ment, '-'■ 011 resume la senilite -par tin seul mot: atrophie,^'' though 
probably too narrow for a generalization, is quite in harmony with 
the observations just described. 

In discussing the problem of age, growth, and death, Minot^ has 
recently said that, " the growth and differentiation of the protoplasm 
are the cause of the loss of the power of growth," and that "The 
older we are the longer it takes us to grow a definite proportional 
amount." These statements, originall}'^ made with reference to the 
human organism, apply with equal force in the realm of plant physi- 
ology, and make it more readily seen how a retardation or even a 
complete cessation of certain processes may really be an expression 
of what is fundamentally a stimulation. The facts here reviewed 
substantiate the conclusion, drawn from other results,* that radium 
rays act as a stimulus to living -protoplasm. 

Bibliography 

1. Gager, C. S. Acceleration of the approach of senescence by radium 

rays. Torreya 8: 172. 1908, and Science, N. S. 28. 1908. 

2. Metchnikoff, E. L'Annee Biologique 3 : 256. 1897. 

3. Minot, C. S. The problem of age, growth and death. Pop. Sci. Mo. 

71 : 460. 1907. 
* See p. 157. 



CHAPTER XVII 

EFFECTS OF RADIUM RAYS ON NUCLEI AND NUCLEAR 

DIVISION * 

Some of the reactions of cells to radium rays have already been 
indicated.! Koernicke* was the first to investigate the influence of 
the rays on nuclear division, and his results, noted on page 65, need 
not be restated here. 

My own experiments were made with root-tips of Zca Mays (aerial 
roots) and Allium cepa. Negative results, so far as mitosis is con- 
cerned, were obtained with the corn, as the nuclei, in the control as 
well as in the exposed plants, proved to be not dividing at the time 
the material was collected and fixed. The effect of the rays on the 
relative size of the nuclei in the corn was observed, and has been 
described on page 229. 

Root-tips of Allium cepa, grown from bulbs in a moist chamber 
in the dark, were exposed by placing the sealed glass tubes of radium 
bromide close to, but not touching them. Thus, as previously ex- 
plained, only the beta and gamma rays were effective, the alpha rays 
being screened out by the walls of the tube. Roots for control were 
grown under precisely similar conditions, except for the absence of 
radium, and were collected and fixed at the same time and in the 
same manner as those irradiated. 

The material studied was exposed, in part, as follows : 

A. For 7 hours 20 minutes to RaBrg of 10,000 x . Collected 
at 7 : 20 P. M. 

B. For 52 hours 30 minutes to RaBrj of 10,000 x . Collected 
at 3 : 20 P. M. 

C. For 8 hours to RaBr, of 10,000 x . Collected at 4 P. M. 
Other conditions of exposure are mentioned later. 

Our incomplete knowledge of the periodicity of cell-division in 
the onion leaves some doubt as to the best hour for collecting material 
in order to secure the largest nuhiber of divisions. The subject was 

*The substance of most of this Chapter was given before the Botanical Society of 
America at the Chicago meeting, December, 1907. 
tPp. 181, 187, and 229. 

230 



EFFECTS ON NUCLEI AND NUCLEAR DIVISION 23 1 

first investigated by Lewis, ^ who found tliat, in normal light, the 
greatest percentage of dividing nuclei occurred at midnight, while in 
roots grown in darkness the lowest percentage was at midnight and 
the highest at 4 P. M. 

Kellicott^ reported the occurrence of two maxima and two minima 
in the rate of cell-division during 24 hours. A " primary maximum " 
was detected shortly before midnight (11 P. M), and a "primary 
minimum " about 7 A. M. " Secondary maxima " occurred at about 
I P. M., and "secondary minima " at about 3 P. M. No corre- 
spondence was observed between the rate of nuclear division and 
slight variations in temperature. On the basis of this fact the slightly 
higher temperature in the vicinity of the radium-tube has been dis- 
regarded as a factor in the following experiments. 

In Kellicott's experiments the roots were grown in moist sand or 
pine sawdust, while in those of Lewis they were grown in moist air. 
Since the latter method was adopted in the radium experiments, it is 
probable that the roots exposed as in B and C above, if not in those 
of ^, were collected at suitable hours for favorable results. At any 
rate division figures in all phases were very numerous in roots ex- 
posed in all three ways. 

It has not seemed necessary to give here normal division figures 
for comparison, as this process in the onion departs little from the 
typical karyokinesis of the higher plants, and its individual peculiari- 
ties are well known through the work of Schaffner,^* Nemec,'' Mer- 
riman,^ and Gregoire.^ Miss Merriman's observations indicate that 
the number of chromosomes in Allium cepa, commonly reported 
as 16, is not constant, and may vary from 10 to 30 or more. 
In one instance she figures as many as 38 in one nucleus. In the 
material used for the radium experiments the number, as shown in 
the figures (plates 5 and 6), was clearly more than 16, and as it 
appeared to vary in the normal, unexposed roots, any attempt to 
detect a variation in number as a result of exposure to radium rays 
was impractical. 

All the tissues exposed to the rays blackened more rapidly than 
those unexposed when placed in the Flemming solution for killing 
and fixing. 

* Subsequent cell-studies, as is well known, have not confirmed the occurrence of 
centrosomes in Allium cepa (or in any other higher plant) as reported by Schaffner. 
It is hardly necessary to add that no traces of such bodies were found in my material. 



232 EFFECTS ON NUCLEI AND NUCLEAR DIVISION 

An exposure of not longer than 6 hours and 45 minutes to radium 
bromide of 1,500,000 activity was sufficient to completely inhibit 
nuclear division, and a marked tendency to double nucleoli was 
shown in cells of roots thus exposed. In material exposed for 24 
hours to radium of the same strength similar effects were noted, and, 
in addition, the cytoplasm appeared disintegrated. 

In roots exposed for 8 hours to rays from radium bromide of 
10,000 activity, and collected at 4 P. M., the nuclei possessed an 
amoeba-like lobing that was not observed in the unexposed tissues 
(plate 5, FIGURES i-io). The nuclei in roots exposed for 7 hours 
and 20 minutes to the same preparation and collected at 7 : 20 P. M. 
possessed this same lobate appearance and contained from two to 
three nucleoli. In some instances the nucleoli appeared to be 
dividing (plate 5, figures 9-12). 

Practically all of the mitotic figures, in whatever phase, appeared 
distorted, or abnormal in some other way.* In almost ever3Mnstance 
the chromosomes advanced at unequal rates toward the poles of the 
spindle. Sometimes one or more chromosomes would appear to 
have been carried beyond the pole, and would then frequently fail to 
become incorporated in the daughter-nuclei (plate 5, figure 17 ; 
plate 6, figures 2, 5). Again there would be a lagging behind 
of some chromosomes near the equator of the spindle or at various 
points between the daughter-nuclei (plate 5, figures 16-18; 
PLATE 6, figures 5, 7-9). In some cells the chromosomes were 
displaced to one side of the spindle (plate 5, figure 17 ; plate 
6, figures 4, 7-10), while in others they were distributed with the 
greatest irregularity all along the spindle fibers from pole to pole 
(plate 5, figures 14, 15). Instances were numerous where one 
or more abnormally elongate chromatin masses would extend entirely 
across the spindle, connecting the two daughter-nuclei (plate 6, 
figure 5), or would possess the appearance of having been stretched 
and drawn out into a fiber at one end or in the middle (plate 6, 
figure 7). All combinations of these irregularities were found in 
individual nuclei. 

In figure 5 (plate 6), nine or ten chromatin masses (probably 
not all individual chromosomes) have failed to take part in the organi- 
zation of one of the daughter nuclei. Figure 2 (plate 6) illustrates 

*For an explanation of the conditions of exposure for the figures of plates 5 
and 6, see page 230. 



EFFECTS ON NUCLEI AND NUCLEAR DIVISION 233 

a condition frequently observed, where some of the chromosomes ap- 
pear to have been hindered in their advance to the poles, and project 
out from the mass of the daughter-nuclei along the spindle, extending 
almost to the equator. In figure 13 (plate 5) is shown a tend- 
ency of the spindle to separate into two independent and parallel 
portions, suggesting that, if the process had continued, two separate 
nuclei would have formed in each daughter-cell. This figure should 
be compared with figure i, plate 6. 

Frequently one or more of the chromosomes that failed to become 
incorporated into the daughter-nuclei would organize smaller, second- 
ary nuclei, thus giving the cell the appearance of being multi- 
nucleate. As many as six of these secondary nuclei were observed 
in some cells, in addition to the main nucleus (plate 6, figures 
I, 3, and 6). 

One of the most interesting variations observed is illustrated in 
PLATE 6, figure I. One nucleus had formed in one daughter-cell, 
and two in the other, all three appearing abnormal ; but, in addition 
to these, a group of chromosomes that failed to participate in the 
major mitosis, has organized a secondary nucleus near one wall of 
the mother-cell, and this nucleus has undergone an independent and 
tardy karyokinesis, the late telophase of which is shown in the figure. 
Possibly an early stage of this process is illustrated in figure 17, 
PLATE 5, and FIGURES 7 and 9, plate 6. 

Such an instance as this is some evidence that a multinucleate 
cell in material exposed to radium rays, may not always be correctly 
explained as due to amitosis. This variation also suggests interest- 
ing possibilities in connection with sectorial variation and bud-sport- 
ing, and this will be referred to later in Chapter XVIII. 

A number of exposures were made of ovaries of Henierocallis 
fulva and H. Ititea^ to rays from radium of various activities, but, 
for some unexplained reason, none of these ovaries, nor indeed of 
those on neighboring plants, set seed, and, as no other suitable plants 
were at hand in flower when the radium preparations were available, 
only negative results can be reported on these experiments. The 
effect of the rays on vegetable cells, however, as just described, con- 
firms Koernicke's* results with the pollen-mother-cells and embryo- 
sac-mother-cells of Lilitim fuartagon, and indicates the ability of the 
rays profoundly to modify indirect nuclear division. 



234 effects on nuclei and nuclear division 

Bibliography 

1. Gager, C. S. Effects of radium rays on mitosis. Science, N. S. 27: 

336. 1908. 

2. Gregoire, V. La structure de I'element chromosomique au repos et en 

division dans les cellules vegetales (Racines d'AUium). La Cellule 
23: 311. 1906. 

3. Kellicott, W. E. The daily periodicity of cell-division and of elongation 

in the root of Alliutn. Bull. Torrey Club 31 : 529. 1904. 

4. Koernicke, M. Ueber die Wirkung von Rontgen- und Radiumstrahlen 

.^uf Pflanzliche Gewebe und Zellen. Ber. Deut. Bot. Ges. 23 : 404. 
1905. 

5. Lewis, A. C. Contributions to the knowledge of karyokinesis. Bot. 

Gaz. 32 : 423. 1901. 

6. Merriman, Mabel L. Vegetable cell divisions in Allium. Bot. Gaz. 

37: 1 78. 1904. 

7. Nemec, B. Ueber die karyokinetische Kerntheilung in der Wurzelspitze 

von Alliuni cepa. Jahrb. Wiss. Bot. 33: 313. 1S99. 

8. Schaffner, J. H. Karyokinensis in the root tips of Allium cepa. Bot. 

Gaz. 24 : 252. 1898. 



CHAPTER XVIII 

EFFECTS OF EXPOSING GERM-CELLS TO THE RAYS OF 

RADIUM 

At the New York meeting of the American Association for the 
Advancement of Science (1906-7), I announced^ before Section G 
that certain results had been obtained by exposing egg- and sperm- 
cells of Onagra biennis to radium rays, and that these effects were 
character changes that gave promise, if inherited, of being of specific 
value. That is, the results visible in ten-weeks old seedlings war- 
ranted the expectation that the mature plants would differ from their 
parent so profundly and fundamentally as to exclude their inclusion 
within the species of the latter. Individual variation of certain char- 
acters would fluctuate about a new mean. If these modifications 
should prove to be transmitted in sexual reproduction, then the 
new form would be entitled to at least the rank of the " elementary 
species" of de Vries.* 

The species question, however, is here regarded as secondary to 
that of variation. By whatever method or combination of methods 
species are produced in nature, our immediate and fundamental 
concern should be with the causes and behavior of variations. Varia- 
tions are the materials out of which species are manufactured, and 
it is essential in experimental work to center attention on the under- 
lying question of variation before attempting to solve the problem of 
how nature handles these variations in the making of a new species. 
All this, in a sense, is a truism, but I state it here for the purpose of 
making it clear that I do not believe that I have experimentally pro- 
duced a new species. Nor indeed do I believe it probable that we 
shall ever do so in the laboratory, at least with the higher green 
plants. However much we may differ as to what a species is, the 
term, as now used in taxonomy, always refers to a groiif of organ- 
isms. The characters that distinguish the group as a grou^ are the 
truly specific characters, and they develop under the influence of 
forces that are not only physiological and ecological (in the strictest 
sense), but also geographical and cosmical. With these facts clearly 

* Or, following Britton's* terminology, to the rank of a " race." 

235 



236 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

in mind it seems almost self-evident that such a natural group of 
higher plants may not be artificially produced in the laboratory, nor, 
indeed, within the narrow confines of an experimental garden. 

But whether we may artificially produce a parent or ancestor of 




Fig. 65. Onagra biennis. Permanently x\rrested Development. The Ovary, after 
Pollination, was exposed for 53 Hours to the Rays from Radium Bromide (10,000 X) 
Contained in a sealed Glass Tube. Cf. figure 66. 

a species is quite another question. A species has distinguishing 
marks because the individuals that compose it have those marks, 
and the group as a whole is separated from other groups of the same 
systematic rank for at least two reasons : (i) Because its individual 
members differ from the individual members of the other groups, 
and (2) because these distinguishing characters, within the range of 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 237 

fluctuating variability, are transmitted from parent to offspring in 
sexual reproduction. 

