LIBRARY OF THE NEW YORK BOTANICAL

GARDEN

University of California Publications in

BOTANY

VOLUME V

1912-1922

EDITOR

WILLIAM ALBERT SETCHELL

UNIVERSITY OF CALIFORNIA PRESS

BERKELEY, CALIFORNIA

1922

ACKNOWLEDGMENT

The tobacco investigations reported upon, in part, in this volume of the
University of California Publications in Botany have been made possible in large
measure by grants to the Department of Botany by the College of Agriculture
of the University from its allotment under the Adams Fund. First made some
fifteen years ago, these annual grants were continued until 1921. Two grants
have been made by the National Academy of Sciences, from the Bache Fund,
for the support of certain aspects of the work. The cost of -field operations
having greatly increased, the Research Board of the University of California
has for the last three years provided certain funds to supplement the allotment
from the Department of Agriculture.

In addition to the seventeen papers included in this volume, the following
articles based upon results obtained in this same series of investigations have
been published elsewhere.

Variation of Flower Size in Nicotiana. T. H. Goodspeed and R. E. Clausen.
Proc. Nat. Acad. Sci., vol. 1, pp. 333-438, 1915.

Parthenocarpy and Parthenogenesis in Nicotiana. T. H. Goodspeed. Ibid., pp.
341-346, 191.5.

Factors Influencing Flower-Size in Nicotiana with Special Reference to Questions
of Inheritance. T. H. Goodspeed and R. E. Clausen. Amer. Jour. Botany,
vol. 2, pp. 332-374, 1915.

Hereditary Reaction-System Relations — An Extension of Mendelian Concepts.
R. E. Clausen and T. H. Goodspeed. Proc. Nat. Acad. Sci., vol. 2, pp. 240-
244, 1916.

Mendelian Factor Differences versus Reaction-System Contrasts in Heredity.
T. H. Goodspeed and R. E. Clausen. Amer. Nat., vol. 51, pp. 31-46 and
92-101, 1916.

A Preliminary Note on the Results of Crossing Certain Varieties of Nicotiana
Tabacum. W. A. Setehell, T. H. Goodspeed, and R. E. Clausen. Proc. Nat.
Acad. Sci., vol. 7, pp. 50-56, 1921.

Inheritance in Nicotiana Tabacum. II, The Existence of Genetically Distinct
Red-Flowering Varieties. R. E. Clausen and T. H: Goodspeed. Amer. Nat.,
vol. 55, pp. 328-334, 1921.

Volume 11 of the University of California-Publications in Botany will contain
further articles dealing with the tobacco investigations.

[i]

CONTENTS

PAGES

Acknowledgment i

No. 1. Studies in Nicotiana, I, by William Albert Setchell 1-86

No. 2. Quantitative Studies of Inheritance in Nicotiana Hybrids, by

Thomas Harper Goodspeed 87-168

No. 3. Quantitative Studies of Inheritance in Nicotiana Hybrids, II,

by Thomas Harper Goodspeed 169-188

No. 4. On the Partial Sterility of Nicotiana Hybrids Made with 2S'.

sylvestris as a Parent, by Thomas Harper Goodspeed 189-198

No. 5. Notes on the Germination of Tobacco Seed, by Thomas Harper

Goodspeed ^ 199-222

No. 6. Quantitative Studies of Inheritance in Nicotiana Hybrids, III,

by Thomas Harper Goodspeed 223-231

No. 7. Notes on the Germination of Tobacco Seed, II, by Thomas

Harper Goodspeed 233-248

Xo. 8. Parthenogenesis, Parthenocarpy, and Phenospermy in Nicotiana,

by Thomas Harper Goodspeed 249-272

No. 9. On the Partial Sterility of Nicotiana Hybrids Made with N.
sylvestris as a Parent, II, by T. H. Goodspeed and A. H.
Ayres 273-292

No. 10. On the Partial Sterility of Nicotiana Hybrids Made with N.
sylvestris as a Parent, III, by T. H. Goodspeed and J. N.
Kendall 293-299

No. 11. The Nature of the Fi Species Hybrids between Nicotianci syl-
vestris and Varieties of Nicotiana Tahacum, by T. H. Good-
speed and E. E. Clausen 301-346

No. 12. Abscission of Flowers and Fruits in the Solanaeeae, with

Special Eeference to Nicotiana, by John N. Kendall 347-428

No. 13. Controlled Pollination in Nicotiana, by Thomas Harper Good-
speed and Pirie Davidson 429-434

No. 14. An Apparatus for Flower Measurement, by T. H. Goodspeed

and E. E. Clausen .' 435-437

No. 15. Note on the Effects of Illuminating Gas and its Constituents
in Causing Abscission of Flowers in Nicotiana and Citrus,
by T. H. Goodspeed, J. M. McGee, and E. W. Hodgson 439-450

No. 16. Notes on the Germination of Tobacco Seed, III, by T. H.

Goodspeed 451-455

No. 17. Inheritance in Nicotiana Tahacum, I, A Eeport on the Crossing
of Certain A'arieties, by William Albert Setchell, Thomas
Harper Goodspeed, and Eoy Elwood Clausen 457-582

[ii]

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 1, pp. 1-86, pis. 1-28

Issued December 5, 1912

STUDIES IN NICOTIANA. I.

BY

WILLLiM ALBERT SETCHELL

LIBRARY
NEW YORK
fiOTANICAL

In 1906, as a consequence of a certain interest in the history
of the origin and spread of the use of tobacco, I began to culti-
vate such species of Nicotiana, both native and horticultural, as
I could obtain seed of, in the Botanical Garden of the Univer-
sity of California. In all a total of 103 packets were sown that
year, and from 75 packets good plants were obtained. Of many
of these, seed was produced under bag and for the most part
this "pure seed" was from a single plant. Since 1906 the sow-
ings have been continued each year, from seed of the previous
year, as well as from seed from new sources, until finally a very
considerable assortment of species and varieties have been
grown. Gradually the number of plants have been reduced and
selected to a certain number to serve as a stock for breeding.
It is my intention in the present volume to publish the results
of the experience of myself and others, in connection with the
cultivation and experimentation with this stock of Nicotiana in
the Botanical Garden of the University of California.

The expenses of these investigations have been borne partly
by the funds granted by the President and Regents of the
University of California for the up-keep of the Botanical Gar-
den and partially by certain allotments from that portion of
the Adams Fund of the United States Department of Agricul-
ture granted to the Agricultural Experiment Station of the
University of California. Through these means the work on the
Nicotiana species, detailed in this volume, has been carried on.

C5

Lu

2 University of California Publications in Botany [Vol. 5

The sources of supply for seeds have been collectors and
botanical gardens. From various collectors, seeds of wild species
have been obtained, particularly of the Pacific Coast and of
Texas. From the botanical gardens of Europe and America I
have been able to obtain seeds of most of the cultivated species,
and from the various divisions of the Bureau of Plant Industry
I have been able to obtain seeds of many of the cultivated
varieties and forms of Nicotiana Tahacum.

At first the study was largely systematic and morphological,
with the entirely and naturally to be expected result that it was
found that very considerable confusion existed in the naming of
the diff'erent plants. Some two or three years were devoted to
growing almost everything that could be obtained and attempting
to straighten out the nomenclature, which has been a matter of
no little difficulty. The only recent revision is that of Comes
(1899) and this has been used, so far as it clearly applies, in
unravelling the tangle of names current in trade and in the
botanical gardens.

After careful growing and selecting, about seventeen species
as generally recognized, remain, together with some well-marked
varieties. It seems best to enumerate and discuss these to some
extent, in order that a basis may exist for more exact knowledge
of the work in the following pages. I hope, also, to be able
to return to these later and publish a critical discussion of them.

Comes in his "Monographic du genre Nicotiana" (1899),
divides the genus into four sections, viz., I, Tahacum ; II, Rus-
tica; III, Petunioides, and IV, Polidiclia. This classification is
that of G. Don (1838) as well as of Dunal (1852). For reasons
which will be discussed in a later paper, it seems that IV, viz.,
Polidiclia, cannot be separated from III, viz., Petunioides. Con-
sequently I have retained I, II, and III, and will discuss the
stock of species and varieties collected in the Botanical Garden
of the University of California under these three sections. (At
the very time of writing this, I receive East's paper (1912) en-
titled "A Study of Hybrids between Nicotiana Bigelovii and
N. quadrivalvis." He also gives very convincing reasons for
combining the sections Petunioides and Polidiclia) .

1912] Setchell: Studies in Nicotiana

Section I. Tabacum G. Don

Nicotiana Tabacum L.

Under this section there is usually included only one species,
viz., Nicotiana Tabacum L. It seems to include all those species
of Nicotiana in which the corolla is of various shades of red or
occasionally white (albino?), infundibuliform, with the throat
somewhat to much inflated, and with the limb patent. The
flowers are in panicled corymbs. Under the single species N.
Tabacum is grouped a most varied assemblage of varieties, forms,
and suspected hybrids as ever were brought together under one
specific name. Comes (1895, 1899, and 1905) has attempted
to arrange the various forms under some six varieties and also
under various supposed combinations of hybrid origin. The re-
sult has been to bring some order out of chaos and to point
out certain experimental possibilities. Anastasia (1906) has also
concerned himself with an inquiry into the typical varieties of
Nicotiana Tabacum. He differs somewhat in his ideas from
Comes. Howard and Howard (1910) have attempted to arrange
and illustrate the types of Indian tobaccos constant in their char-
acters, and Hasselbring (1912) has just discussed the types of
N. Tabacum grown in Cuba, showing that they remain true to
type when grown also in Michigan.

In these various papers it is evident that all the variety of
plants to be referred under N. Tabacum in its broad and com-
prehensive use fall under seeming combinations of a few types.
The further question as to the origin of these combinations has,
as yet, been merely suggested but not proven. Probably there
will be no exact agreement, for a while, as to just what the
simplest expressions of the fundamental types are, nor can it
be settled except by continued and extended experimentation,
if it can ever be settled at all. Comes has selected and described
six typical varieties and referred all others as combinations of
two or more of these. Anastasia thinks that there are only four.
I have tentatively selected five as seemingly fundamental. These
three sets thus selected are not coincident for the greater part.

4 University of California Publications in Botany [Vol.5

Since it is my intention to discuss this matter later and since,
at present, it is desirable only to enumerate and make reason-
ably plain what plants have been used in the work carried on
in the Botanical Garden of the University of California (U. C.
B. G.), I shall content myself with giving a list with descriptive
remarks of the types which have appealed to me as being
possibly fundamental or of other interest in experimentation.
In connection with each I shall use the number by which it
has been designated in the U. C. B. G.

"Brazilian"

11
TJ. C. B. G. 05. — The seed of this number was received

under the name of "Choice Brazilian American" from the
United States Department of Agriculture in 1905. Its habit
and general characters are well shown in the photograph repro-
duced in plate 1. It is a tall plant, averaging about six feet
in height, producing laterals in succession above, but barely
being overtopped by them. The leaves are long, broad, and
decidedly cucullate at the tip. They are thin and silky in
texture, being minutely glandular-pubescent. The corolla is
pink, tubular below graduallv and moderatelv infundibuliform

_fi8 ' 12

above, being more swollen than 07, but less so than 05. about

18

equally so with those of 05. Altogether the plant is very near
to a plant grown in the U. C. B. G. from seed sent by Professor
Dr. 0. Comes, labelled as being of his Nicotiana Tahacum var.
hrasiliensis. It does not seem to answer exactly to his figure
of that variety (1899, VI) nor exactly to that of .V. Tahacum
var. havanensis {loc. cit. VII). In his later work (1905, p.
81, fig. 27) Comes figures a plant which he designates as
"Bahia" and which he considers as a combination of
his varieties hrasiliensis and havanensis which is close to our
plant, but not exactly of the same inflorescence at least. The
plant designated by Anastasia (1906, opp. p. 102) as A. Tah-
acum var. hrasiliensis is verv nearly the same as ours. It seems

21
therefore, that we may designate the plants bred from 05

U. C. B. G. seed as "Brazilian." Its exact characters and

relation to other "Brazilian" combinations as well as "Havana"

combinations will be considered when certain experiments involv-

1912] Setchell: Studies in Nicotiana 5

ing it as one of the factors are discussed in a paper which it
is hoped may be published later.

"Cavala"

U. C. B. G. 05. — The seed from which the plants were raised
and continued under this number in our botanical garden was
obtained from the United States Department of Agriculture.
They were labelled "Cavala Tobacco" and w^ere No. 11497 of
the U. S. D. A., obtained from Turkey. The habit and general
characters of the plant are well represented in the photograph
reproduced on plate 2. It is a tall plant with upper and middle
laterals which more or less overtop the original panicle. The
leaves are short, compared with those of nearly all the other
members of the N. Tabacum-group, peculiarly and more de-
cidedly rugose on the upper surface as well as velvety, shaped

22

more like those of 07 {Nicotiana Tahacum var. macrophylla
Comes) but more tapering towards the base and long and nar-

oo

rowly decurrent. The flowers are also nearer to those of 07
than to the others. In color, how^ever, they are pink. The lobes
are broad and rather shallow, but they are tipped with a short
recurved point. The tube is slender below but is stout and
broadly infundibuliform above.

This plant is not to be identified with any of the typical
varieties of either Comes or Anastasia. Nor do I identify it
with any of the cultivated varieties figured by them. I shall
simply call it Cavala and discuss its position and influence in
breeding, later. The texture of the surfaces of the leaf and the
shape and decurrence of the leaf make it a desirable plant in
crossing.

"Maryland"

13.
TJ. C. B. G. 05. — The seed from which the stock of plants

designated by this number has been obtained was distributed

by the United States Department of Agriculture in 1905, and

designated as "Maryland," with the identifying number "205-

20-7." In habit, as well as other characters, it is decidedly

different from the two varieties just described. It is of some-

6 University of California Piihlications in Botany [Vol. 5

what lower stature and the spreading leaves at the base give it
a sort of pyramidal (or conical) shape (cf. plate 3). The leaves
are long, broad in the middle and tapering very rapidly to each
end. At the apex is a fairly long point curved to one side, while
the base is narrow, to expand at the junction of the stem into
two broad clasping auricles. The panicle is ample as compared
with that of other members of this section. The flowers are
very light pink, with slender tube and infundibulum and with
the limb broadly but deeply lobed. The lobes have slender in-
curved points. It would be classed by both Comes and Anas-
tasia as a combination form under Nicotiana Tahacum var. vir-
ginica. It comes near to the plant figured by Anastasia (1906,
opp. p. 30) and hy Comes (1899, pi. V) but is not identical with
either. It seems best to call it "Maryland." The original
Nicotiana virginica Ag. (1819, p. 18 ), as represented by the
type-specimen in the Herbarium of the University of Lund, is of
the same general type, as is also the type of Nicotiana Tahacum
L. of Linnaeus 's herbarium in London. The type-specimen of
N. fruticosa in the Linnaean Herbarium seems also to belong
here but may possibly, however, represent the plant referred

71

by Anastasia (cf. above under U. C. B. G. M) to var. hrasili-
ensis. The plant in Hb. Agardh is decidedly narrow-leaved and
may be near to what ComeS (1899, p. 10, pi. IV) has called
var. lancifolia. From what could be seen of the flower, it
seemed to be broader-lobed than that represented by Comes for
this latter variety.

Nicotiana Tabacum var. calycina

UO
V. C. B. G. 05. — This is the plant known in botanical gar-
dens as Nicotiana Tahacum var. calycina. The seed was re-
ceived from the Botanic Garden of the University of Cambridge
in 1905. It has remained constant in its peculiarities, ever
since, under conditions of pure-line breeding. In habit, it is
peculiar, as shown in the photograph reproduced in plate 4. The
lower laterals soon come to equal the main axis or even slightly
to overtop it, so as to obscure it as a main axis. The leaves are
large, approaching in shf^pe the members of the firgr mica-group

1912] Setchell: Studies in Nicotiana 7

13.
(such as U. C. B. G. 05). The lower leaves are broader (pro-
portionally) in the middle and taper more abruptly to each end

78.

than do those of the Maryland (U. C. B. G. 05). The auricles
at the base are hardly discernible in the calycina, while they are
decidedly pronounced in the Maryland. While this plant is
distinct in habit and leaf, it is still more characteristic in its
flower. The flower is double of the "hose-in-hose" pattern. The
calyx is more or less petaloid and colored bright pink or light
red, as is also the corolla. Sometimes the whole calyx is petaloid
in color (whitish tube, pink above and deep pink limb) or it
may have some green in it, usually irregularly distributed. Both
calyx and corolla are split on one side, in most cases, and even
to the very base. Both are deciduous, leaving the capsule
naked. The lobes of the limb of both calyx and corolla are
broadly but deeply lobed and the lobes have long laterally curved
points. The capsule is more oblong than that of other members
of the Tahacum-groii'p. The inflorescence is more compact
than that of other members of the Tahacum-grouj) with the
exception of the members of the group surrounding N.

angustifolia {N. TahacMm var. fruticosa Comes, not Hook.,

fis UP

U. C. B. G. 07). In fact, this plant (U. C. B. G. 05) com-
bines characters of the angustifolia- and of the virginica-^edion^
with its own peculiar teratological features. This plant will be
referred to as Nicotiana Tahacum var. calycina, or simply as
calycina.

"White Tobacco"

30

U. C. B. G. 06. — A plant of the Ta&acwm-group with cream-
white flowers has been bred in our botanical garden for sev-
eral years, and in the pure-line cultures has retained its color
and other characters perfectly. It came from seed distributed
from the Missouri Botanical Gardens in 1905. An inquiry
directed to Director William Trelease in 1910 as to its source,
brought out the information that the original plants were
found by him in Mexico, growing "in that interesting
little village, Maltrata, at the foot of the first descent from the
table-land down toward Vera Cruz on the Orizaba side." He

8 University of California Publications in Botany [Vol. 5

says further : "I found the ordinary piuk-fiowered form and
the white one growing as wayside weeds and gathered a con-
siderable quantity of the white form because of its striking
appearance. From the occurrence of the plants I should sup-
pose that there was every reason to anticipate crossing of the
two forms but, so far as I knew of it, all of the seedlings that
we raised from the white seed bred true." Our experience has
been that it breeds true when protected by bag, but one year,
seed which had been taken from an unprotected plant gave a
pink-flowered form whose bagged seed, in turn, gave a consider-
able variety of colors, stature, etc., in the plants raised from
them.

The White Tobacco as we have called it, is a tall plant,
up to six feet high and over, of simple habit, only the upper
flowering laterals developing. It is well shown in the photo-
graph reproduced in plate 5. The leaves are much like those

22.
of A'^. Tahacum var. macrophylla Comes (U. C. B. G. 07) except

that they are more rounded at the middle, have a decidedly

prolonged point, and are rugose and downy above. The flowers

22
are like those of U. C. B. G. 07 except in color.

This is a most interesting plant. It has the habit more

72

of the Cavala (U. C. B. G. 05) of which it has also the pecul-
iarities of the surface of the leaf (both rugosity and downiness).
It has, however, the general leaf-shape and flower-shape of

22

U. C. B. G. 07 (iV. Tahacum var. macrophylla Comes), and
these are combined with an apparently albino character
in the flower. It is a poor seeder, a characteristic pointing
toward a possible hybrid origin. The seed is apt to be both
comparatively scanty and of poor germinating power.

Nicotiana Tabacum var. macrophylla

22.
V. C. B. G. 07. — This is the Nicotiana Tahacum var. macro-
phylla of Comes and was grown from seed kindly supplied by
Professor Comes from his plants at Portici near Naples. It
has the essential characteristics described and figured by him
for this variety (cf. Comes, 1899, p. 18, pi. VIII), but does not

1912] Setchell: Studies in Nicotimm 9

correspond perfectly' to his figure. It is a low plant with ascend-
ing laterals and broad leaves. The habit is well represented
in the photograph reproduced in plate 6. The leaves are broad
proportional to their length, rounded and abruptly narrowed
into a very short point above, but gradually tapering to a broad
clasping base below with rounded but not prominent basal
lobes (hardly to be termed auricles). A comparison of the
habit-photograph mentioned above with the plate of Comes will

22.
show how U. C. B. G. 07 differs from his var. macrophylla.

The flowers are deep rose color to red with stout tube and

abruptly swollen, broad infundibulum, and with the limb almost

pentagonal. It is marked at the very shallow sinuses with

triangular depressed whitish areas as represented in the figure

of Comes (1899, pi. I and pi. VIII). The capsule is broad,

short, rounded and nearly enclosed in the calyx (cf. Comes,

1899, pi. I). This will be referred to as Nicotiana Tabacum

var. macrophylla.

Nicotiana angustifolia

U. C. B. G. 07. — The seed whence the plants designated by
this number have sprung was obtained in 1907 from the authori-
ties of the Jardin Botanique de la Faculte de Medecine du Lyon,
under the name of Nicotiana angustifolia. It is the plant known
early under the name of Petum angustifolium (cf. Clusius,
1605, p. 310) and has passed by the name under which we
we received it since 1768 (cf. Miller Diet. ed. viii). It belongs
to the group of Tahacum varieties placed under N. fruticosa or
those with distinct and non- or only slightly alate petioles. It
is very near the N. Tabacum var. fruticosa of Comes (1899, p.
8, pi. I, III), but that is evidently not the Nicotiana Tahacum
var. fruticosa of Hooker (1876, pi. 6207) which is a plant with

11
a sessile clasping leaf and much nearer to U. C. B. G. 05. It

is not the same plant as the one in the Linnaean Herbarium
preserved as the type-specimen of N. fruticosa L. It is impos-
sible for me, at present, to attempt to unravel the synonymy
of this plant further, but it will be quoted in the following pages
as N. angustifolia, using this binomial simply as a convenient

10 University of California Publications in Botany [Vol.5

designation for the present. It is not X. angustifoUa Ruiz &
Pa von, however.

N. angustifoUa, or U. C. B. G. 07, is a comparatively low
plant, about three feet in height as a rule, of decidedly corym-
bose habit, i.e., the main axis is of limited growth in height and
is soon equalled or even overtopped by several (or all) of the
laterals. A young plant is represented in the photograph repro-
duced in plate 7. The leaves are distinctly petioled and the
petiole is naked, at least in the lower half or third. The blade
of the leaf is obliquely ovate-lanceolate, tapering gradually into
a long, laterally curved point. The base of the blade is broadly
rounded and is decurrent along the upper half (or even two-
thirds) of the petiole as a narrow wing. The blade is more
or less conduplicate. The upper leaves are shorter-petioled, nar-
rower, and shorter-pointed than the lower, while the upper-
most are often reduced to very narrow linear shapes. The
petiole is provided with two sharp angles at the junction of
the upper (almost flat) and the lower (very convex) surfaces.
There are no auricles at the base of the petiole. The panicle
is crowded with slender flowers. The calyx is narrow and with
long slender lobes. The tube of the corolla is slender below,
expanding gradually and not considerably, into a narrow infundi-
bulum. The tube of the corolla in .V. angustifoUa is the most
slender, especially as to the uifundibulum, of any of the A"".
Tahacum group. The limb is very light pink and deeply divided
into narrow lobes which are broader below but above are abruptly
narrowed into long, slender lanceolate tips.

In habit U. C. B. G. 07, or X. angustifoUa as we mav call

22
it. is near to U. C. B. G. 07, being more slender, but in its

petioled leaves, its crowded panicle, its slender flowers with

narrowly and deeph' lobed limb, it is most distinct from all

others of the Jafoaci/m-group under cultivation at present in

the U. C. B. G.

Nicotiana Tabacum var. macrophylla purpurea

U. C. B. G. 06 was received from the Missouri Botanical
Garden in 1906 under the name of Xicotiana sanguinea. It is

1912] Setchell: Studies in Nicotiana 11

one of the plants usually known in gardens under that name.
It is tall, six feet high or over, with large deep-red flowers,
of the same shape as, though with rather deeper color than,

22

those of .Y. Tahacum var. macrophylla (ef. U. C. B. G. 07).
N. sangninea is designated by Comes (1899, p. 20) as "N. Tah-
acum var. macrophylla purpurea,' ' but it is to be noted that
he expressly states that his .Y. Tahacum var. macrophylla pur-
purea includes both .Y. sanguinea and N. purpurea of the gar-
dens, but only partially as to each. These two garden tobaccos
vary in height, robustness, and color of flower. Even the shape
of the flower varies among the different plants referred here.
The leaves are ample, with f&irly long, broad-winged petiole,
broadly ovate blade, which is more or less cucuUate at the tip.
There are combined in this plant characters of our .Y. angusti-

folia (U. C. B. G. 07) as to petiole, .Y. Tahacum var. hrasiliensis

(our Brazilian, U. C. B. G. Oo) as to cucullate tip, tallness, and

perhaps also the wing on the petiole, and N. Tahacum var. macro-

22
phylla (cf. U. C. B. G. 07) as to flowers. I have produced plants

similar to this, but lacking tallness and the cucullate tip to the

blade of the leaf, in F, from crosses between U. C. B. G. 07 and

07. X. sanguinea, at least so far as U. C. B. G. 06 is concerned, is
a poor and uncertain seeder. This leads one to suspect a pos-
sible hybrid origin. It has bred true in the U. C. B. G., how-
ever, for several years. This tobacco is grown, chiefly at any

rate, as an ornamental plant. U. C. B. G. 06 is well represented
in plate 8. The two garden species, known as .Y. sanguinea and
N. purpurea vary in height and robustness but those with the
darker flowers are called N. purpurea while those with the lighter
flowers are called .Y. sanguinea.

Section II. Rustica G. Don

In this second section of the genus are placed all the yellow-
flowered species and varieties. The color is usually simply yel-
low, but, at times, in certain species, it may be mixed with red
or even with white. The shape of the corolla varies much. It
may be infundibuliform, hypocraterimorphous, ventricose, or

12 University of California Publications in Botany [Vol. 5

even nearly tubular. The corolla of all species of Nicotiana is
more or less irregular, being slightly zygomorphous merely in
most cases, but in two species of the i?Msfica-section, viz., N.
glutinosa and N. tomentosa, it is decidedly irregular as well as
being deeply tinged with red. The flowers are in simple or
p&uicled racemes. Of about sixteen species credited by Comes
(1899) to this section, six are commonly cultivated in gardens
and are represented in the collections of the U. C. B. G., together
with several fairly distinct varieties.

Nicotiana rustica L.

Many varieties and forms of Nicotiana rustica are cultivated
and while, perhaps, the variability of the plants included under
this name is not quite so great as is the case with those included
under N. Tahacum, yet it is certainly very great. Forms of
this species were cultivated and used for smoking by the North
American Indians from Mexico and Texas north along the west-
ern banks of the Mississippi River to Minnesota, eastward
to the Atlantic seaboard and north thence to Canada. It was
the first tobacco cultivated by the English in Virginia, although
it was soon supplanted by varieties of Nicotiana Tahacum
brought from northern South America and the West Indies.
Its culture spread to Europe, where it is cherished locally as
a peasant tobacco, as well as to Asia and to Africa. It is to be
expected that many varieties may be found in a species so
widely and so long cultivated. Comes (1899, pp. 20-24) has
distinguished six varieties, all of which have been grown in the
U. C. B. G. from seed kindly furnished by Professor Comes
himself. Many sowings of this species of seed from other sources
have also been made and the following seven varieties have been
selected for further work.

Nicotiana rustica var. asiatica

Z7. C. B. G. 07. — Nicotiana rustica var. asiatica Schrank
(1807, p. 264), as interpreted by Comes (1899, p. 22, pi. II,
XII), is fairly tall, with ample leaves, which are more or less
heart-shaped, and a spreading panicle. The seed came from Pro-

1912] Setchell: Studies in Nicotiana 13

fessor Comes and the plant has held its characters in the U. C.
B. G. since 1907. It comes near to .Y. rustica var. jamaicensis

Comes (U. C. B. G. 07) in its spreading habit, but the leaves
are more cordate than in the latter variety. The photograph
reproduced in plate 9 represents one of the less ample plants.

Nicotiana rustica var. brasilia

13.
U. C. B. G. 07. — Nicotiana rustica viar. hrasilia Schrank

(1807, p. 264) as interpreted by Comes (1899, p. 22, pi. II, XI),
is a fairly tall, robust plant, very distinct from the other varieties
of N. rustica. The stem is stout, clothed below with large, thick
heart-shaped leaves which are decidedly rugose. The panicle,
when well developed, is long tapering and of massive appear-
ance, with crowded flowers. This is well shown in the photo-
graph reproduced in plate 10. Later, by the growth and flower-
ing of the laterals, the panicle appears more spreading, as repre-
sented in the plate of Comes (1899, pi. XI). The seed came from
Professor Comes and the plants have preserved their charac-
teristics when bred in the pure line, in the U. C. B. G., since
1907.

Nicotiana rustica var. humilis

1±
TJ. C. B. G. 07. — Nicotiana rustica var. humilis Schrank (1807,

p. 264), as interpreted by Comes (1899, p. 23, pi. II, XIII),
is a fairly robust plant, but of low stature and early blossom-
ing and ripening. A fairly typical plant is represented in
plate 11. The leaf is broad and ovate, being broadly, but slightly
cuneate at the base. The panicle is comparatively simple. This
variety is nearer to N. rustica var. jamaicensis Comes than to
any other variety, but is more simple in habit and with leaves
more perfectly ovate with the base more cuneate and even. The
seeds were obtained from Professor Comes and the plant has
held its characteristics in the U. C. B. G. since 1907. This species.

14

at least as represented by No. 07, comes near to N. rustica var.

17

texana, at least as represented by U. C. B. G. 07. The two plants
are still being studied.

14 University of California Publications in Botany [Vol.5

Nicotiana rustica var. jamaicensis

15

U. C. B. G. 07. — Nicotiana rustica var. jamaicensis Comes
(1899, p. 21, pi. II, X) is a plant not always to be readily
distinguished from N. rustica var. asiatica, on the one hand, and
N. rustica var. humilis on the other. It has a less spreading
habit than the former, but more than the latter. Its leaves are
not so cordate as those of the former, but at the same time
they are more rounded than those of the latter. It holds its
characters when bred in the pure line as it has been in the
U. C. B. G. since 1907. The seed was received from Professor
Comes himself. It is shown in plate 12.

Nicotiana rustica var. scabra

V. C. B. G. 07. — Nicotiana rustica var. scahra (Cav.) Comes

as interpreted by Comes (1899, p. 23, pi. II, XIV) is a most

characteristic plant and seems worthy of independent specific

rank, so much does it differ from the other varieties of N.

rustica. It is a tall plant and decidedly pruinose. While the

plate of Comes {loc. cit.) represents a plant of rather spreading

habit, the plants of the U. C. B. G., grown from seed sent from

Portici by Professor Comes himself, are more strict; some of

them are in fact of very narrow habit. Unfortunately I have

no photograph to represent this number as vet, but a fairlv

26
typical specimen of this variety is represented by U. C. B. G. 06

and is reproduced in plate 13. The var. scahra is not only dis-
tinct in its general habit, size, and pruinose appearance, but
it has a bluish purple color to the buds and young twigs and
smaller and more crowded flowers, which are greenish yellow.
It lacks glands except on the flowering axes, being clothed else-
where by a thick and compact covering of white, slender hairs
abruptly bent at the middle. Above, among the flowers, these
are mixed with the ordinary stalked, multicellular glands com-
monly found in the species of Nicotiana.

I9i2] Setchell: Studies in Nicotiana 15

Nicotiana rustica var. texana

1 7

U. C. B. G. 07. — Nicotiana rustica var. texana (Naud.) Comes,
as interpreted by Comes, is shown in plate 14, representing a
plant from pedigreed seed kindly sent by Professor Comes in
1907. It is a coarse plant, next lowest in stature to var. humilis,
to which it approaches more nearly than it does to other varieties
of i\^. rustica. Its habit is looser, as to the panicle, and the leaves
are more rounded at the base. The flowers are more slender
than those of N. humilis. On the whole, however, the two
varieties are very close to one another, (cf. plate 14).

Considering all the varieties and forms of Nicotiana rustica
which I have been able to obtain and cause to grow in the
U. C. B. 6., the varieties brasilia and scahra are the most dis-
tinct, yet all have more or less definite points of distinction.
Most of the plants of this species from other sources which have
been grown may be referred more or less definitely to one or
other of the six varieties enumerated above or seem to be inter-
mediate betw^een some two of them. One other stock, besides

169
those mentioned above has been retained, viz., TJ. C. B. G. 08.

Nicotiana rustica var. puniila ?

TJ. C. B. G. 08. — This is referred with doubt to Nicotiana
rustica var. pumila Schrank (1807, p. 264) and is represented
in the photographs reproduced in plates 15 and 16. This plant
is the lowest of all the members of the N. rustica assemblage
which have come under my observation. It is 12 to 14 inches
high, matures early, and is loose in habit. Its leaves are ovate-
lanceolate and unequal at the base. They are small compared
with those of the other varieties of N. rustica. For three seasons,
bred in the pure line, it has retained its lowly habit, earliest
flowering of all the varieties of .V. rustica, and its narrow leaves.

Nicotiana Langsdorffii Weinm.

This species was described by Weinmann (p. 323) and by
Schrank (pi. 72) in 1819 as coming from Brazil and was intro-

16 University of California Publications in Botany [Vol. 5

duced into cultivation the same year apparently. It was
originally collected by Langsdorff, who sent the seeds to "Wein-
mann. The description speaks of the flowers as green and the
anthers as azure. The type of the species is a fairly well-known
garden plant. It has been cultivated in the U. C. B. Gr. under

22 102

various numbers, such as 02 and 05. The latter number is
well represented in the photograph reproduced as plate 17.

N. Langsdorffii is a plant of three or four feet in height, of
loose and spreading habit. Its leaves are elliptical-lanceolate,
patent, narrowed and sessile by a long decurrent base. They
are decidedly rugose above. The corollas are funnel-shaped
below with a gibbous ring above and a concave, spreading limb
slightly notched in five broad, shallow lobes. They are
greenish yellow and pendent, or at least nodding. The pollen
is azure. The capsules are for the most part 2-celled, but 3-celled
capsules are not uncommon.

While the type is unmistakable and is well represented in
the plates in the Botanical Magazine (cf. Sims, 1821, pi. 2221
and 1825, pi. 2555), there are plants often referred to it which
Comes has mentioned as varieties.

iV. Langsdorffii var. grandiflora Comes (1899, p. 28) is the
plant of the gardens usually known as N. commutata Fischer et
Meyer (1846, III, p. 377). It is a plant of less slender and
less spreading habit, larger flowers, which are more deeply
notched, more decidedly zygomorphous, and with the limb more
spreading. The outside of the corolla is greenish yellow as in
the type, but the inner (upper) surface of the corolla is milk-
white. The flowers also are ascending, not pendent or hanging.
The pollen is slightly bluish, not at all azure, but the anther
coats are purplish brown. Altogether, the characters recall
those of Nicotiana alata var. grandiflora Comes (1899, p. 37)
which is N. affinis Moore (1881, p. 141, fig. 31), except that the
flowers are smaller and more decidedly yellow outside. It may
be of hybrid origin. It is said to have been known in gardens
since 1835, but its native country is uncertain. In the U. C.

]07

B. C, it is represented by number 08 (cf. plate 18), where its
behavior is being studied and about which it is hoped to publish

1912] Setchell: Studies in Nicotiana 17

something at a later date. Thus far it has produced both whites
and pure yellows. Lock (1909) has made some experiments in
crossing N. Langsdorffii and N. alata, with very interesting re-
sults as to corolla-shape and color, and also as to color of the
pollen. Both the F^ and the Fo generations in Lock's experi-
ments presented intermediates.

X. Langsdorffii var. longiflora Comes is another intermediate
sort of variety described by Comes {loc. cit.). I have not had
any plants which answer exactlv to his description, but under

173

No. 08 U. C. B. G. (cf. plate 19), there appeared yellow-flowered
forms (even the inner, or upper, surface of the limb being yel-
low) which comes close to it, as do also certain plants cultivated

70.

under the number 06 U. C. B. G., which also have given both
yellow and white-limbed flowers. All these are being bred in
pure line to be reported on later.

Nicotiana paniculata L.

This well-known and widely cultivated species has been

grown in the U. C. B. G. under several different numbers and

106
from several different sources. No. 05 U. C. B. G. is well

represented in the photograph reproduced in plate 20. It is
a spreading plant up to three or four feet high, the panicle
being very effuse. The leaves are broad and slightly cordate,
moderately long petioled. The flowers are pale yellow and long
tubular, being slightly gibbous just below the limb. The limb
is narrow, at first concave, but flattened or somewhat reflexed
in full anthesis, broadly and very slightly rounded five-lobed.
The capsule is narrow.

This species is reported to have been under cultivation since
the middle of the eighteenth century, having been discovered
in Peru in 1752. The plant in the Linnaean Herbarium is exactly
the one grown in the U. C. B. G. It is said to be used as a tobacco
for the pipe, being mild and of exquisite aroma. It remains con-
stant when cidtivated, although at times the flowers are curved
nearly into a circle.

18 University of California Publications in Botany [Vol. 5

Nicotiana glauca Graham

N. glaiica is a tree tobacco, since it is a perennial and forms
a trunk of considerable height and girth. It has spread from
its original habitat into a considerable number of tropical and
warmer temperate countries. It is probably a native of central
South America. It is a common escape in Southern California
where it is thoroughly naturalized and commonly reaches a
height of ten or twelve feet. It grows fairly well in central Cali-
fornia too and has appeared in abundance in San Francisco in the
section burned over in 1906. The stem is woody and much
branched. The leaves are long petioled, ovate-lanceolate, glabrous
and glaucous. It is the most nearly glabrous Nicotiana we have

5

cultivated in the U. C. B. G. (No. 10). The flowers are pale
yellow, long tubular, slightly gibbous above and with the almost
pentagonal limb deepl,y concave. In flower, it comes nearest
to N. paniculata. W. J. Hooker has accurately figured and

described it (1827, pi. 2837). Comes (1899, p. 27) has de-
scribed three varieties which I have not, as yet, been able to
distinguish.

Nicotiana glutinosa L.

This is one of the most peculiar of the annuals of the
section Rustica in its foliage and its flowers. It is a very robust
plant, as represented in the photograph reproduced in plate 21.
The leaves are broadly and deeply cordate and abruptly acumin-
ate. The whole plant is pubescent-villose and extremely glandu-
lar sticky. The racemes are long, circinate at the tip, and with
the flowers alternate in two ranks on the same side. The
flowers are unlike those of any Nicotiana in shape except those
of N. tomentosa. They are short cylindrical below, suddenly
swollen above, where they open out in an irregular obliquely one-
sided funnel. The limb is fairly bilabiate, the stigma and
anthers being connivent just under the middle lobe of the upper
lip. The color is light yellow tinged with deep red. The flowers
easilv fall especially when there is a drop in temperature.

79.

Under No. 07 it has been cultivated in the U. C. B. 6., in the

1912] Setchell: Studies in Nicotiana 19

pure line, for several j-ears and retains its characters perfectly.
The plant in the Linnaean Herbarium is exactly the one cul-
tivated in the U. C. B. G. and elsewhere, and which passes
universally under this name.

Nicotiana tomentosa Ruiz & Pa von.

N. tomentosa is a second "tree tobacco" rivalling N. glauca
in height and exceeding it in display as a foliage plant because

|()8

of its huge leaves. U. C. B. G. 08 is the number applied to
plants of this species grown in Berkeley, where one plant has
survived three winters outside, the first under protection of
a cheese-cloth tent and with some heat at nights, the second
and third without protectioii. It is now a bushy plant of spread-
ing habit, about twelve feet high, and has blossomed thrice, but
since it begins to blossom in midwinter, few of the earlier blossoms
arrive at anthesis. Some of the latest do, however, and in the
present year (1912), it has produced abundant panicles for
several months. The shape of the corolla is nearest to those of N.
glutiiiosa, being obliquely inclined, very gibbously inflated into a
broad funnel above and nearly bilabiate. The color is light yellow
tinged with red. The style and stamens are exserted, projecting
fully as much as the length of the corolla. Both flowers and leaves
are well figured by Hooker (1892, pi. 7252). On account of the
peculiarities of the flower, Sprengel (1817, p. 458) made it the
type of his new genus, Lehmannia. It was named by Andre
(1888, p. 511) Nicotiana colossea, and it has appeared in gar-
dens and has been cultivated as a foliage plant under this
name. It is usually raised under glass and placed outside only
in the warmer season. It begins to flower in the U. C. B. G.
in December and continues to do so for several months. It is
a native of Brazil and Peru. A small plant grown from a cutting
is represented in plate 22.

Section III. Petunioides G. Don.

The species of Nicotiana belonging to the Petunioides-^Qoiion
have salver-shaped corollas, which are white or tinged with red
or purple, arranged in racemes or panicles. In this section,

20 University of California Publications in Botany [Vol.5

I have included the section PoUdidia of Gr. Don, an arrange-
ment which seems to me natural and which I shall hope to
justify further on (cf. also Miers, 1846, p. 182 and East, 1912).
Of the twenty-four species included by Comes (1899) in these
two sections, ten are cultivated in the U. C. B. G.

Nicotiana noctiflora Hook?

The description of this species as given by W. J. Hooker

(1827, pi. 2785) is such that I hesitate to apply the name to

the plants cultivated for several vears in the U. C. B. G. under

_9
No. 07. The principal differences are in the corolla lobes and

in the inflorescence. The corolla lobes are represented as broad
and emarginate by Plooker. In our plant they are broad and
bluntly pointed, but the blunt point is revolute and the super-
ficial appearance is of a blunt and emarginate lobe. The inflor-
escence represented in Hooker's plate is more paniculate than
I find in the U. C. B. G. plants. The leaves appear to be very

much the same in both.
9
U. C. B. G. 07 came from seed sent by Professor 0. Comes

and was labelled "Nicotiana noctiflora var. alhiflora." Its habit

is low (about two feet in height), rather effuse, and sprangly.

The leaves are coarse, especially the lower ones. They are

elliptical-lanceolate to simply broadly lanceolate, sessile and

slightly clasping at the base, more or less bullate above, slightly

toothed, sinuous and undulate, with sparse, coarse prickly hairs.

The upper leaves are narrowly linear-lanceolate, very much and

coarsely crisped. The flowers are in long simple racemes. The

corolla is salver-shaped, with a slender tube, about double the

length of the calyx, and expanded gently at the summit. The

five lobes of the limb are broad and deep, abruptly contracted

at the tip, which is revolute, thus giving the lobes a certain

appearance of being broad and obcordate. The corolla is reddish

purple without and white, or slightly purplish, within. U. C.

_£_

B. G. 07 is a near relative of N. longiflora, from which it is
to be distinguished particularly by its strictly annual character,
lower habit, its lack of a long persistent basal rosette of radical
leaves, and much shorter corolla. Although it seems to pass for .V,

1912] Setchell: Studies in Nicotiana 21

noctiftora, it may well be doubted whether it is identical with
the plant described under this name by W. J. Hooker {loc. cit.).
So far as flower and inflorescence is concerned, Hooker's plant
seems to be nearer to N. acuminata. Hooker's plant is credited
as being perennial, ours is annual. The flowers open at about

7 :30 P.M. and close by 8 a.m They are odorless. U. C. B. G. 07
is shown in plate 23.

Nicotiana longiflora Cav.

The present species is fairly well known in botanical gardens

and as a weed in warmer countries. It has appeared in the

eastern United States as a ballast weed. It has been grown in

the U. C. B. G. under several numbers, from as many different

100
sources. No. 05 has been the principal cultivation and the

plant (in daytime with its flowers closed) is well represented

in the photograph reproduced in plate 24. One characteristic

of N. longiflora is very striking in contrast with other species of

Nicotiana cultivated in the U. C. B. G. and that is, the forming

of a compact rosette of large, coarse leaves which lie flat on the

ground and persist for a considerable time before the flowering

stems arise from it. The rosette persists for most of the first

year and is well represented in the figure just quoted. The

flow^ering stems are spreading, bearing narrower leaves than the

radical ones, and the loose panicle bears somewhat distant flowers

with long, slender, bluish-purple corollas.

The radical leaves are broadly lanceolate or oblanceolate,

coarsely bullate and rugose above, undulate, smooth but with

coarse spine-like glandular hairs on surface and margins. The

tube of the corolla is four to six times as long as the calyx and

proportionally slender. The broad spreading limb is deeply

divided into five moderately broad blunt-pointed lobes, which

are somewhat recurved. The flowers open only at night. Occa-

]00

sionally a 3-celled capsule is found. In the U. C. B. G., No. 05
has persisted as long as three years, but no more. It usually
lives for two years, at least.

U. C. B. G. OS seems to be the iV. longiflora var. acutiflora

22 University of California Publications in Botany [Vol. 5

of Comes (1899, p. 44). It was received under the name of
Nicotiana acuti flora, as have been also one or two other plants
from other sources. Our plant is certainly very near to N.
longiflora, as cultivated in the U. C. B. G., differing chiefly in
the decidedly more yellowish green stems and foliage, flowers
greenish white with only a slight tinge of purple in some of
them, more sinuous lobes recurved to the limb of the corolla,
and more conduplicate and twisted cauline leaves. Its perennial
character in the U. C. B. G. is limited to two or three years,
as in typical N. longiflora.

Nicotiana alata Link et Utto.

Nicotiana alata in one form or another has been a favorite
in cultivation for a long period, partly for ornamental purposes,
but partly, it is claimed by many authorities, to provide the
Persian tobacco so highly esteemed for its delicacy and perfume.
The most commonly cultivated variety is the plant called Nico-
tiana affinis Moore (1881, p. 141, fig. 31). Comes (1899, p. 37)
has designated this as var. grandiflora of N. alata. Another
variety of N. alata, according to Comes, is N. persica Lindley
(1833, pi. 1592). This is N. alata var. persica (Lindl.) Comes
(1899, p. 36). The differences between these three (?) sets of
plants seem to be largely in the more or less amplexicaul base
of the leaf as well as its varying degree of decurrence, the
varying size of the flower, and the variety exhibited in the
disproportionality (zygomorphism) between the upper three
lobes of the limb of the corolla and the lower two. In the type
of the species, all five lobes are said to be very nearly equal,
obtuse and not emarginate and the limb very little oblique;
in var. persica the limb is said to be decidedly oblique, the lobes
scarcely unequal but strongly emarginate ; in var. grandiflora
the tube of the corolla is said to be longer and stouter, the limb
very oblique, broader, with larger lobes, the lower two being
much the larger, but only slightly emarginate.

I have cultivated several different sets of N. alata in the
U. C. B. G. and have obtained a variety of plants, but without
being able to separate the varieties satisfactorily. The plants,
clearly and distinctly belonging to N. alata, are all of var.

1^12] Setchell: Studies in Nicotiana 23

grandiflora or very close to it. What seems in many ways to

107

be the var. persica is represented by U. C. B. G. 08. It was

received under the name of N. viscosa. I have referred to it

in the present account under A". Langsdorjjii var. grandiflora.

The corolla tube is provided with a gibbous ring at the summit.

It is to be suspected as of hybrid origin, the most probable

parents being N. alata var. grandiflora and N. Langsdorffi. It

has given plants both yellow and milk-white for the color of

the upper surface of the limb of the corolla during cultivation

in the U. C. B. G.

98
N. alata var. grandiflora is represented by U. C. B. G. 05

_l_
(ef. photograph, reproduced in plate 25), and by U. C. B. G. 06.

They are both clearly the N. affinis of the gardens, but differ

slightly from one another. The flowers are large, with the tube

gradually enlarging up to the limb and with very little trace

of a gibbous swelling at the very top and that only on the upper

side. The tube is greenish yellow without and the lower (outer)

surface slightly purplish. N. alata var. grandiflora has been

crossed with N. Forgetiana Hemsley (1905, pi. 8006) to produce

the brilliant red plant of the gardens known as N. Sanderae.

This hybrid has been grown in the U. C. B. G. under several

numbers and has exhibited a considerable variety of form and

color of flower and some variability in habit and fertility. All

the true N. Sanderae show the influence of the red-flowered

parent {N. Forgetiana) not only in color, but also in the strongly

developed gibbous ring in the throat of the corolla just below

the limb. Other hybrids of N. alata var. grandiflora are known

in gardens, with flowers varying from white, through pink and

red to dark purple (bluish in fading). In size and shape, the

flowers, as well as the habit, vary very little from typical X.

' 174

alata var. grandiflora. U. C. B. G. 08 is such a hybrid, giving
uniformly dark-red flowered plants in pure-line breeding.

Nicotiana acuminata (Graham) Hook.

Our knowledge of Nicotiayia acuminata is based on W. J.
Hooker's (1829, pi. 2919) description and plate. In the U. C.

24 University of California Publications in Botany [Vol. 5

B. G.. there have been cultivated several plants which seem
certainly to belong to the same species. They differ from one
another slightly, but chiefly in the varying diameter of the limb
of the corolla. Comes (1899, p. 39) has described two varieties
based on this character and we have followed him in adopting
designations for our plants. The acuminata-gvou\> is to be dis-
tinguished from the longiflora-grouj) by having the lobes of the
limb of the salver-shaped corolla comparatively shallow and
rounded. The varieties of X. acuminata have petioled leaves,
whose blades are almost or quite cordate below but ovate-lance-
olate to narrowly lanceolate above. The plants are rather spread-
ing at maturity, as represented in plate 26. The seed of the
type of the species (apparently var. parvi flora Comes) came
originally from Chili (Hooker, loc. cit.). One of the varieties
(var. grandiflora Comes, cf. plate 26) probably originated (or
segregated) under cultivation, but one or more varieties occur
wild in California. Since the subject of N. acuminata and its
varieties is to be treated by T. H. Goodspeed in a paper about
to appear in this series, nothing further will be said about its
characters here. Plants belonging to this species appear in botan-
ical gardens under the names of N. suaveolens and of N. vincae-
flora, Australian plants which were at one time cultivated but
of which I have been unable to get reliable seed. I suspect that
most of the plants cultivated under these names belong to N.
acuminata, from which they are to be distinguished by their
lack of a petiole.

Nicotiana attenuata Torr.

This is a widespread species of Western North America,
extending from New Mexico, Arizona, and southern California,
east as far as Colorado, and north through Wyoming to southern
British Columbia. It grows in arid and desert localities, as
a slender, often decidedly bushy herb of straggling habit. It
is well represented by Watson (1871, pi. 26, fig. 1, 2) in his
figure in the Botany of King's Expedition, except that the
flowers seem to be sharp-lobed and funnel-shaped, while the
large very extremely swollen-based glandular hairs are not

1912] Setchell: Studies in Nicotiana 25

represented. The large swollen based hairs are most charac-
teristic and constitute a mark of identification. They are usually
very conspicuous upon the calyx. The plant bears a certain
fairly close but superficial resemblance to the last {N. acumin-
ata), especially to the smallest flowered varieties. It differs from
it in the swollen-based glands just mentioned, in the lower
leaves never being so broadly ovate or even cordate at the base,
and in the shorter, stouter tube of the corolla. The leaves are
petioled and lanceolate or ovate-lanceolate and the lobes of the
limb of the corolla are broad and shallow, but not emarginate.
It has never been cultivated to any extent and does not grow
well in the adobe soil of the U. C. B. G. Two numbers, viz.,

78. 46

U. C. B. G. 09 and 11, have been grown with fair success.
Both numbers are from plants used by Indians for smoking,
the former from seed from Oregon, the latter from seed from
British Columbia. It seems to have been smoked by the Indians
throughout its range to some extent, at least wherever it was
the chief or only species of Nicotiana to be obtained. In the
northern part of its present range it was undoubtedly intro-
duced by the Indians.