The modification of a specific group, therefore, is an expression 
of the variation of one or more of its component individuals, and it 




Fig. 66. Omagra biennis. Permanently Arrested Development. The same Plant 
as is shown in figure 65, six Months later. Cf. figure 65. 

is clearly conceivable that the variation of only one individual, pro- 
vided it is of the nature known as discontinuous, and transmissible 
by heredity, would be quite sufficient material out of which to form 
a new specific group. 

It was from some such point of view as this that I undertook to 
see what would result on exposure of the germ-cells, male and 
female, of Onagra biennis to the rays of radium. I chose Otiagra 
biennis because it was the only species available when the radium 
could be had that had a pedigree, and of whose purity I was there- 
fore certain. I chose the germ-cells from a belief that, if they are 
uninfluenced by the environmental change, the resulting variation is 
not likely to be transmitted.* 

* Blaringhem/' ^'^ however, has reported the inheritance of certain monstrosities 
produced in Zea Mays, oat, barley, and other herbaceous plants by traumatisms, such 
as compression, torsion, and cutting. 



238 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

In the experiments here recorded the radium was used in the form 
of radium bromide of strengths of 10,000 and 1,500,000 activity, in- 
closed in sealed glass tubes, and also in the form of Lieber's radium- 
coated rods of 25,000 activity. Thus, as previously described,* by 
the use of the sealed glass tubes only the gamma rays and the more 
penetrating of the beta rays were available, while in the case of the 




Fig. 67. Otiagra biennis. Functionally asymmetrical Rosette. The Pollen was 
exposed for 21 Hours to Rays from Radium of 1,500,000 Activity contained in a 
sealed Glass Tube. Ovary not exposed. Cf . figures 68, 69, and 70. 

coated rods the « rays could act. The method of treatment was to 
tie the tube or rod so that it touched the ovary or anthers or both. 
*Cf. p. Si. 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 239 

In some of the experiments the ovary (egg-cell) only was exposed, 
in others the anthers (sperm-cell) only; in a third set both egg- and 
sperm-cells were treated. In each of these three cases the exposure 
preceded pollination and was discontinued after pollination. In 
still other cases exposure of the ovary was made after pollination 
with unexposed pollen, and again exposure of the ovary was made 
while it was maturing and the exposure continued after pollination 
and until fertilization was presumed to have taken place, or in some 




Fig. 6S. Otiagra biennis. Functionally Asymmetrical Rosette. Close Pollina- 
tion followed an exposure of both Ovary and Pollen to Rays from a Radium-coated 
Rod of 10,000 Activity for four Days. Cf. figures 67, 69, and 70. 



240 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

cases until the seed was mature. Throughout the experiments the 
usual precautions of pedigree-culture methods were followed, such 
as guarding with bags during pollination, and sowing in soil previ- 
ously heated sufficiently to kill all seeds it might contain. f 

Seeds gathered in September, 1906, after the various treatments 
described, were planted in soil in the propagating house, some in 
late September or early October, others in late January or early Feb- 




Fk9. 69. Oiiagra biennis. Asymmetrical Rosette. The Ovary was exposed before 
Pollination for four Days to the Rays from a Radium-coated Rod of 10,000 Activity ; 
Pollen not exposed. Cf. figures 67, 68, and 70. 

ruary, 1907. In no instance was germination completely inhibited 
by the radium treatment; that is, there was no case observed of fail- 
ure of any considerable number of seeds to germinate. The per- 
centage of germination seemed unaffected in any instance, though 

tSee Shull,i3p. 256. 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 24I 

rather more than usual variation was shown in the rate of germina- 
tion of seeds from a given capsule. In all the cultures there were 
seeds that did not germinate until two months after the appearance 
of the first seedling in the same culture. Nor did the plants from 
the seeds that germinated late vary more in structure than any of the 
others. 

One plant that followed exposure of the ovary after pollination 
with radium of 10,000 activity for 53 hours, never passed beyond the 
rosette stage. The stem elongated, lifting the rosette about 15 cm. 
above the surface of the soil, and one very short branch developed 
on the lower part of the stem (figure 65). The rosette persisted all 
winter after the plant was removed from the experimental garden to 
the propagating house, the old leaves dying and new ones forming. 
But the plant finally died soon after it was photographed in the fol- 
lowing spring (figure 66). There was here a complete loss of 
reproductive capacity, and a generally diminished vitality. Careful 
examination during transplanting failed to disclose any fungus dis- 
ease or other unfavorable circumstance that might account for the 
arrested development. 

Among other effects that followed exposure to the rays, the fol- 
lowing are worthy of mention : 

I. Functional Asymmetry : Figures 67 and 68 illustrate this. 
These rosettes show a variation in leaf-character which is doubtless 
not to be attributed to the influence of the rays, falling as it does 
within the range of fluctuating variability. The asymmetry of the 
rosette followed exposure of either egg- or sperm-cell, and was esti- 
mated to occur in about one per cent, of the plants. It may result 
from either a retardation of growth on one side or an acceleration 
of it on the other, presumably the former. 

In figure 69, however, is shown an asymmetrical rosette from a 
seed whose ovary had been exposed for four days to a radmm-coated 
rod of 10,000 activity. At the close of this exposure the stigma was 
pollinated with unexposed pollen. In this rosette the leaves on the 
more vigorous side are crisped, resembling the leaves of O. La- 
marckiana^ and some other species, but not typical in O. biennis. On 
the other side. of the rosette the leaves are of the normal biennis type. 
If we look upon the crisping as an expression of growth-vigor, then 
the asymmetry of this rosette is logically to be attributed to an accel- 



242 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

eration of growth on one side. Evidence warranting this interpre- 
tation is wanting in the case of the two rosettes first described. 

Asymmetry of the rosettes is not unknown in other species of the 
evening-primrose without special antecedent treatment,* but its fre- 
quency in the radium-cuhures, and more especially the subsequent 
behavior of the asymmetrical plants, and which is lacking in unex- 




Fig. 70. Onagra biennis. Functionally Asymmetrical Rosette from a Seed 
whose Ovary was exposed for 53 Hours after Pollination to Rays from Radium of 
10,000 Activity in a sealed Glass Tube. The Cauline Stem is beginning to grow 
horizontally, leaning toward the narrower Portion of the Rosette. 

posed specimens, seems to justify the inference that, in these in- 
stances the asymmetry is a result of the exposure to the radium rays. 
This subsequent behavior is illustrated in figure 70, which is a 

* MacDougal,* figure 13. A hybrid between O. Lamarckiana and O. biennis. 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 243 

photograph showing a later stage of development of a plant whose 
rosette was asymmetrical. The main stem is developing, but instead 
of growing vertically up, as normally, it is bent over, growing nearly 
horizontally. In each instance of this kind the stem bends over 
toward the smaller side of the rosette, showing that growth in length 
is more rapid on the other side of the plant. The photograph also 
shows that on this main stem the leaves on the more rapidly growing 
side are larger than those on the opposite side. The tip in such 
plants is usually turned up, apogeotropically, as shown in the figure, 
and the stem eventually begins to grow vertically. 

As to how the radium rays acted in order to bring about the 
effects just described, of course we do not know. That the asym- 
metry was not due to differences of illumination or to crowding is 
certain from the known conditions under which the plants were 
grown. Recalling the nutation of a growing stem, caused by the 
fact that the region of most rapid growth travels around the stem in 
a direction opposite to that of the nutation, it is possible that the 
asymmetry of the rosette and the bending of the stem is due to an 
inhibition of the migration of the region of maximum growth. Thus 
the effect is analogous to the modification of nutation by a unilateral 
stimulus in any tropism. 

2. Morphological Asymmetry : Superficially resembling func- 
tional asymmetry, are results of which figure 71 shows an example. 
Here the rosette is one-sided, but, on more careful observation, it is 
seen that the one-sided appearance is due to something more than 
mere difference in rate of growth. The leaves on one side of the 
plant are not onl}^ smaller than those on the other, but they are of 
different shape, being narrower in proportion to length, and with the 
margin of the basal portion not notched as normally. Furthermore 
the transition from the character of one side to that of the other is not 
absolutely abrupt. The individual leaves between the unlike sides 
are themselves asymmetrical, the side of the leaf next to the broader 
leaves of the rosette being wider from midrib to margin than the 
other side. The tips of these bilaterally asymmetrical leaves turn 
toward the narrower side of the leaf. 

Here, of course, is functional asymmetry, but because the form 
also is modified and the asymmetry thus accentuated, I have called 
this result morphological asymmetry . There is a qualitative as well 
as a quantitative difference. 



244 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

The morphological asymmetry was not confined to the rosette 
stage, but persisted throughout the entire life of the plant, giving 
narrow leaves on one side of the narrow upright stem, and on the 
secondary branches growing in their axils, and broad leaves on the 
opposite side and branches (plate 7, a different plant than figure 71). 




Fig. 71. Onagt-a biennis. Morphological Asymmetr}'. From a Seed developed 

in an unexposed Ovary whose Stigma was pollinated with Pollen exposed for 24 

Hours to Rajs from Radium of 1,500,000 Activity in a sealed Glass Tube. Cf. 
PLATE 7. 

The difficulty of explanation is greater here than in the former 
case. The rosette (figure 71), bearing leaves of both kinds sug- 
gests that a fertilized egg may have been unequally influenced by 
the radium rays, but such a condition is excluded by the fact that 
only the pollen was exposed. An untreated ovary was pollinated 
with pollen that had been exposed for 24 hours to the rays from 
radium bromide of 1,500,000 activity. There seem to exist in the 
germ-cells of this species two factors expressed in the mature organ- 
ism by a different ratio between the length and breadth of the leaves. 
Most frequently the broad-leaved type appears, while at times, under 
some unrecognized environmental stimulus, the narrow-leaved form 
results. The radium rays may affect this unit-character in either 
germ-cell, and, when we recall that, after fertilization, the male and 
female chromatins do not fuse until synapsis immediately preceding 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 245 

the reducing mitosis in the sporogenesis of the mature zygote, it is 
not difficult to imagine how a plant with two unlike sides might result 
from altering the nature of either chromatin-mass. 

In the normal production of an elementary form by mutation, the 
mutation is believed by de Vries,^^ to be " decided within the seeds." 
There is no experimental evidence, however, for not considering 
that, in sexual reproduction, the change may occur at any point in the 
life-cycle of the germ-plasm, at least from gametophyte mother-cell 
on, in either the maternal or the paternal line, or in both. 

We may conceive of the morphologically asymmetrical plant as 
the result of some such sequence of events as follows : 

1. A destruction (or change from a dominant to a recessive con- 
dition) by the radium rays, of the factor in the exposed pollen essen- 
tial for the production of the biennis type of leaf. 

2. By the fertilization of a presumably normal biennis egg by a 
sperm-cell from this pollen, an oosperm may result containing fac- 
tors representing different peculiarities of leaf-form from each 
parent. 

3. A unilateral expression of these peculiarities in the resulting 
plant. This step would result from a division of the fertilized Q.gg in 
its first and subsequent mitoses in such a way as to confine the mater- 
nal chromatin to one side of the organism and the paternal chromatin 
to the opposite side. This would offer a reasonable explanation, 
also, of the transitional leaves between the opposite halves, for the 
primordia of these leaves are probably composed of adjacent cells 
from each side of the plant, thus giving rise to the observed bilateral 
asymmetry of the leaves. The plant, then, so far as this one fea- 
ture is concerned, is really a hybrid between two elementary forms. 
The leaf-character of one of the parents has formerly existed only 
potentially in the male germ-cell, and finds morphological expres- 
sion for the first time in the offspring of the first generation. 

In " The Variation of Animals and Plants under Domestication," 
Darwin^ records the testimony of Salter who, he says, " informs me 
that at first a branch often produces variegated leaves on one side 
alone, and that the leaves are marked only with an irregular edging 
or with a few lines of white or yellow. To improve and fix such 
varieties he finds it necessary to encourage the buds at the bases of 
the most distinctly marked leaves, and to propagate from them 
alone." 



246 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

In his paper on infertile hybrids, Wilson ^'^ describes a zonal 
pelargonium-hybrid of interest in this connection. In making a 
cross between two variegated zonal pelargoniums, the variegation of 
the seed-parent, he says, was of the usual kind, "the peripheral 
zone of white enclosing a green center and sending into it pro- 
jections of more or less intense variegation. In the pollen parent 
the variegation, also white, occupied the center and margin of 
the leaves. . . . The seedlings resulting from the cross were in 
the majority of cases non-variegated and coarse. A few were 
variegated from the first, but only one has been made special note 
of. Its cotyledons were blotched with white, etc. . . . Very 
soon three distinct vegetative regions were differentiated in the 
seedling under discussion ; one including leaves with normal chlor- 
ophyll development, the next with variegated leaves, and the third 
with leaves quite destitute of chlorophyll. If a leaf arose in a plane 
between any two regions it embodied in itself features of both. . . . 
Ultimately a branch lying wholly in each region was produced. 
Variegation was only once seen in the green branch, a small patch 
of white occurring in one leaf. The variegation of the variegated 
branch was identical with that of the seed-parent. The albino 
portion showed marked persistence. . . . No trace of green was seen 
in the branches."* 

Here we have recorded the case of a known hybrid in which 
the characters entering into combination expressed themselves in 
such a way that only one set of characters appeared on one side of 
the plant, the other set on another side, while the organs in an 
intermediate position partook, in bilateral fashion, of both sets of 
characters. 

It is in view of the above facts and considerations that I believe 
that the morphologically asymmetrical evening-primrose is funda- 
mentally a hybrid, and that its asymmetry may be due to a segre- 
gation, in opposite sides of the plant, of the characters brought 
together in the cryptomeric crossing. 

One other possible explanation of this plant must not be over- 
looked, and that is an interpretation of it as a bud-sport in which 
only one half of the bud was affected. In this particular instance, 
and on this theory, the sectorial variation may be an expression of a 
change from dominancy to latency of some of the specific biennis- 

*The white portion was regarded as a parasite on the green portion. 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 247 

characters, the effects being distributed unilaterally throughout the 
plant as a whole because of the fact that the sporting occurred in the 
terminal bud of the entire shoot-system. Even so, the initiation of 
the sporting may be logically attributed to the radium rays, their 
effects being brought into the offspring through the sperm-cell. But 
thus we are brought back again to the idea of the plant as funda- 
mentally and essentially a hybrid. 

Possible Induction of Mutation : The appearance in the 
radium-cultures of elementary forms already recognized in normal 
pedigreed cultures was rather to be expected, and the occurrence of 
such a form is to be attributed to the influence of the rays only with 
great caution. A description and discussion of a few aberrant forms 
that appeared after the radium treatment follow. 

Among the progeny from an unexposed pistil whose stigma was 
pollinated with pollen that had been exposed to rays from radium 
bromide of 1,500,000 activity for 24 hours, there was found a seed- 
ling with unusually narrow rosette leaves. Some of the characters 
displayed by this plant at maturity are shown in the photograph, 
PLATE 8. The narrowness of the rosette leaves is seen to have 
persisted throughout the life of the plant. Furthermore its habit of 
growth differs considerably from that of a mature biennis. In numer- 
ous characters pertaining to the buds, petals, and mature capsules, it 
differs from the biennis type. The specimen closely resembles an 
elementary form observed by MacDougal ' in a normal pedigreed 
culture, and described by him as a mutant. Other plants like this 
one followed the treatment with the radium. 

The plant shown in plate 9 (5c of my cultures) is from seed 
produced in an unexposed capsule with the stigma pollinated with 
unexposed pollen, and then exposed to rays from radium bromide of 
1,500,000 activity for 48 hours after pollination. It differs, not only 
from the typical biennis, but also from the other variant forms ob- 
tained. Following is a systematic description of the plant,* together 
wilh the description of O. biennis as given in Britton and Brown's 
"Illustrated Flora." 

* I wish to express here my best thanks to Dr. John K. Small, of the New York 
Botanical Garden, for writing all of the sj'stematic descriptions in this chapter. They 
were written without any knowledge on Dr. Small's part of the antecedent history of 
the specimens. 



248 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

Onagra biennis Onagra jc 

Erect, generally stout, annual or Rosette leaves finely and sparingly 

biennial, simple and wand-like or pubescent, the larger ones i 2-14 cm. 

branched, i°-9° high, more or less long; blades narrowly linear-lanceo- 

hii^sute-pubescent, rarely glabrate. late, acuminate at both ends, undu- 

Leaves lanceolate, acute or acumi- late, much longer than the j^etioles ; 

nate, narrowed and sessile at the stems 7 dm. tall, with several rather 

base or the lowest petioled, repand- large ascending branches below the 

denticulate, i'-6' long; flowers spi- middle ; stem-leaves drooping ; blades 

cate, terminal, leafy-bracted, bright almost linear, often narrowly so, 

yellow, open in the evening, 1-2' tapering to both ends, entire ; bracts 

broad; calyx-tube slender, much similar to the stem-leaves, but slightly 

longer than the ovary, the lobes smaller; hypanthium about 40 mm. 

linear, contiguous at the base, re- long; sepals about 20 mm. long, 

flexed; capsules oblong, narrow fully one half as long as the free 

above, erect, pubescent, %'-i' long, portion of the hypanthium, the free 

2>^"-3" thick, nearly terete, seeds tips in the bud stout, 2.5-3 "'"^• 

angled. long; petals about 15 mm. long, 

retuse at the apex. 

Why, in the two aberrant plants described above, the entire speci- 
men showed the changed characters, instead of one half only, as in 
the case of the morphologically asymmetrical specimen, cannot of 
course be said. Possibly the pollen-grains were differently affected 
in the different exposures to the rays, possibly, and quite probably, 
the mitoses that followed fertilization were different, resulting in the 
one instance in a segregation of the parental chromatins, but not so 
in the other case, or possibly the eggs that were fertilized by the 
irradiated pollen were unlike, or there may have been a combination 
of any two or of all three of these possibilities. Attention should 
also be called to the fact that these aberrant forms may not be results 
produced by the rays of radium, but only spontaneous mutations, 
whose cycle happened to coincide with the time of the experiment. 

Of far greater interest were the two plants illustrated respectively 
in PLATE ID {loa of my cultures), and plate ii (ii<!; of my cul- 
tures). These plants are as unlike each other as they are different 
from the parent biennis^ or any of its hitherto observed mutants. 
The seed that produced loa came from a capsule exposed after pol- 
lination with unexposed pollen for 53 hours to rays from radium 
bromide of 10,000 activity. Both sperm- and egg-cells, therefore, 
were exposed to the rays. A description of the plant follows : 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 249 

Rosette leaves finely and rather copiously pubescent, the longer ones 
9-10 cm. long; blades oblong to oblong-spatulate, undulate, longer than 
the petioles; stems 3 dm. tall, with very long spreading branches on the 
lower part; stem-leaves spreading; blades oblong to oblong-linear, acute 
at the apex, shallowly undulate-sinuate; bracts similar to the stem-leaves 
but much smaller; hypanthium 35-45 mm. long; sepals about 15 mm. 
long or shorter, one half as long as the free portion of the hypanthium, the 
free tips in the bud stout, 1-1.5 mm. long; petals 15 mm. long, or smaller, 
nearly truncate at the apex; capsules columnar, slightly tapering to the 
apex, about 20 mm. long, rather broader than the bracts. (See plate 12, 
FIGURES f-k.) 

The second specimen (plates 1 1 and 12) is equally as distinctive. 
The spreading tips of the calyx in the bud (plate 12, figures c and 
d) indicate the pressure of the stigmatic lobes within, and in many of 
the buds these lobes force their way through the tip some time before 
anthesis, a feature seldom, if ever, observed in biennis, and favor- 
ing cross-pollination instead of the close pollination characteristic of 
biennis. The plant, about 6 dm. tall at maturity, produced flowers, 
fruit, and seed in great abundance. The leaves were of a slightly 
darker green than is usual in biennis, and both they and the bracts are 




Fig. 72. Onagra biennis. Radium Culture, No. I5rt. Two Rosettes, one narrow 
leaved, and one broad leaved, on one Tap-Root. Cf. figure 73, and plates 13 
and 14. 



250 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

strikingly thick and almost brittle. The radium was of 1,500,000 
activity, and the period of exposure 24 hours. With pollen thus 
treated the stigma of an unexposed pistil was pollinated, and this 
plant was from one of the resulting seeds. Below is the taxonomic 
description. 

Stem 6 dm. tall, with several erect-ascending branches from near the 
base, nearly as tall as the stem; stem-leaves spreading; blades lanceolate to 
oblong-lanceolate, acute at the apex, undulate-sinuate; bracts similar to the 
stem-leaves, but shorter and relatively broader; hypanthium about 35 mm. 
long; sepals about 15 mm. long, or shorter, fully one half as long as the free 
portion of the hypanthium, the free tips in the bud stout, about 1.^-2.5 mm. 
long; petals nearly 15 mm. long, notched at the apex; capsules columnar, 
more or less tapering at the apex, nearly 20 mm. long, much narrower than 
the bracts. (See plate 12, figures y"->^.) 

The most interesting and novel result of all was the plant shown 
in FIGURES 72 and 73, and in plates 13 and 14. The antecedent 
treatment was an exposure of the ovary for 24 hours to the rays from 
radium bromide of 10,000 activity, after which the stigma was pollin- 
ated with unexposed pollen. Among the young seedlings in the 
seed-pan, I thought I had detected one of the narrow-leaved variety 
growing close to a more typical plant. But when I started to separate 
the two plants for re-potting, I found that, instead of two plants, I had 
onl}' one, this one bearing two rosettes on the same root (figure 72). 
The anomaly cannot be called a bud-sport, as that term is generally 
used, unless, keeping in mind that the plumule is a bud, we decide 
that there was an early bifurcation in the developing embryo, of such 
a nature that, after the cotyledons were laid down, there was a divi- 
sion of the growing-point, accompanied by a separating out of antag- 
onistic characters, and resulting in the formation of two morpho- 
logically as well as physiologically different shoots. 

The seedling was very carefully freed from soil, and after 
thorough examination, the above conclusion seemed to be the only 
one warranted. There was absolutely no evidence that a lateral bud 
had formed early on the main stem. There were to all appearances 
two epicotyls, one in the axil of either cotyledon. This plant was 
carefully protected, and after it was transplanted into the experi- 
mental garden both rosettes sent up cauline stems, in which the dif- 
ferences, so marked in the rosettes, were continued (figure 73). 
One half of the plant, as is clearly shown in the illustration, was a 
typical O. biennis in every respect. The other and narrower leaved 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 25 1 



half, in general appearance and behavior, was similar to the narrow- 
leaved form described above, and illustrated in plate 8. This 
plant, in light of its method of treatment, offers evidence, in addition 
to what we already possess, that mutation is not confined to the period 
during and after fertilization, but that it may occur, or at least be 
initiated previous to fertilization, and in either the male or the female 
gamete. Taxonomic descriptions of the two halves of this plant 
(i5« broad and 15a narrow of my cultures) are appended. 



15a broad 
Rosette leaves finely and sparingly 
pubescent, the larger ones about 15 
cm. long; blades spatulate to ellip- 
tic-spatulate, sinuate-dentate espe- 
cially below the middle, often sharply 
or prominently so near the base, 
much longer than the petioles ; stem 
7 dm. tall, with elongate ascending 
branches on the lower part; stem- 
leaves mostly spreading ; blades nar- 
rowly elliptic, somewhat acuminate 
at the apex, sinuate-dentate ; bracts 
similar to the stem-leaves but smaller 
and usually broadest below the mid- 
dle; hypanthium about 35 mm. 
long; sepals about 25 mm. long, 
slightly shorter than the free portion 
of the hypanthium, the free tips in 
the bud subulate, 2.5-3.5 ^'^^^' loiig ; 
petals about 15 mm. long, nearly 
truncate at the apex ; capsules colum- 
nar, slightly narrowed to the apex, 
about 35 mm. long, much nari-ower 
than the bracts. 

A functional difference between the two halves is shown by the 
fact that after the broad-leaved half was entirely through flowering, 
the narrow-leaved portion still bore opening buds and flowers. The 
equivilancy of the two shoots was ultimately obscured by the more 
vigorous and rapid development of the broad-leaved half. 

Let us briefly consider this plant in light of the morphologically 
asymmetrical plant described on page 243. Here is also morpho- 



15^! narrow 
Rosette leaves finely and sparingly 
pubescent, the larger ones 10-12 cm. 
long; blades almost linear, acumi- 
nate at both ends, undulate, some- 
what longer than the petioles ; stem 
6.5 dm. tall, with relatively short 
ascending branches throughout ; 
stem-leaves mostly di'ooping ; blades 
narrowly linear-lanceolate to almost 
linear, tapering to both ends, undu- 
late-sinuate ; bracts similar to the 
stem-leaves but smaller; hypanthium 
about 45 mm. long; sepals about 30 
mm. long, fully as long as the free 
portion of the hypanthium, the free 
tips in the bud long-subulate, 3-4 
mm. long; petals about 20 mm. 
long, nearly truncate at the apex ; 
capsules almost columnar, about 25 
mm. long, slightly narrower than the 
bracts. 



252 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

logical asymmetry, more perfectly accomplished than in the earlier 
mentioned case, and participated in, not by the leaves alone, but by 
the entire shoot. In the former instance the entire main axis of the 
plant is presumably physiologically double, though structurally one, 
but in the latter plant the difference is expressed in the splitting up 
of the entire shoot-system into two main axes, each with its own 
secondary branches and characteristic foliage. 




Fig. 73. Ouagra biennis. Radium Culture, No. I5«, showing two distinct Shoots, 
morphologicallj unlike, on one Root. Cf. figure 77, and plates 13 and 14. 

As with the earlier described plant, this one may be interpreted 
as a kind of bud-sport, but calling it a bud-sport does not explain it. 
Bud-sporting in pedigreed plants is not unknown, and has been 
described for pedigreed evening-primroses by MacDougal,^ who says 
that a possible hybrid ancestry is indicated by the bud-sporting of 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 253 

*' Oenothera^'' * amnwpkila into characters of O. biennis. But where a 
seed-mutant of biennis, from carefully guarded seed, produced by a 
pedigreed plant, gave a bud-sport bearing the characters of the an- 
cestral type or true biennis, the significance of the bud-sporting as 
pointing to the hybrid nature of the plant seems to be excluded. 

However, in the cases of the morphologically asymmetrical plant 
and the plant with two diverse shoot-systems we know that, in the 
first case the sperm-cell and, in the second the egg-cell were sub- 
jected to a treatment (exposure to radium rays) which has the power 
to affect marked change in the chromatin, as is shown in Chapter 
XVII. We further know that such exposure has, in another experi- 
ment been followed by the appearance of a plant similar to a type 
that has previously appeared by spontaneous mutation. 