Nicotiana Bigelovii (Torr.) Watson.

One of the most interesting of all the Nicotiana species cul-
tivated in the U. C. B. G. is this species of California and, to
some extent perhaps, of adjacent states. It has been cultivated
in various forms and under various numbers in the U. C. B. G.
since 1905, these latter years in pure lines. I do not think that
it has been successfully cultivated elsewhere to any extent (cf.
however Comes, 1899, p. 43 and East, 1912) and the only time
I saw the name was in the seed-list of a botanical garden. I
obtained some of the seed but the plants proved to be N. longi-
flora. It does not grow readily or uniformly in the U. C. B. G.,
but it has always given some results and these have been of such
interest that I expect to give them more in detail later.

What passes for the type of Nicotiana Bigelovii is a large
and tall, coarse plant with large w^hite or purplish (outside)
corollas which are five-lobed. The leaves are sessile and usually

26 University of California Publications in Botany [Vol.5

tapering towards the base, although, in some plants, some of
the leaves are truncate at the base and partly clasping. The
capsule is large and two- or three-celled. It generally grows
in sandy banks or bottoms of rivers, overflowed in spring, but
drv in summer. There are several variations of the type upon

40

which it is hoped to report later. U. C. B. G. 05 represents

60

such a plant, while U. C. B. G. 07 a, represents a lower, spread-
ing plant which may possibly be nearer the strict taxonomic
type. The figures given by Watson (1871, pi. 26^ fig. 3, 4) in the
Report of the Botany of King's Expedition resemble U. C.

B. G. 07 a, more nearly than any other and the type (or cotype)

in the Gray Herbarium of Harvard University seems to be the

same. These plants are the more common in central California.

N. Bigelovii var. Wallacei Gray is a slender plant, with slender,

narrower corolla, with elongated deltoid leaves. This is the

43.
more abundant form in Southern California. U. C. B. G. 05

represents this type.

Nicotiana quadrivalvis Pursh.

Nicotiana quadrivalvis seems to be a lost species in nature.
It was described by Pursh (1814, pp. 141, 142) from the plants
collected by Lewis and Clark in their expedition across the con-
tinent. Lewis and Clark got their plants from the Ricaree
Indians who cultivated it. The type-specimen is still preserved
in the Herbarium of the Academy of Natural Sciences at Phila-
delphia, where I have had the opportunity of examining it
through the courtesy of Mr. Stewardson Brown. It seems ex-
actly like the plants developed in the U. C. B. G. and somewhat
unlike the plants grown in the past in various botanical gardens.
It was introduced into gardens in 1811 (cf. Don, 1838, p. 466)
and was figured by Sims (1816, p. 1778). Lehmann (1818, p.
45, pi. 4) also described and figured it. How long it persisted
in botanical gardens is not certain, but it seems to have been
extensively cultivated, judging from herbarium specimens. It is
still offered in some seed-lists, but seed obtained from such lists
have given me only varieties of A^. Tahacum or N. rustica.

1912] iSctchell: Studies in Nicotiana 27

Comes (1899, p. 54) indicates that he has seen it in the living
condition. Seed received from him failed to germinate in the
U. C. B. G., even after repeated trials. East (1912, p. 244) has
just stated that he succeeded in producing plants from Italian
seed and that these were so close as to seem of the same species
with a derivative of N. Bigelovii produced in the U. C. B. G., of
which East was furnished with seed.

As to the wild plant, I have considerable doubt as to its ever
having existed. In various floras it is listed without special
comment, but very few specimens other than those from botan-
ical gardens are to be found in the herbaria and even such other
specimens are likely to have been from Indian cultivation. Some
of such specimens, however, are either robust N. Bigelovii or
N. multivalvis. Gray (1876, p. 546) suggests that it is merely
a cultivated variety of N. Bigelovii to which it is very close in
every character except that of the four-celled capsule and its

tendencv to have more than five lobes to the corolla. i\Iv ex-

35 '
perience with N. Bigelovii, especially U. C. B. G. 05, seems

thoroughly to support this statement, since N. quadrivalvis has

appeared in a pedigree of A^ Bigelovii (cf. also East, 1912, p. 245

et seq. ) .

Nicotiana multivalvis Lindl.

This plant is more commonly assigned as a variety under N.
quadrivalvis, which it resembles closely except in the many-
celled indehiscent capsule, in which the cells are arranged in
both an inner group and an outer row and the many-lobed limb
of the corolla. In fact, N. multivalvis (cf. Lindley, 1827, pi.

1057) seems like a monstrous form of N. Bigelovii. Yet it is

90. 143

reproduced uniformly from the seed. U. C. B. G. 06 and 07

have been grown for several years in the U. C. B. G., mostly in

the pure line, giving constant results. Gray (1876, p. 546)

suggests that "A". Bigelovii is perhaps the original of it," and

I feel that he is right, since it has appeared in the pedigreed

cultivation of N. Bigelovii in the U. C. B. G.

iV. multivalvis has been cultivated in botanical gardens since

1826 (cf. Don, 1838, p. 467) and still persists. The first seed

were procured by David Douglas (1836, p. 92), who obtained

28 University of California Publications in Botany [Vol. 5

it in 1825 on the banks of a small branch of the "Multnomak
River," one of the southern tributaries of the Columbia River.
The plants cultivated today are, with little doubt, descended
from the plants grown from the seed collected by Douglas. No
plants of iV. multivalvis are found wild at the present time, and
it is more than probable that even in the time of Douglas it
was not known except in Indian cultivation. It is still cul-
tivated and used ceremonially by certain Indian tribes.

Nicotiana repanda Willd.

Lehmann (1818, p. 40, pi. Ill) is responsible for the pub-
lication of this species which Willdenow apparently christened
as an herbarium specimen. The native country of the type
specimen is given as Cuba. The species grows in Mexico and
southwestern Texas, where seeds were obtained through the kind-
ness of Professor F. D. Heald of the University of Texas. The

plants are not easilv grown but have been continued on under

Hi
U. C. B. G. 09. They agree with Lehmann's figure {loc. cit.)

as well as with that of Sims (1823, pi. 2484). They are well

represented by the photograph reproduced in plate 27. Our

plant is probably the N. repanda var. pandurata (Dunal.)

Comes (1899, p. 47).

Nicotiana trigonophylla Dunal.

In the southwestern United States and northern Mexico, in
the drier regions, there grows a species which varies quite a little,
which has been, and even still is, used by certain Indian tribes
for smoking. This is Nicotiana trigonophylla. It has been

grown, but with difficulty, in the U. C. B. G. for several seasons

Ilil JL

under Nos. 07 and 09. The seed of the former was from San

Bernardino County and of the latter from Inyo County, both

of the State of California. In both cases it was from wild plants.

In 1911 by planting in soil well underdrained and by using
cheese-cloth protection, the plants were grown successfully and
some of them with protection have even withstood the winter.

The species is correctly placed in the Petunioides-^QcXion of

1912] Setchell: Studies in Nicotiana 29

Nicotiana, although the flowers are a yellowish white. The
individuals vary in being more green or more glaucescent. They
are straggly, with narrow, broadly lanceolate leaves narrowed
at the base and then suddenly expanded into broad, partly
clasping auricles. The flowers are in more or less incurved, one-
sided racemes. The corolla tube is almost straight tubular, with
the limb spreading at right angles or slightly deflexed in full
anthesis. The lobes of the limb of the corolla are broad, obtuse,
and shallow. The flowers are deep creamy yellowish white.
The capsule is nearly or entirely enclosed in the calyx, varying
in this respect. Var. pulla Comes (1899, p. 49), var. sordida
Comes (loc. cit.) and var. iponiopsiflora Comes of N. trigono-
phylla and N. Palmeri Gray (1886, p. 242) seem to belong to
the same species.

Nicotiana sylvestris Speg. & Comes.

This is one of the most important of the showy species of
Nicotiana for garden culture. Spegazzini sent the seeds from
Argentina to Comes in 1897 (cf. Comes, 1899, p. 35), and the
plant was soon widely distributed in botanical and other gar-
dens. It has been grown continuously in the U. C. B. G. since
1901. It is a tall, shortlived perennial with long, slender white
flowers, pleasantly fragrant after dark. A slender plant just
coming into flower is represented in the photograph reproduced
in plate 28. The figure of Comes {loc. cit., p. 34) does not well
represent the proportions of height, length of leaf, and length
of flower as found in the plants cultivated in the U. C. B. G.
The plate of J. D. Hooker (1899, pi. 7652) is better in these
respects, but the habit-figure does not seem characteristic. The
plant represented from the U. C. B. G. is young; older plants
branch and become more bushy. The flowers are long and
white, with a slight tinge of yellowish outside. The tube is
slender, enlarging slightly and gradually above the middle but
gradually contracting below the top. The limb is moderately
broadly lobed one-third to one-half way in from the margin. The
lobes are broadly triangular. The flowers are pendent in bud,

30 University of California Puhlications in Botany [Vol. 5

ascending to nearly horizontal as anthesis proceeds. While they
are open in the daytime as well as at night their perfume is
faint until after nightfall. The ripened capsules are erect. The
leaves are elliptical to spatulate-oblong with a broad clasping
and slightly decurrent base. They are coarsely rugose.

LIST OF PAPEES EEFEERED TO

Agakdh, C. a.

1819. Nagra Ord om Tobaks Odligens Forbattring.
Anastasia, G. Emilio

1906. Le Varieta Tiijiche della Nicotiana Tabacum L.
Andr6, Ed.

1888. Eevue Horticole, p. 511.
Clusius, Carolus

1605. Exoticorum Libri Decern.
Comes, O.

1895. Snlla Sistemazione Botanica delle Specie e delle Razze del Genere
Nicotiana, Atti del E. Instituto d' Incoraggiamento di Napoli,
vol. 8.

1899. Monographie du genre Nicotiana comprenant le classement

botanique des tabacs industriels, Atti del E. Instituto d'
Incoraggiamento di Napoli, ser. V, vol. 1.

1900. Historie, geographie, statistique du tabac, etc.

1905. Delle Eazze dei Tabacclii Filogenesi, Qualita ed Uso, Atti del
R. Instituto d ' Incoraggiamento di Napoli, vol. 57.
Don, George

1838. A General History of the Dicblamydeous Plants, vol. iv, Corol-
liflorae.
Douglas, David.

1836. A sketch of a Journey to the Northwestern parts of the Con-
tinent of North America during the years 1824, 5, 6, and 7,
in W. J. Hooker's Companion to the Botanical Magazine, vol. 2.
DuNAL, Michel Felix

1852. Solanaceae, in A. de Candolle, Prodromus Systematis Naturalis
Eegni Vegetabilis, vol. xiii, 1 : pp. 1-690.
East, E. M.

1912. A Study of Hybrids between Nicotiana Bigelovii and N. quad-
rivalvis, Botan. Gazette, vol. 53.
Fischer, F. E. L. et Meyer, C. A.

1846. Sertum Petropolitanum.
Gray, Asa

1876. Gamopetalae, in Botany of Geol. Survey California, vol. 1.
1886. Synoptical Flora of North America.
Hasselbring, Heinrich

1912. Types of Cuban Tobacco. Botan. Gazette, vol. 53.

1912] Setchell: Studies in Nicotiana 31

Hemsley, W. Botting

1905. Curtis 's Botanical Magazine, vol. 131.
Hooker, J. D.

1876. Curtis 's Botanical Magazine, vol. 102.

1892. Ibid., vol. 118.

1899. Ibid., vol. 125.
Hooker, W. J.

1821. Curtis 's Botanical Magazine, vol. 48.

1827. Ibid., vol. 54.

1828. Ibid., vol. 55.

1829. Ibid., vol. 56.
Howard, A. and Howard, G. L. C.

1910. Studies in Indian tobaccos, Mem. Dept. Agr. India (Bot. Ser.),
vol. 3.
Lehmann, Joannes Georgius Christianus

18i8. Generis Nieotianarum Historia.
LiNDLEY, John

1824. Edwards's Botanical Register, vol. 10.
1827. Ibid., vol. 13.

1833. Ibid., vol. 19.
Lock, R. H. "

1909. A Preliminary Survey of Species Crosses in the Genus Nico-
tiana from the Meudelian Standpoint, Annals Royal Bot.
Garden, Peradeniya, vol. 4.
MiERS, John

1846. Contributions to the Botany of South America (continuation),
Hooker's London Journal of Botany, vol. 5.
Miller, Philip

1768. The Gardeners Dictionary, ed. viii.
Moore, T.

1881. Nicotiana affinis, Gardener's Chronicle, new (2d) ser., vol. 16.
Pursh, Frederick

1814. Flora Araericae Septentrionalis, vol. I.
Schrank, (Franz von Paula)

1807. Botanische Beobachtungen, Botan. Zeitung (Regensburg), 6

Jahrg. (pp. 260-265).
1819. Plantae Rariores Horti Aeademici Monacensis descriptae et
iconibus illustratae.
Sims, John

1816. Curtis 's Botanical Magazine, vol. 43.
1821. Ibid., vol. 48.

1823. Ibid., vol. 50.

1825. Ibid., vol. 52.
Sprengel, Kurt

1817. Anleitung zur Kenntniss der Gewachse.
Watson, Sereno

1871. Botany, in U. S. Exploration 40th Parallel ("King's Expedi-
tion"), vol. V.

EXPLANATION OF PLATES

All the plates are from photographs taken by Mr. B. F. White under
the direction of W. A. Setchell.

PLATE 1

71
"Brazilian" Tobacco. U. C. B. G. 05- X %2 ^iam.

[32]

UNIV. CALIF. [PUBL. BOT. VCL. 5

[SETCHELL] PLATE

PLATE 2

72
'Cavala" Tobacco. U. C. B. G. 05- x%2 diam.

[34]

UNIV. CALIF. PUBL. BOT. VOL, 5

[SEtCHELL] PLATE 2

PLATE 3

78
■■ Maryland ' ' Tobacco. U. C. B. G. 05- x T/g^ diam.

[36]

UNIV. CALIF. PUBL. BOT, VOL- 5

[SETCHELLJ PLATE 3

PLATE 4
Nicotiana Tabacum var. calycina. U. C. B. G. 05- X %4 diam.

[38]

UNIV. CALIF. PUBL. BOT. VOL. 5

[SETCHELL] PLATE 4

PLATE 5

30
White Tobacco." U. C. B. G. 06- x n/igg diam.

[40]

UNIV. CALIF, PUBL. BOT. VOL, 5

[SETCHELL] PLATE 5

PLATE 6

99

Nicotiana Tabacum var. macrophylla. U. C. B. G. of- X 1%4 diam.

[42]

UNIV. CALIF. PUBL. BOT. VOL. 5

[SETCHELL] PLATE 5

PLATE 7

M
Xicotiana aiigustifolia. U. C. B. G. 07- X ^28 diam.

[44]

UNIV. CALIF. PUBL. BOT, VOL. 5

[StTCHELL] PLATE 7

PLATE 8

Nieotiana Tabacum var. macrophylla purpurea. U. C. B. G. 06-
X %4 diam.

[46]

UNIV. CALIF. PUBL. BOT. VOL. 5

[SETCHELL] PLATE 8

PLATE 9
Nicotiana rustica var. asiatica. U. C. B. G. 07- X -%28 diam.

[48]

UNIV. CALIF. PUBL. BOT. VOL. 5

[SETCHELL] PLATE 9

PLATE 10

13
Nicotiana rustica var. brasilia. U. C. B. G. qT- X % diam.

[50]

UNIV. CALIF. PUBL. BOT. VOL. 5

[SLTCHELL] PLATE 10

PLATE 11
Nicotiana rustica var. humilis. U. C. B. G. 07- ^ Wm t^iani.

[.32]

UNIV. CALIF. PUBL BOT. VCL. 5

[SETCHELL] PLATE I I

PLATE 12

15
Nicotiana rustiea var. jamaicensis. U. C'. B. G. 07- X ^%4 diam.

[54]

UNIV. CALIF. FUEL. BOT VCL, 5

[SETCHELL] PLATE 12

• PLATE 13

26

Nicotiana rustiea var. scabra. U. C. B. G. 06- ^ %4 diam.

[56]

UNIV. CALIF, PUBL. BOT, VOL. 5

[SETCHELL] PLATE 13

..•'•<-"i,-

-'!»- '

PLATE 14

H
Nicotiana rustiea var. texana. U. C. B. G. 97. x %g diam.

[58]

UNIV, CALIF. PUBL, BOT. VOL. 5

[SETCHELL] PLATE 14

PLATE 15

ifig

Nicotiana rustica var. pumila? U. C. B. G. 08- x'^gdiam.

[60]

UNIV, CALIF. PUBL, BCT. VOL. 5

[SETCHELLl PLATE 15

PLATE 16

169
Nieotiana rustiea var. pumila ? U. C. B. G. 08- x^M28 diam.

[62]

UNIV. CALIF PUBL. BOT. VOL. 5

[SETCHELL] PLATE 15

PLATE 17

102
Nicotiana Langsdorffi. U. C. B. G. 05- x Vs tliani.

[64]

UNIV. CALIF. PUBL. BOT, VOL. 5

[SETCHELLj PLATE 17

PLATE 18

107
Nicotiana Langsclorffii var. graudiflora? U. C. B. G. 08- ^ •^%4 diam.

[66]

UNIV, CALIF. PUBL, BOT. VOL. 5

[SETCHELL] PLATE 18

PLATE 19
Nieotiana Langsdorffii var. longiflora ? U. C. B. G. 08- ^ ^%4 <iiam.

[68]

UNIV. CALIF, PUBL. BOT. VOL. 5

[SETCHELL] PLATE 19

PLATE 20

106
Nicotiana paniculata. U. C. B. G. 05- X Wei diam.

[70]

UNIV, CALIF, PUBL. BOT, VOL, 5

[SETCHELL] PLATE 20

PLATE 21

11
Nicotiana glutinosa. U. C. B. G. 07- x Vs diam.

79 Tfi

(The label 09 should be 07).

[72]

UNIV. CALIF, PUBL. BOT. VOL. 5

[SETCHELL] PLATE 2!

PLATE 22

1L93
Nicotiana tomentosa. U. C. B. G. Qg. x i%4 diam.

(A small plant grown from a cutting).

[74]

UNIV. CALIF. PUBL BOT. VOL. 5

[SETCHELL] PLATE 22

PLATE 23
Nicotiana noctiflora? U. C. B. G. Qy. X i%4 diam.

[76]

UNIV. CALIF. PUBL. BOT. VOL. 5

[SETCHELL] PLATE 23

PLATE 24

Nicotiana longiflora. U. C. B. G. Qo- x Vs diam.

(The flowers are closed; daytime condition).

rr

8]

UNIV. CALIF. PUBL, BOT. VOL. 5

[SETCHELL] PLATE 24

PLATE 25

98
Nicotiana alata var. grancliflora. U. C. B. G. 05- X %2 diam.

(The flowers are closed; daytime condition).

[80]

UNIV. CALIF. PUBL. BOT. VOL. 5

[SETCHELL] PLATE 25

PLATE 26

150
Nicotiana acuminata var. grandiflora. U. C. B. G. 07. X %4 diam

[82]

UNIV, CALIF. PUBL, BOT, VOL, 5

[SETCHELL] PLATE 26

PLATE 27

79
Nieotiana repanua. U. C. B. G. qq. x %^ diam.

[84]

UNIV. CALIF. PUBL. BOT, VOL, 5

[SETCHELL] PLATE 27

PLATE 28

107
Nicotiana sylvestris. U. C. B. G. Ql- X %2 <3iam.

[86]

UNIV. CALIF. PUBL. BOT. VOL. 5

[SETCHELL] PLATE 28

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 2, pp. 87-168, pis. 29-34

Issued December 6, 1912

QUANTITATIVE STUDIES OF INHERIT-
ANCE IN NICOTIAN A HYBRIDS *

I. THE RELATION BETWEEN THE WEIGHTS OF
HYBRID TOBACCO SEED AND THE INHERIT-
ANCE OP CERTAIN CHARACTERS IN F,.

II. QUANTITATIVE EXPRESSION OF IMPERFECT DOM-

INANCE IN THE COROLLA DIAMETERS OF
THE FLOWERS ON THE HYBRIDS PRO-
DUCED FROM THREE VARIETIES OF
NICOTIAN A ACUMINATA

BY

THOMAS HAKPER GOODSPEED

LIBRARY
NEW YOkK
BOTANICAL

OARDBN,

THE RELATION BETWEEN THE WEIGHTS OF HYBRID

TOBACCO SEED AND THE INHERITANCE

OF CERTAIN CHARACTERS IN F^

CONTENTS

PAGE

I. Introduction 88

II. Description of experimental material 89

(1) Distinguishing characteristics of parents and appear-
ance of the hybrid in Fj 89

III. Division of the hybrid seed according to —

(1) Size and shape 91

(2) Color 92

(3) Weight 92

* A thesis in partial fulfillment of the requirements for the Degree
of Doctor of Philosophy in the TInivorsity of California.

88 University of California Publications in Botany [Vol. 5

IV. Germination of the seed 96

(1) In the germinating case 96

(2) In the propagating house 98

(3) Total germination and discussion of rates of germination. 99
V. Development of Seedlings 101

(1) Early development of seedlings 101

(2) Number and condition of plants in the field 101

VI. Appearance of the plants in the field 103

(1) Scheme of grouping 103

VII. Discussion of inheritance of characters according to weight of

seed 106

(1) Shape, size and weight of parental seeds of 1906 and

1907 106

(2) Correlation between inheritance of characters and weight

of seed 107

VIII. Summary of results 108

IX. Discussion of results 109

I. INTRODUCTION

The investigation herein reported Avas undertaken for the
purpose of determining the possible relationship between the
physical characteristics of pedigreed seed and the segregation of
the so-called " unit characters" as manifested in the plants grown
from such seed — especially the relation between the weight of hy-
brid tobacco seed and the appearance of the ¥^ generation individ-
uals produced therefrom. The introduction of evidence to support
a strict Mendelian interpretation of experiments in plant breed-
ing, the results of which fail to show segregation in accordance
with any of the accepted formulae, has very naturally reached
such a point that some interest must be attached to the amount
of germination, viability, and general physical constitution of
the seed from which the pedigreed plants have developed, or
are to develop. Indeed, in any scientifically conducted experi-
ment in plant breeding, there should be more attention paid to
such supplementary data as the variations in color, size, weight,
and germination of the seed.

There seems to be no mention throughout the literature of
any recorded data in this particular connection (see, however,
Groth, 1911, part I, page 9), though a great number of practical
experiments, dealing with the relation between the physical char-
acteristics of seed and the vigor, etc., of the resulting plants.

1912] Goodspeed: Nicotiana Hyhrids 89

have been fully reported. Thus Clark (1904) worked upon the
value of seed-selection according to specific gravity and sum-
marizes the work, along this particular line, of previous investi-
gators—Haberlandt, Wollny (1885), Hellriegel (1883), and
others. Shamel (1904), Weber and Boykin (1907), Lill (1910),
Scherffius (1909), and many others have conducted investiga-
tions connected with the relation of weight, size and density to
germination and subsequent development of wheat, cotton-seed,
tobacco seed, etc. The general result of all this work has been
to establish the value for the agriculturist of careful seed-selec-
tion and especially the advantage of sowing heavy rather than
light seed for the subsequent production of uniformally vigorous
plants and thus of the most valuable crops. In agricultural
practice the plants grown from heavy tobacco seed have been
found to give often over 90 per cent germination and to produce
plants that grew more rapidly, matured earlier and were best
developed and most vigorous; while from light seed "small,
irregular and undesirable" plants develop (Shamel, 1904, p. 440;
cf. Waldron, 1910, and Love, 1910, p. 423). These conclusions
are based upon the separation of well-known commercial strains
of tobacco and give no results directly applicable to the investi-
gation in hand.

II. DESCRIPTION OF EXPERIMENTAL MATERIAL

Distinguishing Characteristics of Parents and Appearance

OF Hybrids in F^

The experimental material consisted of the second hybrid
generation seed produced by self-fertilizing the flowers of one
Fj hybrid plant, representing the cross Nicotiana Tadacum var.
macrophylla ^y^ Nicotiana Tabacum var. virginica (^. Nicotiana

22

Tabacum var. macrophylla is U. C. B. G. 07 (Setchell, 1912,
p. 8, plate 6) ; the original seed was received under the name
quoted from Professor 0. Comes. Nicotiana Tabacum var. vir-

78

gi7iica is U. C. B. G. 05 (Setchell, 1912, p. 6, plate 3), a form of
N. Tab. var. virginica. Comes (1899), but is better referred to
under the trade name of Marijland, under which name the

90

University of California Puhlications in Botany [Vol. 5

original seed was received from the United States Department
of Agriculture. The parental types have been grown in the
University of California Botanical Garden (U. C. B. G.) for
five and seven years respectively under the direction of Pro-
fessor W. A. Setchell and have almost from the first been propa-
gated, in both cases, from "pure" seed in the pure line. The
principal and most striking characteristics which distinguish the
two types and the F^ hybrid are summarized in the following
table :

FLOWER

A

HABIT

A

LEAP

A

Color

Size

Corolla limb

Height

Width

Petiole

Tip

Auricle

Nicotiana Taha-

magenta

large

flat, pentag-

average

wide and

heavily

blunt

flat

cum variety

onal, angles

90 cm.

branching

winged

macrophyUa

shallow

from base

Nicotiana Taha-

light

smaller

cut into lobes

average

upright and

light

curved

ruffled

cum var.

pinkish

each tipped with

150 cm.

not branching

winged

long &

virginica

a recurved hook

from base

narrow

Hybrid between

pink to

fairly

As iV. macrophylla,

from

wide and

heavily

two

some-

Nicotiana Taba-

light red

large

but angles not

62 to

branching

winged

above

what

cum var. macro-

so shallow and

170 cm.

combined

ruffled

phylla 5 and

tipped with

Nicotiana Taba-

recurved hooks

cum var

virginica ^

It can be seen from the above table that, in general, one
would be justified, on the Mendelian basis, in considering the
N. Tahacum var. macrophylla parent as dominant and the N.
Tahacum var. virginica parent as recessive. After a general
examination in the field of the F^ generation, this dominance
would have been rather striking and, for convenience of refer-
ence and later discussion, the fact that such dominance was
apparent will be recognized. The fact that on close examination
of the hybrids the influence of the virginica parent was shown
in the leaf-shape and auricle, the flower-color and corolla lobes
and that, among the fifty individuals grown, the height of the
central axis was found to vary between 62 and 170 cm., the
width of the broadest leaf from corresponding regions between
15 and 37 cm., while the length of the longest leaf varied be-
tween 28 and 59 cm., all these, in general, support the con-
clusion arrived at in the following communication (cf. p. 117).

1912] Goodspeed: Nicotiana Ilyhrids 91

III. DIVISION OF F, HYBRID SEED

The technique and methods in obtaining pure seed, perform-
ing the cross-pollinations and the cleaning and sowing of the
seed, has been fully described elsewhere in this combined paper
(pp. 126-131). The parent plants were crossed during August,
1909, and the hybrid plants produced from the seed of this
cross, and which yielded the experimental material, w^ere grown
during the summer and fall of 1910.

When the seed, produced by self- (close) fertilizing one of
the plants of this hybrid, was" cleaned in January, 1911, there
were five ripe and well-seasoned capsules in the bag. During
February, 1911, the seed of this one plant was examined for
size, color and weight as follows.

1. Size and Shape

Under the lens the seed presented a characteristic appearance
in all instances. The shape was more or less oval to flattened
pear-shape, with the funiculus often forming a little hook at
the smaller end of the seed. In most cases, also, a seam was
to be seen running from the short funicle for some distance
around the seed soon to fade, however, into the pimply seed-
covering. This pimply appearance is caused by a great number
of sharply raised points occuring on the surface of the seed
coat, which thus appears quite rough under a low magnifica-
tion. Under a considerable magnification these raised points were
seen to be connected with one another by fine, much curved and
twisted, thread-like lines. Under the lens an arbitrary division
was made according to size into (1) large, (2) intermediate,

(3) small — all of these were w^ell filled out, plump seed — and

(4) ill-formed, flattened and wrinkled seed. The seed placed
in division 4 presented a great variation in appearance, from large
seed coats, so flattened as to appear empty, to very small seeds
with simply much wrinkled coatings. The average length,
breadth and the length-breadth index for the seed of grades
1, 2 and 3 are given in the following table:

92

University of California Publications in Botany [Vol. 5

Grade Length Breadth Length-breadth index

1. 0.85 mm. 0.60 mm. 70.58

2. 0.75 mm. 0.58 mm. 77.33

3. 0.66 mm. 0.43 mm. 65.15

Measuring ten fields, indiscriminately chosen, under the low
power of the dissecting microscope and including in each field
from 90 to 115 seeds, the proportion of the various grades per
field was as follows:

Grade 1 26 %

Grade 2 46 %

Grade 3 22 %

Grade 4 6 %

The separation of seed according to size was combined with the
separation according to weight and will be taken up in this
connection later on.

2. Color

In color there were practically^ no variations from the typical
very dark brown coloration of the seed coats. A few seeds at
times seemed to present a somewhat lighter appearance, but their
number was so small and the normal color so often found to be
present on some one of the other faces of the seed, that no
separation according to color was attempted.

3. Weight

For the separation of the various weights of seed an im-
provised "grader," on the general style of that described in
the work on wheat separation in the Kansas Agricultural Experi-
ment Station (Lill, 1910), was employed for the first step in
the process. A large centrifugal fan on a 110-volt alternating
current supplied a constant draft of air which was caught in
a large paper funnel and conveyed through a three-foot section
of glass tubing, one inch in diameter. The tube was tilted
upward from the source of the air-current at an angle of fifteen
degrees and the seed introduced through a tin funnel at its lower
end. The proper point, near the lower end of the tube, at which

1912] Goodspeed: Nicotiana Hybrids 93

the seed could be poured in and neither be driven back up the
tin funnel by the air-current nor fall back down the tube into
the pan, was determined by experiment, as was also the proper
angle at which the tube should be tilted to give the necessary
"throw" to the seed after it left the upper end. A large paper
shield, reaching to the table, was fastened two inches back of
the upper end of the tube and thus effectuall}- excluded any
current of air in the region through which the seed fell and
about the receiving boxes. These boxes, • eight of them and
placed end to end, extended for three feet from a point directly
below the outlet of the tube. A box with high, sharply sloping
sides, partially closed at the extreme end and open above the
receiving boxes, extended the full length of the boxes to catch
any scattering seed and direct it downward. The maximum drop
of the seed into the boxes from the mouth of the tube or during
its progress through the air above the boxes, was about twenty
inches, though by far the majority of the seed began to fall, to
some extent, as soon as it was free from the tube.

After considerable effort had been expended in perfecting
the arrangements and determining by direct experiment the
proper position for the receiving boxes, etc., it was possible
to accomplish the entire grading of the seed on two successive
days during approximately the same hours. Since a motor at-
tachment was not available, it was not possible to regulate the
speed of the fan exactly and thus secure a perfectly constant
blast of air for any length of time. But by using the apparatus
on two successive days and at the same hours, it was judged
and proven by actual test that the blast was approximately the
same during the whole time of grading the seed.

The seed was slowly poured into the funnel directly from
the packet into w^hich it had been cleaned until perhaps a
thousand seeds had fallen into the receiving boxes. This first
grading was always very rough and gave only an approximate
separation according to density. Contrary to expectation, it
was found that the heaviest seed continually fell in the boxes
furthest from the opening of the tube, while the lightest and
medium seed fell into the first five boxes. The ill-formed, chaffy
seed was distributed throughout the whole of the eight boxes.

94 University of California Puhlications in Botany [Vol. 5

probably because of the inequality of the surfaces which the
seed presented to the air-blast. The seed that had fallen into
the first three boxes — nearest the opening of the tube — was then
put into the grader a second and a third time, at the end of
which the second box was found to contain the majority of the
seed. The seed from this second box was then run through
the apparatus three or four times more and, at the end, fifty
to sixty seeds remained. By marking certain of the seeds it
was found that they continually fell during each of the six or
seven gradings into the same receiving box or, rarely, struck
the edge to fall into the box just before. The same method was
employed in the combined boxes four and five and the majority
of the seed was at the end found in box five. Similarly for
the heaviest seed in boxes six, seven and eight the seed at the
end was taken from box seven. After twenty-one gradings,
approximately' two hundred seeds of three grades had altogether
been obtained. The remaining seed in the boxes was then mixed
and, after two or three hundred seeds from the original packet
had been added, the whole process Avas repeated. Over two hun-
dred and seventy-five gradings were made and, in all, twenty-
seven hundred seeds were separated out into grades.

All the seed was then examined under a low-power magni-
fying glass — i.e., a reading-glass lens four inches in diameter,
with a focus of nine inches. The extremely small size of tobacco
seed makes any such examination a relatively slow and tiresome
process. The seed was moved about under the lens on a glass
plate with a fine-pointed camels-hair brush. The removal of
the ill-formed, chaffy seed that was found in all the grades was
the first object of this examination and some 350 individuals of
this type were picked out from the whole 2700 seeds examined.
In the heavy seed a remarkable uniformity in size and shape
was noted, though there were among the 1100 heavy seeds ex-
amined some thirty markedly smaller seeds which were arbi-
trarily discarded. In all such cases the discarded seed was
thrown away and not used in making up other groups of seed.
The examination of the medium seed, which had fallen
into the intermediate boxes four and five, showed a considerable
variation in size. All seed that approximated the size noted

1912] Goodspeed: Xicotiana Hybrids 95

for the heavy grades was discarded and also the very minute
seeds noted above as having occurred among the heavy grades —
64 seeds in the first case and 80 seeds in the second, out of
400 seeds examined. The remaining seed was fairly uniform
in size and distinctly smaller than the heavy seed. Among the
light seed, which had been taken from box two, the
greatest number of ill-formed seed occurred and also twenty
per cent of the minute seed — -this on the basis of twelve hundred
seeds examined. It was found possible to separate out these
very small seeds and still have a light grade of seed that was
distinctly set apart from the medium seed in size and was about
one-half the size of the heavy grade. From the various grades
and the ill-formed seed a total of 2200 seeds, in separate packets
of 100 each, were counted out preparatory to weighing.

The scales used were the mechanical balances manufactured
by Josef Nemetz of Vienna and weighing from 0.0001 of a
gram to 1 gram only. Since more delicate balances were not
available, it was necessary to weigh the extremely small tobacco
seed by hundreds and then by tens. The following table gives
the weights of the various grades of seed, as divided by the
air-blast, in terms of 100 seeds for each number and thus really
expresses the average weiglit of groups of 100 seeds from
each grade.

Ill-formed seed Light seed Medium seed Heavy seed

1. 0.0042 3. 0.0044 7. 0.0063 13. 0.0086

2. 0.0041 4. 0.0057 8. 0.0064 14. 0.0091

5. 0.0059 9. 0.0065 15. 0.0094

6. 0.0061 10. 0.0067 16. 0.0095

11. 0.0070 17. 0.0095

12. 0.0073 18. 0.0097

19. 0.0098

20. 0.0099

21. 0.0099

22. 0.0111

In each case the 100 seeds were counted into the pan of
the balances — picking up each seed with a brush — weighed, then
removed and weighed again by tens. The weights of the groups
of ten seeds were, with the exceptions noted below, in every
case found to be so nearly the same that it was felt, by ex-

96 University of California Publications in Botany [Vol. 5

pressing the weights of the seeds in terms of 100 individuals, a
true average weight per seed could be calculated. For the same
reason it was felt that few individuals, if any, weighed much
more or less than this average or, in other words, that every one
of the hundred seeds of group 9, for example, which weighed
0.0065 grams, corresponded, more or less closely, to a theoretical
weight of 0.000065 grams. The above is also, in effect, a com-
bined table expressing the various sizes and densities of the
different groups of seeds, as well as their weight, since all three
characters were found to be so closely correlated as^ mutually to
represent one another. Groups 1 and 2, the ill-formed seed,
showed naturally a considerable difference in weight among
the groups of ten seeds, since they included all abnormally
shaped seed, from those that were simply shrunken and wrinkled
to those whose seed-coats were flattened and practically empty.
The minute seed, that was picked out in the final examination
after grading from the group of least density, is included in 3.

IV. GERMINATION OF THE SEED

1. In the Germinating Case

For germinating the seeds it was necessary to use an im-
provised germinating case. This was made by heavily insulating
a large glass-sided box with herbarium blotters and using a
16-candle power electric light, immersed in water, to obtain
the desired temperature within the box. It was so arranged that
the germinating case could be entirely closed after the seed had
been put in and the water about the electric light renewed
through a tube. The jar of water in which the light was placed
was tightly surrounded by a blotter and the opening at the top
of the jar was covered with a zinc plate so that practically
no light could be seen within the box. The blotting-paper in-
sulation was left free on one side and could be removed when
observations of the progress of germination were to be taken.
The seeds were counted out from the packets in which they had
been placed after weighing onto circular pieces of blotting-paper

«

1912] Goodspecd: Nicotiana Hybrids 97

so cut that their diameter was a little greater than that of an
ordinary drinking-glass. These circular pieces of blotting-paper
were placed upon glasses nearly filled with tap water and a
connection was so made with strips of blotting-paper reaching
down into the water that the seed-holders were kept continually
moist without allowing an excess of water to collect about the
seeds themselves. A watch crystal covered each group of 100
seeds and their seed-holder and served to keep the drops of
moisture which condensed on the top of the germinating box
from falling onto the seeds and also aided in maintaining a
constant temperature about the seed (see Garman, 1910, p.
44). The temperature was very fairly constant within the box,
at 21° C, and never varied over three degrees throughout the
first twenty-six days of the experiment. The germinating case
was sterilized as thoroughly as possible and the seeds, arranged
as above described, placed within it on February 28. The fol-
lowing table gives the extent of germination between March
3 and March 31 for the different weights of seed. The numbers
given in the first vertical column refer to those used in the
table on page 95 to designate the 22 different weights of seed.

March 3 5 7 9 10 11 12 13 14 16 17 18 20 21 23 27 29 31 %

'1 & 2 9 8 7 1 .... 1 .... 1 1 .... 2 16 ^

3 6 9 5 8 6 .. .. 4 .. 1 .. 3 .. 42 o

5!J 4 16 27 12 2 2 4 2 .. .. 4 .. 1 .. 3 73

5 * 40 8 6 1 2 1 5 4 67 ^

6 20 29 .. 8 2 5 4 .... 6 2 1 2 3 82 ^

g [ 7 * 44 .. 3 .. 5 1 .. .. 3 4 .. 3 6 .. 2 .. .. 71 ] vo

« 8 12 18 10 .... 4 1 3 .. 4 .. 1 1 5 59 ^

5'J 9 * 45 6 2 1 .. 3 5 .. 4 .. 1 2 6 .. 1 .... 76 I «

B I 10 * 41 4 4 1 .... 6 2 .... 1 59 | ^

I 1] * 44 3 4 3 3 2 .. 2 5 66 |

^ [ 12 * 39 .. 4 2 1 2 2 1 1 2 .. 1 .... 55 J <

13 10 15 4 6 7 .. 4 3 .. .. 7 4 .. 3 63

14 4 4 4 .... 1 1 4 1 3 2 6 .. 8 38 ^

a 15 6 11 10 4 6 5 6 .. 3 6 6 3 .. 1 .. 1 .... 68 05

S 16 7 11 .. 7 .. 1 6 .... 3 .... 8 3 47 "S

"r^J 17 3 .. 12 9 3 .. 3 .. .. 4 .. 2 4 12 .. 3 .. .. 55 >-g

18 1 .. 12 6 5 6 4 2 15 7 4 53 ^

19 6 8 6 5 6 .... 5 .. 3 .. 2 3 11 5 2 1 1 64 *<

20 2 4 .. 4 .. 3 2 7 .. 4 .. 1 3 .. 3 33

21 6 11 .. 3 2 1 2 .. 3 3 2 .. 4 .. .. 37

22 6 .. 2 10 .. 5 1 3 2 .. 5 - 1 .. .. 35

* Over 25 had germinated but the number was not counted ou this date.

98 University of California Publications in Botany [Vol. 5

When germination was first noted on March 3, the numbers
given above under that date express the number of seeds from
which, in each ease, the white caulicle was protruding and the
cotyledons also were beginning to appear. This condition of
the seeds was throughout taken as the criterion of germination.
The germinating case was not opened until March 10, at which
date many of the seedlings were entirely free from the seed
coats, the greenish cotyledons were fully expanded and con-
siderable growth of the first rootlets had taken place. On this
date and on i\Iarch 13, 16, 20. 27, and 31, all the seeds were
removed from the case and all the seedlings, free from the seed
coats, were planted in four-inch pots of sterilized soil and each
pot covered with a glass plate. The pots were watered from
beneath and placed near an east window.

Though no difficulty, except in the case of the ill-formed,
chaffy seed, was experienced in connection with moulds attack-
ing the seed in the germinating case, the pots containing the
seedlings were much affected and quite a number of the young
plants damped off during the first three weeks, because of the
thick laver of mould over the surface of the soil.

2. In the Propagating House

Since germination had been very slow throughout all the
weights of seed between March 21 and 31, it was thought best
to change the conditions under which germination had been
taking place. To this end. on April 1, the remaining seeds
were picked off from the blotting-papers and lightly sown in
sterilized soil. The pots containing the seed that had not ger-
minated were then removed to a propagating house in which
temperature and moisture conditions suffered daily a wide
degree of variation. No sign of germination was observed among
any of the weights of seed for six days and then only a slight
germination among the light-weight seed. When it was next
possible to note the germination — i.e., April 28 — extensive ger-
mination was found to have taken place, especially among the
hea\'y weights of seed, as noted below. •

1912]

Goodspeed: Nicotiana Hybrids

99

U-forined
seed

Numbers of
seed weights

^ 1&2

L

Number of seed ger-
minated between
April 1 & 31

0

Total percent
of germination

16 1

1

Average percent of

total germination of

grades of seed

16

3

10

52 '

Light
seed

4
5

L «

7
8

13
12

5

16
23

86
79

87

77 ^
82

76

Medium

9

13

89

80

seed

10
11
12

13

14
15

21

20
18

26
47
22

80
84
73

89

85
88

>

Heavy

seed

16
17
18
19
20
21
22

39
25
31
24
54
56
62

86
79
84
88
87
83
97

88

3. Total Germination and Discussion of Rates op

Germination

Under constant experimental conditions over 50 per cent of
the light-weight and medium- weight seeds germinated in less
than four weeks. Under the same conditions and during the
same period of time 40 per cent of the heavy-weight seeds ger-
minated (Shamel & Cobey, 1907, p. 58).

There was fairl}^ regular diminution in the amount of
germination under these constant experimental conditions and
during this month, as the weight of the seeds increased.

Under widely varying conditions of temperature and light,
the heavy-weight seed which had not germinated in the ger-
minating case gave an average germination of 38 per cent in
four weeks. Under these widely varying conditions and during
this period of time the light and medium weights of seed gave
an average germination of 18 per cent.

Tlie final count, which includes germination in the genu in-

100 University of California Publications in Botany \yo\.. 5

ating ease and in the propagating house, showed a fairly regular
increase in total germination, beginning with the lightest grades
of seed and running up to the heaviest.

The results of numerous investigations on the delayed ger-
mination of seeds and the water and oxygen requirements for
germination, point out the probable causes of the early ger-
mination of the light seed and the delayed germination of the
heav}^ seed (Shull, C. A., 1909 and 1911, and the literature there
cited). Thus (1) the seed-coverings of the majority of the light
seed may be more permeable to water and oxygen than those of
the hea\'y seed, or (2) the water and oxygen requirements for
the germination of the heavy and light seeds may not be the
same and, (3) the oxygen content of the medium surrounding
the seeds in the germinating case and in the propagating house
was certainly higher in the latter situation. Thus, again, with
a high permeability for water and oxygen in the seed coats and
a low oxygen requirement for the germination of the light seed,
we should find this light seed showing high average germina-
tion in the germinating case. On the other hand, with slight
permeability of the seed coats of the heavj' seeds for water and
oxygen and a high oxygen requirement for their germination,
we might expect to find the average germination in the ger-
minating case relatively low and that rapid increase in ger-
mination would sooner or later be apparent with the increased
oxygen about the seed in the propagating house. The conclu-
sions of various investigators (Strasburger, Noll, etc., p. 258)
that variations in temperature increase germination may also
give a suggestion as to the cause of the high average germina-
tion of the heavy seeds in the propagating house (see also Raci-
borski, 1900) .

1912] Goodspeed: Nicotiana Hybrids 101

V. DEVELOPMENT OF SEEDLINGS

1. Early Development of Seedlings

Since there was space available for growing only 230 plants
of the hybrid N. Tahacum var. macrophylla $X ^- Tahacum var.
virginica J', twenty-five of the developing seedlings only of each
weight of seed were retained. Each group of twenty-five, with
the exception of numbers 1 and 2, from which only ten plants
were available, was composed in practically every case of seed-
lings of all ages, i.e., those developed from seed which had ger-
minated in the germinating case and those produced from seed
which had germinated after April 1 in the propagating house.

The groAvth and early development of all the seedlings was,
in general, normal and corresponding in every way. As the
seedlings were passing into the typical semi-rosette stage, it
was observed that the plants grown from heavy seed were de-
veloping more rapidly than those grown from the light seed,
though these last had in general germinated a month earlier.
This difference in size and general development on May 18 is
shown in plate 34, figure 1. As can be seen, the difference in
size of the two groups of plants was mainly due to retarded
development of the plants from the light seed or, on the other
hand, to abnormally rapid growth of the plants from the heavy
seed, and was not to any great extent due to a weak or sickly
condition of the former.

2. Number and Condition of Plants in the Field

The plants were set out in the field early in July. They were
placed in two long rows of approximately 110 plants each, with
the plants 3i/> ft. apart in the rows and with ten plants repre-
senting each number given in the table of the various weights
of the seed. Tlic following table gives the number of normal
and vigorous plants growing in the field when first carefully
examined on September 2 :

102 University of California Puhlicatious in Botany [Vol. 5

Weights of seed Number of plants
Numbers of in field Sept. 2

Ill-formed

r 1

seed

&

I 2

8

3

7

Light

4

10

seed

5

8

6

10

' 7

10

8

6

Medium

9

10

seed

10

10

11

8

12

8

' 13

7

14

10

15

■ 10

16

8

Heavy

17

7

seed

18

8

19

10

20

8

21

8

22

7

}

% of plants, origin-
ally in each number,
growing on Sept. 2

80

87

86

82

From the above it will be seen that the number of plants
grown from the ill-formed seed, from the light seed, from the
medium seed and from the heavy seed, that came to maturity
as fully developed, vigorous plants, was practically the same.
This is especially evident when we consider the fact that the
averages given above are based upon such a small original num-
ber as ten plants set out in the field. I am told that there were
as many surviving seedlings ready to be set out in the field
from the light and medium weights of seed as from the heavy
seed. On September 2 these plants had formed over twenty
capsules of seed apiece, were or just had been fully in flower and
were, in most cases, making vigorous laterals on which numerous
flower buds were forming.

1912J

Goodspeed: Nicotiana Hyhrids

103

VI. APPEARANCE OF PLANTS IN THE FIELD

1. Scheme for Grouping Plants on the Basis of the Com-
binations OF Characters which they Exhibited

Between September 18 and 25, all the plants were carefully
gone over, separately examined, and the exact appearance of each
plant was noted under the following headings :

I. Flower

1. Color

(a) pinkish

(b) i^ink

(c) magenta

2. Corolla limb.

(a) flat, pentag-
onal, angles
shallow

(b) cut into lobes
tipped with a
recurved hook

II. Habit

1. Tall

2. Short

3. Spreading

4. Not spreading

HI. Leaf

1. General shape

(a) elongated
lanceolate

(b) ovate sub-
rotund

(c) lanceolate
subrotund

2. Leaf tip

(a) Slender-
pointed and
curving

(b) sharp pointed
and not as (a)

3. Auricle

(a) flat

(b) ruflled.

On the basis of such a tabulation of characters, a plant which
reproduced the N. Tahactim var. virginica parent in appearance
would have been noted as follows :

Flower color — Pinkish.

Shape of corolla limb — Cut into lobes each tipped with a
recurved hook.

Habit — Tall and with no laterals broadly spreading from the
base.

Leaf shape — Elongated lanceolate with the tips of the leaves
slender-pointed and curving and the auricle ruffled.

Similarly for a plant reproducng the N. Tabacum var. macro-
phylla parent in appearance:

Flower color — Red.

Corolla limb — Pentagonal with the angles shallow and not
hooked.

104 University of California Puhlicafions in Botany [Vol. 5

Habit — Short, with laterals widely spreading from the base,
and the

Leaf — ovate subrotund, with a short, almost blunt tip and a
flat auricle.

There was not a single individual which corresponded to
either of these two descriptions.

A plant that could be spoken of as "intermediate" would
have exhibited the

Flower color — Pink.

Corolla limb — Pentagonal with angles elongated into short
hooks.

Habit — Tall, with numerous laterals spreading from the base,
and

Leaf — Lanceolate subrotund. with a long, curved, slender
tip and a somewhat ruffled auricle.

A plant said to "resemble" one or the other parent would
show some three or four of its minor characteristics differing
from, but othenvise nearly identical with, the parent the ap-
pearance of which it most nearly approximated — i.e., approach-
ing the typical appearance of one of the parents as nearly as
the F^ (so-called) dominant approximated the appearance of
the y. Tabacum var. macropliylla parent. Finally, the plant
called a "blend" would show a typical flower of one parent com-
bined with an "intermediate" leaf-shape and the habit of the
other parent, or ?iny other of the possible combinations in which
one or two characters each, of both parents appears fully de-
veloped in the hybrid.

2. Number of Plants in A^irious Groups

The following table gives the number of plants from each
weight of seed and the combination of "characters" which they
exhibited. The meaning of the terms "intermediate," "re-
sembling" and "blend" have been described above.

'o

1912]

Goodspecd: Nicotiana Hyhrids

105

Ill-formed
seed

Light
seed

Medium
seed "^

Heavy
seed

Numbers of
weights of seed

1&2

3

4
5
6

7

8

9

10

11

12

13
14
15
16
17
18
19
20
21
22

Heavy seed
Medium seed
Light seed

Resembling Resembling

Inter A'. Tabacum N. Tabacum

mediates var. rnacrophylla var. virginica

1

2

2

1

1
1

2
2
1
1
2
4
1
1
2
3
1
1
2
2

1
2
1
2.

2
2
2
4
2
2
1
4
4
3
3

o

2
4
5
3

2
3
2

4

3
1
3
1
3
2

1
0
1
0
0
2
2
2
0
0

Blends
2

1
3
3
3
4
2
3
3
2
3

3
2
4
2
2
3
3
1
1
2

19 (24 %) 31 (39 %) 7 (9 %) 22 (28 %)
8 (15%) 14 (26%) 13 (25%) 17 (33%)
6 (18%) 6 (18%) 11 (33%) 10 (31%)

No possible statement in tabulated form or otherwise could
be included in a paper of this scope which would give any
accurate summary of the multitude of combinations of the
parental characters in the most widely varying degrees which
the 175 F^ generation plants exhibited. Indeed no two indi-
vidual judgments on any one plant would coincide except in
a general way. Thus, for the table given above, there can be
claimed no absolute degree of accuracy. The main results as
given, however, were certainly present in a rather marked degree.
These results seem to indicate that some correspondence exists
between the various weights of first generation hybrid tobacco
seed and the appearance of the F, generation plants produced
from the various divisions of this seed according to weight.

106 University of California Publications in Botany [Vol. 5

YII. DISCUSSION OF INHERITANCE OF CHARACTERS
ACCORDING TO WEIGHT OF SEED

1. Shape, Size and Weight of Parental Seed of 1906 and 1907.

The seed which was used to reproduce .Y. Tahacum var.
macropJiylla and X. Tahacum var. virginica in 1907 and 1908
was examined under the lens and also weighed. There was
under the reading-lens a greater uniformity in shape and size
of the seed of both parents than that which has above been
noted in reference to the shape and size of the F^ hybrid seed
produced by the cross between these plants. The average length
and breadth and the length-breadth index of the seed .V. Tah-
acum var. virginica and the seed of .V. Tahacum var. m,acrophylla
harvested in 1907 is given in the following table.

A'. Tahacum var. virginica N. Tahacum var. macrophyUa

Length Breadth Length- Length Breadth Length-

breadth index breadth index

0.76 mm. 0.55 mm. 72.48 0.88 mm. 0.61 mm. 69.31

The average weight of 200 seeds of N. Tahacum var. virginica har-
vested in 1906 was only 0.0001 gr. less than the average weight of 200
N. Tahacum var. virginica harvested in 1907.

400 N. Tahacum var. virginica seed harvested in 1906 and 1907 weighed
(average for 100 seeds), 0.0069.

200 N. Tahacum var. macrophylla seed harvested in 1907 weighed (aver-
age for 100 seeds), 0.0078.

These 600 parental seeds were weighed just as before de-
scribed in connection with the weighing of the F^ generation
hybrid seed. In picking out the seed to be weighed, no effort
was made to make any distinction between seeds of slightly dif-
ferent sizes and shapes — i.e., the average run of seed was taken
except that the small number of ill-formed, chaffy seed that
occurred was not included.

1912] Goodspeed: Nicotiana Hyhrids 107

2. Seeming Correlation between Weights of Seed and Inher-
itance OF "Dominant" and "Recessive" Characteristics

The fact that the "dominant" parent — X. Tabacum var.wiac-
rophylla — when self- (close) fertilized in 1907 produced seed
which was heavier than the seed produced in the same manner by
the "recessive" parent — N. Tabacum var. virginica — in both 1906
and 1907, seems to be significant when we consider the weights of
the seed produced by the cross between these two parents and
when we consider the appearance of the F, generation produced
from the various weights of the hybrid seed. For the heavy
portion of the seed produced by self-fertilizing the hybrid
between macro phylla and virginica gave F„ hybrid plants of
which 39 per cent more closely resembled the macrophylla parent
than they did the virginica parent. Secondly, among the plants
produced by this heavy hybrid seed only 9 per cent resembled
virginica. Again, from among the lighter weights of the Fj
generation hybrid seed there were produced, as Fg generation
hybrids, 33 per cent of plants resembling virginica as against
18 per cent resembling macrophylla. Finally, from medium
weights of hj'brid seed there were produced approximately the
same percejntage of plants resembling macrophylla and re-
sembling virginica.

Thus the parent of the cross .Y. Tahacum var. macro-
phylla $X ^^- Tabacum var. virginica (^ which possessed the char-
acteristic of bearing heavy seed is reproduced, more or less in-
tact, in the Fo generation grown from the heavy weights of the
Fi hybrid seed. Thus, again, the parent of the above cross which
is distinguished by bearing relatively light seed likewise appears,
more or less intact, in the Fo generation and is produced therein
from the lighter weights of F^ generation hybrid seeds. Finally,
the medium weights of F^ hybrid seeds gave plants in the Fa
generation approximately 50 per cent of which resembled N.
Tabacum var. macrophylla and 50 per cent resembled N. Tab-
acum var. virginica in appearance.

108 University of California Publications in Botany [Vol. 5

VIII. SUMMARY OF RESULTS

1. The hybrid in F^ produced from the cross Nicotiana Tah-
acum var. macrophylla JX '^- Tahacum var. virginica ^ resembles
more closely the macrophylla parent.

2. The absence of complete dominance of the macrophylla
parent was shown by the occurrence in the F^ heterozygote of the
ruffled auricle, the hooks terminating the shallow angles of the
pentagonal corolla limb, the lighter color of the flowers and the
more gradually tapering points of the leaves; all characteristic
of virginica.

3. The seeds produced by close fertilizing one F^ hybrid plant
of the cross N. Tahacum var. raacrophylla^y, N. Tahacum var.
virginica ^ showed a great variation in size and in weight.

4. The divisions according to size, density and weight cor-
responded closely — i.e., large seeds showed highest specific den-
sity and were the heaviest, etc.

5. Of the light and medium seed 65 per cent germinated in
the germinating case within a month, while only 49 per cent of
the heavy seed germinated during the same period and under
the same conditions.

6. During a month in an unheated propagating house the
heavy seed germinated to such an extent that the final count
for the two months' germination gave 88 per cent as the average
of 1000 heavy seed germinated, while the light and medium divi-
sions of seed in the propagating house gave such a low percent-
age of germination that the total per cent of germination of
1000 light and medium seeds for the two months was only 78 per
cent.

7. The number of plants in the field four months later showed
that a larger percentage of the seedlings set out into the field
from the light and medium grades of seed had come to normal
maturity than from the heavy seed.

8. The appearance of the F^ generation individuals made it
possible to distinguish four classes of plants, the division being
based upon the combinations of the distinguishing characters of
the two parents which they exhibited.

1912] Goodspeed : Nicotiana Hybrids 109

9. From the hea\'y seed 39 per cent of "dominants" (re-
sembling macrophylla) , 9 per cent of "recessives" (resembling
virginica) and 52 per cent of "intermediates" and "blends"
could be distinguished.

10. From the medium-weight seed 26 per cent of "domin-
ants, ' ' 25 per cent of ' ' recessives ' ' and 49 per cent of ' ' blends ' '
and "intermediates" can be reported.

11. From the light seed 18 per cent of "dominants," 33 per
cent of "recessives" and 49 per cent of "blends" and "inter-
mediates" could be recognized.

12. The seed produced by close fertilizing one plant of N.
Tabacum var. macrophylla, which was harvested in 1907, showed
under a reading-lens a much greater degree of uniformity in
shape and size than did the F^ hybrid seed similarly examined.
The same was true for the seed of N. Tabacum var. virginica
similarly produced on two successive years — 1906 and 1907.

13. The average weight of 100 virginica seeds of 1906 was
0.0001 grams less than the average weight of 100 virginica seeds
of 1907.

14. The average weight of 100 virginica seeds of 1906 or
1907 was 0.009 grams less than the average weight of 100 macro-
phylla seeds of 1907.

IX. DISCUSSION OF RESULTS

The results obtained when the rate of germination of seeds
of different weights, under the germinating conditions described
above, was compared, are interesting and of some significance.
As has been mentioned above, the differing degrees of permeabil-
ity to water and oxygen probably explains the early germination
of most of the light seed that did germinate at all and the slow
germination of the heavy seed. The seed of 1906 and 1907 of
N. Tabacum var. virginica and of 1907 N. Tabacum var. macro-
phylla has, within the past month, been germinated in an
unheated propagating house. One hundred seeds of each year
and of each variety were used. The macrophylla seed showed
the first signs of germination within nine days and at the end
of sixteen days 89 per cent had germinated. The germination of

110 University of California Puhlications in Botany [Vol. 5

the 1906 and 1907 virginica seed was somewhat slower. At the
end of nine days there was no sign of germination and after
sixteen days 68 per cent of the 1906 and 71 per cent of the
1907 seed had germinated. The total germination after 20 days
showed that

1906 — virginica seed germinated to the extent of 81 %

1907 — virginica seed germinated to the extent of 88 %

1907 — macropliylJa seed germinated to the extent of 91 %

The appearance of mould about the seed that had not germinated
necessitated a termination of the experiment at the end of
twenty days.

This parental seed was, as before noted, indiscriminately
chosen and showed throughout a marked uniformity in size and
shape of individual seeds. That within less than three weeks
such a high percentage of germination should have taken place
among the relatively old parental seed (Shamel and Cobey, 1906,
p. 35, Hayes, 1912, p. 3) is interesting and also somewhat unex-
pected when we recollect the results obtained in germinating the
hj'brid F^ seed.

That the parental seed possesses a considerably greater degree
of uniformitj^ in shape, size and weight than does the hybrid
seed is, in general, shown by its appearance under the lens, in
particular by the close agreement between the weights of various
samples of the seed, and finally by the fact that its germination
was fairly simultaneous within each group. In other words,
there seems to be sufficient evidence to warrant the statement
that for the parental seed there is no such distinct and well-
marked division into grades according to physical characteristics
as was found in the hybrid seed of a plant produced by crossing
these parents.

The facts of greatest significance in connection with the ger-
mination of the difi:erent divisions of F^ hybrid tobacco seed
according to weight are (1) that the seedlings in the rosette
stage — i.e., sufficiently developed to be set out in the field —
showed a superiority of vigor for the young plants grown from
heavy seed over those grown from light seed, and (2) that at
the period of maturity the number of plants fully grown and
normally developed which had been produced from light seed was

15^12] Goodspeed: Nicotiana Hybrids 111

as great as or greater than the number produced from heavy seed.
Conehision 1 is in accord with the generally observed facts, while
conclusion 2 is distinctly opposed to the report sent out by
those who, in agricultural practice, have matured plants grown
from heavy and from light weights of seed. The point of great-
est interest, however, lies in the fact that, if there had been
no careful division of the seed according to weight and if there
had been no especial interest in growing separately the plants
developed from heavy and light seed, the appearance of the
seedlings at the time of planting out would have led a plant-
breeder to choose his further experimental material largely from
seedlings grown from heavy seed, since they would be the most
vigorous and would be expected to produce more normal plants
than would the backward seedlings from the light seed. In the
light of the experimental results reported in the foregoing pages,
and even without further confirmation of these results, it seems
advisable to urge upon those experimenting in plant-breeding-
(1) the devoting of a greater measure of attention to the physical
characteristics of their pedigreed seed, (2) the making of every
effort to germinate all types and grades of their seed, and finally
(3) the bringing to development, in so far as practicable, seed-
lings which show all degrees of vigor and development at the
time when they are placed in the field. That the lightest weight
and even chaffy, misshapen seed will germinate under the proper
conditions has been shown and, of still more significance, it has
been demonstrated that seedlings produced from such seed,
though backward in appearance, may ultimately come to vig-
orous and normal maturity (see, in this connection, Harris, J. A.,
1912 fo).

From the appearance of the F^ heterozygote we seem, as
before stated, to be dealing with a case of Mendelian dominance
to the extent that the influence of the N. Tahacuni var. macro-
phylla parent predominates in the F^ hybrid. From the appear-
ance of the Fo hybrid plants we find a certain indication of
segregation, but that we are dealing with a case of Mendelian
segregation cannot, in the present instance, be demonstrated. It
hardly appears possible, even with the extent to which factorial
analysis has recently been carried and the number of IMendelian

112 University of California Publications in Botany [Vol. 5

ratios and interpretations which have been advanced, that the re-
sults obtained upon tabulating the combinations of characters ex-
hibited by the F, generation plants are susceptible of a Mendelian
interpretation. As is noted in the following, however, the small
number of plants grown may be the cause of the situation. Grant-
ing that this is the cause, we may briefly set down the situation
we should encounter upon endeavoring to arrange our experi-
mental data according to a Mendelian scheme of analysis. The
two parental forms differ from one another in respect to at least
seven definite pairs of characters. The hybrid in F^, which re-
sults from a cross between the two parents, exhibits an approx-
imately complete dominance for one parent. There was, how-
ever, no difficulty in distinguishing between the heterozygote in-
dividuals and the plants of the dominant parent. To observe
among the F^ generation plants even an approximation of the
expected Mendelian ratios, at least 15,000 plants would not only
have to be grown but would need to be critically examined in
order that they might be arranged into the more than 2000
possible combinations that might appear. Making our calcula-
tions along this line we should not be surprised to find that among
the 175 plants grown in this experiment not a single true
homozygote could be found. It has, I think, elsewhere been
noted that the ordinary plant-breeder, without unlimited field
space and a number of trained assistants, is forced to group the
various appearances of the individuals which constitute his
limited F^, F-j, etc., generations under general headings, when
he attempts an investigation of the inheritance of a polyhybrid
character in which the power of )i is greater than 3 or 4. As has
been seen, such a method of grouping has been adopted in this ex-
periment (see Baur, 1911, p. 213). Certain plants in the F2 gen-
eration resembled, usually rather closely, the general appearance
of one parent or the other, while many other plants produced a
typical flower of one parent along with a typical leaf of the other
parent, or appeared to possess flowers and leaves in which the dis-
tinguishing characters of both parents were hopelessly mingled.
Thus we have classified the plants in F^ as "resembling" one
parent or the other, as "intermediates" or as "blends." We
certainly have no basis for either definitely affirming or denying

1912] Goodspeed: Nicotiana Hybrids 113

the presence of a Mendelian ratio within our limited experi-
mental material, and the following brief discussion in no way
attempts to exclude the possibility of such an interpretation.
Our effort is primarily to ally ourselves with those who feel that
"what is urgently needed is an accurate description of the
various waj's in which the characters of domesticated animals
and plants are inherited. It will be time enough to interpret
them when our knowledge of them is a great deal more perfect
than it is at present" (Darbishire, 1911, p. 240).

The experimental results in general seem capable of explana-
tion on the assumption that we are dealing here, in the case
of the seed produced by the F^ hybrid, with an infinite series.
By growing plants from the two extremes, the heavy and the
light seed, we have produced a high percentage of plants re-
sembling the two parents — one parent from the heavy seed and
one parent from the light seed. Again, by using the medium
weights of seed we produce 50 per cent of plants intermediate in
appearance and 25 per cent each of plants resembling each of
the two parents. The fact that approximately 50 per cent of
the plants from each of the two extremes were "intermediate"
or "blends" may be due to the inaccuracy of the weighing or to
the small number of F^ generation plants grown. In other
words, had it been possible to weigh each seed separately or to
grow 1000 Fo plants, the percentage of plants from heavy seed
resembling N. Tabacum var. macrophylla and of plants from
light seed resembling N. Tabacum var. virginica, might have
been far higher.

From another point of view, the occurrence in the F^ hybrid
seed of three readily distinguishable divisions according to weight
and size is significant, and especially so when we find a rather
marked uniformity in weight and in size among the seeds of both
parents. The possibility suggests itself that whatever segrega-
tion there may be has taken place in such a manner within the
ovary of the F^ hybrid that it (the segregation) becomes apparent
only in the physical characteristics of the seed which the F^ hybrid
plant produces. Thus on close fertilization of the F^ hybrid plants
of the cross N. Tabacum var. macrophylla ^yi N. Tabacioii var.
virginica 1^— these two parents producing seed of different

114 University of California Piiblications in Botany [Vol. 5

weights, but seed which is uniform in size and in weight for
each parent — we obtain from the matured ovaries seed ap-
proximately 1/4 of which is heavy, 14 ^^ which is light, and i/^
of which is intermediate in Aveight between the heavy and light
seed. Now upon growing the F2 plants from the heavy weights
of this Fi hybrid seed, we obtain 31 plants, the appearance of
which approximates that of the macrophylla parent as against
seven plants which resemble virginica. Among the Fo individuals
produced by the light seed, eleven plants resemble virginica
and six plants resemble macropliylla. Finally, from the seed
intermediate in weight, approximately 25 per cent of the F,
plants resemble one parent and 25 per cent the other parent.
Thus the fact of segregation, to the extent to which it has taken
place, becom.es apparent when the Fo plants are grown, in that
for the heavy seed one parent is "dominant," for the light seed
the other parent is "dominant"' and from among the medium
weight .seed 50 per cent each of the two parents are produced.
In addition the "dominance" seems to follow the weights of the
parental seed in each case, since the heav3'-seeded parent appears
in Fo in greatest number among the plants grown from heavy
seed and the light-seeded parent from the light F^ hybrid seed
(see, in this connection, Waldron, 1910, p. 56 ; also Harris, J. A.,
1912 a).

In this connection the following suggestion is tentatively ad-
vanced. There may be such an organization of the developing
pollen from the anthers of the hybrid in F^ that the generative
nucleus in each mature pollen grain bears one of two influ-
ences. The first constitutes a "determiner" (Davenport, '08),
functioning to produce the outward appearance of the macro-
pliylla parent. The second influence may be one which functions
for the production of the outward characteristics which dis-
tinguish the virginica parent. The tube nucleus may, like-
wise, bear any one of two influences. The first is one which
functions for the production of heavy seed, after its union
with the fusion nucleus in the embryo sac and the second
functions for the production of light seed. Corresponding
conditions may be present within the embryo sac in the case
of the e^^ nucleus and in the case of the fusion nucleus

1912] Goodspeed: Nicotiana Hybrids 115

respectively, the first bearing one of the two determiners for
outward characters and the second one of the two determiners
for seed-weight. Thus with the union of the proper tube
nucleus and the fusion nucleus bearing the same "influence"
the seed resulting from this fertilization would be heavy. With
our present cytological knowledge of the processes involved, it
is a matter of speculation whether this mature seed is heavy
because of the relatively high specific gravity of the contents
of the endosperm cells, or because the fully developed endosperm
results from a large number of cell-divisions, or finally, because
the endosperm is made up of a smaller number of very large
cells (see East and Hayes, 1911, p. 101 ; Harris, 1911, and
the literature cited therein). If, in the same fertilization we
were describing above, the generative nucleus of the same pollen
grain and the egg nucleus of the same ovule on uniting both
carry the macropliylla influence, a heavy seed capable of pro-
ducing a plant in Fo which resembled macro pliylla would be
produced.

Other com.binations of nuclei might give medium weight
seed plants resembling either one parent or the other, or plants
to express the composite appearance of which the terms "inter-
mediate" and "blend" have above been used. Still other pos-
sible combinations might result in the formation of light seed
in the mature ovary of an F^ hybrid, a certain portion of which
would give rise to plants in F^ resembling one parent, another
portion to plants resembling the other parent, and still another
and larger portion to plants called "intermediates" and
"blends."

Without attempting to include any schematic representation
of the possible combinations of nuclei and the resulting weights
of seed and F, generation plants, it will only be said that such
a scheme seems to represent fairly closely the numerical propor-
tions which we have noted above as occurring in the weights
in the F^ hybrid seed and in the appearance of the F2 genera-
tion plants produced therefrom. Any such explanation of our
experimental results is, as previously mentioned, only tentatively
advanced and it is recognized that little can be claimed for it
without more evidence than that whicli we are able to offov.

116 University of California Publicafions in Botany I ^ol. 5

The question of Xenia and the double fertilization in the
seed of maize (East and Hayes, p. 101, and the literature there
cited), is the only matter which bears directly on the above
explanation. The discussion given by Bateson (1909, p. 270), is
interesting in this connection, yet we seem to have some experi-
mental evidence which goes to show that the two nuclei brought
into the embryo sac by the pollen tube do not bear similar or
even corollated allelomorphs and that all the nuclei of the embryo
sac are not similar in composition. The above explanation, in
general, seems possible from a cytological point of view (Coulter,
Barnes and Cowles, 1910, p. 269), and is as theoretically con-
ceivable as certain other methods of interpretation which have
recently been put forward.

1912] Goodspeed: Nicotiana Hyhrids 117

PAKT II

QUANTITATIVE EXPRESSION OF IMPERFECT DOMIN-
ANCE IN THE COROLLA DIAMETERS OF THE
FLOWERS ON THE HYBRIDS PRODUCED
FROM THREE VARIETIES OF NICO-
TIANA ACVMIN ATA (Grab.) Hook.

CONTENTS

PAGE

I. Introduction 118

II. Discussion of the experimental material 119

(1) Description of experimental material 119

(2) Basis of identification of our experimental material and

description of a wild form of N. acuminata 119

(3) Growing conditions — soil and climatic conditions 123

(4) Description of tlie Nicotiana flower 125

III. Technique and methods 126

(1) Obtaining "pure" seed 126

(2) Cross pollination 127

(3) Cleaning of the seed 129

(4) Sowing of the seed 131

IV. Experimental work— 1910 132

(1) General habit of the parental types 132

(2) Distinctions in corolla diameter and measurements of

the same 133

(3) Cross pollinations made between parents 135

V. Experimental work — 1911 136

(1) Cleaning, sowing, and germinating of the 1910 seed 136

(2) Number and condition of the plants in the field 137

(3) General habit of the hybrid plants 137

(4) Method of measuring corolla diameter 138

(5) Results of the measurements 139

VI. Summary of results 144

VII. Discussion of results 145

VIII. Literature cited 152

IX. Explanation of plates 158

118 University of California Publications in Botany [Vol. 5

I. INTRODUCTION

Probably the most recent discussion of plant and animal
breeding, especially from the point of view of the Mendelian
discovery, contains the following statement in reference to
dominance, that "unessential feature of the Mendelian phenom-
enon"— "The fact that the dominant and hybrid tall (in Men-
del's classic experiment with Pisum) appear to us identical is
probably no more than a measure of the crudeness of the means
which hitherto have been adopted to distinguish between them — "
(Darbishire, 1911, p. 38). Thus, leaving aside the question
whether or not the condition and appearance of the hybrid in F^
is an "unessential feature," the report on the quantitative es-
timation of the condition in which certain parental characters
are inherited in F^ seems of interest and value.

Despite such assurances as the above in reference to the rather
unessential nature of dominance (Bateson, 1909, pp. 13 and 53;
see, also, Stockberger, 1912, p. 152, and Baur, 1911, p. 52),
a considerable number of references to the "Law of Dominance"
are to be found in the literature on plant-breeding which has
appeared since the rediscovery of Mendel's experiments (East,
1907, p. 40, and Brainerd, 1907). With either point of view, the
Fi generation, throughout the literature as it has been accessible
to me, does not receive any great measure of critical attention.
When dominance can be reported, the ground is cleared for a
direct advance toward the hoped-for Mendelian segregation in
Fo and, on the other hand, when a strikingly intermediate hybrid
appears in F^ we look up the situation and find that we are
justified in merely making a note of this relatively unimportant
stage in our experiment and in reserving our efforts in anticipa-
tion of cliificulties in i^roperly interpreting the Fo generation.

The present paper contains the results of a strictly quanti-
tative investigation of an easily measured character — corolla
diameter, in the hybrids of three varieties of Nicotiana acuminata
which are to be distinguished from one another in respect to this
character alone.

1912]

Goodspeed: Nicotiana Hyhrids

119

II. DISCUSSION OF EXPERIMENTAL MATERIAL

1. Description of Experimental. Material

The experimental material is described in tabulated form
as follows :

Variety number I

II

III

Source

Cambridge Bot.
Garden

La Mortola

Fort Bidwell, Cal

Identified as

N. acuminata

A^. acuminata

N. acuminata

grandifora

parviflora

variety

Length of corolla

IVo to 1% cm.

1 to 1% cm.

1 cm.

tube

Color of corolla

white

white, purple

white

tube

at base

Diameter of

3 to 4 mm.

2 to 31/4 mm.

2 to 21^, mm.

corolla tube

Color of corolla

white

white

white

limb

Shape of corolla

salverform

salverform

salverform

limb

Diameter of fully

26 to 29 mm.

19 to 22 mm.

13 to 15 mm.

extended flower

Radical leaves

acuminate, petioled

(as var. I)

(as var. I)

Cauline leaves

narrowly lanceolate
and petioled

(as var. I)

(as var. I)

Height of mature

60 to 75 cm.

70 to 105 cm.

60 to 110 cm.

plant

General habit

widely branching
from the base

(as var. I)

(as var. I)

First grown in

1907

1908

1903 (?)

U. C. B. G.

Plant number in
the V. C. B. G.

150
07

125 192

08 and 08

53

2. Basis of Identification of our Parental Material and
Description of a Wild Form of N. acuminata

The identification of our experimental material as X. acuniin-
ata is based upon the description and figure given by Hooker
(Bot. Mag. Tab. 2919; cf. also, Setchell, 1912, p. 24, plate 26).

120 University of California Puhlications in Botany [Vol. 5

This description seems to approximate variety I of our experi-
mental material most closely. Comes (1899, p. 39) recognizes
under N. acuminata "variety grandi flora" and "variety parvi-
flora." With the first of these we connect our large-flowered
form (variety I) and with the second the form in which the
corolla diameter is intermediate in size (variety II). Comes
gives no definite measurements of flower size for varieties
" grandiflora" and "parviflora" but the fact that he does recog-
nize two cultivated varieties principally distinguished from one
another in respect to corolla diameter makes it seem justifiable
to identify the two cultivated varieties among our three parental
types wath those he names.

The small-flowered form (variety III) was first noticed in
the University of California Botanical Garden some four or
five years ago and it is possible that the original seed was sent
from Fort Bidwell, California. At least, the small-flowered form
was first noticed in a portion of the Botanical Garden in which
the Fort Bidwell seed w^as originally sown (1903?). One N.
acuminata plant came to maturity in that same part of the
garden this past summer (1911), and a measurement of its
flowers showed that a fairly small fluctuation in corolla diam-
eter was operative in this type, w^hich has been self-sowing itself
for seven or eight years. Only eleven flowers were measured and
their corolla diameters varied between 13 and 17 mm., with the
average diameter approximately 15 mm. It seems probable that
our small-flowered variety III is a particular form which has
become segregated from among the plants which, in some genera-
tion previous to 1908, grew from the seed originally sent from
Fort Bidwell. In 1908 the striking and uniformly small flowers
borne by some one of the plants in the original garden plot
attracted attention, and since that year variety III has been
propagated by pure seed and has come true each year to uni-
formly small flowers on all its plants.

Plate 29 is drawn from fresh material of variety II of our
parental types. Figure 1 shows a typical lateral from a vigorous
plant with the narrowly lanceolate cauline leaves, secondary
lateral shoots, a fully opened flower, a number of buds at the
top and maturing seed capsules, all one-half natural size. Figure

1912] Goodspccd: Nicotiana Hijhrids 121

2 and figure 3 are normal flowers of variety II and figures 4
and 5 are views of half mature seed capsules. Figure 6 shows
a typical radical leaf, most of which by the end of the season
are much torn or dried and obscured by the soil about the base
of the main axis of the plant. The leaf shown in figure 7 nor-
mally occurs along the main axis up to one-third of the distance
from the roots to the top of the plant and along the basal
portions of the larger laterals.

Quite recently a considerable collection of wild plants, iden-
tified as N. acuminata, has been made in Niles, California. Th^
plants were growing in, and on the sides of, a dry, sandy,
river-bed in about equal numbers with N. Bigelovii. Ap-
proximately 75 measurements of corolla diameters of the flowers
on these wild plants were made in the field. The fluctua-
tions of corolla diameter in flowers on the same plant were usually
less than 5 mm., but between different plants standing side by
side the mean of the corolla diameters of their flowers varied
over 6 mm. Thus one of the wild specimens bore flowers the
corolla diameters of which varied between 12 mm. and 16 mm.,
with an average diameter of 13 mm., and on another plant in
a slightly different situation the corolla diameters of the flowers
varied between 15 mm. and 20 mm., wdth the average at ap-
proximately 19 mm. In other words, the wild varieties of N.
acuminata, at least as we have found them in California, exhibit
a wide range of fluctuation in corolla diameter of flowers on
individual groups of plants and a relatively small degree of
fluctuation in the size of flowers borne by the individual plants
themselves. The largest flower found on the plants at Niles
was one measuring 22 mm. in diameter and the size of flower
most usually occurring, together with the general habit of the
wild plants, duplicated rather closely the appearance of variety
II of our experimental material.

Plate 30 was drawn from fresh material obtained in the
above mentioned collection of the wild X. acuminata variety made
at Niles during November, 1911. On comparing this plate with
plate 29, in which variety II of our experimental material is
shown, the resemblance between the wild and the cultivated
varieties is evident. Figure 1 of plate 30 shows an entire young

122 University of California Puhlications in Botany [Vol. 5

plant drawn one-half natural size. Its cauline leaves corres-
pond fairly exactly to those in figure 1 of plate 29, except that
the waviness along the leaf margins of the leaves of variety II
is not so strongly marked in the leaves of the wild variety. The
third leaf from the base of the stem in figure 1 of plate 30 re-
sembles figure 6 of plate 29, while figure 7 of plate 30 approxi-
mates the appearance of the leaf shown in figure 7 of plate 29,
though in this last case, and as is very evident, the narrow
leaf -tip of the wild variety does not arise so sharply from the
broad cordate leaf-base as in the leaf of variety II. The corolla
tubes of the flowers shown in plate 30 are both longer in pro-
portion to the size of the flower and somewhat more dilated at
the top than in the flowers of variety II. The calyx teeth also are
longer in the flower and the calyx in the ripening ovary does
not so completely envelop the maturing seed capsule as in the
cultivated variety.

Varieties I and II have been grown in a number of Botanical
Gardens under such names as Nicotiana vincae/lora,, N. suaveo-
lens, as well as N. acuminata.

In the three varieties of N. acuminata described above we
have individuals identical, within the limits of normal individual
fluctuation, in almost every respect except the diameter of the
flattened salverform corolla. This point of difference is plainly
marked and entirely constant. On the first occasion, four years
ago, upon which the three were assembled and grown near one
another, Professor W. A. Setchell observed the sharp gradation
in this character and the absence of other distinguishing and
delimiting characteristics. During the past two years, in which
this species has been turned over to me, a large number of
measurements and careful examination confirm these observa-
tions. As has been said, the present paper deals with the general
appearance and corolla diameter of the first hybrid generation
resulting from crosses between these three varieties of N. acumin-
ata. Seed is being gathered at the present time which will make
it possible to continue the investigation along the same lines in
the Fo and, possibly, the Fg generation.

1912] Goodspeed: Nicotiana Hyhrids 123

3. Growing Conditions — Soil and Climatic Conditions

All three varieties have been cultivated continuously from
the years named up to the present time in practically the same
situation and under similar conditions. Constituting a part
of a considerable collection of Nicotiana types that has been
accumulated during the past ten years under Professor W. A.
Setchell's direction and for experimental purposes, this species
has received the special care universally accorded material propa-
gated for research work. The only portion of the Botanical
Garden at the present time available for experiments in plant-
breeding — suitably fenced and near a small propagating house
and cold frames — is not well adapted to the most successful
pursuance of such experiments. The "inclosure" lies at the
lowest level of any part of the garden, is not well drained and
is much shaded at all hours of the day by eucalyptus trees
which exhaust much of the vitality of the somewhat fertilized,
natural adobe soil.

Climatic conditions in Berkeley during the out-of-door grow-
ing season — May to December — are very fairly constant through-
out a given number of years. Extracts from the records kept
at the University of California observatory follow:

124

University of California Publications in Botany [Vol. 5

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1912] Goodspeed: Nicotiana Hybrids 125

4. Description of the Nicotiana Flower

In general the structure of the Nicotiana flower adapts it
unusually well for hybridization experiments. In the case
of N. acuminata the flower is amply formed — the corolla tube
never less than 1 cm. in length, the diameter of the tube from
2-4 mm. and varying in diameter of flattened corolla limb from
13 to 29 mm. in the fully opened flower (see plate 29). It is
vespertine in common with many species of Nicotiana, es-
pecially the white flowered forms. In the bud the limb of the
corolla is somewhat plicate. The anthers — with the exception of
the one standing lowest in the tube — are not shedding pollen
until the corolla lobes are fully extended. The fifth anther
stands 2-3 mm. lower in the tube than the others and is shedding
pollen first and just as the flower opens fully. I have observed
on many occasions that two or three hours may separate
the two conditions and, in the case of a flower that opens fully
and for the first time after dark, the anthers may not break
until the following morning. The two-lobed stigma is receptive
from six to eight hours before the flower in general is in
anthesis and continues receptive for a considerable time after
all the anthers are open. A castrated flower under the bag may
be successfully pollinated toward the end of the bud stage or
while the corolla lobes are still folded and during the middle
of the day when the other flowers on the plant are completely
closed and deflexed. There is no difficulty in self-fertilization
naturally or under experimental conditions. It perhaps takes
place naturally when the flower closes during the middle of the
day. The corolla will withstand considerable mutilation and
still persist otherwise normally. I have never observed that the
buds are perforated or entered by insects nor that the plants in
general were injured in any way by insect pests. It has been
impossible to determine whether cross pollination is, under
natural conditions, effected by outward agencies and, in the
case of such a white vespertine species, this undoubtedly takes
place at night, if at all.

126 TJniversity of California Publications in Botany [Vol. 5

III. TECHNIQUE AND METHODS

1. Obtaining "Pure" Seed

In obtaining "pure" seed — naturally self- (close) pollinated
or artificially self- (close) pollinated seed from the protected
flowers of a parent or a plant of the F^ (or subsequent hybrid
generations) — a vigorous lateral near the top of the main axis
of the plant is selected and prepared by stripping off leaves, buds
and small branches for a distance of a foot or more below the
terminal buds and flowers. The choice of a lateral on the
upper two-thirds of the main stem means nearly total absence
of the seed which in the case of lower branches falls from above
and adheres to the sticky, minutely glandular epidermis. AH
opened flowers and all but three or four buds are then picked
off the terminal inflorescence with forceps and a fresh paraffin
bag, placed over these remaining buds and secured at the base
with a copper-wired pot label suitably marked, allows sufficient
room for a number of flowers to expand normally and effectually
excludes the entrance of foreign pollen b}' practically any agency.
As mentioned above, self fertilization is accomplished readily and
in the majority of cases, after the bag has been carefully opened
at the end of two or three weeks to make sure that seed is being
set, no further attention need be given the material until the
seed is gathered at the end of another two or three weeks. In
this connection it might be said that, in the case of .V. acuminata
the ripe seed often begins to fall from the promptly 2-cleft apex
of the capsule while the lower two-thirds of the maturing ovary
is still green. The semi-transparent paraffin bag makes it pos-
sible to watch the development of the capsule without opening
the bag. If the seed capsule is gathered and hung to dry when
the tip of the capsule first begins to show a brownish coloration,
the seed ripens perfectly within the capsule and danger of a
mouldy condition of the seed is eliminated.

In gathering seed the lateral is cut three inches below the
bottom of the bag. placed and wired in a larger heavy manila
bag with the pot label showing, and hung to dry out of doors.

1912] Goodspecd: Xicofiaua Hyhrids 127

2. Cross Pollination

In preparing flowers for cross fertilization a number of pre-
cautions and as exact a routine as the circumstances permit
are rigidly enforced and any slip that can be detected serves to
put a stop immediately to the work in hand. It can be fairly
stated that the technique and methods developed in connection
with all matter pertaining to the iVi'co^iana-experiments have
reached a degree of refinement which cannot reasonably be sur-
passed without introducing minutiae of detail too complicated
to be practicable. The small size and great number of seed
borne by a Nicotiana plant introduce one of the greatest sources
of error in these experiments and has led to unusual precautions,
especially in the matter of cleaning, sowing and germinating
the seed.

In the field the first precaution taken is one which undoubt-
edly is universally observed in such work (Shull, 1908a). The
arms are bared to the elbows and arms and hands are sterilized
in 95 per cent alcohol. A curve-pointed forceps and a small
pair of scissors are kept immersed in 95 per cent alcohol when
not immediately in use. Until the conclusion of the particular
operation under way the hands touch only the instruments and
the flower or flowers that are being worked with, and any contact
between them and the clothing or other plants nearby necessitates
at once a new sterilization. When an assistant is at hand it is
entirely possible in making, for example, a cross-pollination, for
the operator himself to do nothing more than pick out with the
forceps a stamen from one flower which has been brought to
him in its bag and apply the pollen-covered anther to the stigma
of the female parent.

The male parent is prepared just as described above in con-
nection with the obtaining of pure seed. The label is given the

plant number with the male sign writen directly after it — e.g.,

53

03 J*. In work on .V. acuminata four or five sets of buds were

prepared on a male parent at about the same time in order that

there might bo no doubt of a sufficient supply of pollen in case

of any errors in the sul)sequent operations.

128 University of California Puhlications in Botany [Vol. 5

In the profusely branching species of Nicotiana much care
is necessary in picking all buds out of the axils of leaves and
thoroughly stripping the lateral chosen on the female parent so
that small branches and flowers may not develop within the bag
while the hybrid seed is being formed. The lateral is carefully
gone over with the scissors and usually only one bud on the
terminal inflorescences is left. The hands and instruments are
now sterilized again. With the forceps the corolla tube is
carefully split from the top of the calyx teeth to the corolla
lobes, or until the corolla can be gently pushed liack and the
stamens and pistil exposed. The unopened stamens, one or two
at a time, are then pinched off with the forceps half way down
the filament, or often the anthers themselves are picked out
separately. The corolla can now be closed back and around
the pistil, the effort being to mutilate and derange the normal
condition and position of the perianth as little as possible. A
bag covers the castrated bud and the label attached to the bag

]_50
carries the plant number and the female sign — e.g., 07 $• It

may be mentioned here that this label remains with the bag
while on the plant, during the drying of the seed, and is placed
in the seed envelope when the seed is cleaned. A number of
such castrated buds are prepared and often the date and hour
is noted on the labels attached. References to all such opera-
tions are, of course, placed in the record book for the particular
experiment.

These flowers in both the parents will be ready for use in
two or three days. When the two parents have been prepared
at about the same time and the buds are of the same size I
usually watch the pollen parent, since, as noted above, the
stigma is practically sure to be receptive as soon as the anthers
are open. This holds true for each of the three varieties of N.
acuminata as well as for different flowers on the same plant.
The developing buds can be seen through the paraffin bag and
on the second day after bagging, when the corolla of the pollen
parent is fully extended, it may be safely assumed that condi-
tions are favorable in both parents for cross-pollination.

The lateral upon which the male parent has been bagged is

1912] Goodspeed : Nicotiana Hybrids 129

cut below the bag and brought unopened near enough to the
female parent plant to be within easy reach. The copper wire
with male label attached is unwound from the neck of the bag,
placed upon the field table near by and the bag itself partially
opened. The label from the female parent bag is next placed
beside the male label and the bag loosened. AVhen the hands
have been sterilized the bag is lifted from the castrated flower
and laid aside. The pollen parent is taken from its partly
opened bag and a pollen-covered anther is extracted with the
forceps and applied to the receptive stigma of the female parent.
The proper bag is again placed over the pollinated flower
and labeled with the original designation of the female

plant with now in addition the name and sign of the male

150 5.3

parent — e.g., 07 5 X ^'i c^- If l^nt one crossing operation at a

time is attempted, and if the male and female labels are placed
side by side during the short period when they are not attached
to the plants themselves, there is little danger of mixing the
parent labels with subsequent difficulties of identification.

3. Cleaning of the Seed

The seed is practically all gathered and dried before Decem-
ber 15, is cleaned during February and March and sown late
in March and in April. The exceedingly small size and great
number of seeds in a single capsule from a Nicotiana plant makes
necessary the utmost precautions to prevent contamination in
connection with the cleaning and sowing of the seed. During
the past three years the seed has been cleaned in a difi^erent
room on each occasion. One person is required to do the "book-
keeping" and wrapping of the seed envelopes and another to
do the actual handling of the seed itself. The bookkeeper lays
on a clean table a sheet (4 by 5 feet) of heavy brown manila
paper and on it a smaller sheet (12 by 16 inches) of ordinary
white paper. The seed cleaner then places a white earthenware
saucer upon the white paper and receives the first bag of seed
from the bookkeeper. The latter cuts off the tops of the bags,
thus opening them and also freeing the seed label. Tie then

130 University of California Puhlications in Botany [Vol. 5

copies the hybrid or parent designation from the label onto two
sizes of envelopes and returns to the "cleaner" with the smaller
of the two envelopes. During the copying of the label, the
cleaner has lifted the original paraffin bag from the larger
manila bag in which it has been dried and has drawn out the
withered stem and the seed capsule or capsules. Usualh^ most
of the seed is still retained within the capsule and the cleaner
"shells" it out into the saucer and discards any seed which
may have fallen out into the bag. The rougher chaff, etc., pres-
sent may be picked out and laid on the larger brown paper.

The seed is then poured from the saucer onto the white paper
and from it into the smaller of the two envelopes which the
bookkeeper holds out. He seals the envelope, makes two folds
over the sealed end, places the envelope and the original label
on a small sheet of white paper and wraps them securely. This
paper is then put into the larger envelope and the latter sealed.
During this last operation the cleaner has laid aside the two
sheets of paper, cleaned the saucer and thoroughly' washed his
hands and wrists. The bookkeeper now lays out two clean sheets
of paper, the saucer is replaced and another bag of seed cleaned.
The bookkeeper, of course, takes notes upon the yield and con-
dition of the seed in each particular case. It will be noted
that only one person actually touches the seed, that he has only
this part to play in the whole operation, that his hands are
thoroughly cleaned each time, and that every effort is made, in
general and in particular, to insure cleanliness of surroundings
for the work. The danger of mixing labels and making mistakes
in copying is limited, since each package of seed contains three
identifying marks. The careful sealing and wrapping of the
seed envelope is necessary because of the small size of the seed
and the fear of loss and contamination, should there be any
possibility of its working out of the package.

l^'i2j Goodspeed: Nicotiana Hyhrids 131

4. Sowing of the Seed

The sowing of the seed is usually commenced during the lat-
ter part of March. Pots, 8 inches in diameter and 2^^ inches
deep, have been especially provided. They are filled with a
mixture of sand and garden soil and sterilized in the autoclav
for three hours, at eighteen to twenty pounds pressure. For
each pot cheese-cloth covers suitably cut are sterilized at the
same time. When the pots come from the autoclav these cover-
ings go on at once and are secured by wire rings about the pots.

Two persons also are needed in sowing the seed. Two sizes
of clean paper are again laid upon the table and the covered
pot placed upon them. The bookkeeper gives the first package
of clean seed to the "sower" and, lifting the covering off the
pot, lays it on the white paper always with the side that has
been nearest the soil uppermost. The sower then opens the
outer seed envelope, unwraps the paper, and compares the label
with the designations on the two envelopes. If no mistake has
been made and the three agree, the sower reads the seed numbe^'
from the label and it is checked off on the bookkeeper's list.
The sower now tears open the seed envelope proper and shakes
out the seed rather thickly over the surface of the soil. Any
seed remaining is wrapped up again and laid aside. Granite
pans, one for each pot and previously sterilized in the flame, are
used to press down the seed into the earth. The bookkeeper
now returns the cloth covering, secures it and writes the proper
designation on the side of the pot. The two papers and the
pan for pressing down the seed are now discarded, the sower
washes his hands and the whole operation is repeated.

Since this paper constitutes one of the first of a considerable
series on breeding investigations in Nicotiana which will prol>
ably be published from this laboratory, under Professor Setch-
ell's direction, it has seemed necessary in the above to go with
some detail into the technique he has adopted, which holds rigidly
for this particular experiment and in general method for all other
allied investigations in the Botanical Garden of the University
of California.

132 University of California Publications in Botany [Vol. 5

IV. EXPERIMENTAL WORK— 1910

1. General Habit of Parental Types

In 1910 the seed of .V. acuminata was sown on March 14 and
taken to the propagating house on the same day. The propagating
house was thoroughly cleaned and sterilized and the ventilators
covered with cheesecloth. The pots were watered from beneath,
with the covers on. and these last were replaced in two or three
days by glass plates. I have no record of the time of germina-
tion or of its amount. The glass plates were not lifted from
the pots until the size of the young plants made it necessary.
Quite generally toothpicks or pot labels were slipped under one
side of the glass so that there might be a slight circulation of
air within the pot. After the glasses were removed, much care
was taken never to lift or pass one pot over another. When the
cotyledons were large enough to be picked up and held between
thumb and forefinger, twice the required number of plants was
"pricked out" into flats. These wooden boxes or flats — 18 by
18 inches — were filled with rich garden soil and the plants so
spaced that each flat held 25 seedlings. In "pricking out" a
fresh toothpick is used for each seedling to loosen the earth and
scrape off soil particles which come up with the fine roots. By
carefully spacing the plants in the fiat and watching their
development every day or two, there is little danger of any
foreign seed germinating and getting established before being-
detected. When in the rosette stage and about the tenth of
June, the required number of plants was lifted from the flat
and placed in the portion of the inclosure set aside for them.
The remaining plants in the flat were held for a month in case
of accident to those permanently set out. Lack of room neces-
sitated the growing of a relatively small number of the X.
acuminata plants as well as undue crowding of these. When I
saw them first in August there were six plants of variety I,
eight of variety II. and fourteen of variety III. In each case
the groups of plants were spaced two feet apart, the rows of
plants one foot apart and twelve inches left bet^veen the plants
in the row. Varieties II and III were within six feet of each
other and varietv I was some distance awav.

1912] Goodspeed: Nicotiana Hybrids 133

On August 20. the three varieties were fully developed and
covered with flowers. In general habit variety II and variety
III were almost identical. Some trace of fasciation was ob-
served in two plants of variety III and its habit throughout was
a trifle the least robust. The leaf characters were the same in
these two numbers, though variety III has always exhibited a
somewhat ragged appearance in this connection which is not
shared by variety II. but is also present, though less pronounced,
in variety I. Variety I was growing in an especially unfavor-
able situation and seemed stunted and far from vigorous. One
plant, however, stronger than the rest, compared very closely
with the members of variety II and variety III.

2. Distinctions in CoroliLa Diameter and Measurements of

THE Same

The distinctions in corolla diameter were most clearly marked
as shown in figure 2 on plate 34. This photograph was taken
in 1908, but the gradations in size hold good equally well for the
years 1910 and 1911. Some three hundred measurements of
the corolla diameters of the three varieties were made during
August and September. 1910. Corolla diameter is taken to
mean the average of two measurements at different angles across
the flattened surface of the fully opened salverform corolla limb
— (plate 32. A to B and B to C). A flexible celluloid millimeter
ruler was used and simply laid on the flower at the two angles
and the measurements recorded. The condensed record of these
measurements follows :

Variety Number of Diameter of Diameter of Average all Degree of

number flowers meas. smallest flower largest flower measurements fluctuation

I. 108 26 mm. 28 mm. 26.93 mm. 3 mm.*

II. 131 19 mm. 22 (23?) mm. 20.66 mm. 4 or 5 mm.*

III. 82 13 mm. 15 mm. 13.98 mm. 3 mm.*

(* The fluctuation between diameters 13 mm. and 15 mm. amounts, of
course, to a difference of but 2 mm. By speaking of the fluctuation as
amountiii};- to 3 mm. is meant that corollas of flowers of variety III were
meJiMured whieli were found to be 13 mm., 14 nun. and 15 mm. in diameter.
The same method of notation for matters of degrees of fluctuation holds
throughout in the above table and in similar tables expressing fluctuation
in parent and hyl^rid diameters).

134 University of California Publications in Botany [Vol. 5

In reference to the diameter of the largest flower measured
in variety II there is doubt about extending the limit to 23 mm.,
since but one record of this diameter was noted and the figure
"3" is somewhat obscure in the original record. It may be
claimed that a degree of variation in corolla diameter as slight
as that noted in variety III — 13 mm. to 15 mm., or 3 mm. — or
even in variety II of 5 mm., is impossible. A superficial glance
at the plants in flower would certainly seem to substantiate such
a claim. The diameters given, however, have reference to
measurements made upon flowers of the same age or, better, in
the same stage of development. Only such flowers were measured
as exhibited all the anthers shedding fresh pollen. It is not
a difficult matter to decide by a far from critical examination
whether or not this condition is present in a given flower and,
after a considerable acquaintance with the flowers of N. acumin-
ata, it has been found possible to decide very quickly.

All the measurements in 1910 were made between 7 :45 and
9 :30 a.m. The newly opened flowers often show the corolla lobes
fully extended and flattened but the anthers still green. There
is a certain characteristically immature look about such a flower
very easy to recognize at a glance. In such a flower on a bright,
warm day the anther lowest in the tube will usually break during
the afternoon and on the following morning all the remaining
four will be shedding pollen. I have found that the difference in
corolla diameter in these two conditions usually exceeds 2 mm. in
all varieties of N. acuminata. Thus adding 2 mm. to the corolla
diameters for the two extremes given for variety I we might
have on the same plant flowers measuring 24 mm. and 30 ram.
and all sizes intermediate. Likewise for variety II, 17 and
24 mm. and for variety III, diameters measuring 11 and 17 mm.
and all diameters between. If Ave add, again, the appearance
of partially opened buds and flowers past anthesis, there
would seem to be on a plant, for example of variety II, the
greatest individual fluctuation in corolla diameter. Still it may
be seen that, allowing 2 mm. l^eyond either extreme of fluctua-
tion in corolla diameter of fully opened flowers as noted in the
above table, there is yet a definite division into the three
varieties — i.e., a large (24 to 30 mm.), a small (11 to 17 mm.).

1912] Gooclspeed: Nicotiana Hyhrids 135

and an intermediate variety (17 to 24 mm.) This matter will
be further discussed in connection with the measurements of
corolla diameters of hybrids and parents in 1911.

3. Cross Pollinations made between Parents

Between September 2 and October 5 seventeen cross-pollina-
tions were, to all appearances, successfully performed. The cross
I5X II d^ was made twdce and its reciprocal II $X I d^ twice.
Variety I was crossed with variety III on two occasions and
IIIJX I c^ twice also. Cross II 5 X HI c^ was made five times
and III 5X II cJ* four times. To obtain pollen for these cross-
pollinations twenty-two sets of buds were prepared and bagged
and twenty-eight female parents were castrated and bagged.
In variety III there was a most annoying tendency of the buds
that were being worked with to snap off and it was quite diffi-
cult to perform the castrations successfully. Fully opened
flowers were not so delicate in this respect. Fourteen of these
crosses had been made before September 7 and on the 20th the
bags were opened and a few small buds, inconspicuous and
overlooked in preparing the lateral two weeks before, were picked
off. In all but three cases seed seemed to be forming. The
three doubtfully successful crosses were repeated. All seed was
gathered and hung to dry before October 15.

Because of the extent to which variety III dropped its buds
this parent was artificialh' self- (close) pollinated. In the other
two varieties there was no difficulty in obtaining naturally self-
( close) pollinated seed. The parental seed was gathered and
hung to dry along with the hybrid seed.