If one of the altered gametes takes part in an act of fertilization, 
the resulting zygote, as already suggested (p. 245), is fundamentally 
of hybrid nature ; as truly so, indeed, as when, without experimental 
treatment, a female gamete of one elementary form is fertilized by a 
male gamete of another. Whether the characters, represented poten- 
tially in the gametes by certain factors, have previously found ex- 
pression in a zygote in the direct ancestral line is immaterial, and, 
for the purpose in hand, of wholly secondary importance. A zygote 
is a hybrid, not because the parents of the fusing gametes are differ- 
ent, but because the gametes themselves differ. A mature plant of 
a mutant of O. biennis has been known to bud-sport into the parental 
ancestral form. If this mutation had taken place in one of the sperm- 
cells of a pollen-grain of this mutant, instead of in the primordium 
of a bud, and if subsequently a "true" biennis egg had been ferti- 
lized by that sperm-cell, the resulting zygote would, in reality, not 
have been a hybrid f at all, though its parents were distinct elementary 
species. Such a zygote might, however, be classed as a " crypto- 
hybrid " of Tschermak.^* At any rate we see that the two cases of 
the bud-sporting of Oenothera ammophila into a true biennis branch, 
and the production, by a seed-mutant of Onagra biennis, of a bud- 
sport bearing the ancestral characters, are capable of the same in- 
terpretation, viz., that the sporting plant in each instance was, in 

*This species {Oetiotkera am7nophila Focke, Abh. Nat. Ver. Bremen i8 : 182. 
1904) is closely related to Onagra biennis, but does not appear to have received a 
binomial name in Onagra, and it does not seem advisable to rename it here. 

tin the customary sense of the term. 



254 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

reality., a hybrid in which the unlike characters separated out in the 
course of the cell-divisions involved in the formation of a bud.* 

The nature of any germ-cell may be altered in one of three ways : 

1. By the acquisition of one or more new factors not previously 
present. 

2. By the change of any factor from the domination to the reces- 
sive condition, or from the recessive to the dominant. 

3. By the complete loss of one or more factors. 

It is hardly probable, reasoning from other known facts, that the 
acquisition of a new factor could be accomplished by exposure to the 
radium rays, but it is quite conceivable that, by such treatment, a 
factor might be changed from the dominant to the recessive condition, 
or that a complete loss of a factor might result. Shull's '^ experi- 
ments with hybrid beans led him to suggest the hypothesis that unit 
characters are determined by the simultaneous action of two or more 
dominant factors or units in the germ-cells, and " that the later 
specific or varietal derivatives were produced by the disappearance 
of one or more of these original units as a dominant characteristic." 
Thus, if the original character is determined by the dominant units 
ABCDEFGH, "the later derivatives may be ABCDEFGh, 
ABCDEFgH, ABCDE/gH, etc., through all the possible permuta- 
tions . . . This conception results in an interesting paradox, namely, 
the production of a new character by the loss of an old unit." 

This hypothesis seems to offer a plausible explanation of the pos- 
sible induction of mutation by exposing either one or both of two 
conjugating gametes to the rays of radium : and furthermore it dis- 
closes a possible mechanism, such as is demanded by the theory that 
the morphologically asymmetrical plant (figure 71) and the specimen 
with two shoot-systems (figures 72 and 73), though falling under the 
head of bud-sports, are fundamentally hybrids. Here also lies the 
warrant for at least one interpretation of the significance of bud- 
sporting, in general, as pointing to the fundamentally hybrid nature 
of the organism thus sporting. This, by no means, excludes the other 
interpretation of a bud-sport as a mutation, pure and simple, taking 
place in the somatic cells during the formation of a bud, rather than 
at some stage in the formation of the germ-cells. 

*This discussion was written in December, 1907, before the appearance of East's^ 
paper on bud-variations (April, 1908). Metcalf ^^ has also recognized that bud-variation 
and seed-variation are practically identical. 



EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 255 

In conclusion then, the double plant may be interpreted as, in 
reality a hybrid between elementary forms, the characters of one of 
which had had expression only potentially in the conjugating gamete. 
In normal cases of hybridity every cell in a given plant of the first 
generation resulting from the cross is of hybrid nature. The charac- 
ters of the two parents are diffused throughout the entire organism, 
though, in Mendelian cases, they may segregate in the I^^ and sub- 
sequent generations, according to the well-known laws of Mendel. 
But, in the case of the double plant, segregation of characters 
occurred before the embryo was complete. Not every cell in the 
mature plant, then, is of hybrid nature (considering merely the 
characters that distinguish the two shoot systems), though hybridity 
may be postulated of the organism as a whole. 

Discussion of the possible causes that might produce a plant with 
two different shoot systems on one root should not be closed without 
reference to the case of anomalous mitosis illustrated in plate 6, 
FIGURE I, and described on page 233. There it is seen that two 
mitotic spindles have developed within one cell. Without going into 
details, it is merely noted here that such a result in nuclear division 
suggests that some such departure induced in a fertilized egg-cell by 
radium rays, might have been the first step in the production of the 
double plant of Onag7'a biennis. 

Heritability OF Induced Changes : Carefully guarded, and 
also unguarded* seed, of the aberrant forms 10a, 11b, i^a broad, 
and i^a broad x i$a narrow were collected, and the second gen- 
eration of plants is now (June, 1908) under observation. Attempts 
to secure seed from 15a narrow were unsuccessful, as were also 
attempts to cross this form with pollen from 15a broad. Seed was 
obtained, however, by crossing i^a broad with pollen from i^a 
narrow, but only one seedling from this cross appeared in the seed 
pan. 

Thus far inheritance of the variations is manifested in only one 
instance, viz., 11b. Two plants in the second generation, from 
unguarded seed resemble the parent in every fundamental character, 
while a third resembles it in every way except in the flower-bud, 
where the character of the stout, spreading tips of the sepals is lack- 
ing, being replaced by the biennis character. It is proposed to con- 

* Mj absence from these plants at the time the seed was maturing resulted in the 
failure to secure carefully guarded seed in some instances. 



256 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 

tinue the observations over the second generation of both lib and I5« 
broad x i$a narrow. It must be concluded, then, that most of the 
variants were not true mutations, and that further evidence is needed 
before we may say with entire confidence that mutation may be 
induced by the stimulus of radium rays. 

Bibliography 

1. Blaringhem, L. Production par traumatisme d'anomalies florales dont 

certaines sont hereditaries. Bull, du Mus. d'Hist. Nat., No. 6, p. 
399. 1904. 

2. . Anomalies hereditaires provoquees par des traumattsmes. 

Compt. Rend. 140 : 37S. 1905. 

3. . Mutation et traumatismes. Pp. 1-239, P'* i-viii. Paris, 1907. 

4. Britton, N. L. The genus Ernodea : A study of species and races. 

Bull. Torrey Club 35: 203. 1908. Cont. N. Y. Bot. Garden, 
No. 106. 

5. Darwin, C. The variation of animals and plants under domestication. 

I : 493. New York, 1S6S. 

6. East, E. M. Suggestions concerning certain bud variations. Plant 

World II : 77. 1908. 

7. Gager, C. S. Effects of exposing germ-cells to the rays of radium. 

Science, N. S. 27: 335. 1908. 
S. MacDougal, D. T. Studies in organic evolution. Jour. N. Y. Bot. 

Garden 6 : 27. 1905. 
9. . Heredity and the origin of species. Pp. 1-32. Chicago, 1906. 

(The Monist, Ja., 1906, p. 28.) 

10. Macfarlane, J. F. Comparison of the minute structure of plant hybrids 

with that of their parents, and its bearing on biological problems. 
Trans. Roy. Soc. Edinburgh 37: 203. 1892. 

11. Metcalf, M. M. Determinate mutation. Science, N. S. 21: 355. 

1905. 

12. Shull, G. H. The significance of latent characters. Science, N. S. 

25: 792. 1907. 

13. . The pedigree-culture: Its aims and methods. Plant World II : 

21,55. 1908. 

14. Tschermak, E. The importance of hybridization in the study of de- 

scent. Rept. Third Internal. Conf. 1906 on Genetics. London, 
1907, p. 281. 

15. Vries, H. de. Species and varieties: Their origin by mutation. 2 Ed. 

Chicago, 1906, p. 28. 

16. Wilson, J. C. Infertile hybrids. Rept. Third Internat. Conf. 1906 

on Genetics. London, 1907, p. 199. 



CHAPTER XIX 

THEORETICAL CONSIDERATIONS 

It has been clearly shown that radium rays act as a stimulus to 
plants, and are therefore able to modify their life processes. In cer- 
tain cases the reaction to the rays is an excitation of function, in other 
cases a depression. But as to the method by which the stimulation 
is brought about, as to just how the protoplast is affected by the 
rays, we are in almost complete ignorance. Nor is the wriier bold 
enough to essay an answer to these questions here. The final solu- 
tion of the problem, however, will involve a careful consideration 
of certain facts and theories which may now be reviewed. 

The term stimulus is employed here and throughout in the 
sense emphasized by Verworn,^- * as any " change in the external 
agencies that act upon an organism." With reference to any indi- 
vidual protoplast this change will involve factors outside the proto- 
plast, but not necessarily outside the organism of which it is a part. 
These external agencies are forms of energy,! of which Verworn'- X 
lists eight, viz., chemical, molecular, mechanical, thermal, photic, 
electrical, magnetic, § and energy of gravitation. In Chapter II of 
this Memoir, it was pointed out that to these forms of energy, hitherto 
commonly recognized, must be added that of radioactivity. It was 
furthermore shown that radioactivity is a factor in the nornial environ- 
ment of probably all plants. Any change, therefore, in this factor 
becomes a stimulus. 

The Biogen Hypothesis : Before we can form any conception 
of the modus operandi of any stimulus we must have some sort of 
picture of the constitution of the cell. That protoplasm is not a 
chemical entity, but a morphological one, is generally accepted. It is 
also recognized that that which fundamentally distinguishes it from 
lifeless matter is its power of metabolism. One of the most thor- 

* Loc. cit. , p. 34S. 

t Or modify some form of energy, as when one plant is shaded by another. 

J Loc. cit., p. 209. 

§ Verworn ^ later (1. c, p. 348-349) states that the only ones of the above classes 
that come into relation with the organism are the first six and the last, but Ewart ^' 
succeeded in modifying the rate of streaming of protoplasm in living cells and the rate 
of motion of spermatozoids by the influence of strong magnets. 

257 



258 THEORETICAL CONSIDERATIONS 

oughly worked out theoretical conceptions of protoplasm is the 
*' biogen hypothesis" of Verworn,^' " and the details of this hypothesis 
are sufficiently tangible to be of service in an attempt to form some 
provisional conception as to how radium rays, or any other stimuli, 
produce their effects. I will first briefly state some of the funda- 
mental notions of the biogen hypothesis and their bearing upon radium 
stimulus, and then, in a similar manner, some of the facts concerning 
a few physiological processes, made known by recent investigation. 

According to Verworn's conception, "The metabolism of living 
substance, in last analysis, depends upon the continual destruction 
and the continual reconstruction of a very labile chemical compound." 
This " hypothetical compound, because of its fundamental relation 
to the genesis of life-processes," Verworn- designates* as " biogen," 
and, since in different forms of living substance there doubtless 
occur very different compounds of this sort, he designates " the entire 
group of them in a chemical sense as the group of the ' biogens,' " 
and proposes the term " biogen molecule " to supplant that of " living 
protein molecule " of Pfliiger. The biogen is designated * as a 
"most highly complex, labile compound that develops at an inter- 
mediate point in metabolism, and by its construction and destruction 
comprehends the sum total of the processes of metabolism." It is 
not a protein body, nor would the author call it a living protein. It 
is not alive, for a molecule cannot be alive. 

The essence of metabolism, then, is the construction and destruc- 
tion of biogen molecules, and, under normal conditions of equilibrium 

Construction ^ , , • r , • 

fs^ — 7^ = I. On the basis of this hypothesis, " the irritabilitv 

Destruction j tr ^ j 

of living substance depends upon the lability of the biogen molecule." 
" In metabolism as a whole two different series of processes are 
to be distinguished: 'functional metabolism,' in which the absolute 
number of biogen molecules remains unaltered and only certain nitro- 
gen-free groups are involved in functional destruction and restorative 
construction ; and ' cytoplastic metabolism,' which governs the abso- 
lute number of biogen molecules, and thereby the phenomena of 
growth, propagation, development, atrophy, regeneration, etc., since 
it extends over the destruction and reconstruction of the entire 
molecule. In case of a disturbance of their metabolic equilibrium, a 
compensatory self-regulation underlies both series of processes, and 

* Loc. cit., p. 25. 



THEORETICAL CONSIDERATIONS 259 

the biogen molecule offers a simple mechanical explanation for indi- 
vidual cases of this sort. . . ." 

Analyzing the phenomena of stimulation on the basis of his 
hypothesis, Verworn^ says:* "Irritability is the capacity of living 
substance to react to a stimulus by an acceleration of the metabolism 
of biogens." Both the dissimilatory and the assimilatory phases of 
metabolism may be stimulated. The degree of dissimilatory stimu- 
lation is, for equally intense stimuli, dependent upon the following 
factors : 

(a) The degree of lability of the biogen molecule. 

{d) The rapidity of the process of restitution after the functional 
destruction of the biogen. 

(c) The absolute number of biogen molecules present. 

(d) The conditions for the propagation of the effects of stimula- 
tion. 

A dissimilatory stimulation, or depression, may therefore be 
brought about by influencing any one of these individual factors. 

On the other hand, the degree of assimilatory irritability is de- 
pendent upon : 

(«) The quality of the raw materials available for nutrition. 

(3) The means for working up the raw material into a suitable 
form of elaborated matter. 

(c) The quantity of the suitable elaborated matter. 

(^d) The rapidity of the transformation of the elaborated matter 
from the reserve depots into the biogen molecules. 

An assimilatory irritability or depression may arise through in- 
fluencing each of these individual conditions. 