136 University of California Publications in Botany [Vol. 5

V. EXPERIMENTAL WORK 1911

1. Cleaning, Sowing and Germinating of 1910 Seed

The .V. acuminata seed was cleaned in April. 1911. and sown
early in ]\[ay. As it was not possible for me to observe the
material before August, the sowing was done later in the spring
than is usual. The germination and entire direction of the
planting out. etc., was in the hands of ]\Ir. W. G. Perrine, the
head gardener of the Botanical Garden of the University of
California, of whose unfailing interest and enthusiasm, ability
and absolute integrity, acknowledgement should here be made.
At the time of cleaning the seed it was found that there would
be sufficient hvbrid seed for sowing but none to carrv over to be
grown with the F., generation. Among the parents it was found
necessary, in order to obtain sufficient seed of variety III, to
use the remainder of the seed sown in 1910. The scarcity of
hybrid seed was due only to the fact that I had not thought
it necessary to repeat the various crosses more than once and
not to any lack of seed in the two capsules which in each case
resulted from the cross-fertilization. The cross II $X HI d^ and
III 5X He? yielded four capsules of seed from the nine at-
tempted cross-pollinations — two from each cross. The cross
II 5 X I cJ* unfortunately gave no seed in either of the two at-
tempts above mentioned.

The germination of both parent and hybrid seed was high.
Twenty-five seedlings of each of the parents and of all the hybrids
except cross II $X HI d^ and its reciprocal, were pricked out into
flats. In this last instance the seed from each of the four cap-
sules was cleaned separately, germinated in the individual pots
and carried into the field with distinguishing labels.

The small plants were set out late in June and occupied one
whole side of the inclosure. In this case there was sufficient room
available so that there could be four feet between groups of
plants, two feet between rows and twelve inches between plants
in the row. The months of June and July were unusually cloudy
and cold and the development of the plants in the field was
correspondingly slow.

1912] Goodspeed: Xicotiana Ilijhrids 137

2. Number and Condition of the Plants in the Field

It was not found possible to work with the N. acuminata
plants in the field before the first week of August. Among
parents and hybrids the following table gives the number of
vigorous plants in each case at this time, the dates upon which
each group first flowered, the date upon which the last flowers
were measured and the number of plants left on November 20.

Parent and

Xumber of

First flowers

Last flower

Number of

hybrid number p!

lants Aug. 10

measured on

measured on

plants on Xov. 20

Var. I

5

9/3

10/4

3

Var. II

15

8/31

11/6

7

Var. Ill

10

9/7

11/6

3

I?X Hid'

7

9/8

11/20

2

iii$x IS

19

9/6

11/6

15

II 5x iiic?

36

9/5

11/20

18

III$X 11 c^

29

9/9

11/18

20

i$x iic^

12

9/8

11/20

10

The parents, though on the same strip of land with the
hybrids, were far from being vigorous plants and remained
throughout, with the exception of variety I, stunted and sickly.
In variety I the plants were identical with the smaller individ-
uals described in the previous year's work on this number. The
flowers were, of course, in all the parents not nearly so abundant
as in the previous year and in the case of variety II it was
possible to measure only ninety-nine flowers. The leaf and
general habit characters were again identical, though, as noted,
the plants throughout all three varieties were smaller in vegeta-
tive characteristics than as observed in 1910.

3. General Habit of the Hybrid Plants

Among the hybrid plants each plant has been carefully gone
over during the season and the following points noted. The
leaves, cauline and radical, were exactly the same throughout.
It lias not l)een possible comparing leaves from corresponding
regions on any two plants to tell them apart except in the
matter of slight variations in size, nor are there distinguishing
marks when compared with the leaves of 1910 and 1911 parents.
Ill habit the hyl)rids were identical with tlic h-ibit of the parents

138 University of California Puhlications in Botany [Vol. 5

in 1910 and also among themselves except as follows. One plant
resulting from the cross I$X HI J* was in habit exactly as all
the plants of variety I in 1911 and as all but one in 1910. Three
plants of I 5X He? were not up to the normal in height and
were more broadly spreading, with thicker main stems and lat-
erals. Lastly, five plants of IIIJX II c^ were very small and
in appearance immature, with few small laterals and small leaves.
The traces of fasciation observed in two plants of variety III in
1910 appeared in five plants in 1911 but only in those hybrids
which had variety III as a male or female parent.

4. IMethod of Measuring Corolla Dlvmeter

Measurements of corolla diameter of the parent and hybrid
flowers, were first made on September 8 and the last record
noted is on November 20. Slightly over 2750 measurements were
recorded during this period. A sheet of zinc. 3 by 4 inches, was
deeply notched and served as a very simple holder for the
flower while being measured. If the flower is picked off, gently
slipped into the notch and pulled down until the flattened corolla
lies upon the surface of the zinc plate, the ruler can be laid
firmly on the face of the corolla, at the desired angles, and the
two measurements taken very readily and after some experience,
sufficiently exactly. Other devices such as a squared sheet of
smooth paper ruled in millimeters, upon which the flower could
be pressed and the diameters read off, were found to be less
accurate than the more simple apparatus described above.

On an average two or three flowers can be accurately
measured a minute. Considerable delay was caused by the
necessity of frequently washing off in alcohol the heavy gum
from the stems of the tobacco plants, which covered the hands
and instruments to such an extent as, at times, to render fur-
ther work impossible. An assistant recorded the measurements,
thus simplifying the work greatly. The records were so taken
that it is possible to refer, on a given date, to the measurements
of flowers on any particular plant in the whole series and, in a
general way, to recognize the region on the plant upon which
any single flower occurred. All measurements were made be-
tween 8 and 10 a.m. with the exception of November 9 and 13,

1^1-J Goodspeed: Xicotiana Hybrids 139

upon which dates the flowers were measured between 5 and 6
p.m. The greatest effort was made to exclude personal bias in
connection with the measurements. As the plants were worked
with nearly every other day for over three months it was im-
possible not to form a more or less definite idea of the direction
towards which the results were tending. Also, when measuring
fifty to sixty flowers on one day from a single group of plants,
one could scarcely avoid keeping certain limits of fluctuation
in mind. It was attempted, however, to make the measuring
as mechanical an effort as possible and the actual limits of
fluctuation, as given below, were not found until practically
the last record was taken. The averages of the measurements,
also, were not calculated until all the measurements were com-
pleted and the experimental portion of the work concluded.

5. Results of the Measurements

The following table gives the number of days upon which
the flowers in each group were measured, the largest and smallest
number of flowers measured on a single day, the total number
of flowers measured, the largest and smallest diameters and the
average diameter in each case, the theoretical size of the true
intermediates between the average diameters of the parents, and
the fluctuations in corolla diameter throughout.

Group number Var. I II III IIIJx I<;;J' IJX IH^ I$X IIJ' HJXIIIJ' III$X H;;?

Number of days upon
which plants were
measured

Largest number meas-
ured on a single day

Smallest number meas-
ured on a single day

Total number measured

Diameter of largest

flower, mm. 29 22 15 27 23 30 20

Diameter of smallest
flower, mm.

Average diameter, mm.

Intermediates between
averages of parents,
mm.

Fluctuation in corolla
diameter, mm.

26

11

24

31

15

27

24

23

18

15

17

86

9

17

33

65

1
228

1

99

1

185

13

849

2
36

3

320

3

374

7
757

26

19

13

17

17

23

13

14

26.9

19.8

13.6

21.63

19.69

24

16.94

16.8

20.25

20.25

23.35

16.7

16.7

4

4

3

11

7

8

S

9

140 JJnwersity of Calif omia Publications in Botany [Vol. 5

Here again we have a very small degree of variation in the
corolla diameters of the parents. The measurements were very
carefully taken and at times a few measurements would be made
upon the parents, then upon the hybrid plants, and again upon
the parents. It was possible in 1911 to watch the plants as they
first came into flower and every effort was made to follow the
development, from the bud to the fully opened flower, of every
individual flower measured either on hybrid or parent plants. By
this is meant that, for example, on September 28 it was observed,
in the case of plant 1 of the cross III JX II d^. that two flowers
were in a proper condition (see page 134) and they were picked
off and measured. On the same date and on this plant three
flowers were almost in the proper condition to be measured — i.e.,
the anther lowest in the tube shedding pollen and the corolla
fully extended but the remaining anthers unopened. There were
also four flowers all with the anthers green and the corolla only
partially opened as well as a considerable number of rather
small buds. Now in this case, it was plain that the anthers of
the first three flowers mentioned above would be shedding pollen
during the afternoon of September 29. and that on the follow-
ing morning these two flowers would be in the proper condition
to be measured. It was also evident that some of the remaining
four fully formed buds might be properly developed by that
time. At eight a.m., September 30, only three flowers could be
measured. One of the three flowers almost ready the morning
before had evidently begun to shed pollen from all the anthers
before noon, for in this flower two of the anther cells were
almost free from pollen, the brownish coloration at the back of
the pollen receptacles was showing, and the stigma was covered
with pollen. In the other two the anthers were balls of light,
fluffy pollen and no pollen could be noticed on the stigma. All
three of these flowers probably could rightly have been included
in the measurements so far as development in corolla diameter
is concerned, but only the last two were considered to be in
exactly the proper condition and the third was picked off and
thrown away. Of the four flowers that had been quite unde-
veloped on September 29, two showed the anthers lowest in the
tube shedding pollen, the third flower showed all the anthers

1912] Goodspeed: Nicotiana Hybrids 141

still green and the fourth flower only was in the proper con-
dition to be measured. On September 30 there were, in addi-
tion, four newly opened buds. The next measurements on this
plant are dated October 2, on which date four flowers were
measured — i.e., three of the four that were newly opened buds
on the 30th and one which had come to maturity since that time.

In other words, when the measurements were finished on each
day, only small buds and immature flowers were left on the
plants. By taking the measurements every other day there was
usually an abundance of material and most of it in the same
condition. The foregoing applies, of course, to measurements
on the parent as well as on the hybrid flowers.

Plate 31 gives the number of flowers measured on sixteen
or seventeen different days, between October 1 and November 8,
on single plants of the various groups and. in the ease of the
plotted figures in the upper right hand corner, the number of
flowers measured on all the plants of the group representing the
cross I5X II c^- The plant upon which the greatest number of
flowers was measured during the five weeks is, in each case, given.
The close similarity between the plotted figures is rather striking.
Climatic conditions (see page 124), operating on all the plants,
undoubtedly is the chief cause of this similarity, though a
probable periodicity in the production of reproductive parts, as
opposed to those strictly vegetative, may enter in as a factor.
It hardly seems, however, that this last can have great signifi-
cance in reference to the similarity between the plotted figures,
since all the plants would not naturally be influenced by such
a periodicity on practically the same dates. Between October
20 and 30, when the production of flowers was in general ex-
ceedingly low, there had been rain, cloudy weather and an
extremely low temperature at night, following a period of
climatic conditions practically the reverse. Probably the direct
result, in this connection, was seen in a tendency throughout to
drop the flower buds. j\Iore favorable weather conditions — Nov-
ember 1 to November 8 — always caused an immediate and rather
disproportionately large increase in the production of flowers.

The degree of variation in corolla diameter among the hybrid
plants is. ill each ease, large. For example. III^X I c^ varies

142 University of California Puhlications in Botany [Vol. 5

between 27 mm. and 17 mm. and III$X II J* between 22 and
14 mm. The relative degrees of fluctuation in corolla diameter
are well brought out in plate 32. All the drawings with the
exception of that marked 11$ X HIJ* were made from fresh
material, suitably selected to show the extremes of variation
among parent and hybrid plants. It must be emphasized that
these extremes of variation were continually observed on single
plants of the various groups of hybrids and did not occur simply
as isolated instances in the measurements of an entire group.
Thus, corolla diameters in plant 2 of III 5 X I d^ vary as follows
between October 2 and November 20. The daily average is also
given.

Date 1911 Get. 2 4 6 8 9 11 13 15 18

Largest flower

in mm. 26 25 27 26 25 26 26 24 26

Smallest flower

in mm. 21 20 23 21 22 21 21 21 17

Daily aver-
age in mm. 24 23.8 24.8 23.7 23.6 23.2 23.9 22 24.2

Date 1911 Oct. 20 27 30 Nov. 13 6 8 18 20

Largest flower

in mm. 27 25 25 26 25 25 25 23 22

Smallest flower

in mm. 19 20 19 19 17 IS 18 19 19

Daily aver-
age in mm. 22.9 23.8 23.6 19.7 21.7 22.8 23.2 21.6 20.8

Thus on a single plant of the hybrid IIIJX I cf we obtain
the extremes of fluctuation — 17 mm. and 27 mm. — which the
flowers of the entire group of plants representing this cross dis-
played. As has been said above, this was true throughout all
the h^-brid groups — i.e., practically every plant of a hybrid
group exhibited in its flowere the extremes of variation in cor-
olla diameter reported for the whole hybrid group. It might
have been possible that toward the end of the flowering season
the fluctuation in corolla diameter would be diminished or that
the full effect of the amount of acquired characters might ex-
hibit itself (Lang, 1908; see also Groth, 1911, p. 8; Moore, 1910,
1912). As will be seen from the above table and plate 33, the

1912] Goodspeed: Nicotiana Hybrids 143

degree of fliictnation was practically as great at the beginning,
at the middle and at the end of the flowering season.

Plate 33 exhibits the degree of fluctuation in corolla diameter
of varieties I and III and the fluctuation of all the plants repre-
senting the cross 111$ X IJ* of each of sixteen different days
between September 15 and November 6. The heights of the
various columns correspond to the number of flowers for each
diameter measured on the various dates. It will be remembered
that the parental varieties did not give as vigorous plants during
the season of 1911 as in 1910 and did not flower anywhere nearly
so profusely as during the previous season. This is the cause
of the shortness of the columns throughout for the parental
varieties I and III as contrasted with the heights of the columns
showing tlie fluctuation of the hybrid plants representing the
cross between these two parents. A comparison between plate
31 and plate 33 will show that, in general, the production of
flowers for the entire group of plants of cross III 5X I c^ (plate
33) corresponds closely to the production of flowers on a single
plant of this hybrid group (plate 31).

It will be noted that upon only two occasions was the diam-
eter 29 mm. found for variety I, while the limits of fluctuation
of the hybrid, 17 and 27 mm., appeared on six occasions for
the diameter 17 mm. and on seven different days for the diameter
27 mm. Diameter 15 mm. was noted on the flowers of variety III
on onl}^ two occasions, both previous to September 15, and for
this reason diameter 15 mm. is not included in the columns of
variety III. It is also plain that the number of flowers in the
hybrid group exhibiting these extremes of fluctuation was large
as compared with the number of flowers giving the limit of
fluctuation 29 mm. in the parent variety I. Also, from plate 33
and the above table (p. 142), it can be seen that there was no
appreciable difference in the average size of corolla diameters as
the growing season advanced ; a difference which might have
been expected to exhibit itself because of an increase of strictly
vegetative growth at certain times and a consequent inhibition of
normal floral development.

144 University of California Puhlications in Botany [^ol. 5

VI. SUMMARY OF RESULTS

The foregoing description of experimental results can be
summed up as follows :

1. The experimental material consisted of three varieties of
Xicotiana acuminata. The three varieties are distinguished from
one another almost solely in the diameter of the limb of the
salverform corolla of the flowers.

2. The differences in corolla diameter among the three
varieties were practically constant throughout two seasons during
which the corolla diameters were measured in the Botanical Gar-
den of the University of California. The three diameters were
13 mm., 20 mm. and 27 mm., with fluctuations never exceeding
2 mm. either greater or smaller than the mean diameter in each
case. The three mean diameters and the fluctuation noted were
obtained on the basis of approximately 800 measurements of
flowers of the three varieties.

3. From six successful cross-pollinations — the three crosses
between the three varieties and the reciprocal crosses— five groups
of hybrid plants were brought to maturity (100 plants at the
opening of the season and 65 at the close). Approximately 2750
measurements of the corolla diameters of flowers on hybrid
plants were made.

4. The measurements of the corolla diameters of the flowers
on the plants of each group of hybrids gave an average diameter
for each group which was practically the same as the calculated
average between the corolla diameters of the corresponding two
parents. In other words, each of the five average hybrid corolla
diameters formed intermediates in size between the corolla
diameters of the parents of the corresponding cross. Each cross
and its reciprocal gave practically the same result in this con-
nection.

5. Variety II, called an "intermediate," in reference to
corolla diameter, is truly an intermediate between the large and
small flowered varieties of X. acuminata. This is shown by the
fact that when the large and small varieties are crossed the
average corolla diameter of the hybrid flowers approximates

1912] Goodspeed: Nicotiana Hybrids 145

fairly closely the average corolla diameter of this "intermediate"
variety.

6. Among' the corolla diameters of the flowers of all the
hybrid plants a wide range of fluctuation was observed. This
fluctuation included diameters from 13 mm. to 30 mm.

7. The fluctuation 13 mm. to 30 mm. is as great as the differ-
ence between the smallest corolla diameter of variety III (the
small-flowered parental variety) — i.e., 13 mm. — and the largest
corolla diameter of variety I (the large-flowered parental variety)
— i.e., 29 mm.

8. The maximum fluctuation in corolla diameter of a single
hybrid group of plants was 11 mm., or almost three times as
great as the parental type which fluctuated most widely — i.e.,
4 mm.

9. The minimum fluctuation for a single group of hybrid
plants was 7 mm., or almost twice as great as the largest fluctua-
tion in corolla diameters of the flowers of the three parental
varieties.

DISCUSSION OF RESULTS

One important exception must be noted to the statement
made in the introductory paragraphs of this paper, to the effect
that no critical attention has been given to F^ generation hybrids.
Reference is made to Darbishire's work on the nature of the
starch grains of round and wrinkled peas (Darbishire, 1908).
As will be remembered, the cross between a round pea with
potato-shaped or p starch grains and the wrinkled pea \^^th com-
pound or c starch grains yields a hybrid starch grain in F^
which is intermediate in shape (length-breadth index), inter-
mediate in the distribution of compoundness. intermediate in
the degree of compoundness and the hybrid round pea itself is
intermediate in absorbtive capacity between the parents. In
F- "the homozygote round peas contain p-grains, the hetero-
zygote round peas contain r-ov intermediate, grains." Since this
work of l)arl)ishire's is practically the only experimental evi-
dence so far accumulated which is comparable with that wliieli
has been reported in the present investigation, it is necessary

146 University of California Puhlications in Botany [Vol. 5

to determine the extent to which the experimental results agree.
In the summary of results given on page 144 the statement is
made that the average hybrid corolla diameter is intermediate
in size between the parental diameters (see East, 1912, p. 247;
also Hayes, 1912). To this extent our results seem to coincide
wdth those reported by Darbishire. The difficulty is that, as
shown in the figure on page 125 (Darbishire, 1908), there are
no hybrid starch grains as round or as compound as the parental
c-grains, nor are there any hybrid grains as potato-shaped as the
parental p-grains. The hybrid grains are half-way between being
potato-shaped and being round and half-way between compound
and not at all compound — that is, they are true intermediates.
The corolla diameters of hybrid flowers are, however, both as
large as the diameter of the large-flowered parent and as small as
the diameter of the small-flowered parent ; both extremes occur
among the flowers of a single plant ; and, finally, only a numerical
average establishes an intermediateness of corolla diameter for
the flowers of a hybrid plant. The important point also is that,
breeding from a hybrid pea the starch grains of which exhibit
one-half the D influence and one-half the R influence, we might
be prepared to have the hybrids in succeeding generations exhibit
some definite degree of segregation. Similarly, if the hybrid
corolla diameter was truly intermediate, in that it exhibited as
above one-half the D influence and one-half the B influence, we
might predict segregation in Fo at least to the extent to which
it took place in the starch grains of the pea hybrids. But now,
when on a single plant of the Nicotiana acuminata hybrids flowers
appear the corolla diameters of which show the unimpaired D
influence and the unaffected B influence and every degree of
intermediateness between the two, what prediction can be made
as to the appearance of the F, individuals with respect to the
corolla diameters of their flowers? In other words, is there
evidence to show that largen&ss of flower vs. smallness of flower,
intermediate flower size vs. small flower size, large flower size
vs. intermediate flower size, etc., in each case, constitute the two
members of a Mendelian pair?

It is interesting in this connection to note the partial report
of an experiment in which peas differing widely in size were

1912] Goodspeed: Nicotiana Hybrids 147

crossed (Darbishire, 1911, p. 211). The F^ hybrid was a blend,
corresponding, probably, to the intermediate position occupied
by the F^ hybrid starch grains above mentioned, and, "so far
as data at present available show, segregation does not occur
when the hj'brids are self-fertilized." The author raises the
question whether, in such experiments, the Fo generation might
not consist "of a complete series of gradations between a 'small'
identical with the pure 'small' at one end, and a 'large' identical
with a pure 'large' at the other end" (Darbishire. 1911, p. 211;
but see also Castle, 1905, and Bateson, 1909, p. 251). The possi-
bility at once suggests itself that just this same condition of
partial segregation is present in the F^ hybrids of the N. acum-
inata crosses — in other words that, just as large seeds, small
seeds and seeds showing all gradations in size between large and
small might occur in the ripe pods of the hybrid peas in Fj, so
on a single plant of the N. acuminata hybrids in F^ large flowers,
small flowers and all degrees of intermediate flower size occur.
As the author suggests, again, the only practical value of con-
tinuing to breed from material showing such a type of inherit-
ance is the possibility that one or both the extremes of the series
may breed true in later generations and that a certain propor-
tion of the intermediate forms, probably those nearer the ex-
tremes, may also breed true. With this in mind, it has been
possible to secure F, seed from hybrid flowers on one plant, the
corolla diameters of which were large, small, and intermediate
in size between large and small. Thus the suggestion that can
in general be made is that such segregation as will definitely
occur (Bateson, 1909, p. 211) in respect to the corolla diameters
of hybrid flowers of N. acuminata, is exhibited in the flowers of
the F^ generation hybrids and that the F2 generation will show
whether or not certain corolla diameters breed true or whether
the fluctuation in corolla diameters which appeared in the hybrid
flowers will be regularly diminished in Fo and succeeding genera-
tions until the two parental types are ultimately regained and
a number of new "flower-size" varieties, with small fluctuations
in corolla diameters, are established.

Certain results obtained by Groth (1911, part 1, pp. 5-10)
in liis examination of the cotyledons on F^ hybrid tomato seed-

148 University of California Publications in Botany [Vol. 5

lings are also interesting in this connection (see also, Gregory,
1909, and Gard, 1911). The flnctuation in the length of
the parent cotyledons was great in each cross, — never
less than 5 mm. and nsnally greater than 10 mm. — and
the degree of fluctuation of cotyledon length in the F^ hybrids,
considerably' diminished {loc. cit., p. 7), for many of the crosses.
A rather strange predominance throughout of the female influ-
ence in each cross is reported (see Hagedoorn, 1908 ; Loeb, King
and Moore, 1910). The general result of the experiments seems
to show that the "absolute size .... tends to be larger in
the cross than the mean between the corresponding characters
of the parents" (Groth, loc. cit.. p. 33). The fluctuation in coty-
ledon length almost always equalled and surpassed the higher
extreme, but in no case reached the lower extreme of the parental
fluctuations. It is in this connection especially that Groth 's
results differ from those reported in this paper. In the case
of tomato seedlings it might possibly be held, since the D in-
fluence was practically always strongly evident; since the R
influence was likewise absent, and finally since the average length
of the hybrid cotyledons was nearly always greater than the
mean between the average length of the parent cotyledons, that
in respect to length of cotyledons, "longness" is dominant over
both "shortness" and " intermediateness. " It will again be
repeated, for comparison, that in reference to corolla diameter
in N. acuminata hybrids both D and B influences were always
present, and the mean between the average corolla diameters
of the parents was practically identical, in every cross, with
the average corolla diameter of the hybrid in each case. In a
second report upon the mature F^ tomato hybrids Groth finds
that in the seedlings ' ' opposing factors .... are still struggling
for mastery .... an equilibrium is reached when the plant
becomes older, and that equilibrium is generally the same for
the same combination of factors." This equilibrium is often
shifted, however, "so that even in grown plants reciprocal and
duplicate crosses may differ in characters of size, shape and
number" (1911, part 2, p. 11). The fact that the F^ generation
of N. acuminata hybrids is far more variable in respect to floral

1912J Goodspeed: Nicotiana Hybrids 149

diameters than the parents must again be noted in connection
with a recent report by Hayes (1912) and the discussion
therein given and the previous observations by Johannsen
(1906).

The use of the term "fluctuation" throughout this paper has
been somewhat loose (Bateson. 1909. p. 210; cf. also, East, 1910,
p. 82) . In reference to the variations in corolla diameter exhibited
by the parental varieties of N. acuminata, the use of the word
"fluctuation" for such variation is undoubtedly valid. In using
the same term for the variations in corolla diameter of the hybrids,
a matter of convenience rather than .strict definition has been
con.sulted. It is probable that such a degree of variation in a
definite floral "unit character" as that shown by the fluctuation
in corolla diameter of the N. acuminata hybrids in Fj^, has never
been reported. That such great variation is due to "disturbing
effects .... of environmental origin" (Bateson, 1909, p. 239;
see also Hayes, 1912) is doubtful, and it is hard to see where the
results arrived at in connection with pure-line breeding are ap-
plicable (Johannsen, 1909). It is moreover clear that the in-
creased vigor generally assigned to the vegetative and floral
characters of hybrids (Groth, 1911, part I; East, 1909, pp. 174
and 177) is not the force compelling the great variation here,
for neither was the habit and foliage of the hybrid of a more
luxuriant type nor (and this is the important point) did the
hybrid corolla diameter in any case exceed by over one milli-
meter the diameter of the large-flowered parent in any cross.

The last point we must take up refers to the purity of the
experimental parental material. To the best of my knowledge,
the three parental varieties of N. acuminata have come true to
certain definite corolla diameters for at least four years. Cer-
tainly during the past two years direct measurements have
shown that the three varieties are definitely distinguished from
one another by certain sizes of flowers, the fluctuations in the
corolla diameters of which are so small as to cause no inter-
grading of one variety into another. The probable existence
of the small-flowered variety as a wild type before its introduc-
tion into the Botanical Garden eight years ago, may suggest

150 University of California Puhlications in Botany [Vol. 5

that the particular type which we have considered to be the
small-flowered X. acuminata variety (III), was of recent hybrid
origin. As has been seen, nothing in the appearance in F^ of
any of the crosses which contain this small-flowered variety as
a parent suggests that we are dealing with a heterozygote in
the case of variety III. Certainly in the result of the crosses
where the parents with large and intermediate flowers are con-
cerned, there can be practically no doubt as to the homozygous
condition of the parental material; and the appearance of the
hybrid between these varieties was practically the same as the
appearance of the hybrids which resulted from crosses in which
the small-flowered parent was concerned. The number of plants
brought to maturity in both the experiments reported upon in
this combined paper is small but compares favorably with the
numbers raised in experiments to the results of which a strict
Mendelian interpretation has been applied (Price and Drinkard,
1908). It is to be noted, however, that the flowers upon only two
generations of the parent plants have been measured and that
thus we may not have fulfilled the criterion set by Johannsen
when, speaking of "the hybridisation of types that are quan-
titatively characterized," he justly states that they "must be
pure lines, the constancy (or, if it may be, the mutability, segre-
gative capacity, and so on) of which has been previously studied
in a sufficient number of generations" (Johannsen, 1906, p.
105). To sum up the above discussion, it may, in general, be
said that the occurrence of flowers on any one hybrid plant in F^,
the corolla diameters of which show the unaffected "dominant"
influence, the unaffected "recessive" influence, and all diameters
intermediate between the corolla diameters of the parents, makes
it difficult to find an explanation for such a type of inheritance
according to any of the most widely accepted hypotheses. The
discussion of "intermediates" (see Macfarlane, 1895) as given
by Bateson (1909, pp. 235-241) and the four important classes
within which intermediate types fall, does not seem to offer the
necessary explanation. The "presence" of both the unimpaired
D and It influences in F^ makes it rather difficult to apply the
" presence-and-absence hypotheses" (Shull, 1909) to a discussion
of the experimental results herein reported. Again, none of

1912] Goodspeed: Nicotiana Hyhrids 151

the parental corolla diameter characters are "latent" (Shiill,.
1908, p. 7 and the literature there cited) in F^ but appear both
fully activated and in various degrees of blending and combina-
tion. Finally, there is no evidence which goes to show that there
is a "variability .... in the potency of determiners" (Daven-
port, 1910, p. 135) in our experimental material or that we are
here dealing with the case of a "stronger determiner meeting a
weaker determiner in the germ" (Davenport, 1908). It must
at times be somewhat a matter of speculation just "what does
meet what" in the germ and, in the case with which we are
dealing, it seems more than commonly a subject for speculation.

We can, in conclusion, simply suggest that the occvirrence
of large flowers, small flowers and flowers the corolla diameters
of which show every degree of gradation between large and
small in F^, of a cross between a large-flowered and small-flowered
variety of N. acuminata, represents the maximum degree of
"segregation" which occurs in such a hybridization ( see, in
this connection: Locke, 1906, and Emerson, 1910). The F.
plants grown from the seed produced by self-fertilizing the
flowers of this hybrid may give us a few plants bearing flowers,
the corolla diameters of which show small variation in size. Suc-
ceeding generations may reduce the variation still further until
we have regained either one or both of the parental varieties
which entered into the production of the F^ generation, or have
established a new "flower-size" variety which will thereafter
come true to a certain corolla diameter of flower which varies
only slightly in size.

The two sets of experimental results reported in this com-
bined paper are, in a broad sense, identical. In one case it has
been possible to carry through the evidences of segregation which
appear in F^ plants and in the seed which they produce, into
the F2 generation ; in the other it has not as yet been possible
to do so. In both cases evidence of segregation appears after
the seed produced by cross-fertilization had been grown and
before the seed that was to produce the Fo individuals had been
germinated. In l)oth cases we have been forced to suggest ex-
planations for the phenomena we recognize which are not strictly
IMendclian. In one case the non-appearance of any ^Mendelian

152 University of California Publications in Botany [Vol. 5

ratio may be due to the small number of plants grown in F2,
while in the other case we have difficulty in interpreting the
wide variations in the outward evidences of such segregation as
was observed to occur in F^, in terms of any Mendelian scheme
of analysis.

In general, both experiments are concerned with the "ques-
tion of the inheritance of bulk" (Darbishire. 1911, p. 241) in
reference to which, as this same writer states, ''the present
available information is very scanty." We are thus justified
in not endeavoring to formulate definitely any general hypotheses
on the basis of our experimental evidence, but have attempted
to suggest, merely tentatively, certain points of view which seem
applicable to the problems in hand.

It is a pleasure to acknowledge my indebtedness to Prof. W.
A. Setchell, at whose suggestion the experiments were under-
taken and under whose direction they have been carried on,
for much helpful advice and criticism ; to the Department of
Physiology of the University of California for placing at my
disposal the use of the mechanical balances used in weighing the
hybrid tobacco seed ; to Mr. Sturla Einarsson of the Department
of Astronomy for providing me with the Monthly Meteorological
Keports of the Students' Observatory which are combined to
form the table on page 124; and to the members of my family
for much assistance in connection with the measurements of the
corolla diameters of hybrid tobacco flowers and in preparing the
manuscript for the press.

LITERATURE CITED

Bateson, W.

1909. Mendel's Principles of Heredity. Cambridge University Press.

Baur, E.

1911. Einfiihrung in die experimentelle Vererbungslehre. Gebruder
Borutraeger. Berlin.

Blaeingheim, L.

1911. La notion d 'espeee et la disjonction des hybrides, d'apres
Charles Naudin. Prog. Rei Bot., vol. 4, part I, pp. 27-108.

Brainerd, E.

1907. Mendel's Law of Dominance in Viola. Rhodora, vol. 9, p. 211.

1912] Goodspeed: Nicotiana Hybrids 153

Castle, W. E.

1906. Heredity of coat characters iu guinea-pigs and rabbits. Car-

negie Instit. of Washington.
1911. Heredity in relation to evolution and animal breeding. Apple-
ton & Co., New York.

Clark, V. A.

1904. Seed selection acording to specific gravity. N. Y. Agric. Exp.

Station, Bull. 256.

COBEY, W. W.

1905. Methods of tobacco seed selection. Maryland Agric. Exp.

Station, Bull. 103.

Comes, O.

1899. Monographic du Genre Nicotiana. Atti d. E. 1st. D 'Incor.
di Napoli, ser. V. vol. I.

CORRENS, C.

1903. Weitere Beitrage zur Kenntnis der dominierenden Merkmale
und der Mosaik-bildung der Bastarde. Berlin, Deutsch.
Bot. Gesellsch., 21:195, ap. 23.

Coulter, J. M., Barnes, C. E., and Cowles, H. C.

1910. A Textbook of Botany. American Book Co., New York.

Darbishire, a. D.

1908. On the result of crossing round and w^rinkled peas, with special
reference to their starch-grains. Proc. Eoy. Soc. B., vol. 80,
p. 122.

1911. Breeding and the Mendelian Discovery. Cassell and Co., Lon-

don.

Davenport, C. B.

1908. Determination of dominance in Mendelian inheritance. Proc.
Amer. Phil. Soc, vol. 47.

1910. The imperfections of dominance and some of its consequences.
The American Naturalist, vol. 44, March.

East, E. M.

1907. The relation of certain biological principles to plant breeding.

Conn. Agri. Exp. Station, Bull. 158.

1910. A Mendelian interpretation of variation that is apparently con-

tinuous. The American Naturalist, vol. 44, p. 65.

1912. Bot. Gaz. vol. 53, no. 3, March.

and Hayes, H. K.

1911. Inheritance in Maize. Conn. Agric. Station, Bull. 167.

Emerson, E. A.

1910. The inheritance of sizes and shapes in plants. The American

Naturalist, vol. 44, p. 739.

Gard.

1911. La loi d'uniformite des hybrides de premiere generation est elle

absolue"? Comptes Eendus, cliii, pp. 120-122.

154 University of California Publications in Botany [Vol. 5

Garman, H.

1910. Seed testing apparatus and some modifications originating in

the Division of Entomology and Botany. Kentucky Agric.
Exp. Station, Bull. 148.

Gregory, E. P.

1909. The forms of flowers in Valeriana dioica. Journ. Linn. Soc.
Bot., 39, pp. 91-104.

Groth, B. H. a.

1911. The Fi heredity of size, shape and number in tomato leaves.

Part I, Seedlings: Part II, Mature plants. New Jersey
Exp. Stations, Bull. 239.

Hagedoorn, a. L.

1909. On the purely motherly character of the hybrids produced from
the eggs of Strongylocentrotus. Archiv. f. Entwm. 27,
pp. 1-21.

Harris, J. A.

1911. Seed weight in Staphylea and Cladrastis. Torreya, vol. 11, no. 8.

1912. (a) On the relationship between the weight of the seed planted

and the characteristics of the plant produced. Biometrika,
vol. 9, no. 1 (quoted from Harris, J. A., 1912 b).

(b) On differential mortality with respect to seed weight occur-
ing in field cultures of Phaseolus vulgaris. The American
Naturalist, vol. 46, no. 549.

Hayes, H. K.

1912. Correlation and Inheritance in Nicotiana Tabacum. Conn. Agric.
hjxp. Station, Bull. 171.

Hellriegel, H.

1883. Beitrage zu den Naturwissenschaftlichen Grundlagen des
Ackerbaues. Braunschweig, Abst. in Bied. Centbl., 1883,
p. 530.

Johannsen, W.

1909. Elemente der exakten Erblichkeitslehre. Fischer, Jena.

1906. Does hybridisation increase fluctuating variability? Inter. Con.

on Genetics, 3, 1906.

JoST, L.

1907. Lectures on Plant Physiology. Clarendon Press, Oxford.

Lang, A.

1908. Ueber die Bustarde von Helix hortensis Muller und Helix

nemoralis, L. Festschrift Universitiit Jena, Fischer.

LiLL, .J. G.

1910. The relation of size, weight and density of kernel to ger-

mination of wheat. Kansas State Agric. College Exp. Station
Circular, no. 11.

1912] Goodspeed: Nicotiana Hybrids 155

LoEB, King and Moore.

1910. tjber dominanzerscheinunge bei den hybriden Pluten des seeigels.
Archiv. f. Entwm., Bd. 29, H. 2.

Lock, E. H.

1906. Ann. Eoy. Bot. garden Paradeniya, 3, p. 130 (quoted from Emer-
son, 1910).

Love, H. H.

1910. Are fluctuations inherited? The American Naturalist, vol. 44,
p. 412.

Macfarlane, J. M.

1895. A Comparison of minute structure of plant hybrids with that
of their parents and its bearing on Biological problems.
Transact. Roy. Soc. Edinburgh, vol. 37, p. 32.

Mathevs^son, E. H.

1908. Cooperative tobacco investigations. Virginia Agric. Exp. Sta-
tion, vol. 16, no. 6.

Moore, A. R.

1910. A Biochemical conception of dominance. Univ. of Cal. Publ.

Physiol, vol. 4, no. 3, pp. 9-15.
1912. On Mendelian dominance. Archiv. f. Entwm. Bd. 34, H. 1.

Price, H. L., and Drinkard,,A. W.

1908. Inheritance in tomato hybrids. Virginia Exp. Sta. Bull. 177.
Raciborski.

1900. Bull. Inst, de Buitenzorg, no. 6 (quoted from Jost, 1907, p. 302).

Robertson, T. B.

1908. On the normal rate of growth of an individual and its bio- .

chemical significance. Archiv. f. Entwm., Bd. 25, H. 4.

SCHERFFIUS, W. H.

1909. The Cultivation of tobacco in Kentucky and Tennessee. U. S.

D. A., Farmer's Bull. 343.

Setchell, W. a.

1912. Studies in Nicotiana. I. Univ. Calif. Publ. Botany, vol. 5, pp.
1-86.

Shamel, a. D.

1904. The Improvement of tobacco by breeding and selection. Year-
book, U. S. D. A., p. 435.

Shamel, A. D. and Cobey, W. W.

1906. Varieties of tobacco seed distributed, etc., with cultural direc-

tions. U. S. D. A. Bureau of Plant Industry, Bull. 91.

1907. U. S. D. A. Bureau of Plant Industry, Bull. 96.

Shull, C. a.

1909. Oxygen pressure and the germination of Xanthium seeds. Bot.
Gaz. vol. 48. p. 387.

1911. The oxygen minimum and the germination of Xanthium seeds.

Bot. Gaz. \ol. 52, p. 453.

] 56 University of California Piihlications in Botany [Vol. 5

Shull, G. H.

1908 (a). The pedigreed cultm-e. The Plant World, vol. 2, p. 21.
1908 (b). a new Mendelian ratio and several types of latency.
Amer. Xat. vol. 42. July.

1909. The "Presence and Absence" hypothesis. The Amer. Xat.,

vol. 43, no. 511. July.

Stockberger.

1912. A literary note on Mendel 's law. Amer. Nat., vol. 46, no. 543,

p. 152.

Strasburger, Noll, Schexck and Karsten.

1908. A Textbook of Botany, Macmillan, London.

Webber, H. J. an.l Boykix, E. B.

1907. The advantage of planting heavy cotton seed. U. S. D. A.,
Farmer's Bull. 285.

Waujrox, L. R.

1910. A suggestion regarding heavy and light seed grain. The Amer-

ican Naturalist, vol. 44, p. 48.

WOLLNY, E.

1885. Saat und Pflege der Landwirtschaftlichen Kulturpflanzen.

The greater portion of the references noted in the bibliographies
appended in Bateson (1909) and Baur (1911) have been examined.

EXPLANATION OF PLATES

PLATE 29

Nicotiana acuminata variety II.
All drawings made from fresh material.

Fig. 1. A typical lateral from a vigorous plant. X %.

Fig. 2. A typical flower, entire. Natural size.

Fig. 3. The same, split longitudinally; the ovary intact. Natural size.

Figs. 4 and 5. The half mature seed capsule. Fig. 4, natural size;
fig. 5, X2.

Fig. 6. Typical radical leaf. Xi/4.

Fig. 7. Typical leaf occurring one-third the distance up the main axis.
Natural size.

[158]

UNIV, CALIF. PUBL. BOT, VOL. 5

[GOODSPEED] PLATE 29

PLATE 30

Wild variety of N. acuminata collected at Niles, California.
All drawings made from fresh material.

Fig. 1. An entire young plant. XVj-

rig. 2. A typical flower, entire. X2.

Fig. 3. The same split longitudinally, the ovary intact. X2.

Fig. 4. The flattened face of the corolla limb. X2.

Figs. 5 and 6. A half mature seed capsule. Fig. 5 natural size, fig.
6. X2.

Fig. 7. A typical leaf occurring one-fourth the distance up the main
axis. Natural size.

[160]

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED] PLATE 30

PLATE 31

Tiie number of flowers measured between October 2 and November 8
on single plants of varieties I, II and III of N. acuminata and of cross
I?X IIIc^, III$X Ic?, I$X II c^, II $X IIIc?, and III$X lid". In the
case of the figure in the upper right-hand corner of the plate the number
of flowers measured on all the plants representing the cross I$X II J'
is shown.

[162]

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED] PLATE 31

PLATE 32

The limits of fluctuation in corolla diameter of flowers on plants of
varieties I, IT and III of N. acuminata and of flowers on plants of the
various crosses between these three varieties.

[164]

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED] PLATE 32

Variety II

IIIQxilc?

!l 9 X Hid"

Variety I)

Variety

19 X lIcT

I 9 x|||(/

Ill9x I d*

PLATE 33

The degree of fluctuation in corolla diameter of flowers on plants
of variety I, variety III and of flowers on plants of the cross 111$ X Ic?,
on each of sixteen different days between September 15 and November 6.
The heights of the columns represent the relative number of flowers
measured, of the various diameters noted as occurring in the flowers of
the two varieties and the cross between them.

[166]

UNIV. CALIF. PUBL. BOT. VOL 5

[GOODSPEED] PLATE 33

Ocfober 18

Number
of i

f lower.s

ll

Lb.

Number

of i
flowers

Number

Of S

flowers

Number

of
flowers

October -25

Jli

October 2 7

■ ■ ■■ll« II_

October 30

Number

of i
flowers

November

L Ji

LU

JL

November 3

Number

of <
flowers

Number
of <

flowers

L

Ji

L li_

November 6

L I

Lj_

Number

of
flowers

Number

of
flowers

October tt

.JUiIIi^ l_

October 2

September 30

Number

of
flowers

Number

of <;

f lovy^ers

Number

of
f lowar-s

Number

of ■\
f/owe rs

Number

of i
flowers

September's

J jIIIL Ji.

September^

L

jjIILi iiL

September.24-

liLL iJ^

September 22 I

_■ _.|1L|l

1

5eptember20

Number

of i
flowers

Number

of
flo we rs

J

1

IIUlL.

September 15

J _LiiL

U

Vanetylll Cross III 9 -^ I (/ Vanet_y I

.Diameters m u-i-m ns n .'.o.^ii; ^ i ;i-.s-:o-:-n--..ri:.\;'i>'C-
Vanetj/lll Crosslll5xld" Variety I

PLATE 34

Fig. 1. F tobacco seedlings of hybrids between Nicotiana Tabacum
variety macropliyUa and Nicotiana Tahacum variety virginica. On the
left seedlings grown from light seed, on the right seedlings grown from
hea\'y seed. Many of the seedlings grown from light seed are one month
older than the seedlings grown from hea^^ seed.

Fig. 2. Typical flowers of three varieties of Nicotiana acuminata
showing the difference in corolla diameter. 150/07 is variety I, 192/08
is variety II and 53/03 is variety III. All approximately X%.

[168]

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED] PLATE 34

Fig. 1

Fig.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 3, pp. 169-188

Issued January 9, 1913

QUANTITATIVE STUDIES OF
INHERITANCE IN NICOTIANA HYBRIDS. II.

LIBRARY
NEW YORK

BOTANICAL
QARDEIV.

BY

THOMAS HARPER GOODSPEED

A preliminary report on the inheritance in F, of flower
size in hybrids produced from three varieties of Nicotiana
acuminata, and notes on certain sterile hybrids of N. Tahacum
varieties and N. sylvestris together with remarks on the present
status of the "unit character" conception in studies of heredity.

In a previous report (Goodspeed, 1912) on the inheritance
of flower size in F^ hybrids of Nicotiana acuminata varieties
the following points were noted: (1) the parental varieties,
(varieties I, II and III) bore flowers during two seasons which
showed small fluctuation in corolla diameter and were definitely
set apart from one another in respect to this character, i.e., there
was no intergrading of one flower size variety into another; (2)
the parental varieties were distinguished from one another almost
solely in respect to this flower-size character; (3) the results of
the measurements of flower size in Fj showed that the fluctua-
tion in corolla diameter was practically twice as great and often
nearly three times as great in this generation as in the pure bred
parents grown in either of the two years during which their
flowers were measured, and (4) the measurements of the corolla
diameters of the flowers on the plants of each group of hybrids
gave an average diameter for each group which was practically
the same as the calculated average between the corolla diameters
of the corresponding two parents — i.e., each of the five average

170 University of California Publications in Botany [Vol. 5

hybrid corolla diameters formed intermediates in size between
the corolla diameters of the parents of the corresponding cross.
A suggestion which was advanced with reference to this situation
in Fj was that "the occurrence of large flowers, small flowers,
and flowers the corolla diameter of which show even,'' degree of
gradation betw^een large and small in Fj, of a cross between a
large flowered and small flowered variety of X. acuminata,
represents the maximum degree of segregation which occurs in
such a hybridization." A tentative suggestion as to Fo, also
made there, was as follows : ' ' The F2 plants grown from the
seed produced by self-fertilizing the flowers of this hybrid may
give us a few^ plants bearing flowers the corolla diameters of
which show small variation in size. Succeeding generations may
reduce the variation still further until we have regained either
one or both of the parental varieties which entered into the pro-
duction of the Fj generation or have established a new flower
size variety which will thereafter come true to a certain diameter
of flower which varies only slightly in size. ' '

During August, September and October of this year (1912)
over five thousand measurements of corolla diameter of flowers
on the parental varieties and F^ hj'brids have been made. The
results of these measurements make plain the necessity of ob-
serving the behavior of F, individuals before these F2 results
can be accurately commented upon. In addition it seems desir-
able to obtain measurements upon the flowers of the following
types of N. acuminata plants in 1913 (1) the F^ hybrids of 1910
grown in the field again and also under various controlled experi-
mental conditions; (2) the F^ hybrid remade in 1912 and grown
under the conditions stated in (1) ; (3) the parental varieties
to be produced from 1909, 1910, and 1911 seed and gtown under
these vsame conditions; (4) F2 generation plants brought to
maturity in the greenhouse; and (5) the obtaining of hybrid
seed in the greenhouse from the parental varieties therein grown
and the production from such seed of F^ plants some of which
will be grown in the field and some in the greenhouse. The value
of certain of these desiderata was not appreciated at the start of
the growing season just past and in the other cases lack of room
and other facilities made their satisfaction impossible. The data

1913] Goodspeed: Nicotiana Hybrids 171

that may be accumulated from the above outlined material to-
gether with that which is at present available should go as far as
it is possible to go toward settling the significance of fluctuating
variability in the experimental results thus far obtained and in
those that it is hoped may be obtained in succeeding hybrid
generations (cf. also, Shull, 1902 and 1904, Tower, 1902 and
1906 and Love, 1910 and 1911). The importance of this factor
has been better appreciated this year (1912) during which the
parental varieties have been grown in a different situation and
have exhibited considerable increase in individual flower size and
a slightly increased fluctuating variability. The present paper
is thus presented merely as a preliminary report which it is hoped
will give a hint as to the various lines along which the problem
involved is to be approached and also serve as the vehicle for the
presenting of certain views concerning a problem of somewhat
larger significance.

As will be seen by reference to an earlier paper {loc. ciL),
during the seasons 1910, 1911 the measurement of flowers on
varieties I, II and III showed that their mean corolla diameters
were respectively 27, 20 and 13 mm. with fluctuations never
exceeding two millimeters either greater or smaller than the
mean diameter in each case. Thus variety I bore flowers having
corollas with diameters from 25 to 27 mm., variety II bore flowers
having corollas with diameters from 19 to 22 mm. and variety
III flowers having corollas with diameters from 13 to 15 mm.
The measurements in 1912 give the following results : Variety
III varied in corolla diameter from 15 to 18 mm., with the mean
diameter approximately 16 mm., Variety II showed fluctuations
between 22 and 26 mm., with the mean diameter approximately
24 mm., and Variety I bore flowers the corolla diameters of which
showed extremes of fluctuation at 30 mm. and 35 mm. with the
mean diameter approximately 32 mm. The size of the flower has
thus been increased throughout and the fluctuation in coroUa
diameter also increased as compared with the results of the pre-
vious two years measurements. The plants, parent and hybrid,
of N. acuminata were grown on higher, better drained, less de-
vitalized land and obtained a maximum of sunlight and heat
(cf. Goodspeed, loc. cit. p. 123). The plants were spaced in the

172 TJniversity of California Puhlications in Botany [Vol. 5

rows and cultivated just as in the cultures of the previous two
years. The figures given are most important, however, in that
they show that with an increase in size and fluctuation due to
more favorable cultural conditions no intergrading of one variety
into another takes place and that on the contrary the three
varieties are even better distinguished from one another in corolla
diameter than before.

The following Fo hybrid generations have been raised during
1912— F, of the crosses III$XlIcf, I$XlId', H^Xlll(^ and
IIIJXlcT- Over five thousand measurements of corolla diameter
have been made upon three of these F. generations while the
fourth is at present just coming into flower. From 15 to 18
plants in each group were brought to maturity and their flowers
measured.

The actual results (calculation of the means and coefficients
of variation) of these measurements have not as yet been com-
pletely determined but the general trend of the results is suf-
ficiently clear to make this preliminary account of them possible.
Contrary to the expectation expressed the variation in corolla
diameter in F, appears to be more or less greatly increased as
compared with that noted in Fj. Thus, whereas in the Fj plants
the range of variation was two or three times as great as that of
the parents, in Fo the minimum range of variation is always over
twice and the maximum range five or six times as great as that
of the parents in 1910 and 1911. In the case of Fj of the cross
I^XIIJ* certain plants show a range of variation in corolla
diameter from a flower 2 mm. smaller than the smallest flower
ever measured on Variety II to a flower 3 mm. larger than the
largest flower borne by Variety I in 1912 and 7 mm. larger than
the largest flower produced by Variety I in 1910 and 1911. An
increase in vigor where size and form characters are being dealt
Avith, is often to be expected in F^ yet this common result of
hybridization was not observed in the F^ previously reported
upon (cf. also. East and Hayes, 1912). Certain plants in the
Fo generation of this same cross, however, exhibit as small ranges
of variation as do the parental varieties this year (1912) and
they are always the plants which bear the largest flowers. F,
individuals of the cross III^XlIJ* similarly exhibit an extended

1913] Goodspeed: Nicotiana Hyhrids 173

range of variation in corolla diameters but in this hybrid the
upper limit of variation of the 1912 variety II is never exceeded
in the flower of any individual though the largest sized flower
is 4 mm. larger than the largest flower on variety II in 1910 or
1911. It is also to be noted that in the Fg of this cross there
are no individuals which exhibit a small range of variation such
as was found in certain plants in F^ of the cross I^XHd^- Every
plant bears flowers smaller than the smallest flowers ever meas-
ured on the small flowered parental variety III and every plant
also bears flowers larger, with possibly one exception, than the
smallest flower measured on Variety II in 1910 or 1911. In
other words the Fo plants from this cross exhibit identical ranges
of variation with respect to the corolla diameters of the flowers
which they bear.