Radium rays, by acting on any one of the eight factors enumer- 
ated above, may therefore excite or depress processes of either 
assimilation or dissimilation. NowVerworn^ has earlier explained! 
that the atoms of his hypothetical biogen molecule are in active 
vibration. "As a result of this, certain atoms come occasionally into 
the sphere of attraction of others, and, becoming united with them 
into a more fixed combination, separate off as an independent 
molecule. In this way the spontaneous dissimilation of the biogen 
molecule results." The residues of biogen molecules thus formed 
may combine with constituents of the food, and thus be rebuilt into 

* Loc. cit., p. 89. 
t Loc. cit., p. 489. 



26o THEORETICAL CONSIDERATIONS 

a whole biogen molecule. " Thus spontaneous regeneration of the 
biogen molecule follows spontaneous dissimilation." 

It is evident, as Verworn points out, that any factor that increases 
or decreases the vibration of the atoms within the biogen molecule 
will correspondingly modify metabolism, causing either excitation or 
depression in response to the stimulus. It is conceivable that the 
radium rays, through their power of ionization, which alters the 
electrical charge of the atom and the electrical relations within the 
molecule, may modify this intramolecular atomic vibration, and so 
produce either an acceleration or retardation of any given process 
or processes, or an acceleration of one or more, and, at the same 
time, a depression of the others. 

But it is quite probable that radium rays, and doubtless other 
stimuli also, may not produce their stimulatory effects by acting 
directly upon the biogen molecule, or whatever the reality may be 
that corresponds to this term, but by acting upon some other sub- 
stance in the individual cells, or by modifying some process either 
preceding or following the elaboration of the biogen molecule. In 
other words, the rays may act, not upon the more immediate physical 
basis of life, but upon some non-vilal constituent other than the 
biogen, or upon some purely chemical process, thus producing their 
effects indirectly. The possibility of this is evident on the basis of 
Verworn's hypothesis, as may be seen by referring to the factors 
involved in his analysis of dissimilatory and assimilatory stimulation. 
It is more clearly evident when we analyze various physiological 
processes in the light of recent investigations. To this end let us 
consider first the process of photosynthesis. 

Photosynthesis : The work of Usher and Priestley " may first 
be referred to. These investigators adduce experimental data 
which lead them to the conclusion that the process called by them 
" carbon assimilation " consists of at least three steps, as follows : 

1. The conversion of CO, and UJJ into CH^O (formaldehyde) 
and H^Oj. In this process the chlorophyll acts as an optical sen- 
sitizer, and the vitality of the cell is not involved. 

2. The formaldehyde is removed and condensed to a sugar dy 
the -protoplasm. 

3. The H2O2 is removed by being split up by an enzyme into 
H2O and O, and the O set free as a gas. Thus all the reducing 
processes are non-vital in character, and the living protoplasm func- 
tions only in condensing the formaldehyde to sugar. 



THEORETICAL CONSIDERATIONS 261 

This second step has been accomplished in the laboratory and 
outside the organism by Meldola/*^ but the gap between CO2 and 
formaldehyde was not bridged until Fenton ^ reduced the former to 
the latter in one step, with the aid of metallic magnesium, without 
the intervention of the formic acid stage. At about the same time 
(January, 1908) Gibson*^ and his collaborators, by means of a feeble 
electric discharge, succeeded in synthesizing the formaldehyde from 
CO3 in the presence of water. The securing of this result forms 
part of the experimental demonstration of Gibson's photoelectric 
hypothesis of photosynthesis. This hypothesis, in brief, is, "that 
the light rays absorbed by chlorophyll are transformed by it into 
electric energy, and that this transformed energy effects the decom- 
position of carbonic acid (H^COg) within the cell, with the concomitant 
formation of an aldehyde and the evolution of oxygen. 

The following facts in confirmation of this hypothesis have been 
demonstrated in Gibson's laboratory : (i) That formaldehyde is 
present in all actively photosynthetic tissues ; (2) that the amount of 
formaldehyde present in the leaf bears a definite relation to the in- 
tensity of illumination ; (3) that formaldehyde may be synthesized 
from CO2 in the presence of water by feeble electric discharge ; (4) 
that electric discharges of sufficient intensity occur in photosynthetic 
tissues when they are adequately illuminated ; (5) that the light rays 
absorbed by chlorophyll are those specially concerned in the genera- 
tion of the electric currents which Kunkle,^ Haacke,^ and others * 
have demonstrated to exist in chlorophyll-bearing tissues. Gibson's 
hypothesis varies from all others in regarding the electric currents 
as due to the transformation of the energy of the light rays, and in 
attributing the formation of the formaldehyde from COg and water 
to the electric energy thus derived. 

Whether further experimentation shall confirm these results or 
not, it is certain that several steps are involved in photosynthesis. f 
Several possibilities are open, therefore, as to the way or ways in 
which radium rays or any other stimulus may affect the process. 
The rays may affect any one or all, or any combination of two or 
more of these steps, or they may modify the power of the plastids to 
produce the necessary chlorophyll, or to convert sugar into starch.^ 

* See citations Nos. 8, 49, 50, 51, 53-5S. 

t Kimpflin ^^'^ ( 190S) considers that there are two distinct acts in the assimilation 
of carbon: i. The production of electricitj', which, bj ionizing the water will increase 
the amount of hydrogen in the nascent state. 2. The reduction of COj bj that 



262 THEORETICAL CONSIDERATIONS 

We know, from other experiments, that the rays can affect living 
protoplasm, and it therefore seems certain that their effects on photo- 
synthesis are brought about, in part at least, in that way.* 

As to the effects of radium ra3'S on chemical analysis and syn- 
thesis we know next to nothing. If, as now seems highly probable, 
the conversion of carbon dioxide and water into formaldehyde and 
hydrogen peroxide is the first step in photosynthesis, and if radium 
rays can modify this reaction, then suitable tests for the formalde- 
hyde and peroxide in exposed leaf tissues ought to reveal the fact. 
Fenton^ has shown that the rays can decompose H2O2, and, there- 
fore, a ^riori^ we might expect the evolution of oxygen in photo- 
synthesis to be accelerated under their influence. 

In his presidential address before the Chemical Society of Lon- 
don, Meldola^" urged the view that several organic substances besides 
sugars may possibly result from the photosynthetic activity of the 
green cell. If this shall be demonstrated, then failure to detect 
starch or sugar in leaves exposed to radium rays will not necessarily 
indicate that all photosynthetic activity has been inhibited. 

Fermentation : In studying the effect of radium rays on fer- 
mentation by yeast we have to consider their effects, not only on the 
living yeast-cells, but also upon the sugar solution, and upon the 
enzymes secreted by the yeast and acting as the immediate cause of 
the fermentation. The literature dealing with the discovery of en- 
zymes in yeast and the proposal of the enzyme theory by Moritz 
Traube,^*' ^^ in 1858, with the isolation of the alcohol-producing en- 
zyme, zymase,! by Eduard Buchner,^^ and with other early discoveries 

hydrogen, according to the known formula, thus setting free formaldehyde and oxygen, 
together with, in some cases, the transitory formation of HjOj. All these phenomena 
he expresses by the following scheme : 

Light 

i 

chlorophyll 

i 
— electricity + 

-%0 + CH,0 = ^J26, ^^ 

(CeHioOjV ^-^CH^O + H^CH. + O 

* The biogen molecule may also be a factor here. 

t Jost "^ suggests the desirability of employing the term zymase in a generic sense 
for all substances produced by organisms and having the power of causing fermenta- 
tive decompositions. To replace zymase he proposes the term alcoholase. This change 
seems unnecessary as it merely involves the substitution of " zymase" for " enzyme," 
which is now used generically. 



THEORETICAL CONSIDERATIONS 263 

is too well known to be reviewed here. A few of the more recent 
contributions will be referred to, as they serve to bring clearly before 
us some of the possible factors to be considered in discussing the stimu- 
lation of the process of fermentation. 

Shortly after Buchner's fundamental discover}?^ of the glycolytic 
zymase, he and Meisenheim.er ^^ announced that the process of fer- 
mentation consists of a number of successive steps, the products of 
which are, in order, glucose, some hypothetical intermediate product 
and water, lactic acid, and CO2 and alcohol. The experiments of 
Brown and Glendenning^^ led them to believe that, in the transforma- 
tion of starch to sugar, the process of hydrolysis is preceded by a 
combination of the hydrolyte with the enzyme, and that "this 
compound is much more unstable and less able to withstand the 
action of the active ions or dissociated molecules of the electrolyte 
than the original cane sugar. . . . According to this view these 
active ions are the true hydrolytes, not the enzyme itself, which 
has only an intermediate action." The enzyme is regarded figure- 
atively " as the vice which holds the sugar molecule in a position 
favorable for the splitting agent to act." 

In 1906 Slator^^ stated that the velocity of fermentation of dex- 
trose varies with the amount of yeast present,* and is independent of 
the concentration of the dextrose. This latter fact is explained on 
the assumption that a compound is formed between the enzyme and 
the sugar, as Brown and Glendenning had previously suggested. 
Slator^^ states that, in the fermentation of sucrose enough sugar is 
almost instantaneously hydrolyzed for the fermentative reaction to 
attain its maximum velocity at once. From previous work and his 
own investigations he conceives that fermentation of dextrose by 
yeast involves the following steps in order : 

1. Diffusion of sugar into the yeast cell. 

2. Combination of dextrose and enzyme. 

3. Decomposition of this compound, forming an intermediate 
compound. 

4. Diffusion of the products from the cell out into the solution. 
It is the third step, he says, which proceeds slowly, and whose 
velocity governs the rate of fermentation. 

*This, says Slator ^^ (p. 130), confirms the work of O'SuUivan,^^ but the latter dis- 
tinctly says that, "The rule laid down by Dumas^^and supported by Brown ^* (for 
dextrose) holds good also for maltose," viz., that the time taken to ferment solutions 
of dextrose and maltose varies with the amount of the sugar present. 



264 THEORETICAL CONSIDERATIONS 

With reference to the stimulation of fermentation Dumas ^^ stated 
in 1874, ^^^t ^^^ ^^^^ ^^ more gradual in darkness and in a vacuum, 
and could be accelerated or retarded or destroyed by acids, bases and 
salts. Acceleration, he said, is very rare. In 1875 Becquerel ^^ an- 
nounced that fermentation was not retarded by the voltaic current 
" as Gay-Lussac observed." Schulz and Biernacki are said by 
Slator to have stated that very dilute solutions of poisons accelerate 
the process, while large doses have the opposite effect (e. g., mercuric 
chloride, iodine, potassium iodide). Slator ^^ was unable, under the 
conditions of his experiments, to secure this acceleration by any such 
reagents, and thinks that the effect previously interpreted as accelera- 
tion of alcoholic fermentation is due to an acceleration of the growth 
of the yeast, or to some other reaction. "We have not yet suc- 
ceeded," he says,* "in finding a substance which will appreciably 
accelerate fermentation by fresh living yeast." And later, f " The 
velocity of such fermentation may be easily lessened by the addition 
of certain inhibiting agents, but cannot be appreciably raised." 
Among other conclusions, Slator-^ infers that, in the fermentation of 
dextrose, laevulose, mannose, and galactose, " the enzyme combines 
completely with the sugar, and that the velocity of formation of 
carbon dioxide is determined by the rate of decomposition of this 
compound. "$ 

At least three enzymes produced by yeast are to be considered ; 
maltose and invertase, early recognized, and amygdalase, discovered 
by Caldwell and Courtauld'' in 1907. Early in the" present year 
(1908) we learn from the investigations of Trillat^®- ^'' and of Kayser 
and Demalon^" that acetic aldehyde is a normal product of alcoholic 
fermentation resulting from a further oxidation of the alcohol by the 
living yeast cells that exist aerobically near the surface of the fer- 
menting mixture. 

The above brief survey of the literature only emphasizes how im- 
possible it is now, and how difficult it will be in the future to explain 
the acceleration by radium rays of the evolution of gas in alcoholic 
fermentation. Referring to the four steps hypothecated by Slator, 
it may be that the radium rays increase the ionization of the sugar 
solution and thus its rate of diffusion into the yeast cell ; or the 
velocity of the reactions in the second and third steps ; or the rate of 

* Loc. cit., p. 234. 

tLoc. cit., p. 23S. 

5: Loc. cit,, p. 241. 



THEORETICAL CONSIDERATIONS 265 

the fourth step. Possibly, in the Hght of Slator's work, the radium 
experiments are to be interpreted as showing acceleration, not of fer- 
mentation itself, but only of the metabolism and growth of the 
ferment-organism. 

Here, as always, the living matter, or the biogen molecule, the 
rate of its construction and decomposition, or of its formation of 
enzymes or other substances, must always be considered as a possi- 
ble, and I believe as a very probable and essential factor, delicately 
sensitive on account of its extreme lability, to the changes of energy 
produced by the rays. Further w^ork may demonstrate that fer- 
mentation by unorganized ferments may be capable of modification 
by radium rays, but this would not in the slightest degree argue 
against the hypothesis that, with living yeast, the effects are due, in 
part at least, to the direct influence of the rays on the living matter. 
The most probable truth is that the rays influence both the vital and 
the non-vital steps in the process. 

Respiration : Respiration is no longer considered a simple 
oxidation, but as a series of both vital and non-vital processes begin- 
ning with atomic changes within the protoplast, and terminating with 
the evolution of carbon dioxide, or, in anaerobic respiration, of carbon 
dioxide and ethyl alcohol. 