Averages of corolla diameter have, in none of the cases, been
calculated. The results at present available and as outlined above
seem, however, to preclude the possibility of a simple Mendelian
interpretation of the inheritance of the flower-size characters
peculiar to varieties of ^V. acuminata. Some difference of opinion
is at present apparent with reference to the interpretation of
the mode of inheritance of morphological characters — size and
form characters. Certain eases of blending inheritance in F^ are
seemingly not followed by the occurrence of segregation in F,.
On the other hand the method of interpretation of certain other-
wise obscure experimental results as given by Nillson-Ehle
(1909), East (19]0), Hayes (1912) and others seems to some
to open the path for the explanation of an almost limitless range
of experimental results, derived from a study of the inheritance
of morphological characters, on what seems to be a modified IVIen-
delian basis (cf. Hayes, 1912, p. 31). Thus the occurrence, as
outlined above, of a seemingly greater degree of variation in F,
than in F^ — and the truth of this situation is open to question
lintil the true meaning of fluctuating variability in our experi-
mental material is more thoroughly determined — appears to make
it plain that segregation does occur (Castle, 1911, p. 137) or, as
one writer has so aptly put it "the segregation of potential
f italics mine) characters in tlic germ cells of hybrids and their
chance recombination in later generations" (Hayes, 1912) has

174 University of Calif oriiia Puhlications in Botany [Vol. 5

actually taken place. The point brought up in this connection is,
to the writer's mind at lea.st, of somewhat broader significance
than the mere fact that certain experimental results in Fj may
or may not be susceptible of a particular interpretation. We are
involving, in jNIendelian interpretations of variation which are
apparently continuous, the old question of what is a "unit-char-
acter" (cf. Darbishire, 1911, p. 131).

In 1909 when this breeding experiment with flower size
varieties of N. acuminata was suggested to me by Professor
Setchell, the facts of size and form inheritance had not received
the amount of attention which has more recently been accorded
them. For this reason, perhaps, the crossing of a large flowered
form with a small flowered form was taken in good faith as likely
to involve a single Mendelian pair of characters and a simple
mono-hybrid ratio was anticipated for the results of measurements
of corolla diameter of flowers on F^ individuals. When one bears
in mind that the parental varieties are in general indistinguishable
one from the other except on the basis of this corolla diameter
character and that the greatest variation in corolla diameter of
their flowers has not exceeded 6 mm. during three consecutive
years (on the basis of over 3000 measurements) it is not strange
that orthodox ' ' unit-character ' ' behavior was looked upon as the
basis for the Mendelian ratios which were vaguely anticipated.
Nothing, to the writer's mind has been — and still is in some
quarters — so firmly fixed in the "genetical" mind as the "Law
of Dominance," the "Law of Segregation" and the "unit char-
acter" conception. The "Law of Dominance" never was a law
and is "no inseparable attribute of Mendelian inheritance"
(cf. Bateson, 1909, p. 13 and p. 53). This seems to be generally
recognized at present, so thoroughly recognized indeed that the
pos.sible deeper and broader significance of "dominance" in Fj in
general is in danger of being almost entirely overlooked. With
reference to the "law of segregation" a leading student of the
problems of heredity has recently said "there can be no reason-
able doubt that ^Mendel's law is of fundamental importance in
genetics" (Castle, 1912, p. 352). And the most important con-
tribution of ^Mendel's discovery to the study of genetics is the
assumption that "segregation of potential characters in the germ

i^i'"^] Goodspeed: Nicotiana Hybrids 175

cells of hybrids and their chance recombination in later genera-
tions" (Hayes, 1912, p. 28) does take place. In 1909 I think
it may be safely stated that, broadly speaking, the "unit-char-
acter ' ' conception had become ' ' an inseparable attribute of Men-
delian inheritance. ' ' The literature dealing with the problems of
heredity had become so permeated with the unit-character
criterion that it was difficult to discuss a hybridization experi-
ment Avithout reference to the more distinct morphological or
physiological attributes of an organism by the use of this term.
At the present time we are led to believe that there are no "unit-
characters" in the sense of "units distinct and indestructible
which may meet in fertilization but separate again at the forma-
tion of gametes" (Castle, 1911, p. 38). Such an attitude may
be one which is entirely in harmony with the progressive spirit of
the times — i.e., the rapidity with which speculation along Men-
delian lines has swept us forward.

The question concerning the "relative constancy of unit-char-
acters," perhaps because of "its illusiveness" and certainly be-
cause the experiment was undertaken in the belief that unit-char-
8.cters were "transmitted as independent units in inheritance"
(Darbishire, 1911, p. 216), has certainly taken on "a perennial
habit" (East, 1912, p. 644) with reference to the behavior of
flower size characters in N. acuminata hybrids. The occurrence
of interesting and seemingly important evidence on the divisibility
of what we may call a strictly "physiological unit-character" to-
gether with the complexity of the "flower size unit-character"
problem was the occasion for the preparation of a note on the
present status of the unit-character conception which was going
to press when Professor East's recent paper (Amer. Nat. 46, 551,
p 663) came to hand. While it is recognized that the greater
part of the whole situation has been reviewed and commented
upon by East (loc. cit.) and Castle (Amer. Nat., 46, 546, p. 352)
it seems nevertheless advisable to present a brief outline of the
above mentioned note together with such experimental evidence,
bearing immediately on the subject in hand, as was therein con-
tained.

It was pointed out that ^lendel chose the experimental
material ns(^(l in the most famous experiment with a view dimbl-

176 University of California Publications in Botany [Vol. 5

less to meeting some such list of technical requirements as is given
by East and Hayes in a recent paper (1911, p. 6). Perhaps all
of the tirst six of the desiderata there stated may have influenced
Mendel's choice but undoubtedly the first was most prominently
in his mind — i.e., "the genus or species under investigation
should be variable. There should be a goodly list of types which
are differentiated by definite characters easy of determination"
{loc. cit., p. 6). The genus Pisum was variable and supplied
a goodly list of types which were differentiated to Mendel's mind
by very definite characters. These definite characters later in-
vestigators have chosen to speak of, often rather loosely, as "unit-
characters" (cf. Darbishire, 1911, p. 131).

Such definite characters which seem to be "unit-characters"
and to be transmitted as "independent units in inheritance" have
many times been dealt with in the past and will continue to be
dealt with in the future. For when "definite characters are suf-
ficiently constant to be expressed by a fixed standard . . . the
whole heredity short-hand is . . . simple" (East, 1912, p. 648).
On the other hand there are quantitative characters which are so
inherited that their mode of inheritance can only be explained in
accordance with the "]\Iendelian notation" by the assumption
that within the character a "multiplicity of factors exist, each
independently inherited and capable of adding to the character
in question." The "philosophical query as to whether the char-
acters of the organic complex of which living organisms are com-
posed can in any sense be dissected and analyzed into the units of
heredity which are the basis of Mendelian inheritance" seems
out of order at this point.

The fact remains that some real and definite distinction has
been made in the past and will be made in the future, so far as
an actual hybridization experiment is concerned, between char-
acters which are sufficiently definite to be represented in the germ
cells by hypothetically fixed determiners or genes and charac-
ters, mostly quantitative, which are heritable potentialities only
and are represented in the germ cells by independent and inter-
changeable units functioning to produce addition, and thus seem-
ingly subtraction, phases of the original character. To the
writer's mind this distinction has been brought to light, and will

1913] Goodspeed: Nicoiiana Hybrids 177

be maintained for a time only, simply by reason of the distinction
in the method of accumulating the experimental results, between
the experiments where quantitative and in those where quali-
tative characters are being dealt with. Experimental results seem
to have established a distinction between characters which appear
to be tangible realities in pure bred parental strains, "atomic,"
and which can be spoken of as "unit-characters" — i.e., "units dis-
tinct and indestructible which may meet in fertilization but
separate again at the formation of gametes" (Castle, 191], p.
38), and characters which appear to be just as tangible realities
in the parents but are really "molecular" in structure, capable
of infinite divisibility and, as characters, really exist in the
parents themselves in possibility but not in reality — i.e., as
potential characters.

"With reference to the divisibility of what might be called a
' ' physiological unit-character ' ' an interesting bit of experimental
evidence has recently appeared among the Nicotiana cultures in
the Botanical Garden of the University of California. In 1910
and 1911 a number of cross pollinations, back and forth, be-
tween N. sijlvestris and a number of N. Tahacum-varieties were
made by Professor Setchell. Ten groups of hybrids, the results
of these crosses, are growing this year (1912). Among them are
those which involve N. Tahacum var. macrophylla (U.C.B.G.
22/07), (Setchell, 1912, p. 8), .V. Tahacum var. cahjcina (U.C.
E.G. 110/05) (loc. cit., p. 6), A^ Tahacum "Maryland" (U.C.
E.G. 78/05) (loc. cit., p. 5), etc., with N. sylvestris (U.C.B.G.
107/01) (loc. cit., p. 29), as either the male or female parent.
These hybrids, in each case, are practically sterile, at least as com-
pared with the heavy seeding character of the parents. The
flowers, in most cases, fall a short time after anthesis, the pollen is
more or less scanty and in general they are of the type of hybrids
of various species of Nicotiana with N. sylvestris which have pre-
viously been reported to be completely sterile (cf. Baur, 1911, p.
224, East and Hayes, 1912, and the literature there cited).

It has been noticed in all the N. Tahacum-Yarietiefi and, to
a lesser extent, in A^ sylvestris that as an infloresence, consisting
often of from 40 to 50 flowers, passes from the flowering to the
seeding stage a few flowers will often appear from flower buds

178 University of Calif ornia Puhlications in Botany [Vol. 5

that have developed late in the season at the base of maturing
seed capsules. The majority of these buds, and numbers of them
may be formed, die and fall but in certain cases -1 to 10 may de-
velop into weak, stunted, at times abnormal, flowers. The appear-
ance of these flowers is rather striking, rising as they do hardly
above the tips of the brown and almost mature seed capsules about
them, with the corolla tube so shortened that the stigma stands
3 to 4 mm. above the flattened limb which limb is much reduced,
flaccid and early withering. This situation very probably de-
pends upon the phj'siological balance between the metabolic ac-
tivities which look to the production of flowers and those which
have to do with the maturing of the seed formed from these
flowers. Some data are at hand which seem to show that on a
given flowering shoot of the indeterminate type the size of the
flowers which it bears is, roughly speaking, inversely propor-
tional to the number of seed capsules which are allowed to
mature. The agricultural'practice of "topping the bald sucker"
and "suckering" tobacco plants is merely an efi'ort, and ap-
parently an eff^ective one to restrict the growth and especially
the metabolic activities of the plant body to the vegetative struc-
tures as opposed to those strictly reproductive. The reactions
normally proceeding in one direction are forcibly reversed or
perhaps reaction products are not allowed to accumulate in the
usual regions and the metabolic reactions reach a point of equil-
ibrium at a later period and in another part of the plant. Simi-
larly what is recognized as a periodicity in the production of
flowers means the concentration of the products of metabolic ac-
tivity in different regions at different times to accomplish special
and individual results. The conditions, in the ease of a large old
infloresence maturing seed, are not such as to allow of the pro-
duction of normal, vigorous flowers — they are out of place and
the constructive materials for their proper development are not
present in sufficient quantity. Phenomena, as closely correlated
as these, so dependent upon broad, general physiological states
common to all plants are not ordinarily thought -of as "unit-
characters," and, yet, on the other hand, they might seem to be
the fundamental, truly indivisible "unit-characters" on the basis
of which our experimental mingling of less fundamental, heretible

1913] Goodspeed: Nicotiana Hybrids 179

peculiarities is possible. A plant that is making seed cannot
produce better than stunted, functionless flowers among the
maturing seed capsules yet if the young seed capsules are re-
moved as they form, the secondary flower buds will produce nor-
mal flowers almost indefinitely. It is a repetition of the "top-
ping" and "suckering" under different conditions to accomplish
the same type of ends and a rather perfect set of cause and
effect phenomena.

With these facts in mind it Avas a surprise to find, in the
case of the hybrids between N. sylvestris and N. Tabacum-
varieties, that on an inflorescence, and usually with all old flowers
fallen and the stems bare, these same late flowers were as thor-
oughly stunted as in the case of the parents. Five to eight
flowers on these older hybrid 'infloresences, on which no seed has
been formed, often stand on the naked branches and are as
abnormal, stunted and poorly formed as in the parent plants.
In other words though no subtraction takes place from later
flowers in favor of maturing seed capsules in these hybrids, still
the phenomenon of reduced reproductive parts is apparent in
these later flowers. Here Ave have a '"physiological unit-char-
acter" dependent upon metabolic activities and one which is
seemingly an indivisible unit connected with cause and effect
relations common to all plants which, nevertheless, is so split
up in crossing that the effect is inherited when the cause is absent.
Undoubtedly the real situation here is too obscure to offer more
than an interesting field for speculation but the fact seems of
sufficient interest to be noted. In the parent plants it is possible
to eliminate the effect (reduction in size and vigor of older
flowers) by eliminating the cause (removing young seed cap-
sules as they form) — in the hybrid individuals the cause is self,
automatically, naturally removed but the effect is present un-
changed.

An explanation of this phenomenon, which has hardly more
than the minimum of experimental e\adence as its basis, should,
however, be mentioned here. It is just conceivable that the
factor for the production of abnormally reproductive organs
represents a dominant character in these hybrids commonly
considered to be completely sterile and wliidi normally are

180 University of California Publications in Botany [Vol. 5

undoubtedly partially sterile. This supposition is supported by
the fact that generally only a few axillary buds are found
to be produced at the bases of maturing seed capsules in
the iV. sylvestris parent and that where a Hower does develop
from such a bud reduction in its size, noted under similar con-
ditions in the N. Tahacum parental varieties, is not so striking.
The factor introduced by the ^V. sylvestris parent thus may stand
for the recessive condition of this abnormal-flower character. The
normal production of seed may, also, be looked upon as a separ-
ately inherited tendency which in these sterile hybrids appears
to be in a latent condition or possibly represents the recessive
member of another Mendelian pair with reference to these
hybrids. Though it may not be profitable to push the analogy
too far it is to be noted in this connection, that N. sylvestris has
the very interesting tendency, strongly emphasized in our cul-
tures, of reproducing ' ' vegetatively " from the roots year after
year and that the hybrids made with N. sylvestris as one or other
parent also possess quite markedly this peculiarity which is
rather unusual in the genus Nicotiana but is common in other
genera of the Solanaceae. Thus, following out the analogy, it
may be possible that sexual reproduction vs. its absence (vegeta-
tive reproduction) constitute the members of a Mendelian pair
and that the absence of vigorous seed production in these hybrids
represents a recessive condition. While the experimental basis
for these suppositions is rather vague the facts brought out in
connection with them may prove to be of some importance with
reference to the well recognized sterility of hybrids in which A\
sylvestris is involved as a parent. In this connection it may be
said that a considerable variety of experiments are at present
being carried on in the effort to bring about normal seed produc-
tion in the case of these "sterile" hybrids and also that a
quantity of cytological material has been collected from them and
from the parental varieties in the hope that a considerable mass
of data on the nature of sterility in such hybrids may be at hand
before the end of the coming year. The above, in general, is
interesting principally in that it adds weight by analogy to the
point of view which looks upon the "unit-character" not as an
"atom" but as a "molecule" or indeed as a heritable potentiality

1913] Goodspccd: Nicotiana Hybrids 181

capable of infinite divisibility and innumerable states of semi-
union with other correlated potentialities.

All experimental studies in the physiology of heredity have
shown the necessity of consciously allowing a hypothetical term
to take the place of any visible outward expression of a certain
tendency — physiological in practically every instance— peculiar
to or inherent in an organism. This hypothetical term is de-
manded primarily for the formulation of a mathematical ex-
pression which can then express a multitude of situations in-
volving the tendency in question. This hypothetical term is
secondarily of real value in that it serves a-s a short-hand expres-
sion for this same tendency which may be utilized in referring
thereto in a considerable number of connections where mathe-
matical expression is not called for. It is, however, perfectly
evident that this hypothetical term has by reason of its associa-
tion with the living tendency to serve the above two ends, gained
absolutely nothing in the extent to which it actually represents
a tendency, peculiar to or inherent in a living organism. This
has many times been pointed out by East and others. The fact,
on the other hand, remains that the accumulation of experimental
results in the past 12 years that have been more or less readily
susceptible of interpretation according to the IMendelian notation
has resulted in a situation wherein hypothetical terms have abso-
lutely overshadowed the tendencies dealt with. The distinctions
between qualitative characters and quantitative characters rest
upon as hypothetical a basis and involve the use of hypothetical
terms as surely as does the use of such clearly hypothetical ex-
pressions as unit- character, factor, or gene. This is evident in
that we now know that certain qualitative characters and the ex-
planation of their mode of inheritance may rest upon the same
assumption or series of assumptions which originally was sug-
gested primarily to explain the facts concerned in the inheritance
of quantitative characters. The more carefully and "quanti-
tatively" the inheritance of qualitative characters is investigated,
the greater will be the field for the application of the assumptions
involved in Mendelian interpretations of variations which are
apparently continuous, if the experimental results can hope to
be explained according to the Mendelian notation. In other

182 University of California Puhlicatio US in Botany [Vol.5

words, a great assumption was made in the early years of ]\[en-
delian interpretations in that the hypothetical term unit-char-
acter was assumed to represent a simple, indivisible, more or
less independent and dependable entity and it was this unit-
character that was expected to reappear unaffected in F.,. Does
not the perennial character of the question relating to the sta-
bility of the unit-character depend simply upon the unwillingness
or inability to appreciate the fact that blackness is as hypo-
thetical a something as the term "unit-character" which is ap-
plied to it ? The fact that blackness behaves as an orthodox Men-
delian dominant makes the heredity short-hand simple and also
seems thoroughly to obscure the fact that three factors may
fundamentally be responsible for the outward expression of the
black tendency just as truly as that three factors are necessary
for the production of the purple color in the aleurone cells in
certain varieties of maze. Equallj^ truly it is conceivable that
30 factors may be concerned in this purple maize color tendency
if 30 factors, units or genes are found to be responsible for the
outward expression of flower size in a large flowered form of
N. acuminata. Black, purple and large flower size are equally
involved in this situation. In other words whereas blackness has
apparently been shown to be an entity, sufficiently a unity to
remain unchanged in hybridization, the true significance of more
fundamental units underlying purple aleurone color, height of
plant, number of rows, length of ear and size of seed in maize,
and responsible for various fruit sizes, number of leaves in
tobacco, etc., has been made apparent by the same means. In other
experimental material, however, each of these characters may in
time be shown to behave as a simple Mendelian dominant also.
It seems probable that in time the majority of characters, both
"qualitative" and "quantitative," may be found to be modifiable
under selection. Each individual addition or subtraction stage
will " Mendelize " — using this term to signify experimental results
in accord with the Mendelian notation in its present expanded con-
dition— with the same pure line individual in each instance. It
has been shown that each may behave as a simple oMendelian
"recessive unit" (cf. Castle, 1912, p. 356) or each may so
behave that a multiplicity of more fundamental interacting units

1913] Goodspeed: Nicotiana Hyhrids 183

or genes must be assumed as the basis of the character appearing
in modified condition in each stage. Considerations of this sort
simply serve to show that certain characters are sufficiently stable
within themselves so that the fundamental interacting units upon
which they depend for their outward, somatic expression, do not
appear while other characters, not so stable, under the stress of
hybridization do manifest the fundamental units through the
interaction of which they are able to appear in substantial form.
The fact that they are manifested in one ease implies that funda-
mentally the3% though not apparent, are present in all other cases
also. So soon as it can be demonstrated that for any one char-
acter the influences upon which it depends, the factors beneath
the surface, are actually apparent, in that hypothetical terms to
stand for them in mathematical expressions can actually be pro-
posed, at once one postulates for all characters the existence of
similar influences whether they are similarly apparent or not.
In other words, all "unit-characters" are "molecular" in struc-
ture. Aggregates of similar "units or genes" evidently are
responsible for the outward evidence of "unit-characters" and
the unity of this "unit-character molecule" may depend upon
the degree of affinity of the units or genes — a true chemical
affinity perhaps (see East and Hayes, 1912, p. 35 ) . The more
quantitative our investigation becomes, the more clearly is
brought out the looseness, rarely the firmness, of the bond which
holds the innumerable units or genes to the ' ' unit-character ' ' con-
ception. From the Mendelian standpoint it seems clear that we
are getting below the surface with reference to the real sig-
nificance of the "unit-character" conception. The presence of
more fundamental, basic heritable influences within the seemingly
indestructible "unit-character" is assumed in order to make the
mode of inheritance of both "qualitative" and "quantitative"
characters susceptible of interpretation according to the Mende-
lian notation. All "unit-characters" mu.st then be assumed to be
alike in the possession of these fundamental, "subepidermal"
influences whether their presence needs to be assumed or not.
Otherwise we have to recognize two categories (1) "unit-charac-
ters"— distinct, atomic, indestructible and (2) potential charac-
ters— molecular in structure and dependent upon the interaction

184 University of Calif ornia Puhlications in Botany [Vol.5

of independently heritable units for their somatic expression.
These interacting units may be looked upon as the substances en-
tering into a reaction which is represented at a point of equil-
ibrium by an outward, visible, seemingly or truly indestructible
"unit-character" peculiar to an organism. The individual re-
acting substances are separately inherited but may be so linked
(a chemical affinity) in the case of certain characters that the
same reaction will reach the same point of equilibrium time after
time and we then appear to be dealing with a unit distinct and
indestructible. Such analogies (cf. in this connection Moore,
1910 and 1911) supply a limitless field for speculation yet
it may be interesting to note that increase of size and pre-
cocity of somatic characters due to heterozygosis might be
concerned with an increase in the rapidity of growth reactions
caused by an increase in amount of reacting sustances. An atti-
tude in general analogous to the above is taken by East (1912,
p. 648) with reference to the changes in the expression of a
character under the stress of what he refers to as "modifying
conditions both external and internal" — "when external we
recognize their usual effect in what we call non-inherited fluctua-
tions, when internal we recognize their cause in other gametic
factors inherited independently of the primary factors but
modifying its reaction during development." In so far as this
is an assumption which seems to postulate a limitless extent of
organic complexity as the fundamental basis for those tangible
characters we seem to see in an organism and draws an analogy
between chemical reactions and the interrelations of these "fac-
tors," the above is "a physiological conception of heredity."
On the other hand if it is to become a question as to how many
separatelj^ inherited tendencies contribute to the entity which
we loosely speak of as a "unit-character" the logical end of the
inquiry will be found to lie in a biochemistry of the individual
cell (cf. Czapek, 1911, ch. 10).

It is well to bear in mind in connection with such elusive con-
siderations as these that as we "bid farewell to the broad day-
light of observation" we at once proceed to "enter the dark and
treacherous alleys of inference." Observation, however, has re-
sulted in the accumulation of certain experimental results the

1913] Goodspeed: Nicotiana Hyhrids 185

interpretation of which according to the ]\Ienclelian notation is
only possible after a certain number of assumptions have been
indulged in. My point is simply that if in one case it is neces-
sary to assume an interaction of units within a certain "unit-
character" then within all "unit-characters" we must recognize
similar fundamental units whether the mode of inheritance of
the character in question calls for such an assumption or not. On
this assumption that all characters are molecular in structure,
representing aggregates of units each of which is capable of modi-
iymg the character being dealt with, w^e have a basis for the
explanation of all such considerations as those presented by
Castle (1912). On this basis there is nothing more inconstant
than the individual characters peculiar to an organism except the
organism itself which represents the sum of these individual char-
acters. On this basis again the range of results capable of inter-
pretation according to the Mendelian notation is limitless and
there can be no question of stretching the Mendelian notation
to cover any particular case for, by reason of its assumptions, it
has become immeasureably extensible.

The question then arises to what extent are these primary
assumptions valid or in other words does the end justify the
means. The end is nothing more important — with reference to
the limits of our present knowledge of the phenomena involved —
than the natural desire and valuable effort to interpret all ex-
perimental results in accordance with a notation which has been
found to apply to a relatively small group of characters — prob-
ably less than three hundred characters peculiar to domesticated
animals and plants. The means employed to accomplish this end
are beginning to involve the complication of the mathematical
expressions used to such an extent that nothing can actually be
gained for the practical breeder and the necessity of raising
and examining the extremely large F^ and F., generations de-
manded will restrict independent investigation immensely. In-
deed it seems hardly in accord with the "progressive spirit of
the times" and the growing recognition of the immensity of the
problem involved, to demand a strict conformity of effort and
interest. The value of the ]\Iendeli;in notation as a (jencraliza-
iion certainly fails if it is true that not more than a few hundred

186 University of California Publications in Botany [Vol. 5

characters, the great majority of which exist in a state of domes-
tication, are inherited in Mendelian fashion (cf. Darbishire, 1911,
p. 239). On the other hand these same few hundred characters
may represent almost the sum total of those which are of inter-
est to the practical breeder. When the breeder finds that he is
dealing with a Mendelian dominant his heredity "short -hand" is
simpler than it ever could have been without the Mendelian nota-
tion. If the inheritance of the character he is interested in is
more complex — i.e., if it is a "bulk character" — he will follow
such obvious suggestions as those given by Castle {loc. cit., p.
362). In either case the breeder will probably be primarily in-
terested, just as he always has been, in only one thing — i.e.,
increasing variability by crossing. The value of the JMendelian
interpretation for the breeder has from the start been made ap-
parent in practice and by no means all the characters which he
is interested in and w^hich will "Mendelize" have been dealt
with at this time. Likewise the theoretical value for the science
of heredity in the Mendelian point of view^ "that the contents
of the germ cells and not the outward characteristics of the
animals and plants dealt with must be our guide in breeding"
cannot be overestimated. No one, it seems to me, can wish "to
give up ' ' the Mendelian point of view and its ' ' handy and help-
ful notation" especially in those cases in which it is so handy
and so helpful. On the other hand with reference to those cases
in which, both for the student of the problems of genetics and
for the practical breeder, the notation is neither handy nor help-
ful, though theoretically capable of application, a question must
be answered — i.e., which is the way for progress?

I am indebted to Professor W. A. Setchell for much helpful
suggestion and criticism in connection with the preparation of the
above note.

1913] Goodspeed: Nicotiana Ilyhrids 187

LITEEATUEE CITED
Baur, E.

1909. Einfiihrung in die experimentelle Vererbungslehre. Gebruder

Borntraeger, Berlin.

Castle, W. E.

1911. Heredity. (D. Appleton and Co., New York.)
CZAPEK, F.

1911. Chemical phenomena in life. (Harper and Bros., New York.)
Darbishire, a. D.

1911. Breeding and Mendelian discovery. (Cassell and Co., London.)
East, E. M.

1910. A Mendelian interpretation of variation which is apparently

continuous. Amer. Nat., vol. 44, pp. 160-174.

1912. The Mendelian notation as a description of physiological facts.

Amer. Nat., vol. 46, no. 551, p. 633.

East, E. M., and Hayes, H. K.

1911. Inheritance in Maize. Conn. Agric. Expt. Stat., Bull. 167.

1912. Heterozygosis in evolution and in plant breeding. U. S. D. A.,

Bur. PI. Ind., Bull. 243.
Goodspeed, T. H.

1912. Quantitative Studies of inheritance in Nicotiana hybrids. Univ.
Calif. Publ. Bot., vol. 5, pp. 87-168.
Hayes, H. K.

1912. Correlation and inheritance in Nicotiana Tahacum. Conn. Agric.
Expt. Stat., Bull. 171.
Love, H. H.

1910. Are fluctuations inherited? Amer. Nat., vol. 44, pp. 412-423.

1911. Studies of variation in plants. Cornell Agric. Expt. Stat., Bull.

297.

Moore, A. E.

1910. A biochemical conception of Dominance. Univ. Cal. Publ.

Physiol., vol. 4, pp. 9-15.

1911. On Mendelian dominance. Arch. f. Entw-Mech., vol. 31, 1,

pp. 168-175.

Nillson-Ehle, H.

1909. Kreuzungsuntersuchungen an Hafer und Weigen. Lunds Uni-
versites Arsskrift, N.F., Afd. 2, Bd. 5, Nr. 2, pp. 1-122.
Setchell, W. a.

1912. Studies in Nicotiana, I. Univ. Calif. Publ. Bot., vol. 5, pn. 1-86.
Shull, G. H.

1902. A quantitative study of variation in the rays, bracts, and disk-
florets of Aster Shortii Hook., A. Novae- Anglicae L., A. puni-
ceus L. and A. prenantJwides Muhl. from Yellow Springs,
Ohio. Amer. Nat., vol. 36, pp. 111-152.

1904. I'lace constants for Aster prenantlioides. Bot. Gaz., vol. 38, pp.
333-375.

188 University of California PuMications in Botany [Vol. 5

Tower, W. L.

1902. Variation in the ray-flowers of Chrysanthevium leiicanthemum L.
at Yellow Springs, Green County, Ohio, with remarks on the
determination of modes. Biometrika, vol. 1, pp. 309-315.

1906. An investigation of evolution in Chrysomelid beetles of the
genus Lei^tinotarsa. Carnegie Inst. Publ., no. 48, pp. 93-105.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN
BOTANY

Vol. 5, No. 4, pp. 189-198

Issued March 21, 1913

ON THE PARTIAL STERILITY

OF NICOTIANA HYBRIDS MADE WITH

iV. SYLVESTBIS AS A PARENT

LIBRARY

NEW YOi^K
BOTANICAL

BY

THOMAS HAEPEE GOODSPEED

In 1910 Professor W. A. Setchell. in connection with other
similar experiments, all of which have been made possible by
a grant under the Adams Fund, made a number of cross pollina-
tions back and forth between Nicotiana Tahacum var. macrophylla
purpurea (U. C. B. G. 25/06) (Setchell, p. 10) and N. sylvestris
(U. C. B. G. 107/01) (Setchell, p. 29) which species form a part
of a considerable Nicotiana collection in the University of Cali-
fornia Botanical Garden. The F^ hybrid plants produced from
the seed obtained as a result of these crosses were grown in
1911 and exhibited a striking increase in size (habit) and size
of flower as compared with the parent plants (cf. East and
Hayes, 1912). There seemed to be a possibility, also, that these
hybrids might be only partially sterile, though as noted below
no ' ' pure ' ' seed was formed under bag. On account of the inter-
esting appearance of the 1910 hybrids in general and in particu-
lar with this suspected partial sterility in mind, all the N. Tah-
acttm-varieties available, i.e., grown from pure seed in the pure
line for a number of years, and one F^ Iwbrid made between two
such N. Tahacum-yarieties, were in 1911 crossed back and forth
with N. sylvestris. In the following list are given the hybrids
produced from the seed of the 1910 and 1911 crosses with the
hybrid numbers prefixed in each case.

190 University of California Piiblications in Botany ["^"ol. 5

191.0 crosses.
H33 — X. sylvestris X X. Tabacuni var, macrophylla purpurea.

H34 — ]S. Tabacum var. macrophylla purpurea X X. sylvestris.
1911 crosses represented this year (1912) by Fj plants.

H3o— X. sylvestris X X. (Tabacum) angustifolia (U. C. B. G. 68/07)
(Setchell, p. 9).

H36 — X. (Tabacum) angustifolia X X. sylvestris.

H38— X^ Tabacum var. macrophylla (U. C. B. G. 22/07) (ibid., p. 8)
X X. sylvestris.

H40— X. Tabacum var. calycina (U. C. B. G. 110/05) (ibid., p. 6) X X.
sylvestris.

H41— X. sylvestris X X\ Tabacum "Maryland" (U. C. B. G. 78/05)
(ibid., p. 5).

H43 — X. sylvestris X the Fi hybrid— X. Tabacum ' ' Maryland "XX.
Tabacum "Cavala" (U. C. B. G. 72/05) (ibid., p. 5).

H44— The F^ hybrid— X. Tabacum "Maryland" X X. Tabacum "Cav-
ala ' ' — -X X. sylvestris.

H45 — X. sylvestris X the Fj hybrid — X. Tabacum "Maryland" XX.
Tabacum ' ' Cavala. ' '

A detailed report upon these 1910 and 1911 F^ hybrids is in
preparation and it will only be said here that the 1911 F^ hybrids
duplicate in general the increase in vegetative and floral develop-
ment noted for the 1910 series.

As will be noted in the above the reciprocals of only two of
the five 1911 crosses were represented in the field in 1912. In
the other cases viable seed was not obtained. This fact and the
germination of the seed resulting from the various crosses made
in 1911 are of interest in connection with certain results noted
in a recent paper by East and Hayes {loc. cit., p. 28). As will
be seen there the seed produced from 18 crosses between Nicotiana
species and between Nicotiana varieties which list includes the
cross ''N. sylvestris Speg. and Comes X A. Tahacum L." and its
reciprocal — germinated to the extent of 100 per cent. Which
one of the numerous A. TaftacMm-varieties was employed in this
cross with X. sylvestris is not stated, but of the four varieties
used in our crosses made in 1911 it is doubtful whether under
the conditions employed in our cultures (Goodspeed, 1912, p.
132) — and these are the conditions commonly available in similar
work — the seed resulting from any of these crosses of ours ger-
minated to the extent of 100 per cent. Results are at hand for

1913] Goodspeed: Nicotiana Ilyhrids 191

germination tests of parent and hybrid tobacco seed involving
over 22,000 seeds and including over 10 species and varieties of
Nicotiana (Goodspeed, 1913 (2)). These germination tests deal
with the seed taken from approximately 60 different plants. It
was possible to fairly well control the conditions under which
germination took place and the arrangement of the seed to be
germinated was such that a minimum error for the observations
can be claimed. In only one case, however, employing duplicate
tests for the seed of each plant, did 100 per cent germination
take place. In the case of the seed of one other plant one of the
two tests of 100 seeds each germinated 100 per cent, but in the
other test of this same seed only 97 per cent germination took
place. Thus there seems to be some reason to doubt whether
100 per cent germination is normal in the case of seed produced
by Nicotiana species and varieties or by the hybrids made between
them. Unfortunately it has not at this time been possible to
test the germination of the seed produced by the crosses between
N. sylvestris and N. Ta6flcwm-varieties mentioned in the above
tabulation. In general, however, it is well to understand what
is meant when germination percentages are given.

There are a number of references in the literature to the
sterility in F^ of species crosses involving N. sylvestris as a
male or female parent (cf. East and Hayes, loc. cit., p. 28;
Baur, 1911, p. 224). On the hybrids, mentioned above as
being made in 1910 and growing in 1911, no "pure" seed was
formed under bag so far as was determined at the time and
indeed all maturing seed capsules that were protected fell long
before the calyx had begun to wither or the ovary turn brown.
Twenty or thirty shrunken but dried ripe seed capsules from
unprotected flowers were collected from the plants of this H33
cross and its reciprocal (H34). These capsules were "cleaned"
(Goodspeed, 1912, p. 129) carefully but no seed was found. The
contents of one seed packet resulting from this "cleaning" was
sown on the possibility that a few viable seeds might be j)resent
and have been overlooked, but no seedlings resulted.

A considerable amount of attention has been given this year
to the phenomenon of sterility in the F^ hybrid plants grown
from the hybrid seed resulting from the 1911 crosses. The most

192 University of California Publications i)i Botany [yoi.. 5

noticeable fact in this connection is the readiness with which the
flowers fall from the pedicels at about the same time (peculiar
to each hybrid) after anthesis. This situation seems to be con-
nected with the formation of a definite absciss or separating
layer within the individual pedicel at a distance approximately
1.5 mm. above its point of origin from the peduncle. This par-
ticular matter is at present under further investigation, but it
appears to be true that this absciss layer is similar to that
formed normally in connection with the fall of the leaf in
deciduous trees, that it may in certain cases be formed some time
before the flower bud opens, and in other cases begins its ac-
tivity much later, and finally that it fails at times to form at all.
The various F^ hybrids exhibit considerable differences in con-
nection with this particular point. A slight shaking of the
main axis of one of the plants representing the cross H36 will
cause practically all its flowers past anthesis to fall and also
numbers of freshly- opened flowers and even buds. The same is
true, though in a less pronounced manner, of the plants grown
from the seed of the reciprocal cross. In the case of the cross
H38. on the other hand, the F^ hybrids hold their flowers much
more firmly and, though the great majority of the withering
flowers finally fall, still when newly opened fully 50 per cent
of the flowers will resist considerable strain before becoming
separated from the pedicel. The situation in F^ of the crosses
H43 and H45 and their reciprocal is complicated in that very
certain evidences of segregation are to be seen and various degrees
of resistance to dropping of flowers seem at present to be cor-
related therewith. This will be further considered below. The
flowers of the F^ hyl)rid of the cross H40 fall almost as readily
as do those on Fj plants of the cross H36 mentioned above. The
Fi plants of H41 have not as yet come fully into flower (Dee.
10), but give evidence of possessing this peculiarity of loss of
flowers to about the extent exhibited by the F^ plants of H38.
In all these hybrids it can be certainly stated that climatic varia-
tions, as they occur out in the field at any rate, are in no sense
responsible for the dropping of flowers, nor can it be said that
a period of rainy, cloudy weather will cause any very appre-
ciable increase in this tendency (Goodspeed, loc. cit., p. 141).

1^13] Goodspeed: Nicotiana Hyhrids 193

The first evidence that considerably less than absolute ster-
ility can be claimed for certain of the F^ hybrids from crosses
of .Y. sylvestris with X. To &ac wm-varieties was connected with the
finding of a large number of entirely dry, brown, persisting seed
capsules on the plants of cross H38. Six hundred and fifty of
these capsules have been collected and more than an equal num-
ber remain on the 25 plants representing this cross. From a
similar number of plants of the cross H36, 85 capsules have been
taken. The plants grown in 1911 from the seed of the 1910
crosses have come up from their roots this year (1912) to make
fairly vigorous plants and from one plant each of the cross and
its reciprocal between 25 and 30 capsules have been taken. One
hundred capsules of the 650 mentioned above have been found
to contain nearly 900 perfectly formed seeds. A certain propor-
tion of them undoubtedly are mere shells and contain no embryo
(cf. East and Hayes, p. 30). One hundred of these seeds were
arranged as noted in a previous report (Goodspeed, loc. cit.,
p. 97) and germinated for five weeks under fairly well con-
trolled conditions with the temperature approximately 21° C. At
the end of this time 26 per cent had germinated, 90 per cent
of which germination had taken place in 15 days with the first
signs of germination noted at the end of three days. Five seed-
lings were allowed to develop and at the end of five weeks are
normal in every respect and are considerably past the stage
durins: which highest mortality of tobacco seedlings is usually
expected. Four hundred of the remaining 550 seeds of this lot
are being germinated under the same conditions and at the end
of one week almost 25 per cent have germinated. The 1912 seed
of H33 and its reciprocal have germinated to the extent of 17
per cent and 18 per cent respectively and a number of seedlings
nearly four weeks old are developing normally. The brown, dry
capsules examined were always much shrunken and withered.
They were cut transversely and a brush was forced into the ap-
parently empty spaces between the placentae and the wall of
the matured ovary. When this operation is carried out over a
rough, white surface under a strong light and the ])rush gently
rubbed between the fingers any seeds that may have been taken
uj) by tlic bi-nsh will fall on to the white surface and can be

194 University of California Publications in Botanij [Vol. 5

detected. Of the 100 capsules (above mentioned) that werf
examined in this way 34 only contained no well-formed seed,
while two contained 31 seeds each and a number over 20 seeds
each. This seed was, as above stated, produced from unprotected
flowers, but there is little reason to suppose that only those
ovules matured which were fertilized by foreign pollen. The
various hybrids differ among themselves as to the amount of
pollen which an individual flower produces and in no case does
it approach in amount that which is normal for the parental
species. Sufficient is produced, however, so that in the case of
60 protected flowers examined just after the anthers were open
the stigmas in 52 cases were covered with pollen. The crosses
back upon the parents in which the F^ hybrids are the male
parents have been recently made and may give results, in con-
nection with the amount of seed produced, which bear on this
point. The hybrid inflorescences also are very dense and the
flowers are produced in great profusion, so that in general the
chances are greatly in favor of unprotected flowers being self-
( close) pollinated or pollinated with pollen from other flowers
on the same plant. The parental species are usually recognized
as normally self-fertilized and no visible methods are present on
the hybrids made between them to prevent self- and favor cross-
pollination. Seed has not at this date matured under bag. In
the case of the cross N. Tabacum var. macrophylla X N. sylves-
tris (H38) within each of over 30 bags containing from 30 to 50
flowers and buds an average of two maturing seed capsules can
be seen through the paraffine bag to be persisting. In such cases
the calyx is beginning to turn brown and the period during or
before which the F^ hybrid flowers generally fall has passed.
In the case of the crosses H35 and its reciprocal H40 and H41,
less than 20 maturing seed capsules,- in a total of over 75 bags,
seem to be persisting at this date. In general, however, it is
plain that a small amount of viable seed is produced by hybrids
of N. sylvestris with various N. Tabacum-Yavieiies and there
appears to be little doubt but that normal plants can be matured
from the seedlings developed from such viable seed.

In connection with the seeding character exhibited by the
above hybrids and especially by the F^ plants of the cross N.

1913] Goodspeed: Nicotiana Hijhrids 195

sylvcstris X F^ of the cross i\". Tahacum "Maryland" X N.
Tahacum "Cavala," it is interesting to note the partial report
in the Gardner's Chronicle (vol. 50, 3d series, p. 309) of infor-
mation, in connection with similar hybrids, given before the
Fourth International Congress on Genetics by M. C. Bellair,
Head Gardener at the National Palaces — ''N. sylvestris pol-
linated by T. (sic!) Tahacum gives an F^ generation exhibiting
in many respects the characters of the latter species.* The
Fn germination yields a number of types of which some were
fertile and some sterile. In Fg plants resembling the two
parents were obtained. When crossed with one another they
produce a large series of forms — giants, dwarfs, white, rose,
red colored and striped Howers. " No mention is thus made
of sterility in F^. The X. Tahacum used in ^Ir. Bellair 's cross
is not made plain. In this connection it is to be noted that
in certain F^ plants produced from the seed of crosses H43,
H44, and II45 a considerable quantity of what appears to
be normally developing seed is forming. Though mature seed
capsules at the present time are not obtainable, partially mature
capsules borne on one plant of cross H45 exhibit from 30 to 50
seemingly normally developing ovules on the placentae. The
flowers on this plant persist to a much larger extent than in the
case of any of the other F^ hybrids, no early browning of the
placentae takes place, and in general this plant may be expected
to yield a rather large quantity of seed, some of which should
be viable. Of the 27 F^ plants produced from the seed of this
cross three or four almost exactly typical N. Tahacum "]\Iary-
land" individuals are present while the remaining 24 or 25 plants
seem to exhibit a blending of the characters peculiar to the two
Tabacum varieties involved in its pedigree. The plant refered to
above which seems to be producing an unsual quantity of seed
is of this blended type. The three F^ plants nearly identical with
the N. Tahacum "]\Iaryland" parent also seem to be producing
flowers which in certain laterals are persisting much longer
than in the case of the other .Y. Tahacum-varieties X X- sylvcstris
hvbrids and longer than the flowers in the case of the 23 or 24

* A similar degree of dominance of the N. Tabacum-varieties has been

tlirouijliout observed in imi- cultures.

196 University of California Puhlications in Botanij [Vol. 5

other "blends" of this same hybrid. Evidences of "segrega-
tion" are thus apparent in these F^ plants and this segregation
seems in certain cases to be correlated with increased seed pro-
duction. With these facts in mind it seems possible that the
X. Tahnmm parent of Mr. Bellair's crosses was of hybrid origin
and that F^ individuals involving much the same cross have been
produced in our cultures.

It seems reasonable, thus, to assume that the F^ hybrids pro-
duced as a result of crossing N. sylvestris and .V. Tahacum-
varieties' back and forth can be taken out of the absolutely
sterile category and included among those hybrids that are only
partially fertile (cf. Lock, 1909). "With the reference to the
cytological evidence on the question of the partial fertility of
these hybrids a considerable investigation is under way, but the
following facts previously noted seem pertinent in this connec-
tion. A separating or absciss layer is formed in the case of
at least 50 per cent of the hybrid flowers before any fertilized
ovules could be normalW matured, and in the majority of cases
where such a separating layer is not outwardly visible, a very
small amount of viable seed is formed. Obviously the formation
of this separating layer cuts off all po.ssibilities of the transfer
of food materials to the maturing ovules and it appears to be
plain that in the parental species a very considerable demand
upon available food supplies is made by such maturing seed
(Goodspeed, 1913 (1)), Again it has been found that, given
five or six flowers just past anthesis on the primary, terminal
inflorescence of a lateral shoot, if the remaining buds, smaller
leaves and partially opened flowers present on this lateral are
allowed to remain and proceed to their full development, all or
all but one of these five or six flowers past anthesis will fall in
a week or ten days. On the other hand if all the terminal buds
about these five or six flowers and all buds below in the axils of
young leaves are removed, all or all but one of these five or six
flowers past anthesis will ripen seed capsules which will contain
on an average five viable seeds each. On the one hand, then,
there definitely appear to be certain combined physiological and
structural hindrances to any seed production at all in these F^
hvbrids and on the other hand cvtological investigation mav dis-

1913] Goodspeed: Nicotiana Hybrids 197

close other more fundamental difficulties in this connection that
have to do with the lack of a normal maturing of the sex elements
within the ovule, structural blocks to the proper penetration of
the micropyle, etc. In any case, however, it seems at least con-
ceivable— and the F2 generation which it seems possible may be
produced combined with cytological evidence will, it is hoped,
help to settle this point — that such few viable seeds as are
formed on these hybrids are produced apogomously or partheno-
genetically (East, 1912, p. 131), on the basis of the fact that less
than 1/100 of the number of viable seeds normal for the parental
species are produced in those F^ hybrids that mature any seed
at all. Finally there must at least be borne in mind the sug-
gestion which has also elsewhere been made (Goodspeed, 1913
(1), p. 179) in this connection that sexual reproduction vs.
vegetative reproduction may be definitely inherited "physio-
logical unit-characters" that behave alternatively in inheritance.
As bearing on this later point it may be said that vegetative
propagation by cuttings is comparatively easy in the case
of all the hybrids discussed above just as it is in the case of
.Y. sylvestris and in both cases this fact seems to be correlated
with a biennial or perennial habit w^ell known in the case of N.
sylvestris but, to my knowledge, not previously noted to the
same extent, at least, for N. Tabacum-Yarieties, the hybrids made
between them or for hybrids between N. Tabacum-yarieties and
N. sylvestris. Thus, Nicotiana sylvestris under field conditions
will reproduce itself " vegetatively " for at least three years.
The 1910 N. sylvestris X N. Tabacum var. macrophylla purpurea
crosses first grown in 1911 have similarly come up from their
own roots this year (1912) and the 1911 crosses growing this
year are forming adventitious roots wherever the lower materials
are in contact with the soil.

198 University of California Publications in Botany [Vol. 5

LITERATUKE CITED

Bauer, E.

1911. Einfiihrung in die experimentelle Yererbungslelire. Gebruder

Borntraeger. Berlin.

East, E. M.

1912. 7?i " Heredity and Eugenics. " Univ. of Chicago Press.

East, E. M., and Hayes, H. K.

1912. Heterozygosis in evolution and in plant breeding. U. S. D. A.
Bur. PI. Ind., Bull. 243.

GOODSPEED, T. H.

1912. Quantitative Studies of inheritance in Nicotiana hybrids. Univ.

of Calif. Publ. Bot., vol. 5, no. 2.
1913 (1). Quantitative Studies of inheritance in Nicotiana hybrids. II.

Univ. Calif. Publ. Bot., vol. 5, no. 3.
(2). Notes on the germination of tobacco seed. (In press.) Univ.

Calif. Publ. Bot., vol. 5, no. 4.

Lock, R. H.

1909. A preliminary survey of species crosses in the genus Nicotiatia
from the Mendelian standpoint. Annals of the Royal Bot.
Gardens, Peradeniya, 3.

Setchell, W. a.

1912. Studies in Nicotiana, I. Univ. Calif. Publ. Bot., vol. 5, no. 1.

4

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 5, pp. 199-222

Issued May 15, 1913

NOTES ON THE GERMINATION OF
TOBACCO SEED

HBR/iRY

NEW >

botanical,
Qarden.

BY
THOMAS HARPER GOODSPEED

[The relation between the age of tobacco seed and its viability
and between the viability of parent and hybrid seed; together
with notes on the value of treatment with sulfuric acid in hasten-
ing germination and increasing its amount.]

CONTENTS

PAGE

T. Introduction 199

II. Seed used 201

III. Methods : 202

(a) Germinating conditions in general 202

(b) In connection with sulfuric acid treatment 203

. IV. Results with sulfuric acid treatment 204

V. Age of seed vs. its germination 209

VI. The germination of parent vs. hybrid seed 21.5

VII. Summary of results 219

VTTI. Discussion of results 220

I. INTRODUCTION

The difficulty experienced this year (1912) in germinating
the seed of Nicotiana attenuata (JJ. C. B. G. 78/09) (Setchell,
1912, p. 24) was the occasion for a number of experiments with
reference to the possibility of bringing about more rapid and
complete germination in such cases. The interesting experi-
ments of Love and Leighty (1912) in connection witli the effect
upon germination of sulfuric acid treatment in the case of clover

200 University of California Puhlications in Botany [Vol. 5

seed, cotton seed, etc., suggested the possibility that similar
beneficial effects might be secured in the ease of tobacco seed by
similar treatment. As will be seen later on such has been found
to be the case in that treatment with 70 per cent or 80 per cent
sulfuric acid for lengths of time varying from five to fifteen or
twenty minutes markedly increases the total amount and in
many cases hastens the time of germination of the seed of a
number of species of Nicotiana. In the preliminary experiments,
seed of N. attenuata alone was used, but in order that the value
of sulfuric acid treatment might be further investigated in the
case of other species of Nicotiana it was first found to be neces-
sary to make germination tests with untreated seed to determine
the species which would give small total germination or slow
germination under experimental conditions. This, in a sense,
preliminary portion of the investigation has assumed rather large
proportions and a considerable mass of data is at hand that has
to do with the germination of seed of various ages derived from
single plants of eight species and varieties of Nicotiana and also
with the germination of hybrid seed obtained from crosses made
between certain of these species and between certain of these
varieties. Additional germination tests are at present under
way which are designed to demonstrate the possible wider use-
fulness of sulfuric acid treatment in taking the place of other
methods, peculiar to agricultural practice, of hastening the
germination of tobacco seed and increasing its amount.