Since the publication, in 1876, of I^asteur's^* classic Aiudes sur 
la btere, it has been customary to regard respiration and anaerobic 
respiration as essentially alike. The correctness of this view was 
more fully established by the researches of Stoklasa and Czerny,^''' ^"^ 
and Stoklasa ^^'^* also showed that, in last analysis, normal, aerobic, 
as well as anaerobic respiration, was of the nature of fermentation. 
According to this author, an enzyme similar to Buchner's zymase of 
yeast occurs in the cells of higher and lower plants, in the case of 
both normal and aerobic respiration. It is secreted by living proto- 
plasm. Plant cells contain, in addition to an enzyme that produces 
alcoholic fermentation, one which causes the fermentation of lactic 
acid. Aerobic respiration he considers as a secondary process.* 
The primary process is the motion of the atoms in the " living mole- 

* Kostytschew ^' takes issue with the results reported by Stoklasa, and says, among 
other things (p. 215), that it is premature to regard anaerobic respiration as a first step 
in aerobic respiration. 

Ideas quite similar to those of Stoklasa were presented in 1905 by Barnes,^* who 
proposed the term e«e;'^e5i5 " to designate the disruptive processes by which energy 
is released, leaving respiration to designate the more superficial phenomena of 
aeration. . . ." 



266 THEORETICAL CONSIDERATIONS 

cule," accompanied by a rearrangement of oxygen within the mole- 
cule. By these processes, by which the necessary kinetic energy is 
secured for the maintenance of life, CO^ and alcohol are split off, so 
that there arise within the " living molecule" reduced atom-groups, 
which have a great affinity for oxygen. In aerobic respiration there 
is no possibility for these reduced atom-groups (alcohol) to become 
fixed by the taking in of oxygen, therefore the alcohol is given off 
in addition to carbon dioxide. When oxygen is plentifully present, 
as in aerobic respiration, the alcohol in the nascent state is so com- 
bined that, under the influence of oxygen it serves for the formation 
of new parts of living protoplasm, through the agency of the oxydases 
of the air. 

Maximow's ^" experiments harmonize with the essential identity 
of aerobic and anaerobic respiration. He found that sap, expressed 
from mycelium of Aspergillus nige?', showed, on standing, a gaseous 
exchange analogous to that of normal respiration. This exchange 
was found to result from the activity of enzymes in the sap, inde- 
pendently of each other, and causing, the one an absorption of COg, 
the other a giving off of oxygen. The first is similar to zymase, the 
second belongs to the group of the oxydases. The enzyme which 
splits off CO2 acts, as does Buchner's zymase (alcoholase), equally 
energetically in air and in hydrogen. 

In April, 1908, Palladin'^'^^ published the results of his investiga- 
tions on the respiration-pigment in plants, detected several years 
ago by Schonbein^* and later studied by Reinke.^^ Palladin con- 
sidered that the physiological significance of these pigments is iden- 
tical with that of the haemoglobin of the blood, and proposed for 
them the generic term " phytohaematin." It is the role of these 
substances to receive the oxygen from the air through the intermedia- 
tion of the oxidases of respiration, and pass it on to the catalases and 
reductases. He gives the following diagram to illustrate, not only 

Secondary processes 

Atmospheric oxygen 
Primary processes I 

i i , , 

Anaerobic enzymes (zymase, etc.) Oxydases of respiration 

Katalase, reductase < Phytohaematin 

Fermentation products ^ Respiration products 

(Alcohol and other substances) (CO^, H^O) 



THEORETICAL CONSIDERATIONS 267 

the role of the phytohaematin, but also the relation of aerobic res- 
piration, anaerobic respiration, and alcoholic fermentation, and the 
essential identity of the respiratory process in plants and animals. 
Doubtless further researches will make necessar}- certain modifica- 
tions of this diagram, but it serves to present concisely our present 
knowledge of respiration, and to emphasize the complexity of the 
process. 

For our purpose three points in these conceptions are to be em- 
phasized : first, that the act of respiration is complex ; second, that 
some of the steps apparently do not involve living matter at all, but 
are purely non-vital, chemical changes ; third, that the processes not 
onl}' of normal, aerobic respiration, but of anaerobic respiration and 
fermentation as well, involve the action of enzymes. Thus it is 
clearly evident that radium rays, or any other stimulus, may affect 
respiration in a variety of ways by modifying any of the steps in- 
volved. Not only may the living protoplasm (or some intermediate 
biogen molecule) be stimulated, but the action of the various enzymes 
may be accelerated or retarded or completely inhibited, or the phy- 
tohaematin may be similarly affected or completely destroyed. 
Also, under certain conditions, the protoplasm may be stimulated to 
produce these substances in greater or less quantity, or not at all. 

Germination: The mystery of the so-called "resting" seed is 
yet to be solved. We understand a few things, however, about its 
physiology. We know it is not dead, for it is constantly, at least at 
ordinary temperatures, slowly undergoing certain changes which 
characterize metabolism everywhere. These changes in time are 
sufficient to destroy the power to resume the normal rate of the life 
processes which, with the ripening of the seed, became reduced to 
their lowest terms. 

The resting seed consists, in addition to its integuments, of at 
least three essential things: (i) The embryo; (2) the nourishment 
stored in or around the embryo ; (3) enzymes, secreted largely if not 
wholly by the embr3'o.* Investigations were made byAlbo^-^for 
the purpose of finding out why seeds, apparently normal so far as 
structure and chemical composition are concerned, lose their vitality, 
even though the stored food remains in abundance. He found that 

* Pond's*- studies on the capacity of the date endosperm for self-digestion indicate 
that the enzymes active in the germination of seeds originate, not as was formerly be- 
lieved, within the endosperm, but wholly within the embryo. I have reviewed the 
literature on this subject elsewhere. ^^ 



268 THEORETICAL CONSIDERATIONS 

diastatic activity in resting ' seeds is very feeble, varying with the 
species, and with the conditions under which the seeds are kept. 
Their diastatic power varies with their power of germination, being 
lowest in old seeds. In seeds which have lost their ability to 
germinate the diastatic power is diminished or entirely annulled. 
External agents, such as temperature, light, and chemical stimulants, 
affect enzymes and the germinating power of seeds alike. He con- 
cludes that the energy for the changes going on in seeds originates 
in the action of enzymes, but that the changes take place more gradu- 
ally in resting seeds than in those that are germinating. 

In 1907 Brocq-Rousseu and Gain *^ reported the existence of a 
peroxydiastase in dry seeds of Nymphaeaceae, Ranunculaceae, 
Malvaceae, Umbelliferae, Cupuliferae, Juglandaceae, Liliaceae, 
Gramineae, Coniferae, and other families of plants. This substance 
colors blue a tincture of guiacum in the presence of oxygenated water. 
It is stated that there may be more than one peroxydiastase in dry 
seeds, but the ferment does not exist in them indefinitely. Later the 
same authors ^^ investigated the occurrence of the peroxydiastase in 
seeds of authentic ages of from 2 years to 5)000 years, taken from 
museums and herbaria. The oldest seeds were from the Collections 
■pharaonique du Musee de Boulaq. They found that the peroxy di- 
astases may disappear in a few years (in Galium^ c. g., 20 years); 
and that they may also be preserved for very long periods. The 
oldest seeds in which they determined its survival belonged to the 
i8th century. Seeds which could germinate, however, always con- 
tained the peroxydiastase, but those which have lost that faculty may 
still conserve it. 

In connection with this last point may be mentioned the researches 
of Gain *^' ^^ who found that the embryos of cereals from the tombs 
of the ancient Pharaohs, notwithstanding the seed's external appear- 
ance of good preservation, do not possess a cellular organization 
suitable for germination. The stored food is well preserved and 
may be utilized by a living embryo, but the embryo of the ancient 
seeds has undergone a chemical transformation, and is no longer 
viable. The relative age (and thus viability) of the embryo may be 
detected by a peculiar coloration which grows darker with age. 

With reference to the effects of radium rays on dry seeds and on 
germination, the possibilities, suggested by the above discussion, 
hardly need a formal statement. The rays may act directly on the 



THEORETICAL CONSIDERATIONS 269 

biogen molecule, or on the living matter of the embryo, on the 
food substances stored in and around the embryo, or on enzymes 
present in the seed, or on any two or all four of these factors. 
The molecules of the biogens, of the food, or of the enzymes may 
be shattered and utterly destroyed, either wholly or in part, or 
the rays may onl}^ hasten metabolic processes in such a way as 
either to accelerate germination in the active seed, or to cause a 
premature ageing and ultimate death in the resting seed. If only 
a peroxydiastase or other enzyme, normally present in the resting 
seed, were destroyed it is possible that the embryo, even if it were 
still alive, would not be able to reproduce the ferment fast enough to 
supply the needs arising with the imbibition of water and the re- 
awakening of the protoplasts. Or again, the molecules of the stored 
food might be so altered as not to be capable of being acted on by 
the enzyme. 

How do radium rays affect solutions, starch, oil, aleurone, enz3'mes 
and other substances stored in seeds? Until these questions are an- 
swered we cannot expect much light on the way in which the rays 
affect resting and dry seeds. 

Studies that have so far been made of the effect of radium rays on 
solutions have yielded contradictory results. Soon after the discovery 
of Rontgen rays, Thomson^' (1896) ascertained that, when these rays 
pass through a dielectric, they make the latter, during the time of 
their passage, a conductor. All substances, he says, when trans- 
mitting them, are conductors of electricity. "The passage of these 
rays through a substance seems thus to be accompanied by a splitting 
up of its molecules, which enables electricity to pass through it by a 
process resembling that by which a current passes through an elec- 
trolyte." The experiments of Graetz,'^' four years later, led him to 
believe that radium rays act in a similar way, while the experiments 
of M. Curie, •^'* in 1902, clearly indicated that both radium and X rays 
act on liquid dielectrics as on air, communicating to them a certain 
conductibility. The investigations of Henning,'- and of H. Bec- 
querel,^^ led to the same conclusion. If X rays have such a property, 
then we should theoretically expect radium rays to possess it as well. 

Kohlrausch,^^ however, concluded, in 1903, that such effects, if 
they exist at all, were to be attributed, not to the ionizing effect of 
the rays, but to their accelerating effect on the dissolving of the 
glass of the resistance vessel. Later, he and Henning" found that 



270 THEORETICAL CONSIDERATIONS 

the conductivity of solutions of radium bromide of 1/12,000 to 1/20 N 
concentration was similar to that of analogous, but non-radioactive, 
salts of elements related to radium, c. g., barium, strontium, and cal- 
cium, and in 1906 Kohlrausch'^^ definitely stated that the conductivity 
of water is not increased by drawing through it a current of air that 
has first passed over radium. The quantity of ions thus formed, he 
said, is exceedingly small. Experimenting with NaCl, CaCl, BaCl, 
MgSO,, ZnSO,, K2CO3, HCl, and NaOH, in percentages of from 20 
to 2.5, he found that radium rays increase the conductivity of elec- 
trolytes only in so far as they raise the temperature of the solution. 
He inferred that, if the /9 and y rays do increase the degree of ioni- 
zation of the electrolyte, they do so to a degree too small to be de- 
tected by the delicate means he employed.* 

Growth: As previously stated,! the term growth is here taken 
to mean increase in size or increase in mass, one or both, with or 
without an accompanying change of form. Increase of size with- 
out increase of dry weight involves increased turgor in elastic walled 
cells. Increase of mass involves an excess of constructive over de- 
structive metabolism. Radium rays may affect both processes. 

Since turgor is an expression of the internal osmotic pressure of 
the cell, and since osmotic pressure is a function of the number of 
particles of the solutes present in the cell-sap, radium rays, by their 
power of ionization, may possibly increase this turgor, and thus accel- 
erate or favor an increase of size of the individual cells and of the 
tissues and organs composed of them. Theoretically the rays would 
have this power. That they do alter solutions in some manner seems 
clearly evident from the effects of exposed water on germination and 
growth, as described in Experiments 48-51 on pages 158-173. 

Growth, in the sense of increase of mass, is an expression of con- 
strutive metabolism. Not only is the number of biogen molecules 
increased, but also the amounts of various substances produced by 
them. Here, as in respiration, fermentation, and other metabolic 
processes, the activity of enzymes is involved. The digestion of the 
food is accomplished by various enzymes, and energy for metabolism 
is set free by enzymotic action. Verworn % believes that a molecule 
of an enzyme is the substratum of the metabolic process. It is the 

* Cf . foot-note, pp. 220-221. 
tp. 223. 
t2, p. 15. 



THEORETICAL CONSIDERATIONS 2^1 

same story of multiplicity of factors and complexity of function. 
Therefore, with reference to the influence of radium rays, we must 
consider as many possibilities as there are steps and combinations of 
steps. First and foremost we must take into account the living sub- 
stance itself. Then the rays may affect the enzymotic digestion of 
the food, partly outside and partly inside of the cells to be nourished. 
Furthermore the rays may operate so as to increase or decrease the 
amount of energy available for the work, and, lastly, variations in 
growth may be, either wholly or partly, expressions of the influence 
of the rays on cell-division. 

Cell-division : No one has yet succeeded in accelerating the 
rate of cell-division or in increasing its amount in a given tissue by 
means of radium rays. The only results recorded are the introduction 
of irregularities and complete inhibition. A brief resume of the 
well known life-history of a cell may serve as the first step in attempt- 
ing to explain this effect. 

On the basis of Verworn's theory, the active metabolism of a 
young cell involves, fundamentally, the continual destruction and 
reconstruction of biogen molecules. The latter process is condi- 
tioned, in part, by the supply of suitable food material, and upon 
its preponderance over the breaking down of the biogens depends 
the growth of the cell. With cell-enlargement by growth the area 
of the cell-surface in proportion to the mass becomes finally too 
small to permit of the entrance of enough food and energy to 
maintain the reconstruction of the biogen molecules faster than 
they are decomposed. If the surface area relative to the mass can 
be increased, rejuvenescence will result, but otherwise the biogen 
molecules will continue to break down faster than they can be built 
up again, and the cell enters upon a period of senescence. In grow- 
ing old either certain catabolic products are produced in relatively 
larger quantities than occurs in the pre-senescent period, or new cata- 
bolic substances are elaborated, or both. Normally cell-division 
postpones the approach of senescence.* 

The evidence at hand, and presented in Chapter XVI, indicates 
that radium rays may hasten the approach of senescence. In other 
words, they may accelerate the breaking down of biogen molecules and 
interfere with their reconstruction. This is doubtless accomplished by 

* Of course cell-division cannot indefinitely postpone senescence, nor are the above 
circumstances regarded as the only condition or stimulus of cell-division. 