Detailed reports based upon definite germination tests in the
case of pure lines of Nicotiana species are not, to the writer's
knowledge, at present available. In general I think it has been
assumed, and probably correctly, that tobacco seed will give
rather high average total germination under field conditions and
that little difficulty is experienced by commercial growers of
tobacco in germinating the seed they use. The value of tobacco
seed separation and the greater uniformity and vigor of the
stand when only heavy seed, rather than mixed heavy and light
seed, is sown has been pointed out by Shamel (1904) and others,
while certain other more theoretical considerations in connec-
tion with the inheritance of certain characters in Nicotiana as
correlated with the weight of the seed used to produce the plants

1913] Goodspeed: Germination of Tobacco Seed 201

upon which they appear, have been in part dealt with in a pre-
vious comnranication (Goodspeed, 1912). Recently, also, it
appears to have been shown that the hybrids made between N.
sylvestris and various N. Tafear/rm -varieties may be considered
to be partially fertile rather than completely sterile (Goodspeed,
1913), and this fact was brought to light both by a careful
examination of the relatively few seed capsules (unprotected)
that persist on these F^ hybrids and the germination under con-
trolled conditions of such little seed as was found within them.
Again it is always conceivable that the so-called ratios which
appear to be manifested in the results of breeding experiments
from the Mendelian standpoint on the plant side may be modi-
fied by, or possibly are directly dependent upon, a high or low
percentage of germination of the seed used to produce the plants
the outward appearance of which is to be reported upon. In
view of these several considerations, and especially that the more
or less technical details connected with the breeding experiments
reported upon in this volume may be entirely plain and that
certain of the fundamental factors with which we are dealing
in these experiments may be more thoroughly understood both
by ourselves and by others, a rather detailed report upon the
germination of the parent and hybrid tobacco seed used seems
justified. It is hoped that further studies in this connection now
being pursued may be reported upon in the near future.

II. SEED USED

As will be noted in the tables which follow, the seed used in
the germination tests herein reported upon was taken from
single plants representing the following species and varieties of
Nicotiana and various crosses made between them. The desig-
nations given refer to the acquisition number, the year first sown
and the hybrid number in the U. C. B. G.

110/05— A^. Tabacum var. calijcina (Setchell 1912, p. 6).
22/07 — N. Tahacum var. macrophylla (ibid., p. 8).
78/05— N. Tabacum "Maryland" (ibid., p. 5).
78/09— 2V. attenuala (ibid., p. 24).

53/03 — N. acuminata variety (ibid., p. 23, and Goodspeed, 1912, pp.
119-122).

202 University of California Publications in Botany [Vol. 5

192/08 — N. acuminata parviflora (Goodspeed. loc. cit.)
150/07 — N. acuminata grandiflora (ibid.)

22/02— N. Langsdorfii (Setchell, 1912, p. 15).
107/01— iV. sylvestris (ibid., p. 29).
H18— 110/05 X 78/05.
H20— 78/05 X 110/05.

The germination of the seed obtained in different years from
single plants of the above species and varieties of Nicotiana will
be dealt with in the following pages with reference first to
the effect of sulfuric acid treatment upon germination of seed of
particular strains and seed of various ages, second to the relation
between the age of tobacco seed and its germination and lastly
with reference to the germination of parent versus hybrid seed.
The technique involved in the obtaining of "pure" seed under
bag and in performing cross pollinations has been described
elsewhere (Goodspeed, 1912, p. 126-129) as also the methods
employed in cleaning the seed, sowing it, etc. Pure seed from a
single plant only has been employed in the germination tests in
the greater majority of cases and unless otherwise stated. In
practically every instance also and unless similarly noted the
seed tested was a part of that used on a given year to produce
the plants grown in the U. C. B. G. and thus is definitely related
to the various breeding experiments therein being carried on.
In general the seed had been stored in the laboratory in boxes
and similarly wrapped (Goodspeed, loc. cit.) and thus any con-
dition that might have increased deterioration in viability acted
upon all the seed in the same way.

III. METHODS

(a) Germinating Conditions in General

Entirely satisfactory conditions for germination were not
available. The seeds were counted out on to containers of the
type elsewhere described (Goodspeed, loc. cit., p. 96) except that
in most cases finger bowls rather than drinking glasses were
used and thus larger surfaces were secured to hold the two hun-
dred seeds that were tested in the case of each plant. The seeds
were carefully arranged in rows in groups of one hundred seeds
each. This arrangement made it possible to check rapidly the

1913] Goodspeed : Germination of Tobacco Seed 203

results of each observation. A circle drawn in lead pencil about
one group of one hundred seeds distinguished it in the matter
of keeping the records of duplicate tests. In every case there
was no preference given to the larger, better formed seeds in
arranging the seeds to be tested. On the contrary the relatively
few ill-formed seeds were included as they occurred, since one
of the primary objects of the investigation w^as concerned with
determining what proportion of viable seeds each plant normally
produces. The criterion of germination was the same as that
elsewhere noted (Goodspeed, loc. cit., p. 98). A number of tests
demonstrated the fact that 96.8 per cent of the seeds thus
decided upon as showing germination will give rise to vigorous
seedlings the development of which has been watched for two
weeks after germination. It seems certain that this percentage
would be higher if it were possible to eliminate the injurious
etfects of handling the very small germinating seeds, which are
difficult to pick up lightly.

An even approximately standard germinating case was not
available. The finger bowls covered by the seed holders were
placed on sand in a shallow glass-covered case built on the top
of a greenhouse bench. Unfortunately strictly constant tempera-
ture conditions were not possible in this germination test except
toward the end of the experiments herein reported upon. At
the start of the experiments the temperature of the w^ater in
the finger bowls varied between 27° C for the average day tem-
peratures and 22° C for the night temperatures (cf. Garman,
1910). This amount of variation was somewhat cut down after
the end of two weeks and during the last month of the experi-
ments the temperature conditions under which germination took
place were very fairly constant at 25° C.

(h) In Connection with Sulfuric Acid Treatment

The work herein reported on that is connected with the effects
of treatment with sulfuric acid upon the germination of tobacco
seed is presented merely as preliminary with regard to more
detailed experiments which are at present in progress. The
value of sulfuric acid treatment has been established, however,
and this fact seems to warrant the inclusion of such experi-
mental evidence as is at hand as well as the methods employed

204 University of California Puhlications in Botany [Vol. 5

in this connection. In general the suggestions given by Love
and Leighty (1912) have been followed in modified form. The
action of concentrated sulfuric acid (sp. gr. 1.84) for lengths of
time as short as one minute in the case of 53/03 ate the seed
coats entirely away and destroyed any possibilities of germina-
tion. This was proved by a number of tests and by microscopical
examination. It is, however, entirely conceivable that the seed
of other strains of tobacco, better protected as to seed coats, will
give more favorable results with the concentrated acid — i.e., seed
of IT. C. B. G. 150/07 possibly. A considerable number of
experiments showed that treatment -s^ith 50 per cent, 70 per cent,
and 80 per cent sulfuric acid gave the best results, and the
majority of the tests were made after treatment with 80 per cent
acid for varying lengths of time.

A small quantity of the seed to be tested was placed in a
small vial and covered with the 80 per cent acid at room tem-
perature. After allowing the acid to act for the desired length
of time the vial was at once filled with tap water and the seed
and greatly diluted acid poured through strong cloth which
served to retain the small seeds. The seeds were washed for one
or two minutes on the cloth with a fine stream of tap water
and then transferred to another cloth-covered vial in which
they were further washed with running water. The eifects of
prolonged washing after sulfuric acid treatment will be further
discussed below. After the washing the seed was counted out in
two lots of one hundred each, as above noted, on to the blotting
paper holders and placed in the germinating case in the green-
house.

IV. RESULTS WITH SULFURIC ACID TREAT:\IEXT

The following table expresses the effect of sulfuric acid
treatment — 50 per cent, 70 per cent, and 80 per cent acid — upon
the germination of the seed of 78/09 produced in 1911. Because
of the small amount of seed available duplicate tests were not
possible and only fifty seeds were used in each individual test.
After the treatment with acid the seeds were washed with
running water for an hour while in the control the seeds were
placed dry on the filter paper.

1913]

Goodsjjeed : Germination of Tohacco Seed

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206 University of California Publications in Botany [Vol. 5

From the above figures it is evident that treatment with 80 per
cent sulfuric acid for lengths of time not much greater than
ten minutes will materially increase the amount of total ger-
mination in the case of the seeds of N. attenuata. ]\Iore rapid
germination of the treated seed is not, however, in general
apparent, for at the end of fifteen days in only two instances
— 70 per cent for fifteen minutes and 80 per cent for ten minutes
— was the germination of the treated seed greater than in the
control. The optimum lengths of treatment in this case evidently
lie between thirty and sixty minutes for the 50 per cent acid,
between ten and fifteen minutes for the 70 per cent, and prob-
ably not much beyond ten minutes in the case of the 80 per cent
acid. A considerable number of other tests with seed of 78/09
of 1911, using both stronger and weaker grades of sulfuric acid
for various lengths of time, were carried through. The above
table, however, includes the most significant results, though it
deals by no means with only those tests in which favorable
results after sulfuric acid treatment M'ere obtained.

Seeds of a number of other Nicotiana species which showed
relatively low germination (see page 210) were treated with
sulfuric acid in an effort to increase germination and a number
of the results are shown in tabulated form below. In each case
except the last the seeds were washed after the acid treatment
for from forty-five minutes to one hour in running water.

The prefixes attached to the seed numbers designate the year
upon which the seed was gathered. Thus 1906 53/03 refers to
seed of 53/03 gathered in 1906 or six years old at the time of
making the tests.

As will be seen in the table below, the effect upon germination
of treatment with 70 per cent and 80 per cent sulfuric acid has
been investigated in the cavse of old seed of N. Tahacum "Mary-
land" and old and new seed of two N. acuminata^Y arieties. The
relative amount and rapidity of germination in the old vs. new
untreated tobacco seed is taken up at greater length elsewhere
(see page 210). In every case in the table below treatment with
diluted sulfuric acid has resulted in a rather striking increase
in total germination as compared with the controls and also in
a rather marked increase in rapidity of germination in the case
of the treated seed.

1913]

Goodspeed: Germination of Tobacco Seed

207

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208 University of California Publications in Botany [Vol. 5

The extremely low pet'eentage of total germination in the ease
of 1912 150/07 is rather surprising, but in the table on page 212
it will be seen that the 1912 seeds of 53/03 and 192/08— the
other two N. acuminata-vsirieties cultivated in the U. C. B. G. —
also showed a remarkably low per cent of total germination. In
general no difficulty has been experienced in past j^ears in secur-
ing a fairly high per cent of germination in the case of N. acumi-
7ia^a-varieties under the germinating conditions elsewhere de-
scribed (Goodspeed, 1912, pages 98 and 132), although under
such conditions germination in X. acuminata has always been
slow as compared with practically all the other Nicotiana species
grown. In the case of 1912 53/03, 192/08 and 150/07 the
seed was taken from the ripe and opened capsules on the plants
and did not lie in the seed packets for four or five months as
is the rule where the seed is sown in March or April following
the gathering of the seed in November or December. This period
of ''after ripening" or further drying of the seed of N. acumi-
nata-vavieties may be essential for a high percentage of germina-
tion of their seed under experimental conditions. It is also
entirely possible that conditions for germination in the case of the
seed of N. aciiminata-varieties may be more favorable when the
seed is sown in soil and placed in an unheated propagating house
in which the variation in daily temperature covers a wide range.
In this connection the striking increase in germination when this
1912 150/07 seed is treated with 80 per cent sulfuric acid for
five minutes and the acid washed off for forty-five minutes in
running water is unusually significant. The effect of prolonged
washing after treatment with sulfuric acid is brought out in the
above table (table 2). As will be seen there in the case of 1912
150/07 when washed in running water for forty-five minutes one
of the duplicate tests showed 53 per cent germination, while the
other similarly treated but washed for twenty hours gave only
29 per cent germination. A .similar injurious effect of prolonged
washing after sulfuric acid treatment has been noted by Love
and Leighty doc. cit., p. 314). Additional tests further taking
up this particular point are in progress.

It seems thus possible on the basis of these relatively few
preliminary tests to state that a marked benefit is to be derived

1913] Goodspeed: Germination of Tobacco Seed 209

from the treatment of tobacco seed with 70 per cent or 80 per
cent sulfuric acid for varying lengths of time in hastening
germination and particularly in increasing its amount. It is
hoped that the results of further experiments in this connection
may be reported upon in the near future.

V. THE RELATION BETWEEN THE AGE OF SEED AND

ITS VIABILITY

The following tables deal Avith the results of some thirty-five
germination tests carried through in the effort to determine in
a preliminary fashion the relation between the age of tobacco
seed and its viability. As will be seen in only one case — i.e.
110/05 — was it possible to test any one species as to the viability
of the seed of consecutive years from the year first grown in the
U. C. B. G. to the seed of the present year. In other cases — •
i.e., 22/07 — the tests represent seed of an uninterrupted series of
years but the seed of the first year or so as grown in the U. C.
B. G. is missing. In still other cases — i.e., 53/03 — tests are lack-
ing for the oldest seed and the series is also interrupted.

Table 3 below represents a general compilation by years of
the results of the various tests. Apart from the remarkably high
percentage of germination among the six, seven, and eight-year-
old seed the most interesting points brought out in table 3 have
to do with the germination of the .V. acuminata-vdrieties in
general, the low percentage of germination of 22/02 more than
two years old, and the low germination percentages in many
eases for the seed gathered in 1910.

AVith reference to this last point no explanation can be
offered except that during the season 1910 conditions for maxi-
mum growth and development were not so distinctly favorable
as in the preceding year or in the two following years. Actual
climatic conditions do not seem to liavc differed greatly from
the average, but the garden records show that the parent strains
of tobacco — .V. Taftacwm-varieties in particular — did not germi-
nate as rapidly or as fully in 1011 as normally. A point of this
sort in connection with the j^ropagation of material connected
witli hy])ridiza1ion experiments on the plant side iii.iy in general

210

University of California Publications in Botany [Vol. 5

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1913] Goodspeed: Germination of Tobacco Seed 213

be noted on a given year, but its full significance is lost unless
a little of the seed is germinated each year under controlled con-
ditions and in a manner which makes possible more or less exact
germination counts. In this connection it may be said that the
possession of such records would have been greatly appreciated in
connection with the results of certain experiments reported on
in a previous communication (Goodspeed, 1912, pages 87-117).
The general low germination of the seed gathered in 1910 is
further brought out in table 4 below. This table is a different
expression of the results set down in table 3. It gives the average
per cent of germination for each of the eight years in the case
of all the seed of each year germinated and thus is not an accu-
rate expression of the relative amounts of germination in each
case. In the case of 1912 tests the results of the tests with the iV.
ac?rmf)mia-varieties — 53/03, 192/08, and 150/07 — have not been
included, though appearing in table 3, since their extremely low
percentage of germination seems to show that other factors have
entered in to affect the results which are thus not typical. The
low germination of the seed of 1910 is again seen in table 5,
which is self-explanatory.

These tables show the rather surprising viability of relatively
old tobacco seed (cf. Hayes, 1912, p. 3). The percent of germina-
tion in the case of eight-year-old seed of 110/05 or five-year-old
seed of 22/07 makes it seem probable that twelve and possibly
fifteen-year-old seed of N. Tabarum-Y&r\et\eH would germinate
to a certain extent at least — i.e., that deterioration as to viability
is a gradual process. The germination of the seed of 22/02, on
the other hand, makes it seem at least possible that there is a
more or less sharp end point as to the age limit of viability and
that after being kept a year or two more the seed of 1905 of
110/05 may fail to show any germination. As will be seen
in table 3 the 1909 seed of 22/02 germinated to the extent of
39 per cent, while among the seed of the same species one year
older only one seed in 200 germinated and only six seeds germi-
nated among 200 that were two years older. There is tlicn, in
the case of 22/02, a sharp drop in viability from nearly 40 per
cent to not over 5 per cent in one year as the seed is kept beyond
four years. At the end of the tests this older seed of 22/02 was

214 University of California Publications in Botany [yoh. 5

Year

Pli

TABLE 4

Hit designation

% germinated

1905

110/05

71.0

1906

110/05,

53/03, 78/05,

22/02

33.8

1907

110/05,

53/03, 78/05,

22/02

46.5

1908

110/05,

53/05, 22/02,

22/07, 150/07

47.7

1909

110/05,

78/05, 22/02,

22/07

71.2

1910

110/05,

53/03, 78/05,

22/07, 107/01

66.7

1911

110/05,

53/03, 78/05,

22/02, 22/07

75.8

1912

110/05,

78/05, 192/08,

TABLE 5

Plant

107/01

95.7

Year

designated

% germinated

1905

110/05

71.0

1906

110/05

59.0

1907

110/05

70.5

1908

110/05

74.5

1909

110/05

79.5

1910

110/05

26.5

1911

110/05

84.0

1912

110/05

88.5

1908

22/07

88.0

1909

22/07

96.0

1910

22/07

89.5

1911

22/07

98.0

1912

22/07

96.0

found to be functionle.ss and decaying. The relatively low per
centage of germination in the case of old and also this year's
seed of i\". acicminata-yarieties is interesting in view of certain
experiments with this species previously reported upon (Good-
speed, 1912), which are still being carried on. Table 6 is again
a condensation of table 3 with reference to the three N. acumi-
nata-v arieties.

In general it appears that the older seed of N. acuminata-
varieties gives the highest percentage of germination throughout.
Why this should appear to be true is not plain, but undoubtedly
the conditions — i.e., temperature conditions — under which the
tests were carried out cannot be the most favorable for the germi-
nation of the seed of this particular species. The same fact may,
of course, have influenced the results of the germination tests

1913] Goodspeed: Germination of Tobacco Seed 215

TABLE 6

Plant

Year

designated

9f germinated

1906

53/03

51.0

1907

53/03

38.0

1908

53/03

57.0

1910

53/03

58.0

1911

53/03

25.0

1912

53/03

7.0

1908

150/07

19.5

1912

150/07

9.5

1912

192/08

2.5

in the case of other species also, but in general the conditions
under which germination took place seemed to be the most
generally favorable that were available.

VI. THE GERMINATION OF HYBRID VS. PARENT SEED

On the possibility that there might be some correlation be-
tween the amount and time of germination and such segregation
as was observed in certain of the hybrids produced in the U. C.
B. G. a series of germination tests was carried out with hybrid
seed produced by the hybrids made between a number of iV.
Tahacum-YavietieB. The following table gives the germination
of the seed of 110/05, the germination of seed of 78/05 and the
germination of the seed resulting from the cross 110/05 X 78/05
and its reciprocal, together with the germination of the seed pro-
duced by one F, hybrid plant of both cross and reciprocal and
the seed of three F^ plants produced from the seed of these last
two individuals. H18 represents the cross 110/05 X 78/05 ; H20
its reciprocal.

As will be seen the amount of germination of the seed of the
cross, the seed of the Fj hybrid and of the various F^ hybrids
was very nearly identical in each of the two cases — i.e., 1909
H20, 1910 Fj H20 P26, 1911 F, H20 P26 Pll and P26 P25 all
show practically the same amount of germination and the germi-
nation was scattered over some nineteen to twenty-five days —
while in 1909 H18, 1910 F, H18 P49, 1911 F, II18 P49 P25,
P49 P24 and P49 P22 very heavy germination took place within
a week. In the various generations of cross HIS tlie amounts of

216

University of California Publications in Botany [Vol. 5

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CM

• • ■ '■ '■ ■ '■ : : i-H : i : i : : ; ; : -h ;

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: : : i : : : i : : : : : : : -* lo : : i ;

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^ : ^ „ ^ : : — ; ?i M 1 : : 1 : ^

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;i-(i-i(m; ::^: iisMtM i: :^ i: i:

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^ '^CS UOCO 1--C35 COCO OJIM ^lO <M : ^» ^lO lO(M OlO CIM -—I

T-Ttco— i-H .— ii— i.-i(M.— If— 1 com CO-* :

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1913]

Goodspeed: Germination of Tobacco Seed

217

s

m
<

Eh

Per cent
germinated
average dupli-
cate te.sts

97.5
99.0

99.0

95.0

25.5
77.5
71.5
G2.5
95.0
98.5

4J

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a

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CO ::::;::: ; : : : ; ■ : :

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CO ; I : : : ■ : : ; ; : : : : : : ; •

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lo : : i : i : : : : : i in cq- i ; : ■ :
CM : : ; : : ; ; : : ; : ; : : ; ; ; ;

CO ■ ; ■ ; ■ ■ : : ; : ': ^ : co <m co i ; ; :
CM ::;;::;:;:: ; ; ; : :

••- :: ■ \ :: ;: iic^' iimim-h ■: ■:
CM : : : ; : : : ; i— i : ; ; :

OS :: :: ;: :: jic^iOi— iior-irH :: ::

r>- i; :: :; i:c<i^ icii— loot^io ii '■ oi

us ;: ;: ii— i ii— iificscO'— (•— ci iiO
^- . 1 ; : : : : : i— i ; ■ : ;

CO i 1— 1 ^ i Tt (M ■* i ^ ■ M Ol fO CO

•»- rH i >-l ■ i i i 5-1 ■-( C-5 O OI 00 i UQ t- oo c-1 in t^

■^ : : CO ■* o : c<i 0-1 in ■* — . rt

_, i'-^-Hi-iiooQC i-Hcoco ii-^ooosoo^M
°' : — 1 I ; ; — i — cq co itj Tf

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!3
C
....

F, H18
P49

F.,H18
P49 P25

F,,H18
P49 P24

F0HI8
P49 P22

78/05
78/05
78/05
78/05
78/05
78/05

u

>i

1910
1911
1911

1911

190G
1907
1909
1910
1911
1912

218 University of California Publications in Botany [Vol. 5

total germination are nearly identical except in the case of the
seed resulting from the cross — i.e., the seed of 1909 H18.

In general, then, the most significant facts brought out by
these last tests have to do with the exceedingly high percentage
of germination among the two sets of hybrid seed from one to
three years old and the more or less scattering germination of
the seed of H20 throughout. In connection with this latter
situation the seed of 78/05, as will be seen, shows a remarkably
long period during which germination takes place — i.e., over
four weeks except in the case of this year's seed and that of 1911.
There seems thus to be some difference between the cross and its
reciprocal as to the rapidity of germination and the relatively
slow germination of 78/05 is seen only in that one of the two
hybrids in which this N. T ah acum-var \ety is the female parent.
On the other hand the germination of H20 is practically identical,
in the length of the period during which germination takes place,
with that of 110/05 in general, while the germination of HIS is
much more rapid throughout than either 110/05 or 78/05. The
significance of these facts is not entirely clear. The increase in
amount of total germination in the case of all the hybrid seed
as compared with the seed of the parental varieties during the
various years is rather striking. In connection with the seed pro-
duced by the F^ plants of HI 8 and H20 the increased germina-
tion of the hybrid over the parent seed of the same year might
be referred to the general stimulating effect of heterozygosis
(East and Hayes, 1912). In this connection it may be noted
that the plants which bore this Fj hybrid seed showed in a
general way an increase in vegetative characters as compared
with the parental varieties, but to no such extent as in the F^
hybrids involving N. Tahacum-varieties and .V. sylvestris as
parents (cf. Goodspeed. 1913). The fact, however, that these
latter hybrids were found to produce very little seed, only part
of which would germinate seems to indicate that increase of
vegetative characters due to heterozygosis, is not necessarily
correlated with the production by such hybrids of abnormally
large or even normal amounts of seed or of seed which will show
a high percentage of total germination.

1913] Goodspeed: Germination of Tobacco Seed 219

TABLE 8

Year

Plant designation

% germinated

1909

110/05

79.5

1909

H20

96.5

1909

HIS

89.5

1909

78/05

71.5

1910

110/05

26.5

1910

Fi H20 P26

98.5

1910

FiH18P49

97.5

1910

78/05

62.5

1911

110/05

84.0

1911

F,H20P26P11

91.5

1911

F, H20 P26 P25

95.0

1911

F„ HI 8 P49 P25

99.0

1911

F, H18P49P24

99.0

1911

F, HI 8 P49 P22

95.0

1911

78/05

95.0

Table 8 brings out more elearlj^ the relative amounts of ger-
mination of hybrid and parent seed on corresponding years.

In the case of two and three year-old seed the higher per-
centage of germination for the hybrid seed as compared with the
seed of the parental N. Ta&acMm-varieties is marked, while in
one-year-old seed which involves the seed of F, hybrids the con-
trast is much less striking. Further tests are contemplated which
may throw some light on the significance of such results as these.

VII. SUMMARY OF RESULTS

The following summary of results is based upon the above
description of germination tests and others involving in all over
20,000 seeds produced from single plants of ten species and
varieties of Nicotiana and from single plants representing the
original hybrid seed and the F^ and Fo generations in the case
of two hybrids made between two N. Ta6acum-varieties.

(1) The action of 80 per cent sulfuric acid upon tobacco seed
for lengths of time not over ten to twelve minutes increases
markedly the total amount of germination and in certain cases
increases rapidity of germination.

(2) The action of concentrated sulfuric acid (sp. gr. 1.84)
for periods of time as short as one minute killed the seed used.

(3) A markedly injurious effect of prolonged washing with
running water after sulfuric acid treatment was noted.

220 University of California Puhlications in Botany [Vol. 5

(4) Six, seven, and eight-year-old tobacco seed was found
to give relatively high percentage of total germination in most
cases.

(5) Eapidity of germination in general was found to be
independent of the age of the seed and to be characteristio of
the seed of certain species or varieties throughout and not char-
acteristic of others.

(6) A certain period of "after ripening" seemed to be essen-
tial for average germination percentages as shown in the case
of 1912 N. acuminata-\Siv\ei\e^. Seed taken from dehiscing
capsules on the plants in the field gave very low percentages of
germination in the case of N. acuminata-varieties alone.

(7) Fi hybrid seed three years old gave higher percentages
of germination than the seed of the parents of the corresponding
cross and of the same age.

(8) The relation between the germination of parent and
hybrid seed indicate that interesting and possibly important sup-
plementary results can be obtained by the germination under
controlled conditions of the seed used in hybridization experi-
ments.

VIII. DISCUSSION OF RESULTS

The preliminary nature of this communication makes un-
necessary any detailed discussion of the results obtained.
Throughout mention has been made of further germination tests
at present in progress or contemplated which are designed to
investigate further certain of the more interesting points merely
touched upon in the present paper.

The real significance of the action of sulfuric acid in hasten-
ing or increasing germination opens a field for investigation
which should prove important, especially if such treatment is to
be included in general agricultural practice. Results at present
at hand seem to leave no doubt that in the case of N. acuminata-
varieties at least the action of sulfuric acid is not restricted to
weakening the hard outer coverings of the seeds so that water
can penetrate more rapidly or that the germinating seed can
break them more easily, but that its action is further strikingly
effective in increasing the rate of growth during at least the first
three months of the plant's life.

1913] Goodspeed: Germination of Tobacco Seed 221

Further lines of investigation contemplated have to do with
the germination of seed taken from capsules still green (see
table 3) and taken at various stages during the maturing of the
seed capsules on the plant and the relation between the vigor of
the plant and the percentage of germination of the seed it pro-
duces. In this latter connection it will noted that in table 3
in the case of 1909 78/05 the first of the duplicate tests germi-
nated to the extent of 97 per cent, while the second showed only
46 per cent germination. In this case only the seed used was
taken from two plants of N. Tahacuni "Maryland" and not from
one individual alone. The seed in the first of the duplicate tests
which gave the high percentage of germination was produced
by a tall, much-branched plant of 1909 78/05, while that used
in the second test which gave the low percentage of germination
was taken from a plant of the same year which was relatively
inferior in general vegetative characters.

I am glad to acknowledge my indebtedness to Professor W. A.
Setchell for his interest in and suggestions concerning the experi-
ments reported upon above, and to Mr. W. G. Perrine, upon
whose assistance and cooperation the success of much of the work
has depended.

222 University of California Publications in Botany [Vol. 5

LITEKATUEE CITED

East, E. M., and Hayes, H. K.

1912. Heterozygosis in evolution and in plant breeding. U. S. D. A.
Bur. PI. Ind., Bull. 243.

Garman, H.

1910. Seed testing apparatus and some modifications originating in
the Division of Entomology and Botany. Kentucky Agric.
Expt. Stat., Bull. 148.

GOODSPEED, T. H.

1912. Quantitative Studies of Inheritance in Nicotiana Hybrids.

Univ. of Calif. Publ. in Bot., vol. 5, no. 2, p. 87.

1913. On the partial sterility of Nicotiana hybrids made with N.

sylvestris as a parent. Univ. of Calif. Publ. in Bot., vol. 5,
no. 4.

Hayes, H. K.

1912. Correlation and inheritance in Nicotiana Tabacum. Conn.
Agric. Expt. Stat., Bull. 171, May.

Love, H. H. and Leighty, C. E.

1912. Germination of seed as affected by sulfuric acid treatment.
Cornell Univ. Agric. Expt. Station, College of Agric, Bull.
312, March.

Setchell, W. a.

1912. Studies in Nicotiana. I. Univ. of Calif. Publ. in Bot., vol. 5,
no. 1, pp. 1-86.

Shamel, a. D.

1904. The Improvement of Tobacco by breeding and selection. Year-
book, U. S. D. A., p. 435.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 6, pp. 223-231 Issued April 21, 1915

QUANTITATIVE STUDIES OF INHERITANCE
IN NICOTIANA HYBRIDS. III.

BY
THOMAS HAEPEE GOODSPEED

Two previous reports have partially outlined the results obtained
in an effort to contribute to the knowledge of the inheritance of quan-
titative characters (Gooclspeed, 1912 and 1913). Cro.sses involving
three flower-size varieties of Nicotiana acuminata (Grah.) Hook, have
been investigated up to and including Fg. The first and second gener-
ations of these hybrids have already received consideration and it is
the purpose of the present paper to review the results previously
obtained and to take up briefly the nature of the F.;.

The tables which follow are based upon over 13,000 measurements
of spread and length of corollas of flowers borne upon the three flower-
size varieties of N. acuminata and on the hybrids made between them.
The method of designation of parents and hybrids is the same as that
employed in a previous commimication (1912). The parents, one
F^ and one F^, population, and the F., were grown in the summer of
1913 under conditions as nearly as possible identical with those under
which the plants in this experiment were grown in 1912.

The arrangement of the material in the form of freciuency distri-
butions and the consequent rearrangement of the data, and in some
cases the combination of two or more groups of hybrids of the same
pedigree, give to the figures an appearance somewhat difl'erent from
that presented in the earlier reports upon the same hybrids. The
frequency distributions for corolla spread of individual plants formed
the main basis for these earlier reports. In the present connection
such distributions are not of sufficient interest to warrant their inclu-
sion. The statistical constants for the tables which follow are not
given, as their significance is doubtful with such small populations as
were measured.

224 University of California Puhlications in Botany [Vol. 5

During this past year the length of the corolla as well as the spread
of the corolla, which alone was considered in previous measurements,
has been investigated. The term "length of corolla" refers to the
distance from the point of insertion of the corolla upon the receptacle
to the top of the corolla tube.

The measurement of corolla length as taken in the field was the
distance from the base of the calyx tube to the point where the flat-
tened corolla limb bends more or less sharply to join the corolla tube.
The measurement of "corolla diameter" or "spread" was taken dur-
ing the past two years in the same manner as described in another
report for the earlier measurements (1912).

Designation

20

21

22

23

24

25

Variety I
1910

1911

1912

1913

Variety II
1910

5

1

1911

7

1912

4

5

1

1913

4

5

7

2

1

I X IIFl
1911

1

4

1

I X II F2
1912

1

1

5

I X II F3
1913

1

9

4

TABLE 1
Variety I, Vakiety II and Hybrids — Spread

Class centers in mm.

26 27 28 29 30 31 32 33

.... 6

5 8 19

No. of
plants

Mean

flower

size

6

26.93

5

27.20

5

32.73

8

30.10

6

20.29

7

19.99

10

23.85

19

22.67

7

24.23

17

27.69

51

27.43

TABLE 2
Variety I, Variety II and Hybrid — -Length

_,, . Mean
Class centers in mm. No. of flower-
Designation 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 plants size
Varietv I
1913 2 1 1 .... 1 .... 2 1 8 50.73

Variety II

1913 3 2 7 5 1 ... 1 19 41.34

I X II F3

1913 3 1 14646685231 1 51 45.19

1915]

Goodspeed : Inheritance in Nicotiana Hybrids

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101."] Goodspccd: Inheritance in Nicotiana Hybrids 227

Since the number of plants involved in the above tables is so small,
it is, from one point of view, rather useless thus to express the final
results of this experiment which has extended over four years and
in connection with which such a considerable number of measurements
have been obtained. The demand for larg'e F._, and later hybrid gen-
erations, to give an approximation of the desired complex ratios, was
early met in experiments concerning the inheritance of what may still
be called "qualitative" characters and recently the investigation of
"quantitative" characters has been attempted upon a similar scale.
With reference to certain of the "(jualitative" characters investigated
I have no basis for judging the extent and infiuence of the environ-
mental factors operative, nor as to the modification of the reported
results that would have been produced had careful measurements been
made. Data which have been submitted, however, leave no room for
doubt in my own mind that investigations on the inheritance of flower-
size demand the recognition of certain definite criteria and that the
results of such investigations are vitally influenced by inherent as
well as externally induced physiological states peculiar to the })lant.
Thus it remains to be seen if as many as 800 plants are necessary to
establish the validity of an expanded Mendelian notation in P^ of a
flower-size hybrid, whether the 40.000 to 80,000 measurements, seem-
ingly essential to a fair expression of results, can be accumulated.
In other words, the experiment with which this paper deals has been
a partially successful effort to measure many flowers on a few plants
with the thought that the conception of flower-size would thus be
approximately perfect for a few, rather than certainly imperfect for
many plants. It is undeniably true that the number of plants is
smaller than it should be, and it is perfectly evident that if the flowers
on a larger number of plants cannot be correctly measured the attempt
is not worth making. Further, it has been ascertained that the gen-
eral method of measurement can be greatly improved upon. The
attempt to make measurements of flower-size in the field is next to
useless where more than fifty plants in a single group are grown.
In a flower-size investigation now in progress all the flowers which
the plant produces, from the first flower to the flowers on the plant
two months later, are picked off and preserved in liquid to be measured
in the laboratory. A random selection and careful mea.surement of
fifty flowers among all these flowers picked off from each plant should,
then, give a fair approximation of the situation with reference to the
flower-sizes involved. It is hoped that the parents and three hybrid
generations can be grown together during the coming setison.

228 University of California Puhlicatioiis in Botany [Vol.5

Two points were emphasized in the pre\ious communications
dealing with the experiment on the inheritance of flower-size in
.Y. acuminata hybrids. First, it was demonstrated that, with
reference to the range of variation of the flowers borne on a single
plant of one of its parents, the F^ range was distinctly greater than
the parental range. Further, of all the flowers produced by all the
various hybrid plants, the largest flowers Avere as large as the largest
of all the flowers produced on plants of the large-flowered parent.
This was also true for the smallest flowers. Nothing more was claimed
as to the variability of flower-size in the F^ .Y. acuminata hybrids.
It was not stated that the range of the Fi populations was greater
than the range of the populations of the corresponding parents. In
respect to this particular point, however, the above fre(iuency distri-
butions are at least interesting. In variety I and variety III (table 3),
the large-flowered and small-flowered varieties and the Fj hybrids
between them in 1911, 1912, and 1913, the F^ range is throughout
greater than the range of either parent in corresponding years. The
Fi between varieties II and III in 1911, when compared with the
parents of the same year (table 5), serves to emphasize this point, as
does the Fj of the cross between varieties I and II (table 1). The
number of plants is obviously inadequate, yet there is here an indi-
cation again that the question of the extent of variation in F^ is still an
open one. It might be of some significance if, in place of examining
only one-eighth as many F^ plants as F, plants, an example of the
iLsual procedure, the number of individuals in these two generations
were made more nearlj^ equal in favor of the larger number (cf. Shull,

1914, p. 131).

The second point which was taken up in the earlier reports had
to do with the inadequate nature of the expanded Mendelian notation
as an explanation of the inheritance of quantitative characters and
other complex situations. An apparently widespread doubt as to its
adequacy in such connections makes it possible to note that nothing
during the two years since the publication of the original reports has
made untenable our position on this subject therein stated (cf. Castle.

1915, p. 97). Shull (1914) feels that we have demonstrated a notable
increase in variability as to flower-size in the Fo generation previously
reported on (Goodspeed, 1913) and reports that we "refu.sed to as-
cribe this greater variability to Mendelian segregation." The actual
statement made was that the greater variability of F., as compared
w^th Fi "appears to make it plain that segregation does occur" {ihid.,

■'•^'-^'5] Goodspcfd: InJtcrilancc in Nicotiana Ilijhrids 229

J). 17;^j but that this situation might be dependent upon various con-
ditions external to the experiment and that the Mendelian explanation,
while obviously applicable, was of somewhat doubtful practical value.
It was suggested that the actual significance of this apparent increase
in variability in F. might lie in an increased fluctuating variability
due to environmental causes. A somewhat detailed study of the
parents under stril^ingly different conditions of culture showed that
ordinary greenhouse treatment resulted in a small but distinct increase
in the length of corolla tube as compared with that of sister plants
in the field. The most important factor considered in connection with
the effort to show that the increased variability in Fo was due to non-
inherited effects was the influence of the age of the plant, etc., in
determining the size of the flowers borne on a plant. A discussion
of these points is given in a paper to follow (Goodspeed and Clausen,
1915). In the earliest report, dealing with flower-size in F^ of these
hybrids, emphasis was laid upon the fact that all the fully opened
flowers were taken on each day of measurement from the various
plants and measured. Thus, for the F^ previously reported upon
and contained in the foregoing tables, the "age of plant" and the
"age of floAver" factor (Goodspeed and Clausen), which otherwise
might have accounted for the degree of variation in F,, were both
eliminated. The importance of attempting to do away with the de-
crease in flower-size brought about by the presence of maturing seed
capsules on the plant was imperfectly appreciated up to this past
season. Thus, without attempting to indicate directly the situation,
as has been done for other species of Nicotiana in another paper
{loc. cit.), it may simply be said that a certain proportion of the
increase in variability of the F^ population of the cross I X II 1912
(table 2) and the III X II 1^12 (table 5) was due to non-inherited
eft'ects. The distributions of the parent and Fj populations in 1912
and 1913 are much more nearly representative and accurate, since it
was possible to measure approximately all the flowers produced.

Leaving out of account such situations as the striking difference
between reciprocal F, hybrids (table 5, II X HI, 1912, and III X H,
1012) as due to the small number of plants involved, the foregoing
tables seem to indicate the following facts :

The F, generation of the .V. acuminata flower-size hybrids shows
.1 range of variation as great as and often greater than the parent
plants in corresponding years. The mean flower-size may be approxi-
mately the mean of the parent flower-sizes or it may not.

230 University of California Puhlications in Botany [Vol.5

The F^, populations in some cases show a remarkable increase in
the range of variability as compared with the parents and F^ hybrids.
This range in no case is equal to the total combined range over which
the varialiility of both parents extend. Thus in some cases the means
of individual F. plants may be as small as or smaller than the mean
of the smallest-flowered parent plant, but in no case, for the same
Fo distribution, is the mean flower-size of the largest-flowered Fg
plant as great as the mean of the largest-flowered parent individual.
Indeed, in only one case do Fo individuals approach the size of the
largest-flowered parent plants and at the same time show individuals
with means within the small-flowered parental range. As has above
been noted, a certain proportion of this increase in variability in Fo
populations may be ascribed to the active interference of various
external and internal factors attending development. It is signifi-
cant, in this connection, that the flower-size of the F. hybrids shows
in the greater number of cases an increase of variability 'toward the
smaller end of the parental range.

Though a number of F3 families were groA\Ti, it was not foimd
possible to measure flow^ers on more than one group of plants. The
mean flower-size, for spread of flowers, of the F^, plant from w^hich this
F., population was derived was 24.89 mm., while the mean corolla
spread of the 51 F.. plants was 27.43 mm. The range of this F.
population for spread of flowers was not as great as the range of the
17 Fo plants of the previous year, though it is approximately the same
so far as the limits of the range are concerned. The mean — 27.43 mm.
— is approximately the same as the 1913 F^ mean of 27.59 mm. It is
entirely possible that of many other F.. families some might have
shown significant differentiation but the relatively few measurements
made upon three other F., families showed in general a range corre-
sponding to that of the one F.,, the distribution of which is given in
table 1. The range of this F;. with reference to length of corolla tube
shows an extraordinary extent, yet the mean is approximately the
same as the mean between the parents.

Transmitted February 11, 1915.

1915] Goodspeed: Inheritance in Nicotiana Ilijhrids 231

LITERATURE CITED

Castle, W. E.

1915. Bateson's address, Mendelism and Mutation, Science, N. S., vol. XLI,
No. 1046, January, 1915.

Goodspeed, T. H.

1912. Quantitative studies of inheritance in Nicotiana hybrids, Univ. Calif.

Publ. Botany, vol. 5, No. 2, 1912.

1913. Quantitative studies of inheritance in Nicotiana hybrids, II, ibid.,

vol. 5, No. 3, 1913, in press, American Journal of Botany, vol. 2.

Goodspeed, T. H., and Clausen, E. E.

1915. Factors influencing flower-size in Nicotiana with special reference to
questions of inheritance.

Shull, G. H.

1914. Duplicate genes for capsule-form in Bur.'>a hursa-pastoris, Zeitschr. f.

ind. Abstamm.-u. Vererb., Bd. XII, H. 2, 1914.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 7, pp. 233-248 Issued June 25, 1915

NOTES ON THE GERMINATION OF TOBACCO

SEED, II

BY

THOMAS HAEPER GOODSPEED

In a previous report (Goodspeed, 1913) an outline was given of
the possibly important supplementary results to be obtained by com-
paring the rates of germination and the amount of germination of the
seed used in breeding experiments to produce the pedigreed plants.
The results of the germination tests therein tabulated indicated that
there were, in the first place, distinctions between the rates of germi-
nation of the seed of reciprocal hybrids and, in the second, that the
rates and possibly also the amounts of germination of the seed of F^
and F2 hybrids were significantly differentiated. The present paper
aims to present further evidence in support of these previous sug-
gestions and conclusions. The relation between the age of the seed
of certain of our pure-line cultures, and of the seed of hybrids made
between them, and the viability of this seed, was also taken up in the
previous communication. It will be further considered in what follows.

The tables below give the amount and time of germination of the
seed of various pure lines and hybrids of Nicotiana under their num-
bers in the University of California Botanical Garden (U. C. B. G.).
A list of the species employed, together with the hybrids between them,
follows in the order in which they appear in the various tabulations.

30/06— "White Tobacco" (ef. Setchell, 1912, p. 7).
17/07 — Nicotiana rustica var. texana {ibid., p. 15).
16/07 — A'', rustica var. scabra (ibid., p. 14).
68/07— iV. angmtifolia (ibid., p. 9).
22/07 — N. Tabacum var. marrophyJIa (ibid., p. 8).
78/05— iV. Tabacum "Maryland" (ibid., p. 5).
72/05— "Cavala" (ibid., p. 5).
H 23—30/06 X 22/07.

•OTANIC'L

234 University of California Publications in Botany [Vol.5

H 24—22/07 X 30/06.

143/06 — N. multivalvis {ibid., p. 27).

H 46—16/07 X 17/07.

H 47—17/07 X 16/07.

35/05 — N. quadrivalvis (ibid., p. 27).

60/07— iV. Bigelovii (ibid., p. 25).

H 5—22/07 X 68/07.

H 15—68/07 X 22/07.

H 7—72/05 X 78/05.

H 8—78/05 X 72/05.

The method of conducting the germination tests and the conditions
under which they took place were identical with those previously de-
scribed (Goodspeed, 1913, p. 202). The great majority of the tests
were made under my direction by j\Iiss JNIinnie Yonge during February
and March, 1914. The criterion of germination was a trifle different
from that of previously reported experiments in that the first appear-
ance of the caulicle without the cracked seed coats, rather than the
appearance of both caulicle and cotyledons, was taken to constitute
germination. Over 10.000 seeds were used.

The tables that follow (tables I and II) supplement to a certain
extent the evidence concerning the relation of the age of tobacco seed
and its viability as given in the earlier report {ibid., p. 215). Sixteen
species, varieties, and hybrids are added to the list of those tested
previously {ibid., p. 210) and repetitions of earlier tests are shown in
two cases.

1915]

Goodspeed: Germination of Tobacco Seed

235

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1915]

Goodspeed: Germination of Tobacco Seed

237

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1915]

Goodspeed: Germination of Tobacco Seed

239

Table Ila

Year

Plant designation

Av. per cent
germinated

(1)

1906

30/06

17.5

1907

30/06

83.0

1908

30/06

80.0

1909

72/05, 30/06, 17/07, 16/07,

68/07, 22/07, 78/05

87.9

1910

17/07, 16/07

95.0

1911

16/07,143/07

96.0

1912

17/07,16/07

96.0

(2)

1906

30/06

17.5

1907

30/06

83.0

1908

30/06

83.0

1909

30/06

87.0

(3)

1909

16/07 and 17/07

96.0 71.5

1910

16/07 and 17/07

94.0 96.0

1911

16/07

93.5

1912

16/07 and 17/07

97.0 95.0

Table :

[lb

Plant
designation

30/06

Year
1906

Amount
of ger-
mination,
per cent

17.5

Duration
of significant
germination

8 days( + )

Maximum
germination

16tli day of test

110/05

1906

59.0

9

days

7th day of test

78/05

1906

25.5

25

days

29th day of test

30/06

1907

83.0

10

days

12th day of test

110/05

1907

70.5

9

days

7th day of test

78/05

1907

77.5

15

days

11th day of test

30/06

1908

80.0

11

days

11th day of test

110/05

1908

74.5

11

days

7th day of test

22/07

1908

88.0

9

days

7th day of test

30/06

1909

87.0

9

days

15th day of test

110/05

1909

79.5

13

days

7th day of test

78/05 (1913)

1909

71.5

9

days

11th day of test

78/05 (1914)

1909

95.0

3

days

10th day of test

22/07 (1913)

1909

96.0

11

days

9th day of test

22/07 (1914)

1909

87.0

3

days

8th day of test

68/07

1909

86.0

3

days

8th day of test

72/05

1909

93.5

5

days

8th day of test

17/07

1909

71.5

6

days

5th day of test

16/07

1909

96.0

7

days

7th day of test

110/05

1910

26.5

5

days

11th day of test

78/05

1910

62.5

15

days

1 1 th day of test

22/07

1910

89.5

7

days

7th day of test

17/07

1910

96.0

5

days

5th day of test

16/07

1910

94.0

9

days

5th day of test

110/05

1911

84.0

5

days

7th day of test

240

University of California PuMications in Botany [Vol.

Table 11&

-(C

'oncludecl)

Amount

of ger-

Duration

Plant

mination,

of significant

Maximum

designation

Year

per cent

gei-m

lination

germination

78/05

1911

95.0

7

days

11th day of test

22/07

1911

98.0

5

days

7th day of test

16/07

1911

93.5

10

days

9th day of test

143/07

1911

98.5

2

days

3rd day of test

110/05

1912

88.5

11

days

7th day of test

78/05

1912

98,5

9

days

9th day of test

22/07

1912

96.0

9

days

5th day of test

17/07

1912

95.0

2

days

5th day of test

16/07

1912

97.0

2

days

4th day of test

35/05 (a) (5)

1912

100.0

2

days

3rd day of test

60/07 (a)

1912

97.0

6

days (+)

5th day of test

Table I details the results of germination tests, some of which are
expressed more briefly in tables II, Ila, and 116. The data submitted
furnish a confirmation of the results previously reported, which demon-
strated that tobacco seed five years old and older will give a relatively
high percentage of germination under controlled conditions. As to
whether deterioration in viability is a gradual process or has a sharp
end-point after which viability is greatly reduced we can, again, make
no generally applicable answer. The combined evidence furnished by
the previous experiments and those above submitted seems to make
it clear that for certain species and varieties the end-point is abrupt,
while for others deterioration as to viability is a gradual process.
This distinction can be made even within a species, since the various
N. Tahacum varieties differ from one another as to the amount of seed
which becomes functionless in each succeeding year. In this con-
nection attention should be called both to the uniformity and to the
lack of uniformity in the rates of germination of the seed of various
varieties within a given species. Take, first, the six varieties of N.
Tahacum, the seed of which is dealt with in this and in the preceding
report. Table II& combines results given in Table 3 of the preceding
report (Goodspeed, 1913, p. 210) with certain of those included in
Table I and lays emphasis upon the number of days during which a
significant amount of germination took place as well as the day, dur-
ing the extent of the germination test, upon which the greatest amount
of germination was noted. As Table II& shows, there is an extraor-
dinary uniformity as to the day upon which the greatest amount of
germination took place. There is, in a number of cases, a character-

1915] Goodspeecl: Germination of Tobacco Seed 241

istic day and it is peculiar to both older and younger seed. Thus for
Nicotiana angustifolia (110/05) the seed aged two, three, five, six,
seven, and eight years gave the greatest amount of germination on the
seventh, while the four-year-old seed gave the greatest amount on the
eleventh daj^ of the germination tests. Likewise, in the case of N.
Tahaciim "Maryland", the eleventh day showed the greatest amount
of germination for the seed of four different years, while the youngest
seed germinated most heavily on the ninth day. In the same way the
seed of N. Tahacuni var. macrophylla showed, on the average, maximum
germination on the seventh day. Table II shows that for five-year-old
seed of five N. Tahacuni varieties three gave maximum germination on
the eighth day, one on the eleventh, and one on the fifteenth, while of
two varieties of N. rustica one showed the greatest amount of germi-
nation on the fifth and the other on the eighth day. With reference,
further, to these N. rustica varieties (16/07 and 17/07) as shown in
Table II &, seed of three different ages germinated most heavily on the
fifth day, while seed of four dift'erent years of 16/07 germinated, on
the average, later during the germination tests. Both the total amount
of germination and the length of time during which significant germi-
nation took place varies more greatly for the different species and
varieties used. There seems to be, however, some significant differen-
tiation in this latter respect among the varieties of N. Tahacuni and
N. rustica. Thus seed of 17/07 completes its significant germination
in a shorter space of time than does 16/07. Similarly 78/05 and
110/05 exhibit, on the average, a greater duration of germination than
does the seed of the other N. Tahacuni varieties.