272 THEORETICAL CONSIDERATIONS 

ionizing the atoms of all the various substances (biogens and others) 
that are involved in the metabolism of the cell, the effects being pro- 
duced both directly and indirectly. Thus we should expect, a prt07'i, 
a retardation and finally a complete inhibition of cell-division in all 
tissues exposed to rays of sufficient activity and for suitable periods 
of time. And this is what has been observed to occur. Theoretically 
we ought also to be able to accelerate the process by suitable condi- 
tions of exposure, but such conditions have not yet been discovered. 

The irregularities produced by radium rays in karyokinesis do 
do not seem to call for any special explanation in addition to that 
suggested in discussing the abnormalities of tissues and organs in 
Chapter XVI. Such irregularities are only a morphological ex- 
pression of physiological disturbance, and it may be seriously ques- 
tioned whether we are justified in expecting the morphological 
appearance and behavior of chromosomes to explain things, any 
more than do variations in leaf-margins, or other purely structural 
facts. The problem of the causes of variation and inheritance lies 
deeper than morphologv, and the behavior of the chromosomes, even 
in sexual cells, instead of explaining other and grosser facts of struc- 
ture, quite possibly only presents another feature to be explained. 

Recovery from Stimulus : It has been frequently observed in 
the study of stimulation, not only by radium rays but by other stimuli 
as well, that a depression of function, caused by certain conditions of 
exposure, may be followed, after a period, by recovery of the normal 
rate of functioning, provided that the stimulant is discontinued. In 
like manner excitation is followed by a return to the normal condi- 
tion. This recovery of tonus probably means that the stimulus has 
not been injurious to the biogens, or that it has produced its effect 
largely, if not wholly, by its influence upon the non-vital steps in 
metabolism. Thus, if the rays of radium acting on a resting seed 
destroyed a large percentage of some enzyme necessary for germina- 
tion, but affected the biogens only slightly or not at all, or if they 
destroyed only a relatively small number of the latter, germination 
and early growth would be retarded, but recovery would follow in a 
short time, due to a replenishing of the necessary enzyme by meta- 
bolic processes. A similar course of reasoning would apply to re- 
covery from excitation. 

Radium Stimulus and Plant-electricity: The literature 
dealing with the existence of electric currents in plants is far too 



THEORETICAL CONSIDERATIONS 273 

voluminous to be reviewed here. Vassali-Eandi/^ in 1804, was 
probably the first to detect evidence of such currents, and stated that 
the so-called "vital principle" was only "galvanic fluid." Half a cen- 
tury later A. C. Becquerel ^^'^'^ and Wartmann^'' clearly demonstrated 
that such currents exist in plants, and several years afterwards the 
phenomenon was quantitatively studied by Burdon-Sanderson,^^'^^ 
and Munk.*"' These currents doubtless have their source in the 
chemical changes going on within the tissues,* and Pfeffer | states, 
not only that respiratory metabolism {athmungsstoff'wechseT) contrib- 
utes in an important manner to their formation, but that at present we 
have no clear proof that they originate otherwise. ^ Also, as Pfeffer 
says, it is unknown whether the electricity is merely a necessary by- 
product of chemical transformations that have taken place, or whether 
it plays a special role in the organism, affecting chemical or other 
processes. 

The role of these currents is too little understood to make profit- 
able any attempt to discuss them further as a factor in the response 
of plants to radium rays, but, since the particles of the beta and alpha 
rays carry charges of electricity, we should not fail to recognize the 
fact that the normal electric currents in plants may be a factor in- 
volved in the reactions of the plants to the stimulus of the rays. Their 
effect must be either explained or explained away. 

Conclusion : § This rather involved consideration of the possi- 
ble mode of action of radium rays upon the life-processes of plants 
has served chiefly to indicate the nature of the problem, and to sug- 
gest the direction that future researches should take. If the living 
matter itself is directly affected by the rays it is difficult to conceive 
how any one function could be modified without the others being 
affected, for, with long periods of exposure (24 hours or more) to 
radium of high activity (1,500,000 x or more) it is certain that the 
protoplasm will have its vitality partially or wholly destroyed, and 
all " vital " processes correspondingly modified or stopped. But, on 

* Becquerel.^^ 

t6i, p. 192. 

% Gibson's hypothesis that these currents result from the transformation of the 
energy of light-waves by chlorophyll is referred to on page 261. If his photoelectric 
hypothesis of photosynthesis shall be confirmed, then it is possible that radium rays 
may affect photosynthesis, in part at least, by exerting an influence on these currents. 

\ Theoretical considerations with reference to tropistic response, histological 
effects, and the effects of exposing germ-cells are discussed in Chapters XV, XVI, and 
XVIII, and are therefore omitted from this chapter. 



274 THEORETICAL CONSIDERATIONS 

the other hand, the modification or total inhibition of any one process 
does not necessarily indicate that the living matter has been directly 
affected, for such a condition would result if, as in the case of the 
resting seed, the rays destroyed an enzyme essential to the comple- 
tion of some function. 

The broadest, and at the same time the most definite generaliza- 
tion warranted by the work so far done is that the rays of radium 
act as a stimulus to metabolism. If this stimulus ranges between 
minimum and optimum points, all metabolic activities, whether con- 
structive or destructive, are accelerated ; but if the stimulus increases 
from the optimum toward the maximum point it becomes an over- 
stimulus, and all metabolic activities are depressed and finally com- 
pletely inhibited. Beyond a certain point of over-stimulus recovery 
is impossible, and death results. 

Bibliography 
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1. Verworn, M. General physiology. (English transl. by F. E. Lee.) 

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2. . Die Biogenhypothese. Jena, 1903. 

Photosynthesis 

3. Boehm, J. Ueber Starkebildung aus Zucker. Bot. Zeit. 41 : 33, 49. 

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4. Fenton, H. J. H. The decomposition of hydrogen dioxide under the 

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5- • The reduction of carbon dioxide to formaldehyde in aqueous 

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6. Gibson, R. J. H. A photoelectric theory of photosynthesis. Ann. 

Bot. 22 : 117. 1908. 

7. Haacke, 0. Ueber die Ursachen electrischer Strome in Pflanzen. 

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8. Klein, B. Zur Frage uber die elektrischen Strome im Pflanzen. Ber. 

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9. Kunkel, A. Ueber electromotorische Wirkungen an unverletzten leben- 

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ID. Meldola, R. The living organism as a chemical agency: a review of 
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II. Usher, F., & Priestley, J. A study of the mechanism of carbon assimi- 
lation in green plants. Proc. Roy. Soc. London 77 B : 369. 1906. 



THEORETICAL CONSIDERATIONS 275 

Fer7nentation 

12. Becquerel, S. Electro-physiologie vegetale. Des forces physico- 

chimiques, etc., p. 361. Paris, 1875. 

13. Brown, A. J. Influence of oxygen and concentration on alcoholic fer- 

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14. Brown, H. T., & Glendenning, T. A. The velocity of hydrolysis of 

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15. Buchner, E., Buchner, H., & Hahn, M. Zymasegarung, p. 14. Miin- 

chen u. Berlin, 1903. 

16. Buchner, E., & Meisenheimer, J. Die chemischen Vorgange bei alco- 

holischen Garung. Ber. Deut. Chem. Ges. 37^: 419. 1904. 

17. Caldwell, R. J., & Courtauld, S. L. IX. The enzymes of yeast. 

Amygdalase. Proc. Roy. Soc. London 79 B : 351. ^907. 

18. Dumas, J. B. Recherches sur la fermentation alcooloque. Ann. 

Chim. Phys. 3 : 57. 1874. 

19. Jost, L. Lectures on plant physiology. (English transl. by J. H. 

Gibson.) Oxford, 1907. p. 212. 

20. Kayser, E., & Demalon, A. Sur la formation de I'aldehyde ethyl- 

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1908. 

21. O'SuUivan, J. On the rate of alcoholic fermentation. Jour. Soc. 

Chem. Indust. 17: 559. 1898. 

22. Slator, A. Studies in fermentation. I. The chemical dynamics of 

alcoholic fermentation by yeast. Jour. Chem. Soc. London Trans. 
89^: 129. 1906. 

23. . Studies in fermentation. II. The mechanism of alcoholic fer- 
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24. Traube, M. Zur Theorie der Gahrungs- und Verwesungs-Erschei- 

nungen, wie der Fermentwirkungen iiberhaupt. Ann. Phys. 103 : 
331- 1858. 

25. . Theorie der Fermentwirkungen. Berlin, 1858. 

26. Trillat, A. Sur la formation de I'aldehyde acetique dans les fermenta- 

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27. & Sauton. Formation et disparition de I'aldehyde ethylique sous 

I'influence des levures alcoolique. Compt. Rend. Acad. Sci. Paris 
146 : 996. 1908. 

Respiration 

28. Barnes, C. R. The theory of respiration. Bot. Gaz. 39: 81. 1905. 

Science, N. S. 21 : 241. 1905. 

29. Kostytschew, S. Ueber Atmungsenzyme der Schimmelpilze. Ber. 

Deut. Bot. Ges. 22 : 207. 1904. 



276 THEORETICAL CONSIDERATIONS 

30. Maximow, N. A. Zur Frage iiberdie Atmung. Ber. Deut. Bot. Ges. 

22 : 225. 1904. 

31. Palladin, W. Das Blut der Pflanzen. Ber. Deut. Bot. Ges. 26: 125. 

1908. 

32. . Die Atmungspigmente der Pflanzen. Zeit. Physiol. Chem. 

55 : 207. 1908. 

33. . Les pigments respiratoires des plantes. Bull. Acad. Imp. Sci. 

St. Petersbourg 5 : 447. 1908. 

34. Pasteur, L. Etudes sur la biere. Paris, 1876, p. 258. 

35. Reinke, J. Die Autoxidation in der lebenden Pflanzenzelle. Bot. 

Zeit, 41 : 65, 89. 1883. 

36. Schonbein, C. F. Ueber das Vorkommmen des thatigen Sauerstoffs in 

organishen Materien. Zeit. Biol. 3 : 325. 1867 & 1S68. Jour. 
Prakt. Chem. 105 : 198. Verhandl. Naturf. Ges. Basel 5 : i. 

37. Stoklasa, J. Identitat anaerobe Atmung und Garung. Oesterr. 

Chem. Zeit. 1903. (Not seen.) 

38. . Ueber die Atmungsenzyme. Ber. Deut. Bot. Ges. 22 : 358. 

1904.^ 

39. & Czerny, F. Der anaerobe Stoffwechsel der hoheren Pflanzen 

und seine Beziehung zur alkoholische Gahrung. Beitr. z. Chem. 
Physiol, u. Pathol. Franz Hoffmeister. 3 : 460. Strassburg, 1903. 

40. . Isolierung des die anaerobe Atmung der Zelle der hoher 

organisirten Pflanzen und Tiere bewirkenden Enzymes. Ber. Deut. 
Chem. Ges. 36^: 622. 1903. 

Germination 

41. Albo, G. La vita dei semi alio stato di riposo. Bull. Soc. Bot. Ital. 

Nos. 7-9, p. 93. 1907. 

42. . Les enzymes et la faculte germinative des graines. Arch. Sci. 

Phys. Nat. 25: 45. 1908. 

43. Brocq-Rousseu & Gain, E. Sur I'existence d'une peroxydiastase dans 

les graines seches. Compt. Rend. Acad. Sci. Paris 145: 1297. 
1907. 

44- . Sur la duree des peroxydiastases des grains. Compt. 

Rend. Acad. Sci. Paris 146: 545. 190S. 

45. Gager, C.S. An occurrence of glands in the embryo of Zea Mays. 

Bull. Torrey Club 34 : 125. 1907. Contr. N. Y. Bot. Garden, 
No. 92. 1907. 

46. Gain, E. Sur les embryons du ble et de I'orge pharaoniques. Compt. 

Rend. Acad. Sci. Paris 130 : 1643. 1900. 

47- • Sur le vieillissement de I'embryon des Gramin^es. Compt. 

Rend. Acad. Sci. Paris 133: 1248. 1901. 



THEORETICAL CONSIDERATIONS 277 

48. Pond, R. H. The capacity of the date endosperm for self -digestion. 

Ann. Bot. 20: 61. 1906. 

Growth 

49. Becquerel, H. Conductibilite et ionisation residuelle de la paraffine 

solide sous I'influence du rayonnement du radium. Compt. Rend. 
Acad. Sci. Paris 136 : 11 73. 1903. 

50. Curie, P. Conductibilite des dielectriques liquides sous I'influence des 

rayons du radium et des rayons de Rontgen. Compt. Rend. Acad. 
Sci. Paris 134: 420. 1902. 

51. Graetz, L. Ueber die Quinke'schen Rotationen im elektrischen Feld. 

Ann. Phys. IV. I : 530. 1900. 

52. Henning, F. Ueber radioactive substanzen. Ann. Phys. 312: 526. 

1902. 

53. Kohlrausch, F. Beobachtungen an Becquerelstrahlen und Wasser. 

Verhandl. Deut. Phys. Ges. 5: 261. 1903. 

54. . Ueber die Wirkung der Becquerelstrahlen auf Wasser. Ann. 

Phys. IV. 20: 87. 1906. 

55. & Henning, F. Ueber das Leitvermogen der Losungen von Radi- 

umbromide. Verhandl. Deut. Phys. Ges. 6: 144. 1904. 

56. Sabat, M. B. Ueber den Einfluss der Radiumstrahlen auf das Leitver- 

mogen. Bull. Internat. Acad. Sci. Cracovie. CI. Sci. Math. Nat. 
1906: 62. 1907. 

57. [Thomson, J. J.] The discharge of electricity produced by the 

Rontgen rays, and the effects produced by these rays on dielectrics 
through which they pass. Nature 53 : 377. 1896. 

Plant Electricity 

58. Becquerel, A. C. Recherches sur les causes du degagement de I'elec- 

tricite dans les vegetaux. Compt. Rend. Acad. Sci. Paris 31 : 633. 
1850. 

59. . Recherches sur les causes qui degagent de I'electricite dans les 

vegetaux et sur les courants vegeto-terrestres. Mem. Acad. Sci. 
Inst. France 23: 35. 1853. •^"^- Jo"^"- ^ci. 12: 83. 1851. Ann. 
Chim. Phys. 31 : 40. 1851. Jour, de Pharm. 19: 212. 1851. 
(Last 2 not seen.) 

60. Munk, H. Die Elektrischen und Bewegungs-Erscheinungen am Blatte 

der Dionaea muscipula. Arch. Anat. Physiol. Wiss. Med. 1876: 
30, 167. 1876. 

61. Pfeffer, W. Studienzur Energetik derPflanze, p. 192. Leipzig, 1892. 

62. Sanderson, J. B. Ueber elektrische Vorgange im Blatte der Dionaea 

muscipula. Bot. Zeit. 32: 6. 1874. Centralb. Med. Wiss. 
Nr. 53. 1873 (not seen). 



278 THEORETICAL CONSIDERATIONS 

63. . Note on the electrical phenomena which accompany irritation of 

the leaf of Dionaea muscipula. Proc. Roy. Soc. London 21 : 495. 

1873. 

64. . On the electrical phenomena which accompany the contrac- 
tions of the leaf of Dionaea muscipula. Rept. 53 Meeting Brit. 
Assoc. Adv. Sci. 1873: 133. 1S74. 

65. . On the electromotive properties of the leaf of Dionaea in excited 

and unexcited states. Proc. Roy. Soc. London 33 : 148. 1882. 
Phil. Trans. 173^- i. 1883. 

66. Vessalli-Eandi, A. M. Recherches sur la nature du fluide galvanique. 

Jour. Phys. Chim., d'Hist. Nat., &c. 59: 241. 180-^. 

67. Wartmann, E. Note sur les courants electriques qui existent dans les 

vegetaux. Bibliotheque Univers. de Geneve. Arch. Sci. Phys. Nat. 
15:301. 1850. 

General 

68. Ewart, A. J. Influences of magnetic forces on streaming. On proto- 

plasmic streaming, p. 49. Oxford, 1903. 



EXPLANATION OF PLATES 



PLATE I 

HISTOLOGICAL EFFECTS OF RADIUM RAYS ON LUPINUS ALBUS 

PAGE. 

Fig. A. Cross-section through a fibro- vascular bundle of the hypocotyl 
of a seedling from seed exposed for 72 hours, before soaking, to 
rays from radium of i,Soo,ooo activity. Experiment 27 . . 224 

B. Same as A. Section taken from another plant through a 
fibro-vascular bundle ........ 224 

C. Cross-section through a fibro-vascular bundle of the hypocotyl 
of a seedling from seed exposed for 91.5 hours, before soaking, to 
rays from radium of 1,800,000 activity. Experiment 29 . . 224 

D. Cross-section through a fibro-vascular bundle of the hypocotyl 

of a plant from seed not exposed to radium rays. Experiment 27. 224 

E. Cross-section through the tap-root of the plant from which C 
was taken. Experiment 29 ...... . 225 

F. Cross-section through the tap-root of a seedling grown from 
seed not exposed to radium ....... 225 

All the sections luere taken from the same relative regions of 
the hypocotyls and roots. 



Mem. N. Y.'Bot. Gard. 



Vol.. IV. Pi.. I. 








E F 

IIISTOLOCilCAL EFFECTS OF RADIUM RAYS. 



PLATE 2 

HISTOLOGICAL EFFECTS OF RADIUM RAYS ON LUPINUS ALBUS 

AND PHASEOLUS VULGARIS 

PAGE. 

Fig. A. L. albus. Cross-section taken through a fibro- vascular bundle 
of the hypocotyl of a seedling grown from a seed exposed for 6 
days, during imbibition of water in moist sphagnum, to rays from 
a Lieber's radium-coated rod of 25,000 activity. Experiment 16 . 225 

B. L. albus. Cross-section through a fibro-vascular bundle of 
the hypocotyl of a seedling from an unexposed seed, but of the 
same age as that of A, and grown in moist sphagnum . . .225 

C. L. albus. Cross-section taken through the tap-root of the 
seedling from which A was taken ...... 226 

D. L. albus. Cross-section taken through the tap-root of the 
seedling from which B was taken . . . . . - . 226 

E. P. vulgaris. Cross-section through the hypocotyl of a seed- 
ling from a seed exposed, during imbibition and germination in 
moist sphagnum, to rays from a coated rod of 10,000 activity. 
Experiment 15 . . . . . . . . . . 226 

F. P. vulgaris. Cross-section through the hypocotyl of a seed- 
ling of the same age as E, and also grown in moist sphagnum, 

but from a seed not exposed to radium rays .... 226 



Mem. N. Y. Box. Gard. 



Vol. IV. Pl. 2. 





HISTOLOGICAL P:FFECTS OF RADIUM RAYS. 



PLATE 3 

HISTOLOGICAL EFFECTS OF RADIUM RAYS ON PHASEOLUS VULGARIS 

PAGE. 

Fig. A. Cross-section through the epicotyl of a seedling grown in soil 
from seeds exposed, unsoaked, for 24 hours, to rays from a Lieber's 
radium-coated rod of 10,000 activity. Experiment 1 1 . . 227 

B. Cross-section through the epicotyl of a seedling (a control 
plant of Exp. 11), grown in soil, and of the same age as that from 
which A was taken, but from a seed not exposed to radium rays . 227 

C. Cross-section through the upper part of the hypocotyl of the 
seedling from which A was taken ...... 226 

D. Cross-section through the upper part of the hypocotyl from 
which B was taken ......... 226 

E. Cross-section through the hypocotyl of a seedling grown from 
seed exposed for 5 days (12 hours), during imbibition of water and 
germination, to rays from a Lieber's radium-coated rod of 10,000 
activity. Experiment 19 ....... . 226 

F. Cross-section through the hypocotyl of a seedling grown as 
was that of E, but not exposed to radium rays, of the same age as 

the latter, taken through the corresponding region . . . 226 



Mem. N. Y. Box. Gard. 



Vol. IV. Pl. 3. 





HISTOLOGICAL EFFECTS OF RADIUM RAYS. 



PLATE 4 

HISTOLOGICAL EFFECTS OF RADIUM RAYS ON ZEA MAYS 

PAGE. 

Figs. A, B, D, E. Cross-sections through leaves of seedlings grown 
from grains exposed, before soaking, for 27 hours, to rays from 
10 mg. of radium of 1,800,000 activity ..... 227 
C. Cross-section through the leaf of a seedling grown from a 
grain not exposed to radium rays .... . 227 



Mem. N. Y. Box. Gard. 



Vol. IV. Pl. 4. 








D E 

HISTOLOGICAL EFFECTS OF RADIUM RAYS. 



PLATE 5 

EFFECTS OF RADIUM RAYS ON NUCLEI AND NUCLEAR DIVISION IN 

ALLIUM CEPA 

PAGE. 

Figs. i-io. Amoeboid shapes assumed by nuclei when exposed to 

radium rays .......... 232 

9-12. Stages in the division of nucleoli ..... 232 

13. Tendency to the formation of a double spindle . . . 233 

14-18. Abnormal mitoses. ....... 232 



Mem. N. Y. Box. Gard. 



Vol.. IV. Pl. 5. 



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11 









12 









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1 6 





c S G. d^T- 



EFFECTS OF RADIUM RAYS ON NUCLEI AND MITOSIS. 



PLATE 6 

EFFECTS OF RADIUM RAYS ON MITOSES 

PAGE. 

Fig. I. Occurrence of two independent mitoses in the division of one 

nucleus ........... 233 

2, 4, 7, 8, 9, 10. Irregularities in mitoses .... 232 

3, 5, 7. Failure of some of the chromosomes, or portions of 
chromosomes, to take part in the organization of the daughter 
nuclei ........... 232 

6. Secondary nuclei, doubtless organized by chromosome-frag- 
ments that failed to take part in the organization of the main 
(daughter) nucleus when the cell containing them was formed . 233 



Mem. N. Y. Bot. Gard. 



Vol. IV. Pl. 6. 







b::"::-.-' ,i^l*iji\:-- ■■■■:■■ 










10 



jaS.G.(3e^. 



EFFECTS OF RADIUM RAYS ON MITOSES. 



PLATE 7 

PAGE. 

Figs. a-e. Onagra biennis. Radium culture No. 9a, narrow-leaved 
side of the plant, a, flower (minus corolla) with bract; b, 
flower-bud; C, nearly mature capsule with bract; d, petal; e, 



leaf from main stem 



244 



f-k. Onagra biennis. Radium culture No. 9a, broad-leaved 
side, f, leaf from main stem; g, petal; h, flower (minus 
corolla); i, flower-bud; k, capsule with bract .... 244 



Mem. N. Y. Box. Gard. 



Vol. IV. Pl. 7. 










h ^1 

ONAGRA BIENNIS. RADIUM CULTURE, No. 9 a 




PLATE 8 

PAGE. 

Onagka BIENNIS. Radium culture No. iic. Pollen exposecl £01-24 
hours to rays from radium of 1,500,000 activity in a sealed glass 
tube. Ovary not exposed ........ 24^1 



Mem. N. Y. Box. Gard. 



Vol. IV. Pl. S. 




ONAGRA BIENNIS. RADIUM CULTURE, No. iic. 



PLATE 9 

PAGE. 

Onagra biennis. Radium culture No. 5a. After pollination with 
unexposed pollen, the ovary was exposed for 48 hours to rays 
from radium bromide of 1,500,000 activity in a sealed glass tube. 247 



Mem. N. Y. Box. Gard. 



Vol. IV. Pl. 9. 




If. 






ONAGRA BIENNIS. RADIUM CULTURE, No. 5 c. 



•^ 



PLATE lo 

PAGE. 

Onagra biennis. Radium culture No. loa. After pollination with 
unexposed pollen the capsule was exposed for 53 hours to rays 
from radium of 10,000 activity in a sealed glass tube . . . 248 



Mem. N. Y. Box. Gard. 



Vol.. IV. Pl. to. 







ONAGRA BIENNIS. RADIUM CULTURE, No. loa. 



PLATE II 

PAGE. 



Onagra biennis. Radium culture No. iib. Pollen exposed for 24 
hours to rays from radium of 1,500,000 activity in a sealed glass 
tube. Ovary not exposed ........ 248 



Mem. N. Y. Box. Gard. 



Vol. IV. Pi., ii. 




.;•■' -r^^y-h.---':^ 






' >■- .^^w ^ 



ONAGRA BIENNIS. RADIUM CULTURE, No. iib. 



PLATE 12 

PAGE. 

Figs. a-e. Onagra biennis. Radium culture No. iib. a, flower 
(minus corolla); b, petal; C, bud from lateral branch, with 
bract, showing the bursting open of the calyx by the pressure of 
the stigmatic lobes within ; d, bud, with bract, from main stem ; 
e, leaf from main stem ........ 249 

f-k. Onagra biennis. Radium culture No. loa. f, flower 
(minus corolla); g, mature capsule, with bract; h, petal; i, 
flower-bud, with bract, from main stem ; k, foliage-leaf from 
main stem .......... 249 



Mkim. N. Y. Bot. Gard. 



Vol. IV. Pl. 12. 











ONAGRA BIENNIS. RADIUM CULTURE, Nos. loa and 11 b. 



PLATE 13. 



PAGE. 



Onagra BIENNIS. RacHum Culture No. 1 5a broad leaf . The stigma 
was pollinated with unexposed pollen after the ovary had been 
exposed for 24 hours to rays from radium bromide of 10,000 
activity in a sealed glass tube 250 

Fig. a, flower-bud, with bract (lateral branch) ; b, petal ; C, nearly 
mature capsule, with bract (main stem) ; d, flower (minus 
corolla) ; e, leaf from main stem. 



Mem. N. Y. Bot. Gard. 



Vol. IV. Pl. 13. 




ONAGRA BIENNIS. RADIUM CULTURE, No. 15a, Broad Leaf. 



PLATE 14 

PAGE. 

Onagra biennis. Radium culture No. 15a narrow leaf. The stigma 
was pollinated with unexposed pollen after the ovary had been 
exposed for 24 hours to the rays from radium bromide of 10,000 
activity in a sealed glass tube ....... 250 

Fig. a, flower (minus corolla); b, petal; C, nearly mature capsule, 
with bract (lateral branch) ; d, flower-bud, with bract (main 
stem) ; e, foliage-leaf from main stem. 



Mem. N. Y. Box. Gard. 



Vol. IV. Pl. 14. 






ONAGRA BIENNIS. RADIUM CULTURE, No. 15 a, Narrow Leaf. 



^7-101 



New York Boljnicol Garden Library 

QK757 .G3 

Gager, Charles Stua/Effects of the 




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