As will be seen by a reference to the earlier communication (1913,
p. 215), certain apparently significant facts were revealed when the
germination of parental vs. hybrid seed, through a number of
generations, was tested and the results compared. The first part of
Table V expresses in condensed form the data given in the earlier
paper {I.e., p. 216). H 18 represents the cross 110/05 X 78/05; H 20
its reciprocal. The striking difference between the results of the ger-
mination test carried out with 1909 78/05 in 1913 and the one made
with the same seed in 1914 will be explained by reference to the earlier
paper (I.e., p. 221). As may be seen, H 18 and H 20 are not signifi-
cantly differentiated in any striking fashion with reference to the
duration of germination and as to the day during the extent of the
test upon which the maximum anumnt of germination took place.
The average total amount of germination of the parents, including

242

University of California Publications in Botany [Vol. 5

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1^1^] Goodspeed: Germinaiion of Tobacco Seed 243

1906 to 1912 seed in the case of 78/05 and 1905 to 1912 seed in the
ease of 110/05. is approximately 70 per cent, whereas the seed of
H 18 and H 20, five years old, germinated 89.5 per cent and 96.5 per
cent respectively. The five-year-old seed of 78/05 germinated 71.5
per cent in the 1913 test and 95 per cent in the 1914 test, while the
five-year-old seed of 110/05 germinated only 79.5 per cent. Compari-
sons between the germination of the seed of other N. Tahacum varieties
and that of the F^ seed of hybrids made between them are, some of
them, more significant (tables III. IV, and V). It is certainly re-
markable that the six-year-old seed of 68/07. 22/07, H 5 (22/07 X
68/07). and H 15 (68/07 X 22/07) should show almost exactly the
same duration of germination and that, for all four, the day upon
which maximum germination took place should be the same. Too
much emphasis cannot be laid upon the duration of germination in
this case, since the 1913 test of the 1909 22/07 seed showed this to be
eleven days as contrasted w4th three days for the 1914 test of this
same seed. Attention must, however, be called to the fact that the
important portion of the 1913 germination of the 1909 22/07 seed took
place within five days (cf. Goodspeed, I.e., p. 211), while the remain-
der of the seed that germinated after these five days accounts approxi-
mateh' for the difference between the total amounts of germination
of the five-year-old seed and the six-year-old seed of 22/07. Con-
trasted with the similarities in the duration of germination and the
day upon which germination took place in the greatest amount, we
have a distinct difference between the reciprocal hybrids, H 5 and
H 15, as to the total amounts of germination — i.e., 92 per cent for
H 5 and only 70 per cent for H 15. The seed produced by F^ of the
cross 78/05 X 72/05 and its reciprocal can. likewise, be distinguished
by differing amounts of total germination. Thus while the six-year-
old seed of the parents, 78/05 and 72/05, germinated 95 per cent and
93.5 per cent respectively, the 1909 seed of F^ H 7 (72/05 X 78/05)
germinated 77 per cent and corresponding seed of its reciprocal (F^
H 8) germinated 97.5 per cent. It is also important to note that the
germination of 1909 72/05 is characterized by two maxima of germi-
nation— the sixth and the ninth day of the test — and that Fi 11 7.
also, shows maxima of germination — the seventh and the tenth day of
the test. As noted above, 72/05 is the female parent of the hybrid
H 7. Similarly, comparing the germination of 1909 F^ II 8 and 1909
78/05, the correspondence between the two is striking in that they
both have but one day of maximum germination, and thus that the

244

University of California Publications in Botany [Vol. 5

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1915]

Goodspeed: Germination of Tobacco Seed

245

Table

V

Amount of

Duration

Plant

germination,

of significant

Maximum

designation

Year

per cent

germination

germination on

110/05

1905 to 1912

69.3 (av.)

9 days (av.)

8th day of test

78/05

1906 to 1912

71.7 (av.)

18 days (av.)

13th day of test

110/05

1909

79.5

13 days

7th day of test

78/05

1909 (1913)

71.5

25 daj's

15th day of test

78/05

1909 (1914)

95.0

3 days

11th day of test

H20

1909

96.5

7 days

9th day of test

H18

1909

89.5

9 days

7th day of test

110/05

1910

26.5

7 days

11th day of test

78/05

1910

62.5

29 days

11th day of test

F, H 20 P,e

1910

98.5

7 days

9th day of test

F, H 18 P«

1910

97.5

3 days

5th day of test

110/05

1911

84.0

7 days

7th day of test

78/05

1911

95.0

7 days

11th day of test

F^ H 20 P26

Pu

1911

91.5

16 days

11th day of test

F„ H 20 Poe

P25

1911

95.0

31 days

7th day of test

F, H 18 P,3

P=»

1911

99.0

5 days

7th day of test

*F, H 18 P,„

P.

1911

99.0

5 days

7th day of test

17/07

1910

96.0

4 days

5th day of test

16/07

1910

94.0

10 days

7th day of test

H46

1911

98.0

10 days

8th day of test

H47

1911

91.0

6 days

5th day of test

F, H 46 F^

1912

81.5

13 days

5th day of test

Fi H 46 P,

1912

91.5

9 days

6th day of test

F, H 47 P,o

1912

94.0

8 days

6th day of test

Fi H 47 F,

1912

86.0

9 days

6th day of test

68/07

1909

86.0

3 days

8th day of test

22/07

1909

87.0

3 days

8th day of test

H5

1909

92.0

4 days

8th day of test

H15

1909

70.0

4 days

8th day of test

30/06

1909

87.0

11 days

15th day of test

22/07

1909

87.0

3 days

8th day of test

R H 23 P31

P.5

1911

88.5

10 days

16th day of test

F, H 23 F,,

F,,

1911

95.5

8 days

12th day of test

F, XI 24 P34

P«,

1911

88.0

9 days

9th day of test

F, H 24 P3,

P.3

1911

76.5

11 days

11th day of test

F, H 24 Pb

F,

1911

25.0

12 days

20th day of test

F, H 24 P3,

P.0

1911

33.0

12 days

11th day of test

F„ H 24 Pe

Ps

1911

98.0

12 days

15th day of test

F3 H 24 P3,

,F,,

P2 1912

98.5

9 days

8th day of test

F3 H 24 P,,

,P..

P, 1912

93.5

9 days

9th day of test

78/05

1909

95.0

3 days

11th day of test

72/05

1909

93.5

4 days

6th day of test

F, H 7 Pi

1909

77.0

4 days

7th day of test

F, H 8 Pi

1909

97.5

6 days

7th day of test

* Up to and including this record the table is based upon
article (cf. Goodspeed, I.e., p. 216), except "78/05 1909 (1914
I (p. 235).

results given in a previous
)," which is taken from table

246 University of California Puhlications in Botany [Vol. 5

extent of really significant germination is approximately the same.
78/05 represents the parent of the hybrid H 8. A corresponding
situation holds for the seed of the F^ .V. rustica hybrids. Thus
H 47 and F^ H 47 P20 and P^ correspond in their manner of germi-
nation to 17/07, which was the female parent in the cross. Simi-
larly. H 46 and F^ H 46 P,„ show the extended period of germination
which is characteristic of 16/07, the female parent of the cross. F^
H 46 P-. on the other hand, compares more closely in its germination
with 17/07, H 47 and F, IT 47 P., and P.. F^ H 46 P, and F^ H 47
Poo shoAV a relatively high percentage of total germination, while F^
H 46 Po„ and F^ H 47 P^ show a relatively low percentage.

Tables IV and V exhibit the germination of 30/06 and 22/07 and
the seed of Fo and F.j of hybrids made between them. H 23 represents
the cross 30/06 X 22/07, and H 24 its reciprocal. The seed resulting
from the cross-pollinations and the seed from Fj plants were not avail-
able. As seen in Table I and Table IV, the seed of 30/06 has a
characteristically extended period throughout which germination con-
tinues to take place. This fact may have led to the statement made
by Setchell (1912, p. 8) concerning the "poor germinating power"
of this X. Tahacum variety. If under the most favorable conditions
significant amounts of germination are taking place only after nearly
three weeks in the germinating case, the viability of such seed sown
in soil would have appeared to be low, especially as most of the other
N. Tahacum varieties complete their germination in less than two
weeks.

The F, and F^ seed of H 23 and H 24 are rather distinctly differen-
tiated among themselves in a number of ways. It is characteristic of
the parent 22/07 to have a limited duration of significant germination
(cf. Goodspeed, I.e., p. 210), which is in contrast to the extended period
of germination characteristic of the other parent, 30/06 (Table I).
Thus the day upon which maximum germination takes place occurs
in the case of 22/07 relatively early in the test, while in the case of
30/06 it occurs relatively late. The seed of F, II 23 F., P„,, F, H 23
P31 Poo, and Fo H 24 P^ Po in a general way parallels 30/06 in these
respects, while the seed of F, H 23 Po^ Po^, F3 H 24 P.,, P.,;. P^, and
F3 H 24 Pi3 P04 Pi corresponds more nearly to 22/07. Similarly the
seed of Fg H 24 P34 P03 occupies roughly an intermediate position be-
tween 22/07 and 30/06, while within the germinating period of three
weeks the seed of F, H 24 Pg Po and Fo H 24 Pg^ P^o germinated only
25 per cent and 33 per cent respectively and the period during which

i^^5] Goodspeed: Germination of Tobacco Seed 247

germination probably would have continued would have considerably
exceeded even the extended period characteristic of 30/06.

The germination of hybrid seed was again undertaken this past
year partly in the expectation that the Fo, F^, and F^ seed might give
some evidence of such segregation as was observed to take place among
the plants grown from this seed. Thus it seemed possible that of the
seed produced by a given F., plant a distinct portion might germinate
early in the germination test and other portions have maxima of germi-
nation on later dates. It was then planned to grow separately plants
from the seed that germinated in considerable amounts at distinct
intervals in the test. Such groups of plants would be expected to be
similar within themselves and distinct from other groups. It is evi-
dent that seed of the various pure lines of Nicotiana described in this
and the previous report either complete their germination within three
or four days with little or no scattering germination before or after
this period of maximum germination, or that a few seeds germinate
early in the test and their number increases on succeeding days until
the maximum is reached, after which there is a corresponding gradual
decrease in the number that germinate until germination is at an end.
In only one case, 72/05, are there two unconnected maxima of ger-
mination, and in this case the corresponding situation evidenced by
the seed of F^ H 46 was assigned to the influence of this 72/05 parent.
The germination of the Fg and F^ seeds of H 46 and H 47 (tables IV
and V) realize, in some degree, the expected differentiation among the
seeds produced by hybrid plants of F^ and later generations. F^ H 24
P34 P23 and F3 H 23 P^g P04 Pi, for example, show breaks in the con-
tinuity of germination which are hardly as distinct in the germination
of any of the pure lines of Nicotiana tested with the exception of the
peculiar germination of N. acuminata varieties elsewhere noted (1913,
pp. 207 and 210). The evidence did not, however, seem sufficiently
conclusive to make it desirable to grow plants from the seedlings
produced at different periods during the germination tests.

248 Vniversity of California Puhlications in Botany [Vol.5

SUMMARY

The sum total of the evidence at hand concerning the germination
of hybrid vs. parental seed leaves no doubt that different plants
of F^, Fo, and F. produce seed the germination of which is signifi-
cantly differentiated as to the total amount of the seed that will ger-
minate, or as to the length of time during which germination takes
place, or as to the period, during the extent of the test, within which
the maximum amount of germination occurs. Further, there is evi-
dence that among the seeds of a single F, or Fg plant a portion have
a characteristic period during which they germinate, which is distinct
from the period characteristic of another group of the same seed.
The suggestion is made in this connection that if the plants grown
from the seeds which germinated most heavily at one period were
kept distinct from those resulting from seed with a different maxi-
mum of germination the plants within each group would correspond
one to another in their inheritance of certain characters. Certainly
the results indicate that care must be taken in pricking out seedlings
from the seed pans not to discriminate in favor of the larger seedlings
if the resulting plants are to exhibit a representative progeny of the
parent individual (cf. Goodspeed, 1912, p. 111). Unfortunately our
facilities are such that the germination, under controlled conditions,
of large quantities of seed is not possible, nor is sufficient space avail-
able for growing the number of plants necessary to give final evidence
on this subject. Finally, the F^ seed from reciprocal crosses has been
shown to differ with reference to its germination. In this connection,
either the amount of total germinaion, or the extent of the germinating
period, or the days of maximum germination peculiar to one parent
have been shown also to be characteristic of the cross-pollinated seed
which it bore.

Transmitted April 8, 1915.

LITERATURE CITED

Goodspeed, T. H.

1912. Quantitative studies of inheritance in Nicotiana hybrids. Univ. Calif.

Publ. Bot., vol. 5, no. 2.

1913. Notes on the germination of Tobacco seed. Ihid., vol. 5, no. 5.
Setchell, W. a.

1912. Studies in Nicotiana, I. Ihid., vol. 5, no. 1.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 8, pp. 249-272, plate 35 Issued July 21, 1915

PARTHENOGENESIS, PARTHENOCARPY AND
PHENOSPERMY IN NICOTIAN A

WBW y,
BY •OT/^r^•f ■ ,

THOMAS HARPEE GOODSPEED

• aKOC;.'-

Following the publication in 1909 of an article by Mrs. K. H
Thomas on "Parthenogenesis in Nicotiana,'' the validity of her re-
sults— the production of parthenogenetic seed without difficulty in
species and hybrids of Nicotiana — has been called in question by
a number of investigators who have either made an exhaustive investi-
gation of the subject as a special problem or have included a con-
sideration of it as a preface to their general breeding experiments
(cf. Wellington, 1913, Howard, 1913, Hayes and Beinhart, 1914).
So far as I know, how^ever, no one has attempted to investigate the
behavior of the strains of tobacco which Mrs. Thomas actually em-
ployed in the experiments which she described. The present com-
munication details experiments performed on a variety of Nicotiana
Tahacum, the seed of which was obtained from Mrs. Thomas. From
over 800 castrations and mutilations of buds on the plants raised
from this imported seed, a little normally matured and viable seed
was obtained. In over 100 cases, involving almost 200 flowers, such
treated buds yielded full capsules of seed which was practically normal .
in appearance but which consisted, in almost all cases, of empty
seed-coats only. This latter situation introduces the possibility that
after one or two years additional cultivation in our soil and climate,
the undoubted parthenocarpy of the first year, which was accompanied
by the production of much "abortive" seed, may be increased to, and
accompanied by, a more general parthenogenesis than was found this
past year.

250 University of California Publications in Botany ["^^ol. 5

A complete and careful reading of Mrs. Thomas' original paper
will go far toward convincing anyone that the occurrence of par-
thenogenesis as reported for her cultures «^f Xicotiana is not wholly
the result of errors in technique and manipulation. Wellington
{loc. cit., p. 288) makes the obvious suggestion that Mrs. Thomas
failed to notice adventitious buds which so frequently develop along
with the castrated buds under the bag in Xicotiana. Thus he feels
that the seed she found was produced not by the castrated flowers
but by untreated flowers from adventitious buds which had been
originally overlooked. ^Irs. Thomas' report of her experiments
certainly leaves much to be desired so far as essential, descriptive
detail is concerned. One is. however, convinced that the ordinary
precautions to prevent contamination were observed and that noth-
ing imperfect or unusual in the method of sterilizing the instruments
or trimming or bagging the inflorescences can be claimed. Further,
Mrs. Thomas definitely states in her type description of technique
that she opened a bag ten days after the castration and pinched off
the "one or two tiny buds which were sprouting" alongside of the
castrated flowers which had in that time "set seed" (Thomas, loc.
cit., p. 2). She thus appreciated the fact that in the ready produc-
tion of adventitious buds there was a source of error for her experi-
ments. The fact that approximately an equivalent length of time
is necessary as well for the development of an open flower from a
bud as for the maturing and shedding of seed from an open flower,
makes it evident that at least a week and probably three times that
length of time would have intervened between the ripening of the
seed from castrated flowers and from overlooked, untreated flowers.
It is almost inconceivable that ]\Irs. Thomas could have overlooked one
or a number of flowers which would probably have been fully open
at the time she would have expected the ripened capsules or seed
from the castrated flowers to be ready for removal from the plant.
Wellington {loc. cit.) also calls attention to the fact that "both
self-fertilized and parthenogenetic blossoms produce offspring true
to the mother species; and consequently an error, if it did occur,
could not be detected." This statement should have little signifi-
cance for ]\Irs. Thomas' experiments in that she found seed parthe-
nogenetically produced on five distinct hybrid groups in F, and ¥._..
In such material parthenogenetic and self-fertilized seed should,
according to current views on heredity, give different offspring.

1915] Goodspeed: Parthenogenesis, Parthenocarpy, Phenospernuj 251

However, she makes the following rather ambiguous remark in des-
cribing these same experiments in another publication (1913). "La
Parthenogenese on Apogamie pent se produire dans plusieurs especes
ou varietes de Nicotiana. Les graines parthenogenetiques semees
reproduiseni identiquement I'espece ou la variete, ou bien, si ces
graines sont obtenues comme resultat d'un croisement en F^ ou F.,
la segregation attendue dans la couleur des fleurs se produit. ' ' Bate-
son, also, has confirmed Mrs. Thomas' results for the N. Tahacum
variety which she employed in her experiments (cf. Bateson, 1913).

IMrs. Thomas, at my request, was kind enough to send me seed
of the "Nic. tahaccnm Cuba" which is referred to in her paper
(p. 2). I take the liberty of quoting extracts from a letter of ]\Irs.
Thomas' which describes the origin of the seed and adds certain
details of interest. "Since then [the appearance of her original
paper in the Mendel Journal] I have every season produced parthe-
nogenetic seed from one or more Nicotiana, though the conditions
for growing the plants here [Moyles Court, Ringwood] are not so
favorable as at Creech ( ?) Grange, Wareham, where I first made trials
for parthenogenesis and succeeded in so many varieties." The seed
which I obtained from Mrs. Thomas was one capsule of "the original
seed gathered in the Garden of Casa Loring at Malaga in 1908."
In 1913 this original seed "produced two or three hundred plants"
in Mrs. Thomas' garden. Her letter further states that she uses
" unperf orated wax-paper bags for the protection and very young
buds for castration" and that parthenogenesis had been found for
"the poppy and a variety of Delphinium as well as Oenothera hiennis
and parthenocarpy in many plants which fail to ripen their seed."
Further details as to the origin of "Xic. tabaccum Cuba" are given
in Mrs. Thomas' paper (1909, p. 2; cf. Bateson, 1913).

The record of the germination tests with this seed is unfortu-
nately missing, but no difficulty was experienced in obtaining 95
plants in the field this past season (191-4) from a small sowing
of seed.

Mrs. Thomas thus describes ".Y/c. fahaccuni Cuba:"

The plant is taller than most other N. iahaccums, and is 6i/4 to 7 ft. in
height, and the stems are very thick; it flowers at first in a terminal cluster
and afterwards axially. The limb and tube are pure white; the corolla is some-
times four-petalled with four stamens, sometimes five-petalled with five stamens,
and both forms are found on the same plant. It is a freely pollinating plant,
for under protection from insects it will seed every blossom.

252 University of California PuUications in Botany [Vol. 5

The average height of the 95 plants grown in our cultures this past
year was approximately 2 m., the variation in height having extremes
at approximately 1.5 and 3 m. The average number of leaves was
33 and the range of variation from 31 to 37, while the number of
laterals to the last significant leaf was 17 with a range from 11 to 37.
The stand was remarkably uniform and compared favorably in this
regard with other cultures of N. Tahacum varieties which have been
grown in the pure line for ten years. The flowers are borne in
great abundance, at first from the terminal panicle and later from
the many flowering laterals. In our cultures, the" flowers were not
"pure white" but a greenish white for the tube and a dull white
with a suggestion of greenish for the limb. The color is ''white"
when compared with another white-flowered A". Tahacum variety
grown in our cultures for some years — i.e.. "White Tobacco," U. C.
B. G. 30/06 (cf. Setchell, 1912. p. 7)— but cannot be called white
in the sense that X. sylvestris Speg. and Comes is a white-flowered
tobacco. The length of the corolla tube will average approximately
45 mm. and the diameter of the limb 25 mm. The corolla tube is
slender and the infundibulum slightly swollen. The limb is broadly
and shallowly lobed with the lobes unpointed. The leaves are large ;
the average length of the fourth leaf up being 49 cm. and its
greatest breadth 24 cm. Its shape is elliptical lanceolate, broadly and
decurrently auriculate at the base, with the auricles equal and broadly
acuminate at the tip. A photograph of one of the plants not used
in the experiments until late in the season is appended (plate 35).
As noted by Mrs. Thomas, there is a striking variation in the num-
ber of flower parts. I found a number of three-parted flowers and
at the opening of the flowering season almost equal numbers of
four and five-parted flowers. Toward the end of the flowering season
five-parted flowers predominate. Throughout this report the name
given by Mrs. Thomas in her original paper — i.e., "Nic. tahaccum
Cuba" — is employed. In the University of California Botanical
Garden the plant number is 200/14.

Three points were borne prominently in mind in planning the
carrying out of experiments to test for the occurrence of partheno-
genesis^ in these plants. In the first place, it seemed essential that

1 Lacking the necessary definite cj'tological evidence, the term partheno-
genesis is throughout employed in a more or less unrestricted sense and as
equivalent to the production of normallv matured, viable seed without pollina-
tion (cf. Winkler, 1908, and Coulter, 1914, p. 119.)

191-5] Goodspeed: Parthenogenesis, Parthenocarpy, Phenospermy 253

as much data as possible be accumulated concerning the condition
of the bud to be treated and the condition of the plant at the time
of treatment. Thus the length of each bud at the time of castration
or mutilation was determined and recorded and the date when the
first flowers opened was noted for every plant. These data give
a basis for comparison as to the "age" of the plants at the time of
treatment. The maximum length of unopened buds was 49 mm. —
the measurement being taken from the point of union of the pedicel
and calyx to the tips of the folded corolla lobes. As the tightly folded
corolla lobes begin to open back, the anthers open, and I have rarely
found a bud unopened and less than 48 mm. long in which pollen was
being shed. The length of the buds treated seemed to be the only
reliable method of distinguishing between younger and older buds.
In these experiments of the first year it was desired only to deter-
mine whether the age of the bud when treated was significant for
the production of parthenogenesis or parthenocarpy. It seemed also
desirable that the position on the plant of the bud to be treated
should be determined. Thus the records were so kept that it is
possible to state whether the castration or mutilation was made
upon the terminal inflorescence, on one of the four or five "bald
suckers," or on some one of the lower laterals. These data are in
a sense supplementary to those that describe the age of the plant,
since the lower leafy laterals were in flower later than the terminal
inflorescence or the bald suckers. The number of the flower parts
was also determined in each case, since it seemed at least possible
that the four-parted flowers might give results somewhat different
from the more normally five-parted flowers.

The second point which was considered to be essential with refer-
ence to these experiments had to do with providing all possible checks
upon the treatment given the buds. All doubt as to whether or not
the various operations had been correctly carried out can be eliminated
by saving in every bag all the flower parts. This is not easy to do
when the bag must be opened to pick off adventitious buds, but
it is, to my mind, an absolute necessity for any sure interpretation
of results in such work. In the case of the castrations and mutila-
tions tabulated below the corollas of the flowers originally treated
were in every case available for examination when the seed was
cleaned (Goodspeed, 1912, p. 129) and again when it was sown. Every
corolla ^\•as examined under the dissecting microscope to determine

254 University of California Publications in Botany [Vol.5

whether or not the castration had been complete. This examination
showed that, of over 800 castrations, in only one case had anthers
been overlooked. Two anthers were present on the withered corollas
from the castration of two buds on plant 25 and, as will be seen,
a fair proportion of good seed resulted (cf. table 1). The corollas
are, in most cases, still available for examination in the seed packets
together with the seed not sown.

The third essential point had to do with the technique and
manipulation concerned in treating the buds. For any one familiar
with the technique of making hybrids through cross-pollination the
essential precautions to prevent contamination by foreign pollen be-
come second nature. The important point, in addition to this most
essential one, in such operations is the delicacy with which the manip-
ulations can be performed to prevent injury to the flower parts not
to be treated. The profusion of flowering laterals on the plants used
in the experiments herein described made it necessary to cut away
masses of flowers, from other inflorescences, near the bud before it
could be operated upon. In a certain number of cases this was
not carefully enough done and the close proximity of flowers about
the bud after its castration made it seem best to discard it. A
number of such doubtful castrations were, however, bagged and in
one case undoubtedly self-pollinated seed in fair proportion was pro-
duced— i.e., plant 14 (table 1). The buds were, with the exception
of the smallest, slightly split open along the upper third of the corolla
tube and the castrations or mutilations performed through this slight
opening, which was not sufficient in extent to expose the stigma.
If. in picking out the anthers, the stigma was inadvertently touched
by the forceps the bud was discarded.

The treatment given the 800 buds employed was of three types only.
The first consisted of simple emasculation of the flower by picking
off the anthers of the bud near the tops of the filaments. The second
involved the removal of the stigma as well as the anthers. The
stigma in such cases was pinched off with the forceps, before pick-
ing out the anthers, at the very top of the style. In the third type
of treatment the stigma was pinched off, in the above manner, but
the anthers were allowed to remain untouched. In such cases the
tip of the style, somewhat crushed, had dried down exceedingly before
any pollen could have been shed in the open flower. The last two
types of treatment will hereafter be referred to as "mutilations."

1915] Goodspeed: Parthenogenesis, Parthenocarpy, Phenospermy 255

No success attended a small number of attempts to cut Avith a razor
directly across the whole flower, severing corolla, filaments and style
(cf. Thomas, loc. cit). Such treatment caused the buds to fall within
three days. The number of simple castrations far exceeded either of
the other two types of treatment.

The plants of "Nic. tabacciim Cuba" began to flower during the
first week of September, 1914, and were still in flower, though very
feebly, early in February, 1915. The castrations and mutilations
were begun in the case of plants 1 to 75 on the day that the first
flower of the terminal inflorescence opened, or as near that date as
possible. As the plants came more fully into flower as many buds
as possible were treated. For the first month, flowers on each suc-
ceeding bald sucker were operated upon almost as soon as the first
flowers were open. Later in the season time did not permit any such
close following of the plants. The nineteen plants, 76 to 95, were
growing some fifty feet aw^ay from the rest and most of them were
left untouched until they were "beginning to go off their fullest
bloom" (Thomas, loc. cit., p. 5). These nineteen plants were set out
into the field somewhat later than the rest and came into flower
somewhat later also. When their flowers were first operated upon,
the terminal inflorescence and many of the upper laterals bore many
partially matured seed-capsules. No seed was shed from untreated,
unbagged flowers on any of the plants imtil the last week in October.

The bags which evidently contained seed were taken from the
plant at once. In practically all cases the seed had been shed from
the capsules which had opened normally. The cleaning of the seed
was done with the utmost care and I cannot feel that any contamina-
tion could have occurred in this connection. As a result of the clean-
ing, it was evident that a very considerable number o-f castrated and
mutilated flowers had given seed, a part of which was apparently
normally matured and the majority of which consisted of nothing
but empty seed-coats. It was out of the question to attempt germina-
tion tests of all the seed thus available. According to our usual method
of making such tests with tobacco seed (Goodspeed, 1913), the number
of seeds to be handled would in this case have approximated 10.000
and probably the germination of double that number would have
been found to be neces.sary. It was thus judged best to adopt the
following method for determining which of the packets of seed con-
tained only empty seed-coats and which contained any apparently

256 University of California Publications in Botany [Vol. 5

normally matured seed. From 200 to 300 .seeds were placed in a
watch glass and covered with strong Eau de Javelle. In twenty-four
hours the characteristic dark brown color of the seed-coats was bleached
out and when placed on a dark background the question as to whether
or not the seed-coats were empty could be answered at a glance. In
every case a control was made by similarly treating the selfed seed of
"Nic. tahaccum Cuba" obtained this past season. This control served
to show that the length of time for which the bleaching solution was
allowed to act was not sufficient to dissolve the endosperm and embryo
and served also as an aid in distinguishing between the normal and
abortive seed produced by the treated flowers. Although the chalky
white seed containing endosperm could be distinguished at once from
the transparent functionless seed, quantities of the bleached seed were
examined under magnification in every case. The slightest trace
of endosperm could thus be detected and by gentle pressure on the
cover-glass over the preparation the embryos of the normal seeds
could be forced out of the endosperm through the softened seed-coats.
In a number of cases seed, which according to the bleaching test con-
sisted of empty shells only, was germinated as a check upon the
method but no germination was noted at the end of three weeks. All
seed packets which were indicated by the bleaching test to contain
seed with endosperin or endosperm and embryos were also germinated.
In every case all the seed remaining in the packets was sown accord-
ing to the method elsewhere described (Goodspeed, 1913).

The following table indicates so far as possible all significant
facts concerning the 112 treatments of flowers which yielded abortive
or normal seed, together with the proportions of seed with endosperm
and embryos and seed with endosperm only.

1915] Goodspeed: Parthenogenesis, Parthenocarpy, Phenospermy 257

TABLE 1

5; „ Number of Position on Per cent of

% s Treatment ^i stamens plant seeds with

o S , '•- . „ .

u IS a

'" Zl "" — -= - ^ .

0 "!? o ■t^t^f'SiS- <uj=a c a c'^= ^. s.~ a >■•

« ° ° 2 2a-Sf x§ -S =a S-, i .Si S >^-5 ^a &e

I 11 ^ 2 g-S^ .S.y a g I 3 ?« -^ ^^ ^-^ ^

1 9/20 9/24 X 3 28* 1 2 x 0 0

10/2 X 1 32 .... 1 .... 4th 1 0

11/2 X 1 27 1 9th 0 0

2 9/24 10/2 X 1 34 .... 1 .... 2nd 0 0

3 10/1 10/21 X 1 45 1 .... X 0 0

10/21 .... X .... 1 30 .... 1 .... 1st 0 0

10/21 .... X .... 1 36 .... 1 5th 3 0

4 9/18 10/21 X 2 33t .... 2 5th 0 0

5 9/17 9/18 X 3 28i- .... 3 x 0 0

6 9/15 9/15 X 5 42t 5 .... x 0 0

9/25 X 1 35 .... 1 .... 3rd 0 0

10/30 X 1 21 .... 1 .... 4th 0 0

7 9/12 9/12 X 4 31t 3 1 x 0 0

8 9/8 9/25 X 2 38t 2 4th 0 0

9/25 X 2 48t 11 .- 3rd 0 0

9 9/8 9/18 X 3 43t 2 1 .... 2iid 0 0

II 9/12 9/12 X 1 42 .... 1 X 0 0

9/26 X 4 31+ 4 1st 0 0

9/26 X 2 28t .... 2 .... 2nd 0 0

9/26 X 1 26 1 4th 0 0

10/30 ? 1 46 .... 1 6th 0 0

14 9/8 9/8 X 4 25t 3 1 x 0 0

9/26 ? 2 46t 2 1st 34 0

17 9/13 9/15 X 1 48 .... 1 x 0 0

18 9/22 9/26 x 3 41t 12 x 0 0

20 9/17 9/] 8 X 2 33t 2 .... x 0 0

9/26 X 1 39 .... 1 .... 1st 0 0

21 9/25 9/26 x 3 30i 2 1 x 0 0

9/26 X 1 41 1 2nd 0 0

9/26<^> X 1 38 .... 1 4th 0 0

23 9/17 9/26 x 2 40t 11 .- 1st 0 0

24 9/24 9/26 x 4 27t 3 1 x 0 0

9/26 x 1 37 .... 1 .- 1st 0 0

9/29 X 1 32 1 4th 0 0

9/29 X 1 28 1 5th 0 0

25 9/11 9/26 ? 2 48t 2 1st 51 0

* all buds. 7 both buds. t buds averaged.

'Flowers with 4 stamens were, with very few exceptions, four-partod throughout
and similarly for the flowers with 5 stamens.

= By the use of the word "averaged" it is, in all cases, meant that all the buds
treated were within 2 mm. either larger or smaller than the size stated.

258 University of California Publications in Botany [Vol. 5

Table 1 — {Continued)

OS

o
«

O

0)

Q

a

IS

a

■*^

c3

V

u

o

o

5

u

6

28

9/8

9/29

X

29

9/26

9/29

X

32
33

9/7
9/17

9/29
9/18

X
X

34

9/10

9/29

X

36

9/16

9/18

X

38

9/25

9/29
9/29
9/29
9/29^

X
X
X

40

9/20

9/24
9/29

X
X

41

9/13

9/15
9/29
9/29

X
X
X

43

9/16

9/18
9/29

X
X

44

9/18

9/29
9/29<^'

X
X

45

9/20

9/21
10/1
10/1

X
X
X

49

9/21

9/24

X

50

10/30

10/30

X

53

10/1

10/1

X

56 9/28
Axis No. 1
(56) 9/30
Axis No. 2

10/1
10/1

X
X

58

9/30

10/1
10/1
10/1
10/1

X
X
X
X

59

9/29

10/1

X

60

9/15

10/1

X

61

9/19

10/1
1 buds.

X

tbotl

^ ^ ^ Number of Position on Per cent of

Ireatment ^ stamens plant seeds with

ie >• Z ~ . j: S s <= a

J- ^— — « -^ r. K - - — .- - -^r r^

■- c Si •- VS w 'i -^ -^ o t; s c -^ c " a

Cc3oP-iK ^ )J 02 02 E-i.ScQJi; hSr

2 46t 11 4tli 0 0

1 44 .... 1 .... 1st 0 0

2 40t .... 1 ,5th 0 0

4 30t= .... 4 X 0 0

1 43 .... 1 .... 1st 2 0

1 48 .... 1 X 7 0

2 42t .... 2 X 0 0

1 42 1 1st 0 0

1 43 1 2nd 0 0

X 1 — — _ .... 3rd 0 0

4 37} 3 1 X 0 0

1 45 1 2iid 0 0

2 41t 2 .... X 0 0

1 43 .... 1 3rd 0 0

3 41} 2 1 4th 0 0

3 38} 3 .... X 0 0

3 30} 2 1 3rd 0 0

1 43 .... 1 .... 1st 0 0

2 32t 2 2iid 0 0

3 39} 1 2 X 0 0

1 47 1 1st 0 0

1 35 1 , 2nd 0 0

3 24} 2 1 X 0 0

2 31t 11 X 0 0

3 36} 3 .... X 0 0

3 41} 2 1 X 0 0

3 24} 2 1 X 0 0

3 30} 3 .... X 0 0

1 27 1 1st 0 0

1 27 1 3rd 0 0

2 46} 1 4th 0 0

2 43} 2 .... X 0 0

1 49 1 3rd 0 0

2 28t 11 ..- 1st 0 0

} buds averaged.

' Flowers with 4 stamens were, with very few exceptions, four-parted throughout
and similarly for the flowers with 5 stamens.

-By the use of the word "averaged" it is, in all cases, meant that all the buds

treated were within 2 mm. either larger or smaller than the size stated.

^ In this case, the only instance of such treatment, a large bud was allowed to

open and shed pollen normally and two hours after the opening of the anthers the
stigma alone was pinched off.

1915] Goodspeed: Parthenogenesis, Parthenocarpu, Phenospermy 259

Table 1 — (Concluded)

53 ^ Number of Position on Per cent of

te a Treatment ^ stamens plant seeds with

O 2 / '^ \ "3 =« , ''' N , * . A

iH w S ' ' 3 -a ' ^ ' ^ ' v

0) -^ — J 3 0)

•2 £ S a fc >. ^ J= . i: S g P a

^ " ii i^ ^ S -so t^ S 2 2 so u ojS S.

^ ° ° g So.-- ^2 -=-trc <" <!- -^JJolt.— kC S~

s

= =!ti •=■- = ~ ^ ^ ^o'g ffl O-

62 9/21 10/1 X 2 29t 1 1 x 0 0

63 9/28 10/30 x 1 27 .... 1 x 0 0

10/30 X 1 41 .... 1 .... 2nd 0 20

10/30 .... X .... 1 42 1 3rd 0 0

66 9/18 9/21 X 2 23t 2 .... x 0 0

67 9/13 9/15 X 4 24t= 3 1 x 0 6

10/1 X 3 46t .... 3 4th 0 0

76 9/27 10/13 X 1 38 1 .... x 0 0

10/13 X 1 38 .... 1 .... 3rd 0 0

78 9/26 10/13 X 1 36 1 2nd 0 0

2 0/13 X 1 30 .... 1 .... 3rd 0 0

10/13 X 1 34 1 8th 3 0

10/13 X 1 47 1 9th 0 0

10/13 X 1 47 1 10th 0 0

80 9/25 10/13 X 1 31 .... 1 .... 1st 0 0

81 10/10 11/5 X 2 42t 11 .... 5th 0 0

82 9/25 10/13 X 1 38 .... 1 x 0 0

10/13 X 1 38 .... 1 .... 5th 0 0

83 9/18 10/21 X 1 32 .... 1 .... 1st 0 0

84 9/15 10/21 X 1 32 1 5th 2 2

85 9/26 10/23 x 3 34| 3 1st 0 0

10/23 X 1 38 .... 1 .... 3rd 0 0

10/23 X 2 36t .... 2 .... 5th 0 0

10/23 X 1 29 .... 1 6th 0 0

10/23 X 1 33 .... 1 8th 0 0

86 10/8 10/24 X 1 42 .... 1 .... 1st 0 0

10/24 .... X .... 1 31 .... 1 6th 3 0

87 10/4 10/24 X 1 47 .... 1 .... 1st 0 0

10/24 X 1 33 .... 1 .... 5th 0 0

89 9/26 10/29 x 1 24 .... 1 .... 2nd 0 0

Axis No. 1

10/29 x 1 26 .... 1 .... 4th 2 0

10/29 X 1 26 .... 1 .... 5th 0 0

10/29 X 1 35 .... 1 6th 0 0

(89) 10/29 X 1 41 .... 1 .... 1st 0 0

Axis No. 2

10/29 X 1 41 1 2nd 2 0

10/29 X 1 40 .... 1 .... 3rd 0 0

10/29 X 1 35 .... 1 .... 4th 0 0

10/29 X 1 29 .... 1 5th 0 0

92 9/28 10/29 x 1 31 .... 1 .... 3rd 0 0

95 9/29 11/5 X 1 46 .... 1 .... 1st 0 0

1 1/5 X 2 46t • .... 2 .... 4th 0 0

t both buds. t buds averaged.

' Flowers with 4 stamens were, with very few exceptions, four-parted throughout
and similarly for the flowers with 5 stamens.

-By the use of the word "averaged" it is, in all cases, meant that all the buds
treated were within 2 mm. either larger or smaller than the size stated.

260

University of California Publications in Botany [Vol. 5

Table 2 which follows gives the length and breadth of the seed of
a few of the plants mentioned in table 1. The averages are based
on approximately 20 measurements in each case. For two of the
castrations which produced some normally matured seed (plants 1-4
and 36. below) measurements are given for the length and breadth
of the normal seeds and also of the abortive seed. Many of the seeds
with ' ' empty seed-coats ' ' were of full size, the figures given represent-
ing average sizes. It was possible to select from the abortive seed of
one capsule over 75 seeds which were indistinguishable in size from
the seed resulting from self-fertilization.

TABLE 2

Plant
No. Date

16

Treatment
self-fertilized

14 9/26 castrate(i(?)

9/26 castrated (?)

21 9/26<='> castrated

36 9/] 8 castrated
9/18 castrated

44 9/29<^> castrated

Average Average

length, breadth,

mm. mm.

0.39

Remarks

0.2.J Normal seeds that germinated over
80 per cent.

0.37 0.24 Castration judged to be contami-

nated (cf. p. 254) — seeds with
endosperm and embryos.

0.26 0.20 Seeds of same doubtful castration

— empty seed-coats only.

0.26 0.19 Empty seed-coats only.

0.38 0.25 Seeds with endosperm and embryos.

0.27 0.21 Empty seed-coats only.

0.27 0.19 Empty seed-cor.ts only.

It is thus possible to state that of some 800 castrations and mutila-
tions divided approximately evenly between the 95 plants of ''Nic.
tahaccuni Cuba" grown this past year, there were 112 instances,
involving nearly 200 flowers, in which one or more fruits developed
to normal size and matured seed, almost all of which was normal in
appearance, though small in size, and a small proportion of which
was normal in every way including the presence of endosperm and
embryos.

During the past ten years a very considerable collection of Nic-
otiana species and varieties has been grown in the pure line in the
Botanical Garden of the University of California. They have been
fully described elsewhere (Setchell, 1912). Every year two or three
plants of each of the species and varieties listed below have l^e^^n

1915] Goodspeed: Parthenogenesis, Parthenocarpy, Phenospermy 261

tested by castration and mutilation experiments for the presence of
parthenog-enesis. On the appearance of Mrs. Thomas' original paper,
Professor Setchell made an additional series of experiments to confirm
his previous observations. This past season, in connection with the
experiments detailed above on ''Nic. tabacciim Cuba," I made over
four hundred castrations of flowers of N. Tabacum var. macrophylla,
N. angustifolia, K. Tabacum "Maryland" and N. sylvestris. The
number of plants in each case was twenty-five and the castrations were
made just as the plants were "going out of their first bloom," which,
according to Mrs. Thomas, is the most favorable period for the pro-
duction of parthenogenetic seed. The plants were also so thoroughly
cut back that the castrated flowers were the only ones left on the
plant ; all maturing and mature seed capsules were also removed. This
treatment, as noted by Howard (1913 p. 41) and in our cultures
also, usually induces heav}^ and rapid seed production. In addition,
the occurrence of parthenogenesis has continually been tested for
in connection with the making of a very considerable number of
hybrids between many of the species and varieties listed below.
Whenever a castration, preliminary to cross-pollination, is made, an-
other bud or two on a difi'erent part of the plant is also castrated and
left unpollinated at the time of making the cross. We may further
add to this summary, as being significant, the hybrids between N.
sylvestris and various N. Tahacum varieties. The F^ hybrids are
completely self-sterile since, in our cultures of them, no normal pollen
is produced. Over 500 bag'gings have been made of F^ flowers and
a great variety of efl^orts have been made to stimulate seed production
according to the methods described by Wellington (1913). In no
case did parthenocarpy or parthenogenesis result. It is important to
note in this connection that ]\Irs. Thomas reports an F^ hybrid between
''A^. sylvestris and N. tabaccum Cuba" and an F,, of the cross "N.
sylvestris by N. affinis" as producing parthenogenetic seed. I have
never been able to make the latter hybrid successfully and have yet to
see a strictly fertile F^ species hybrid involving N. sylvestris as a
parent. In our cultures the many hybrids that have been made have
never given any evidence of the production of parthenog'enetic or
apogamous seed in the sense that hybrids have bred true to the maternal
parent from F^ on through later generations.

262 University of California PuhUcations in Botany [Vol. 5

Partial List op Species and Varieties Used in Testing for Parthenogenesis

A description of them is to be found in Professor Setchell's paper (1912).
Nicotiana Tabacum "Brazilian" Nicotiana rustica (seven varieties)

Nieotiana Tabacum "Cavala" Nicotiana Langsdorfii

Nicotiana Tabacum "Maryland" Nicotiana paniculata

Nicotiana Tabacum var. cah-cina Nicotiana alata

(Nicotiana Tabacum) "White Tobacco" Nicotiana acuminata (three varieties)
Nicotiana Tabacum var. macrophylla Nicotiana Bigelovii

Nicotiana angustifolia Nicotiana sylvestris

Nicotiana Tabacum var. macrophylla Nicotiana tomentosa

purpurea
"Nic. tabaecum Cuba"- Nicotiana glauea

* Described in this paper but not in Setchell (1912).

The total number of flowers involved in these various efforts to
produce parthenogenetic seed is well over 1500 and the number of
plants concerned over 450. In not a single instance was any seed of
any sort produced, and only very rarely did the capsules remain
attached for over two weeks and when, in a few cases, thev did
persist the result Avas a shrunken, misshapen capsule containing nothing
but the driecl-up ovules in their entirely immature form. The falling
of castrated flowers in such experiments on Nicotiana species is very
striking. Howard (1913) well describes the difference in this respect
between the result of self- or cross-pollination and the result of
castration :

A great difference was found between the capsules formed from castrated
flowers and those formed by ordinary pollination. In the latter case the
capsule remains firmly attached to the plant. No difficulty is experienced in
removing or replacing bags, and the peduncle would have to be broken before
the capsule could be removed. This is always the case whether the flowers be
self- or cross-pollinated. The capsules of the castrated flowers, on the other
hand, although they also become swollen at first and simulated the fertilized
ones, were very easily detached from the plant. It was exceedingly difficult
to remove the bags, which finally had to be cut away carefully. The capsules
thus exposed to the air were easily blown or knocked off.

Wellington (1913) has given a detailed summary of the literature
dealing with the problems of parthenogenesis on the plant side, and
no further review of it need be given here. I wish, however, to call
attention to two additional references which are of particular interest
here. First the experiments of Howard referred to above, which are
detailed as a preface to the description of breeding experiments with
51 varieties of N. Tahacum. The experiments in castration and muti-
lation included considerably over 5000 flowers and some apparently
parthenogenetic seed was produced. Second, the experiments of
Hartley (1902) with tobacco, which are especially important in con-

1915] Goodspeed: Parthenogenesis, Partlienocarpy, Phenospermy 263

nection Avith the efforts of Wellington to stimulate the production of
parthenogenesis and parthenocarpy. These two references will be
mentioned below in greater detail.

Viable seed supposedly parthenogenetically produced has been
obtained by Professor East in the case of the following crosses:
N. panicidata X N- alata var. grandiflora, N. rustica X N. Tahacum,
N. Tahacum X ^- Bigelovii, N. panicidata X ^- Langsdorfii, N. pan-
icidata X ^ ■ longiflora, N. panicidata X N. Forgetiana, N. Bigelovii X
N. sylvestris, and N. Tahacum var. lanciflora X ^- alata var. grandi-
flora (Wellington, 1913, and East, 1910). The supposition that these
cross-pollinations induced, by the "extraordinary irritation of foreign
pollen" (East, loc. cit.), the production of apogamic or partheno-
genetic seed was suggested by the fact that certain of the seeds pro-
duced plants "like the mother species and also true hybrids" and
that certain of them gave plants "like the mother species and no
true hybrids" and that certain others of them gave "no true hybrids
on one occasion but did produce true hybrids on other occasions"
(Wellington loc. cit.). Species crosses made by Gartner also gave
seed in a few eases that produced the mother species and also true
hybrids (Burbridge, 1877). This phenomenon has apparently occurred
a sufficiently large number of times to preclude the possibility that
errors in technique were the cause. Wellington in his experiments
produced ' ' abortive seed probably without embryos ' ' by singeing young
buds, by exposing young plants to chloroform gas, "cutting away a
portion of the pistil and pollinating the stub both with and without
the accompaniment of a germinative fluid" and by "shortening the
pistils (?) of a flower and grafting the stigma end of another pistil
on to the stub and pollinating the same." In only one doubtful case
was seed produced "by the simple methods of emasculation and
decapitation of blossoms."

As a result of the very numerous castration experiments of Howard
(loc. cit. 1910) on a plant of N. Tahacum — Type 9 (cf. Howard and
Howard, 1910) — one castrated flower produced a capsule "the seed of
which germinated and produced plants similar to type 9." "In 1911,
again, on a plant of type 9, one capsule containing seed was found in
about 100 castrated flowers." Three other capsules in every way
normally matured and apparently containing seed were produced, in
Howard 's experiments, as a result of castrating flowers of another type
of N. Tahacum. These capsules were, however, lost before any definite
determinations were made as to their contents.

264 University of California Puhlications in Botany [Vol.5

Hartley (1902, p. 15) makes the following statement concerning
certain of his interesting experiments on floAvers of "Cuban Tobacco
(Nicotiana tahaccum)" : "Of 60 emasculated flowers that had their
stigmas covered with substances other than pollen, 1-1 set fruits,
while of 20 that were emasculated but never pollinated, 2 set fruits. ' '
Continuing, he says:

As a general thing the capsules, resulting from flowers that were not pol-
linated, and likewise those resulting from flowers whose stigmas were covered
with some substance other than pollen, contained only small, compressed,
undeveloped seeds, but the two pods obtained ... by treating the fully
receptive stigmas with magnesium sulphate contained some spherical seeds of
almost full size which looked like good seeds, but when cut into proved to be
hollow spheres.

]Mrs. Thomas' results have been detailed elsewhere in this paper.
Summarizing these previous efforts to obtain parthenogenetic seed
in Nicotiana, we may state that of the many thousands of castrations
and mutilations of flowers concerned in all the experiments above
noted, only two capsules containing viable seeds were produced. This
statement leaves out of account Mrs. Thomas' remarkable results.
In only a few cases also, and then only after artificial stimulation,
did these castrated flowers produce normal fruits. In the majority
of cases where normal fruits were thus produced, abortive seed was
formed in the mature capsules. Accompanying the general failure
of castrated and mutilated flowers to mature fruits, the early falling
of the flowers has attracted attention. It is therefore remarkable
that in the experiments, some of which are shown in table 1, there
should be a striking absence of this tendency of the castrated or
mutilated flowers to fall soon after the operation. Although over
seven times as many treated flowers fell as remained normally attached
to the plant until maturity, still, except in the case of a complete
severance of the floral organs just above the ovary, a great majority
of the treated flowers remained on the plant for a period twice or
three times as long as is normal for treated flowers of any other
species or variety of Nicotiana in our cultures. Nearly 115 treated
flowers, most of them following castration, matured normal fruits,
ripened their seed and shed it from the dehiscing capsules. In nine
of the 112 cases tabulated in table 1, some seeds of normal size and
appearance were produced. The remainder of the seed produced
in these 112 instances was less than normal size but the great maj-
ority of it was normal in appearance — small, plump seed. I have

1915] Goodspeed: PartJienogenesis, Parthenocarpy, Ph&nospermy 265

found that seed of this same size and appearance, produced occasion-
ally in our cultures of other iV. Tabacum varieties, will give up to or
over fifty per cent germination. The small seed, normal in appearance,
in almost all cases was found to consist of entirely emptj^ seed-coats.
In three cases, however, considerable amounts of endosperm could
be distinguished under magnification but, though the seeds were
carefully dissected, no trace of embrvos could be found.

I know of no special term to describe the production of seed
which appears to be normal but consists of empty seed-coats only —
i.e., the type of seed usually referred to when the word "abortive"
is used. At Professor Setchell's suggestion the term phenospermy
is proposed to cover this production of "abortive seed." The seed
produced by Wellington and Hartley as a result of stimulation fol-
lowing castration may thus be spoken of as plienospermic.

The total number of seeds, all of which were of size similar to
the self-fertilized seed of "Nic. tahaccum Cuba" and a portion of
which, after bleaching with Eau de Javelle, were seen to contain
endosperm and embryos normally formed, was approximately 50.
Unfortunately, a rather large percentage of this number was des-
troyed in the bleaching test. As the seed was shaken from the seed
packets into the watch glasses (cf. p. 256) a large part of the heavier
normal seed fell out in each case. Only 18 seeds, among those re-
maining in the seed packets which were determined by the bleach-
ing test to contain normal seed, were available for germination.
After three weeks eight of them had germinated and six seedlings
are normally developing. Over twenty germination tests of seed from
packets which gave no indication of normal seed with the bleaching
test have not shown any signs of germination. The self -fertilized seed
of ''Nic. tahaccum Cuba" gave germination tests averaging 83 per
cent after three weeks, and practically all the seeds that did not
germinate were phenospermic (cf. Thomas, 1909, p. 4).

It is worthy of note that, of the castrations and mutilations which
produced normal or phenospermic seed, approximately 30 per cent
occurred on the terminal inflorescence; 50 per cent on the terminal
inflorescence and four or five bald suckers normal to this variety,
and 20 per cent only on the lower leafy laterals. Castrations and
mutilations made within two weel« after the opening of the first
flower gave normal or phenospermic seed in 65 instances, as com-
pared with 56 instances for operations performed more than two weeks
after the opening of the first flower. There was also no significant

266 University of California Puhlications in Botany [Vol. 5

increase in successful treatments on the plants which were allowed
to "go off their fullest bloom" before starting experiments on their
flowers. In the total series of 800 experiments buds as short as
11 mm. and as long as 48 mm., were used for castration and mutila-
tion. The number of buds under 35 mm. in length which gave
fruits and seeds following treatment is almost identical with the
number of buds over 35 mm. The size of the bud to be treated has,
then, little significance for the production of fruits and seed following
castration or mutilation. Similarly, four- as compared with five-parted
flowers are not significant for the production of parthenogenetic
or phenospermic seed, since the various castration and mutilation
experiments described in table 1 involve approximately equal numbers
of the two types of flowers. However, seed containing endosperm
and embryos, or endosperm alone, seems to have resulted, in practi-
cally all cases, from the more normally formed, flve-parted flowers.
Similarly the use of a single bud on an inflorescence for treatment
seems, as was perhaps to have been expected, to have been more
efficient for the production of normal seed than the castration or
mutilation of more than one bud on an inflorescence. Of the total
800 operations less than one third involved the pinching off of the
stigma as well as emasculation. Similarly only one tenth of the total
number involved the pinching off' of the stigma only. Thus it is
significant that of the nine cases in which normally formed seeds
were produced, three should represent treatments in which the stigma
was removed. In general for the production of parthenogenetic
and phenospermic seed, simple castration seems most effective. It
seems probable that certain of the stimulating and irritating agents
used by Hartley and Wellington would be more effective for par-
thenogenesis in "Nic. tahaccum Cuba" than in the varieties which
they employed. No experiments of this sort were attempted.

I have assumed throughout that parthenogenetic seed was actually
produced in a few cases following the castration or mutilation of
flowers borne on the variety of N. Tahacum which Mrs. Thomas used
in her much more generally successful experiments concerning par-
thenogenesis in Nicotiana. If there were not a very remarkable
tendency in this iV. Taliacum variety to mature normal fruits and
phenospermic seed following castrations and mutilations of flowers,
or, on the other hand, if anything approximating full capsules of
normal seed had resulted in a number of cases from such treatment
of flowers, I should feel entirely willing to assign the production of

1915] Goodspeed: Parthenogenesis, Parthcnocarpy, PJienospermy 267

the relatively small amount of viable seed that did mature, to errors
in technique. I have attempted to show that the experiments were
planned and carried out with a full knowledge of the sources of
error and with every effort to guard against their becoming operative.
Where contamination was suspected to have occurred in the short
interval between the act of castration or mutilation and the bagging
of the treated bud, it. as noted above, was discarded in all but a few
cases. In these few cases, bags were at once put on and in table 1 is
shown the result in the three instances in which the fruits matured —
i.e., plant 11, 10/30, plant 14, 9/29 and plant 25, 9/26. In one case
nothing but phenospermic seeds were formed, and in the other two hun-
dreds of normal viable seeds. This simply means that if the viable seed,
which was produced following apparently unimpeachable treatments,
was due to chance pollination by wind, or the shaking of neighboring
flow^ers' pollen into the bud, larger amounts of viable seed should
have been present than were actually found in the nine unsuspected
cases of seed production. I cannot feel that the instruments were
non-sterile in as many as nine distinct cases. But apart from these
considerations, reference to Hartley's paper {loc. cit.) will give infor-
mation based upon experiments concerning the effect of premature
pollination which must correspond to the general observations of
anyone who has been concerned in hybridization experiments with
tobacco. Hartley found, that of buds plentifully pollinated with
mature, fresh pollen from the same plants, those pollinated more
than one day before opening matured 4 per cent of fruits which
contained no viable seed, and those pollinated one day or less than
one day before opening, matured 86 per cent of fruits which con-
tained viable seed. It is thus rather inconceivable that chance pol-
lination of small, castrated buds could have resulted in fertilization
in such a distinct number of cases. I do not think that light would
be thrown upon this particular point by delaying this report until
the maturity of the seedlings produced from the parthenogenetic
seeds, because the possibility that pollen of a foreign species was
present and thus that plants of a hybrid nature and appearance
should result, is negligible. It may, in this connection, be stated
that cross-pollination of N. Tahacum "JNIaryland" and other N.
Tabacum varieties made on "Nic. tahaccum Cuba" have given norm-
ally filled capsules of viable seed.

The facts taken together seem to indicate that three stages are
to be observed in the extent to which "Nic. tahaccum Cuba" will

268 University of Calif orma Publications in Botany [Vol. 5

mature normal seeds without pollination either accompanied by the
supposed stimulation of mutilation or not. First the production of
phenospermic seeds. Second, the production of phenospermic seeds
which contain a greater or lesser amount of cellular structure, rich in
starch and proteid, and taken to represent endosperm (cf. Woodburn,
1911, etc.). Third, the production of seed normal in appearance, con-
taining endosperm and embryos fully developed and capable of germi-
nation and initiating the growth of normal seedlings. To my mind the
production of a considerable number of parthenocarpic fruits contain-
ing phenospermic seed is the most significant result of the experiments
above described. I desire again to call attention to the iwssihility
that after one or two years of further cultivation in our cultures,
the large proportion of phenospermic seeds with or without embryos
may be lessened in favor of a greater proportion of entirely normal,
viable seeds resulting from the castration or mutilation of flowers of
"Nic. tahaccum Cuba." I feel, also, that this variety of N. Tahacum
by its rather ready parthenocarpy and phenospermy as it was grown
in our cultures this past year, and entirely apart from such cases of
parthenogenesis as were found, furnishes a partial confirmation of
Mrs. Thomas' results in similar experiments on plants of the same
variety. I fully understand that this is practically equivalent to
the statement that the difference in soil and possibly general climatic
conditions between England and California will account for the small
amount of parthenogenetic seed obtained in the experiments above
described as contrasted with the frequent and ready production of
such seed by the same plants as grown by Mrs. Thomas. Nothing
that has been said, however, must suggest that I desire to confirm
her general experimental results; results which she feels indicate
that parthenogenesis is peculiar to Nicotiana species in general. It
must, on the contrary, be emphasized that our general results point
to exactly the reverse condition and that we have no reason to suppose
that parthenogenesis has occurred in any of our previous cultures.
Speculation, also, as to the time at which and the way in which
parthenogenesis, parthenocarpy and phenospermy arise in " Nic. tabac-
cuni Cuba" must be of little significance until pertinent cytological
data can be accumulated. I have, further, no suggestion to offer, at
the present time, as to the possible origin of this Nicotiana Tabacum
variety which exhibits such marked divergence from the restricted
method of fruit and seed production peculiar to other varieties of
this species and to all other species of tobacco so far as known.

1915] Goodspeed: Parthenogenesis, Parthenocarpy, Phenospermy 269

Summary

The above report has to do primarily with a white flowered variety
of N. Tahacum the seed of which was received under the name "Nic.
tahaccum Cuba." This is the variety in which ]\Irs. R. H. Thomas
found parthenogenesis to be of such frequent occurrence.

1. Over 1500 attempts to produce partheuogenetic seed on a con-
siderable number of species and varieties of Nicotiana have yielded
entirely negative results.

2. In a considerable number of distinct hybrids made between
such Nicotiana species and varieties and grown in some cases through
five hybrid generations, no evidence has been furnished that the pos-
sible irritating and stimulating effect of cross-pollination has resulted
in the production of any partheuogenetic or apogamous seed.

3. Approximately 800 castrations and mutilations of buds borne
on plants of ^'Nic. talacctim Cuba" produced over 100 normally
matured fruits. Following the majority of these 800 castrations and
mutilations, the flowers and maturing capsules, though ultimately
they may have fallen, remained attached to the plant for much longer
periods of time than is the case in other species and varieties of
Nicotiana when similar treatment is applied.

4. In the majority of these parthenocarpic fruits empty seeds
were produced in great numbers. Some were as large as the self-
fertilized seed of the same plant, though the majority were smaller.
Few flattened or shrivelled seeds were formed.

5. For this type of seed production, either with or without pol-
lination, the term phenospermy is suggested. It is taken to be
synonymous with the terms "abortive" and "empty" that have
been elsewhere applied in describing such seeds.

6. Approximately 50 seeds were found in nine of the partheno-
carpic fruits, some of which exhibited normally matured endosperm
and embryos when the color of the seed coats was bleached out with
Eau de Javelle and some of which germinated normally and have
produced normal seedlings. Six seedlings are at present of fair
size from 18 seeds germinated.

7. A small portion of the seed from the parthenocarpic fruits was
neither partheuogenetic nor phonnspcrmic, luit contained traces of
endosperm only.

270 University of California Puhlications in Botany [Vol. 5

8. Mrs. R. H. Thomas' results are thus partially confirmed in so
far as the N. Tahaciim variety employed in her experiments is con-
cerned. All evidence at present available seems to show that par-
thenogenesis in Nicotiana is limited to this one strain of .V. Tabacum —
i.e., "Xic. tahaccum Cuba."

Transmitted March 19, 1915.

LITERATURE CITED
Bateson, W.

1913. 4th Conf. Int. Gen. Rep., p. 209 (comment upon Thomas, R. H., 1913).

BUEBRIDGE, F. W.

1877. The propagation and improvement of cultivated plants. Edinburgh and
London. (Quoted from Wellington, 1913.)

Castle, W. E.

1914. The cytological time of mutation in Tobacco. Science (n.s.), vol. 39,

no. 992, January.

Coulter, J. M.

1914. The evolution of sex in plants. Chicago.

East, E. M.

1910. The role of hybridization in plant-breeding. Pop. Sci. Monthly, vol.
77, p. 355.
Gartner, C. F.

1844. Versuche und Beobaehtungen iiber die Befruchtungsorgane der voll-

kommeren Gewachse. Stuttgart.
1849. Versuche und Beobaehtungen iiber die Bastarderzeugung im Pflanzen-
reich. Stuttgart.
GOODSPEED, T. H.

1912. Quantitative studies of inheritance in Nicotiana hybrids. Univ. Calif.

Publ. Bot., vol. 5, no. 2.

1913. Notes on the germination of Tobacco seed. Univ. Calif. Publ. Bot.,

vol. 5, no. 5.

Hayes, H. K., and Beinhart, E. G.

1914. The cytological time of mutation in Tobacco. Science (n.s.), vol. 39,

no. 999, p. 284.

Hartley, C. P.

1902. Injurious effects of premature pollination. U. S. D. A., Bur. PI. Ind.,
Bull. 22.
Howard, G. L. C.

1913. Studies in Indian Tobaccos, No. 3: The inheritance of characters in
Nicotiana Tabacum L. Mem. Dept. Agric. India, Bot. Ser., vol. 6,
no. 3.
Howard, A., and Hoavard, G. L. C.

1910. Studies in Indian Tobaccos, No. 2: The types of Nicotiana Tabacum
L. Mem. Dept. Agric. India, Bot. Ser., vol. 3, no. 2.
Setchell, W. a.

1912. Studies in Nicotiana, I. Univ. Calif. Publ. Bot., vol. 5, no. 1.

1915] Goodspccd: Parthenogenesis, PartJienocarpxj, Fhenospermy 271

Thomas, R. A.

1909. Parthenogenesis in Nicotiana. Mendel Jour. vol. 1, no. 1. (Reprint,

paging changed.)
1913. Note sur la parthenogenese chez les plantes. 4th Conf. Int. Gen. Rep.,

p. 209.

Wellington, R.

1913. Studies of natural and artificial parthenogenesis in the genus Nicotiana.
Amer. Nat., vol. 47, no. 557, p. 279.

Winkler, H.

1908. Parthenogenesis und Apogamie im Pflanzenreiche. Prog, rei Bot.,
B. 2, 43.

WOODBURN, W. L.

1911. Development of the embryosac and endosperm in some seedless per-
simmons. Bull. Torrey Bot. Club, vol. 38, no. 7.

EXPLANATION OF PLATE 35
" Nic. tabaccum Cuha." U. C. B. G. 200/14.

[272]

UNIV. CALIF, PUBL, BOT. VOL. 5

[GOODSPEED] PLATE 35

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 9, pp. 273-292, plate 36 October 4, 1916

ON THE PARTIAL STERILITY OF NICOTIAN A

HYBRIDS MADE WITH N. SYLVESTRIS

AS A PARENT. II

BY
T. H. GOODSPEED and A. H. AYEES

CONTENTS

PAGE
Introduction 273

Response of the Hybrids and Parental Pollen to Natural and Artificial

Germinating Fluids 276

Experiments upon the Eelation of Nutrition to Sterility and Flower-fall 281

Summary of Eesults 288

I. Introduction

In 1913 one of us reported that the several F^ hybrids made in the
University of California Botanical Garden between five Nicotiana
Tabacum varieties and N. sylvestris agreed with one another in pro-
ducing a small quantity of open-pollinated seed, while no seed was
produced on the same plants under bag (Goodspeed, 1913). These
interspecific hybrids had previously been considered to be completely
sterile with the exception of such evidence as is given by the experi-
ments of Bellair (1913), who grew an F, from seed of apparently
unprotected flowers produced on F, hybrids of probably much the
same parentage as those with which we have been concerned. Since
the publication of the original description of the partially sterile nature
of these F, hybrids further investigations, consisting primarily of
efforts to determine and modify the nature and causes of this sterility,
have been continuously in progress. The present paper is the first
report of tlie results of these investigations.

The general problem as it presents itself to us seems a complicated
one, and tlius it 7n;iy be desiral)le to state it in the most general terms

274 University of California Publications in Botany [Vol. 5

before taking up the particular phase of the problem which is the
subject of this report. The various F^ hybrids between N. Tahacum
varieties and N. sylvestris are replicas on a large scale of the N.
Tahacum parent concerned in the particular cross. The dominance
of the many distinct vegetative and floral characters w^hich are summed
up in the general appearance of the N. Tahacimi parent is, for each
character, practically complete, w'hile the dominant nature of any
given parental character is made more striking through the general
increase in expression due to heterosis. The F^ species hybrids are,
then, distinguished from the N. Tahacum parent almost solely in an
increased expression of all characters peculiar to it and also by the
possession of a short-lived perennial habit which is characteristic of
the N. sylvestris parent. Their flowers are normal in every respect,
with the important exception that the open anthers contain a relatively
small amount of light, dry, almost entirely functionless pollen as con-
trasted with the mass of heavy, more or less sticky pollen which is
produced by the flowers of their parents. Almost every grain of the
parental pollen will germinate in its own stigmatic fluid. Examination
of the Fj hybrid pollen made at the start of the experiment and often
repeated thereafter showed that a very small percentage of what
appeared to be normally matured grains occurs in the mass of shriveled,
degenerated and undeveloped grains (cf. plate 36). These latter
correspond in appearance to those which have often been flgured as
characteristic of the pollen of sterile plants.

One of the most striking peculiarities of the hybrid flowers is their
tendency to fall soon after anthesis. A flower under bag on a hybrid
plant will, in general, fall at approximately the same time that a pro-
tected, castrated flower on one of the parent plants will fall. The only
capsules remaining at the end of the season, and they are relatively
very few in number, contain a little viable seed. Similarly, if the
pollen of the corresponding parents is used to pollinate the F^ flowers
the latter usually persist and in all such cases a little viable seed
is formed. Again, in the case of a number of other attempted inter-
specific crosses in Nicotiana we have found that the foreign pollen,
although in some cases it actually germinates in the stigmatic fluid
of the female parent of the attempted cross, will not inhibit the falling
of the castrated flower. Lastly, the case of the F^ hybrids betAveen
N. sylvestris and N. Tahacum "Cuba" deserves mention in this con-
nection. N. Tahacum "Cuba" has been shown to exhibit a rather
striking parthenocarpy, holding its flowers after castration and

1916] Goodspced-Ayres : Sterility of Nicotiana Hybrids 275

maturing normal fruits and parthenogenetic or phenospermic seeds
(Goodspeed, 1915). The F^ hybrid between this N. Tahacum variety
and N. sylvestris makes apparently no viable seed under bag and its
flowers produce no functional pollen ; thus corresponding to all the
other species hybrids involving N. sylvestris as a parent. Despite the
absence of pollination and fertilization, however, all the flowers remain
attached to the plant and mature normal fruits containing pheno-
spermic seeds.

To sum up what precedes, the F^ hybrids produce no good pollen
or so very little that the chance of a normally matured pollen-grain
fertilizing one of the few normally matured ovules is small. A few
good ovules are matured and after fertilization with normal foreign or
parental pollen yield fruits and viable seeds. Failing pollination with
functional pollen and fertilization of the few good ovules, the hybrid
flowers fall after anthesis. The parthenocarpic tendency of N.
Tahacum "Cuba" is dominant and appears intensified in F^ of the
hybrid with N. sylvestris.

The above is a brief statement of what seems a rather complicated
situation. It includes the various phases of what constitutes the gen-
eral problem of partial sterility in the F, species hybrids of Nicotiana.
We have chosen to attack this general problem under the following
headings.

(1) A cytological problem to be concerned with (a) the nature
and condition of the maternal and paternal chromatin in somatic
mitoses, as contrasted with that of the hybrids, and (&) an examin-
ation of the maturation divisions of the sex cells in the hybrid with
a view to determining, first, the stage at which the degeneration of
the majority of the reproductive tissues takes place and, second, the
chromatic condition of the nuclei in those embryo-sacs which are
capable of fertilization.

(2) A general breeding problem involving a genetic analysis of
the generations which can be grown from (a) the open pollinated
seed of the F, hybrids and (h) the seed resulting from crossing the
parents Iiack on the hybrids.

(8) A histological investigation dealing with the origin and natui'e
of the cutting-off or absciss-layer responsible for the falling of unpol-
linated and unfertilized tobacco flowers.

(A-) A general physiological problem which up to the present time
has been taken up under the following somewhat unrelated headings:
(a) comparison of the rate of growth of parents and hybrids; (6)

276 University of California Publications in Botany [Vol. 5

investigation of the response of the hybrid and parental pollen to
various natural and artificial germinating tluids; and (c) a nutrition
experiment carried on in the hope that the formation of the absciss-
layer might be inhibited or retarded to favor the production of a
larger proportion of normal pollen.

So far as possible we have attempted to attack simultaneously all
these four main aspects of the general problem. The present paper
aims to report such progress as has been made with reference to certain
of the points mentioned in (4) above. The various points of attack
enumerated above are by no means assumed to be the only ones or
the only important ones ; they simply represent those which at present
our facilities and the time at our disposal will permit us to undertake.

II. Response of the Hybrids and Parental Pollen to Natural
AND Artificial Germinating Fluids

As mentioned above, the pollen of the F^ species hybrids contains
a few grains normal in appearance among a great mass of abnormal,
evidently functionless grains. We have made hundreds of attempts
to secure self-fertilized seed. Protected flowers in numbers or trimmed
to a single bud have been allowed to self-pollinate. Great numbers
of protected flowers have by hand been close-pollinated or pollinated
from other flowers on the same plant or from protected flowers o]i
other plants in the same row. Pollen has been collected and put on
the stigmas in great amount, either as a single application or in
successive applications. A variety of experiments in the field have
been attempted in the effort to vary the moisture conditions and the
temperature surrounding individual flowers at and immediately
following pollination. Not a single seed has resulted from any of
these efforts and rarely has a shrunken, empty seed-capsule matured.

As has been said, only a few ovules are capable of fertilization
and the production of viable seeds. In spite of the numerous efforts
mentioned above we have been unable to cause the few apparently
normal i^ollen-grains to fertilize them. This was assumed to be due
either to the slight probability that the pollen tube of a chance pollen-
grain would come in contact with one of the few normally matured
o\ailes, or to the fact that such pollen-grains were unable to germinate
in their own stigmatic fluid, or lastly to structural or physiological
blocks to the proper penetration of the stylar tissue by the pollen
tube. The presumption stood in favor of one of the latter two alterna-

lyi^] Goodspeed-Ayrcs: Sterility of Nicotiaua Hybrids 277

tives, since every effort was made to supply abnormally large quantities
of pollen on the stigmatie surfaces in hand pollinations. Pending the
results of the pollen germination studies we did not attempt to isolate
numbers of the grains of normal appearance for pollination. It might
here be mentioned that the parent species have throughout exhibited
a rather remarkable tendency to mature viable seeds under unfavor-
able conditions accompanying pollination. Thus, in self or cross-
pollination old pollen, overmature pistils and to some extent premature
pollination (cf. Hartley, 1902) seem to have relatively little influence
upon the seeding qualities of a flower of the parents.

The various facts mentioned led to the experiments w^hich are
described in what follows. Of the various F^ hybrids between N.
Tahacum varieties and N. sylvestris which we have had under culti-
vation, only that one involving N. Tab. var. macropliylla (female
parent) will be considered in this report. The F^ hybrid N. Tab.
var. macropliylla X N. sylvestris is known in our cultures as FjH38,
N. Tab. var. macrophylla as 22/07, and N. sylvestris as 69/07.

Table 1 below details the result of one of a number of similar
experiments on the germination of the pollen of F^HSS and its parents
in the three natural stigmatie fluids contained in parent and hybrid
flowers. The stigmatie secretions of all the various species of Nicotiana
are variable in amount and in time of appearance in the development
of the flower and respond differently to varying climatic conditions.
We have found that of the F^ hybrid and the two parent species with
which we are concerned the amount of secretion appearing on the
stigmatie surface is greatest in the case of N. .sylvestris, is less in
F^HSS, and is still less in the case of N. Tab. var. macrophylla. The
amount that can be collected from any one of the three varies from
day to day, but is always very evidently a stigmatie secretion and not
a drop of condensed moisture such as can often be found in the
corolla tube. The secretions were collected as drops on a cover-glass
on the day of the experiment and from flowers whose anthers were
about to open. In the majority of cases these flowers were under bag.
A small quantity of the desired pollen was dusted into the drop of
stigmatie fluid, the cover-glass inverted on a hollow-ground slide and
the preparation sealed with a drop of distilled water. This hanging-
drop culture was examined after lying for five hours in a moist
(•h;niil)ci' at 20° C. Germiiuilidn wiicro indicated in tabic 1 means
the production of pollen-tubes by approximately seventy-five per cent
of the pollen-grains present in the culture.

278

University of California Puhlications in Botany [Vol. 5

Table 1

Geimination of pollen in stigmatie fluids. FiH38 ^ A". Tabaciim var. macro-
phyllaxN. sylvestris; 22/07 =: N. Tab. var. macrophyUa ; 69/07 = N. sylvestris.

Xo
mination Remarks

X Stigmatie fluid from unpro-
tected flowers

X Stigmatie fluid from unpro-
tected flowers

X Stigmatie fluid from pro-
tected flowers

X Stigmatie fluid from pro-
tected flowers

X Stigmatie fluid from pro-
tected flowers

Stigmatie fluid from unpro-
tected flowers

Stigmatie fluid from pro-
tected flowers

Stigmatie fluid from pro-
tected flowers

Stiamatic fluid from pro-
tected flowers

Stigmatie fluid from pro-
tected flowers

Stigmatie fluid from pro-
tected flowers

Stigmatie fluid from pro-
tected flowers

Stigmatie fluid from pro-
tected flowers

Stigmatie fluid from pro-
tected flowers

Exceptional growth of pollen
tubes
X Cell dried out

Stigmatie fluid from pro-
tected flowers

Stigmatie fluid from pro-
tected flowers

No.

1

Pollen
of

F,H38

Stigmatie
fluid of

69/07

Ger
(only

mination
7 grains)

2

F,H38

69/07

(only

4 grains)

3

F,H38

F,H38

4

F,H38

F,H38

5

F,H38

22/07

6

F,H38

22/07

(only

1 grain)

7

69/07

69/07

X

8

69/07

69/07

X

9

69/07

F,H38

X

10

69/07

F,H38

X

11

69/07

22/07

X

12

69/07

22/07

X

13

22/07

69/07

X

14

22/07

69/07

X

15

22/07

F,H38

X

16
17

22/07
22/07

F,H38
22/07

X

18

22/07

22/07

X

It seems obvious from table 1 that the physiological nature of the
stigmatie secretion produced in the flowers of the F^ hybrid is not
responsible for the failure of the hybrid pollen of apparently normal
constitution to produce pollen-tubes. As the table shows, the pollen
of both parent species germinates as rapidly and in as great amount
in the stigmatie fluid of the hybrid as it does in its own. Further, the
appearance of the plants from seed of unprotected flowers makes it
evident that the pollen of a number of other .Y. Tahacum varieties
will germinate on the stigmatie surfaces of the hybrid. None of the
hybrid pollen-grains, however, will germinate in their own stigmatie
fluid or in that of either parent.

1916] Goodspeed-Ayres: Sterility of Nicotiana Hybrids 279

Table 2, below, gives the results of one of a number of attempts
to measure the reaction of the parental pollen to various artificial
germinating fluids. Hanging-drop cultures of the pollen were made
in tap water and in 10 per cent solutions of levulose, dextrose, and
maltose. After four hours in a moist chamber at 20"^ C. the average
length of the pollen-tubes was determined. Twenty-five measurements
taken at random in the preparation gave, in each case, the average
amount of growth. The length of the pollen-tubes is stated in divisions
of the eyepiece micrometer with the 2/3 objective.

Table

2

Growth of Pollen
Tubes of

In Tap
Water

In lO-A-
Levulose

In 10%
Dextrose

In 107^
Maltose

N. sylvestris

2.5

1.2

3.8

11.2

N. Tab. var. macrophylla

10.4

all burst

7.0

6.9

From tbe results given in table 2 it is plain that the pollen of the
two species used reacts differently to the same culture medium. The
pollen of N. sylvestris germinates rather poorly and the pollen-tubes
grow slowly in tap water, as contrasted with the high percentage of
germination and the rapid growth of the pollen and pollen-tubes of
N. Tab. var. macropliylla in the same culture medium. Almost
exactly the reverse is true of the behavior of the two types of pollen
in maltose, while in levulose the pollen of N. Tab. var. macropliylla
will not germinate at all and the pollen of .Y. sylvestris shows very
slight germination and feeble growth of pollen-tubes. The fact that
specific chemical substances appeared to exert a stimulating effect upon
the germination and growth of the pollen on the parents led to the
use of a variety of substances in the hope of finding one which would
induce germination of the hybrid pollen of normal appearance.
Numerous .sugars, dilute acids and various nutritive .substances in
different concentrations were u.secl as culture media. No .success
attended these various efforts, and it seems certain that it is not the
absence of specific chemical .substances in natural stigmatic secretions
Mliich accounts for the failure of the F, pollen normal in appearance
to germinate in its own stigmatic fluid or in that of its parents.

These experiments on pollen geniiination as a phase of tbe general
investigation wero undertaken a number of years ago, and our atten-
tion has more recently been directed to various nutrition experiments
which are to be descrilicd in what follows. In our efforts to bring about
the germination of !!ic a])]iar(»ntly iioniinl ])ollen of the F, hyhfid
we were gni(l('<l i)i-iin;ii"ily by 1hc oldci' concc^ption of tlie iiii]iortant

280 University of California Puhlications in Botany [Vol. 5

role of specific substances in determining whether or not pollen will
germinate. Latterly the views of ]\Iolisch and Burch emphasizing the
importance of specific substances are being replaced in the light of
results obtained by IMartin. Tokugawa and in the later work of Jost,
which indicate that general physical conditions are the determining
factors in pollen germination. Complete reference to and review of
the older and more recent literature is given by Martin (1913) and
Tokugawa (1914). Especially important is the question of water-
supply and its regulation. Jost has demonstrated in a rather wide
range of cases that restricted water-supply is the significant factor
in bringing about germination of pollen. ]\Iartin (loc. cif.) found that
the germination of the pollen of red clover depends upon a proper
water-supply; the range of variation in water-supply within which
pollen would germinate was limited; indeed, conditions giving free
water-supply to the stigma may lead to sterility. The results given
in table 2 above add fragmentary evidence along this same line. Thus,
the reaction of the pollen of N. Tah. var. nmcrophyUa in tap water
and in 10 per cent levulose is not susceptible of explanation on the
basis of osmotic pressure, but is intelligible with reference to the effect
of reagents upon the swelling of cell colloids. Inhibition of water
absorption could be brought about by the calcium salts of tap water,
a result in keeping with the general action of the alkali earths in such
connections (Cranner, 1914, p. 536). This general tendency to assign
greater importance to general physical conditions has, of course, been
increasingly apparent in the work being done on seed germination, in
which field the range of experiments has been far more extensive and
the results apparently conclusive.

The complete failure of numerous efforts to bring about the
germination of the apparently good hybrid pollen made it seem best
to await the results of cytological studies on its condition before
attempting further germination experiments along the newer lines
indicated above. It now seems possible that the relatively few well-
rounded pollen-grains of the hybrid which appear to be normally rich
in c^vtoplasmic and nuclear substance are of abnormal constitution
with respect to chromatic content. In the preparations which we have
obtained ^showing the maturation divisions in the pollen mother-cells
of the Fj hybrid, the chromatin appears greatly fragmented or chromo-
some distribution is incomplete and chromosome fragments or lagging
chromosomes are seen in the equatorial zone or on the spindle in
telophase of the heterotypic division. It is possible that even with

1916] Goodspeed-Ayres : Sterility of Nicotiana Hybrids 281

abnormal nuclear constitution germination of the pollen-grains that
mature can be brought about. To this end it may be necessary to
supply some external conditions which are absent, such as oxygen or
water-supply. Mechanical resistance to enlargement may enter in
as a factor and it is possible that the histology and microchemistry
of the pollen coats may give important evidence concerning the failure
of the hybrid pollen to germinate. We are indebted to Dr. William
Crocker of the University of Chicago for his interest in the work and
for a number of suggestions which have been embodied in the above
discussion.

In summing up the experiments on pollen germination detailed
above we are concerned almost entirely with negative results so far as
the primary objective of the experiments is concerned. It has been
shown, however, that the stigmatic secretion produced in the flowers
of the Fi hybrid is a favorable medium for the germination of tobacco
pollen, the pollen of normal appearance shed in these same hybrid
flowers being the only exception to this statement which we have
found. Further it has been shown that the pollen of N. Tahacum var.
macrophylla differs from the pollen of N. sylvestris with respect to
growth response under the influence of 10 per cent solutions of
dextrose, levulose, and maltose and in tap water. At the time this
seemed to indicate that these or other specific substances might be
required as a growth stimulus for the germination of the hybrid pollen.
Nothing was discovered, however, which would provide this stimulus
and bring about germination.

III. Experiments upon the Relation op Nutrition to Sterility

AND FlOV^ER-FALL

Our purpose in the experiments detailed below was to bring about
such a condition of nutritive balance wnthin the partially sterile F^
hybrids under discussion that a greater proportion of normally con-
stituted pollen-grains and ovules would be matured. As has been
noted above, the flowers in the Fj hybrids fall a short time after
anthesis. Tliis falling of the flower is due to the presence in the
pedicel of an absciss-layer which is formed when pollination and
fertilization do not take place. Castralion of self- fertile species
simil;ii'l\- results in the fall of the flower after anthesis while, at hvist
in the hybrid, the formation of ;iii absciss-layer is inhibited by the
fertilization of a relatively few ovules. The partially sterile character

282 University of Calif ornia Publications in Botany [Vol. 5

of the F^ hybrids is thus particularly characterized by the early falling
of their flowers, and we attempted first to inhibit flower-fall in the
expectation that such inhibition might be accompanied by the pro-
duction of a greater proportion of normally matured ovules and
pollen grains. It is, however, obvious that we might have suc-
ceeded in bringing about an induced parthenocarpy in which the
Fj hybrids would have held their flowers after anthesis irrespective
of the production of normal pollen and ovules and the accompanying
pollination and fertilizations. Particular emphasis also was laid
upon eliminating flower and fruit-fall since the subject is of special
importance in many species cultivated commercially. AVith particular
reference to the nutrition factor in this connection it appears to have
become almost a dictum by gardeners that the tomato will drop its
flowers and young fruits when grown in soil over-rich in barnyard
manure, while many orchard fruits fall at different periods of devel-
opment Avithout specific cause so far as determined. The problem of
flower and fruit-fall has not. so far as we have been able to discover,
been investigated from the strictly physiological point of view, the
only type of investigation that would seem to promise valuable results.
We have, in particular, been unable to find notice of experiments
similar to ours in which an effort was made to eliminate flower-fall
by varying the total and relative concentration of the available mineral
nutrients (cf. Lloyd, 1914).

These experiments have extended over some three years. During
the first two years interest centered upon the eff'ect of the individual
mineral nutrients, while by the experiments of this last year the effect
of varying the total concentration of nutrient salts was sought. Rooted
cuttings FjHSS were employed during the first year and thereafter
seedlings of the same hybrid a month old or less. The plants, in six-
inch pots, heavily paraffined, were grown to maturity under glass. The
temperature about the plants was rather highly variable but moisture
conditions were maintained fairly constant.

Table 3 has to do with the experiments of the second year. Forty-
eight seedlings were planted in pots each of which contained 1720 g.
of washed sand. The plants were divided into three groups which
are mentioned in table 3 as groups A. B. and C. Each group con-
sisted of eight plants, with a duplicate for each of the eight which
received identical treatment in each case. In group A of table 3
nitrogen was the only varying factor and the other salts remained
constant in amount within the group. Similarly in group B phos-

1916]

Goodspeed-Ayres : Sterility of Nicotiana Hybrids

283

Table 3

SOUP A

Nitrogen

( grams of

sodium

nitrate)

Phosphorus

(grams of

mono-calcium

phosphate)

Potassium
(grams of
potassium
sulphate)

Magnesium
( grams of

magnesium
sulphate)

Total

concentration,

grams

Pot 1

.017

1..5

3.0

1.2

5.72

Pot 2

.086

1..5

3.0

1.2

5.79

Pot 3

.172

1.5

3.0

1.2

5.81

Pot 4

.430

1.5

3.0

1.2

6.13

Pot 5

.860

1.5

3.0

1.2

6.56

Pot 6

1.290

1.5

3.0

1.2

6.99

Pot 7

1.720

1.5

3.0

1.2

7.42

Pot 8

2..580

1.5

3.0

1.2

8.28

Group

B

Pot 1

4.0

.086

3.0

1.2

8.29

Pot 2

4.0

.344

3.0

1.2

8..54

Pot 3

4.0

.688

3.0

1.2

8.89

Pot 4

4.0

1.376

3.0

1.2

9.58

Pot 5

4.0

1.720

3.0

1.2

9.92

Pot 6

4.0

2.408

3.0

1.2

10.61

Pot 7

4.0

2.752

3.0

1.2

10.95

Pot 8

4.0

3.096

3.0

1.2

11.30

Group

r

Pot 1

4.0

1.5

.086

1.2

6.79

Pot 2

4.0

1.5

.344

1.2

7.04

Pot 3

4.0

1.5

.688

1.2

7.39

Pot 4

4.0

1.5

1.376

1.2

8.08

Pot 0

4.0

1.5

1.720

1.2

8.42

Pot 6

4.0

1.5

2.408

1.2

9.11

Pot 7

4.0

1.5

2.752

1.2

9.45

Pot 8

4.0

1.5

3.096

1.2

9.80

Table 4

Series I

lUP A

Nitrogen

(grams of

sodium

nitrate)

Phosphorus

(grams of

mono-calcium

phosphate)

Potassium
(grams of
potassium
sulphate)

Magnesium
(grams of

magnesium
sulphate)

Total

concentration,

grams

Pot 1

.02

1.2

2.4

.96

4.58

Pot 2

.20

1.2

2.4

.96

4.76

Pot 3

1.00

1.2

2.4

.96

5.56

Pot 4

2.00

1.2

2.4

.96

6.56

Pot .5

3.00

1.2

2.4

.96

7.56

Group

B

Pot 1

.02

.8

1.6

.64

3.06

Pot 2

.20

.8

1.6

.64

3.24

Pot 3

1.00

.8

1.6

.64

4.04

Pot 4

2.00

.8

1.6

.64

5.04

Pot .o

3.00

.8

1.6

.64

6.04

Group

c

Pot 1

.02

.6

1.2

.48

2.30

Pot 2

.20

.6

1.2

.48

2.48

Pot 3

1.00

.6

1.2

.48

3.28

Pot 4

2.00

.6

1.2

.48

4.28

Pot n

3.00

.6

1.2

.48

5.28

Group

D

Pot 1

.02

.3

.6

.24

1.16

I'ot 2

.20

.3

.6

.24

1 34

Pot 3

1.00

.3

.6

.24

2.14

Pot 4

2.00

.3

.6

.24

3 14

Pot 5

3.00

.3

.6

.24

4.14

284

University of California Publications in Botany [^oh. 5

Series II

Nitrogen

Pliosphorus

Potassium

Magnesium

(

' grams of

(grams of

(grams of

(grams of

Total

sodium

mono-caleium

potassium

magnesium

concentration,

Group A

nitrate)

phosphate)

sulphate)

sulphate)

grams

Pot 1

3.0

.02

2.4

.96

6.38

Pot 2

3.0

.10

2.4

.96

6.46

Pot 3

3.0

.20

2.4

.96

6.56

Pot 4

3.0

1.00

2.4

.96

7.36

Pot 5

3.0

2.00

2.4

.96

8.36

Group B

Pot 1

2.25

.02

1.6

.64

4.51

Pot 2

2'.2.5

.10

1.6

.64

4.59

Pot 3

2.25

.20

1.6

.64

4.69

Pot 4

2.25

1.00

1.6

.64

5.49

Pot 5

2!25

2.00

1.6

.64

6.49

Group C

1

/

Pot 1

1.5

.02

1.2

.48

3.20

Pot 2

1.5

.10

1.2

.48

3.28

Pot 3

1.5

.20

1.2

.48

3.38

Pot 4

1.5

1.00

1.2

.48

4.18

Pot 5

1.5

2.00

1.2

.48

5.18

Group D

Pot 1

.75

.02

.6

.24

1.61

Pot 2

.75

.10

.6

.24

1.69

Pot 3

.75

.20

.6

.24

1.79

Pot 4

.75

1.00

.6

.24

2.59

Pot 5

.75

2.00

.6

.24

3.59

Series III

Nitrogen

Phosphorus

Potassium

^lagnesium

(grams of

(gi

•ams of

(grams of

( grams of

Total

sodium

mono-caleium

potassium

magnesium

concentration,

rROUP A nitrate)

phosphate)

sulphate)

sulphate)

grams

Pot 1

3.0

1.2

.02

.96

5.18

Pot 2

3.0

1.2

.10

.96

5.26

Pot 3

3.0

1.2

.20

.96

5.36

Pot 4

3.0

1.2

1.00

.96

6.16

Pot 5

3.0

1.2

2.00

.96

7.16

Group B

Pot 1

2.25

.8

.02

.64

3.71

Pot 2

2.25

.8

.10

.64

3.79

Pot 3

2.25

.8

.20

.64

3.89

Pot 4

2.25

.8

1.00

.64

4.69

Pot 5

2.25

.8

2.00

.64

5.69

Group

C

Pot 1

].5

.6

.02

.48

2.60

Pot 2

1.5

.6

.10

.48

2.68

Pot 3

1.5

.6

.20

.48

2.78

Pot 4

1.5

.6

1.00

.48

3.58

Pot 5

1.5

.6

2.00

.48

4.58

Group D

Pot 1

.75

.3

.02

.24

1.31

Pot 2

.75

.3

.10

.24

1.39

Pot 3

.75

.3

.20

.24

1.49

Pot 4

.75

.3

1.00

.24

2.29

Pot 5

.75

.3

2.00

.24

3.29

1916] Goodspccd-Ayres: Sterilitij of Nicotiana Hybrids 285

phoriis was the variant, as was potassium iu group C. In making
the applications of the nutrients the constituents of the following
nutrient solution were used:

80 g. sodium nitrate iu 2500 ec. water

25 g. mono-calcium phosphate in 2500 cc. water

50 g. potassium sulphate in 2500 cc. water

20 g. magnesium sulphate iu 2500 cc. water

At intervals of a week varying amounts of each of the above solutions
were added to each pot to give the totals for each nutrient stated in
table 3. A trace of ferric chloride was added to each pot.

The experiments of the first year correspond to the above and
the emphasis was similarly laid upon varying the amount of individual
nutrients. The range of variation in concentrations and the number
of plants employed were, however, considerably less, and a full report
of the experiments of the first year would add nothing to that given
in table 3.

The results obtained during the first two years indicated that
variations in total concentration of available nutrients, rather than
particular concentrations of individual nutrients, might be the im-
portant factor in inhibiting flower-fall. To this end the experiment
detailed in table 4 was devised to give the wide range of variation
in total concentration together with variation in the amount of indi-
vidual nutrients. One hundred and twenty seedlings were transplanted
to pots containing 2000 g. of washed sand. The salts were all added
to the pots along with the sand at the start of the experiment and
thereafter the plants were watered at regular intervals with distilled
water.

As shown in table 4, sixty different combinations were secured and
a duplicate test, as in the work of the preceding year, was carried
through. These combinations were equally divided into three series —
I, II and III — and each- series was in turn divided into four groups.
In series I, table 4, nitrogen as sodium nitrate was the only varying
factor within the group, the amount of each of the other salts being
held constant. Correspondingly in series II phosphorus as mono-
calcium phosphate was the only variant within the grouj), while in
series III potassium ms potassium sulphate was the group variant.
Within each of the four groups — A, B, C, aiid 1) of each series — the
increase t)!' llic varying nutrient was the same from ])ot 1 to pot 5.
Thus in series I, pot 1 in all I'oui- groups contained .02 g. of sodium
nitrate, pot 2 contained .2 g. in all foui- groups, and so on. As we

286 University of California Puhlications in Botany [Vol. 5

pass I'rom group A to group B in any series, however, the amount
of the other salts diminishes, so that B contains two-thirds, C one-half
and D one-fourth the amount of a given salt contained in the pots in
group A. This arrangement gives, of primary importance, a series
in which the total concentration of nutrient salts varies widely and
in addition gives a distinct variation in each individual nutrient both
within a group and between different groups.

The results of these various experiments are almost entirely nega-
tive so far as the effort to inhibit flower-fall completely is concerned.
It was. however, established that when the total concentration of
available nutrients falls below a certain point almost all the young
fruits are held (m the plant for a very considerable period of time
in place of falling, in the majority of cases, shortly after anthesis, a
condition characteristic of the flowers of sister plants under field
conditions. An appreciable number of fruits on many plants came
almost to maturity before falling whenever the total concentration
was low. The effect of low total concentration of nutrients was also
seen in connection with pollinations of hybrid stigmas with normally
matured parental pollen. In the field it is difficult to make such
pollinations at just the proper stage in the development of the hybrid
flower and many attempts are necessary to secure even a little seed.
This seems to be due to the fact that under field conditions the absciss-
layer in the hybrid pedicel is formed when a certain stage of pistil
development is reached without pollination and the fertilization of
the few good ovules matured. Thus in the field successful pollination
could be secured only when the pollen was applied to the stigma ju.st
before the opening of the anthers, the latter often taking place before
the complete opening of the flower. In the case of the pot cultures
of sister plants which were given a low total concentration of nutrients
almost every attempted pollination was successful and to a considerable
extent the stage of development of the flower was of no .significance.
It must be definitely noted, however, that no increase in the number
of ovules capable of fertilization accompanied these more generally
successful back-crosses. Further evidence in the above connection is
given by the fact that plants growing for a number of years in pots
of unrenewed garden soil have in successive years shown a longer and
longer period of retention of flowers and fruits.

On the other hand, so far as our experiments are concerned, there
is no indication that an increase or decrease in the normal concen-
tration of anv one constituent of a nutrient solution will affect flower

1916] Goodspeed-Ayres: Sterility of Nicotiana Hybrids 287

or fruit-fall. Especially in the case of nitrogen the results in many
cases contradicted the expectation in that flowers and young fruits
were retained almost as long on a plant growing in a rich nitrogen
culture as on one growing in a culture of low nitrogen concentration.
The same was true with regard to the other nutrients whose concen-
tration was varied or in some cases the plants under both low and
high concentration dropped their flowers at the same time.

Balls (1912. p. 68) reports that "boll-shedding" in Egyptian
cotton results from the formation in the flower stalk of an absciss-
layer of "extreme simplicity." The stimulus inducing its formation
is, according to Balls, the result of deficient root-absorption or its
equivalent. Thus a disturbance in the water content of the plant is
followed by a "demolition of the delicate balance between root and
shoot" to produce shedding. There seems to be grave doubt as to
the correctness of Balls' interpretation of the histology of the absciss-
layer in cotton and we may quote Lloyd (1914. p. 65) with reference
to the significance of the water relation with regard to abscission :

In general . . . we must conclude, in view of the effects of drought upon
trees and shrubs, that tliere is a relation between lack of water and defoliation,
but it is not possible to attribute abscission directly to a reduction of water
content such as may be measured. It may, however, result indirectly bv the
disturbance of some other relation. . . . very slight departures from the
normal condition of the environment in other regards are sufficient to cause
or to hasten abscission.

Balls further states that non-fertilization is not an appreciable cause
of boll-shedding in Egyptian cotton, a situation evidently occasioned
l)y the lack of rain during the season when cotton is flowering and
not to be taken to mean that fruits develop readily without fertili-
zation. The initial stimulus for the formation of the absciss-layer
which causes flower and fruit-fall in tobacco is non-fertilization. We
have been able to show, however, that a lowering of the total amount
of available nutrients is effective in at least retarding the formation
of this absciss-layer while it has, on the other hand, been shown that
a variation in the concentration of an individual nutrient has little
or no effect in flie same direction. All the evidence at hand seems to
iiidicjile tliat maintenance or disturbance of general physiological
states or conditions of equilibrium is a more potent factor for initiat-
ing or iiiliihiling sliniuli or leactions than the action of specific
chemical substances. Conversely, also, many effects now assigned to
the action of such specific substances are more consistently explaiir'd

288 University of California Puhlications in Botany [Vol. 5

as due to the modification of general physiological conditions, in many
instances probably to nothing more than variations in the hydration
of cell colloids.

The results of the experiments above described appeared to indi-
cate that some phy^siological balance of the plant, a disturbance of
which causes flower-fall, was sufficiently delicate and responsive to
variations in nutrition to make of value the experiments noted below
in which the parent was grafted on the hybrid and vice versa. A very
considerable number of efforts were made to secure graft unions
between FiH38, N. sylvestris, and N. Tab. var. macrophylla. All
attempts to graft F^HSS and N. sylvestris using the former both as
scion and stock have been to date unsuccessful. A number of grafts
of F^HSS and N. Tab. var. macrophylla have been successfully pro-
duced, though the operation is much more certain to succeed when the
N. Tahacum parent is used as the scion. It was held as possible that
the hybrid growing on the parent might produce a larger proportion
of normally matured pollen and ovules or that the parent growing
on the hybrid would show some lessening of reproductive vigor. No
such result was found to occur in either case. The hybrid comes into
flower when growing on the parent with as small a proportion of
pollen of normal appearance as it does when growing on its own roots,
while the parent growing on the hybrid produces an abundance of
normal pollen and the usual proportion of viable seeds is formed.
However, the hybrid flowers and young f rviits were retained for a much
longer period than was the case when the same plant grew on its own
roots under field conditions.

IV. Summary of Results

1. The Fi hybrids between Nicotiana Tahacum varieties and N.
sylvestris produce a very small quantity of pollen of normal appear-
ance, while practically the entire contents of the anther cells consists
of shriveled, functionless grains.

2. Fj pollen of normal appearance could not be caused to germinate
in its own stigmatic secretion or in that of its parents or in any one
of a great variety of artificial germinating fluids.

3. The pollen of the parents germinates readily in the stigmatic
secretion of the F^ flowers. The germination and growth reaction of
the pollen of N. Tab. var. macrophylla and N. sylvestris in tap water
and in 10 per cent solutions of dextrose, levulose and maltose were

1916] Goodspeed-Ayres: Sterility of Nicotiana Hybrids 28<J

such as to give evidence against the view that specific chemical sub-
stances play the important role in determining whether or not pollen
will germinate, and the results obtained are to be explained as the
effect of the reagents upon the swelling of cell colloids.

4. The formation of an absciss-layer in the pedicel of tobacco flowers
is the cause of flower and fruit-fall. Non-fertilization is the stimulus
which is responsible for the formation of this absciss-layer.

5. From a considerable series of pot cultures it was determined
that flower and fruit-fall in tobacco could be at least retarded by
lowering the total concentration of available mineral nutrients, while
variations in the amount of individual constituents of a nutrient
solution were without effect in this connection.

6. A few normalh^ matured ovules capable of fertilization are
prociuced in the F^ flowers and a little viable seed is formed after
pollination with the normal pollen of the parents. The back-crosses
are difficult to make in the field, since it is hard to anticipate the
activation of the absciss-layer. The plants growing under conditions
of low nutrient content retain their flowers so much longer that the
back-crosses were almost uniformly successful. It must be emphasized,
how^ever, that no increase in the number of ovules capable of fertiliza-
tion accompanied this more favorable condition for successful back-
crossing.

7. Grafts between the F^ hybrid and its parent N. Tab. var.
macrophylla produced flowers containing that proportion of pollen
of normal appearance and couvstitution and functionless pollen which
is characteristic of the same plants growing on their own roots. The
retention of the flowers and fruits of the hybrid was, however, favored
when it was grown on the parent as a stock.

We take pleasure in acknowledging our indebtedness to Professor
C. B. Lipman for continued interest in and many suggestions con-
cerning the experiments reported upon and in progress. We are,
further, under obligations to Professor Francis E. Lloyd for many
suggestions as to the nature of abscission in tobacco.

Transmitted February 3, 1916

290 TJniversity of Calif ovnia Puhlications in Botany [Vol. 5

V. Literature Cited

Balls, W. L.

ini2. The cotton plant in Egy]it. London.

Bellair, G.

1911. Report -tth Internat. Conf. on Genetics. Paris.

Cranner, B. H.

1914. tjber das Verhalten der Knlturpflanzen zu den Bodensalzen. III.

Jahrb. f. wiss. Bot., B. 53, p. 536.
GOODSPEED, T. H.

1913. On the partial sterility of Nicotiana hybrids made with A", sylvestris

as a parent. Univ. Calif. Publ. Bot., vol. 5, no. 4.

1915. Parthenogenesis, parthenocarpy and i)henosperniy in Nicotiana. Ibid.,

vol. 5, no. 8.

Hartley, C. P.

1902. Injurious eifects of premature pollination. U. S. D. A., Bur. PI. Ind.,
Bull. 22.

Lloyd, F. E

1914. Abscission. Ottawa Nat., vol. 28, nos. 3 to 6.

Martin, J. M.

1913. The physiology of the pollen of TrifoJium pratciise. Bot. Gaz., vol.

56, no. 2, p. 154.
Setchell, W. a.

1912. Studies in Nicotiana. 1. Univ. Calif. Publ. Bot., vol. 5, no. 1.

TOKUGAWA,

1914. Zur Physiologie des Pollens. Jour. Coll. 8ci. Tokyo, vol. 35, p. 1.

EXPLANATION OF PLATE 36

Fig. 1. Pollen of FJISS photographed after one-half hour in its own stig-
matic fluid, x 150.

Fig. 2. Pollen of Nicotiana sylvestris photographed after ten minutes in
M/10 cane sugar solution, x 150.

[292]

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED-AYRES] PLATE 36

Fig. 1

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY ''^'

Vol. 5, No. 10, pp. 293-299 November 7, 1916

ON THE PARTIAL STERILITY OF NICOTIAXA

HYBRIDS MADE WITH N. SYLVESTRIS

AS A PARENT. Ill

AN ACCOUNT OF THE MODE OF FLORAL ABSCISSION IN

THE F, SPECIES HYBRIDS

BY

T. H. GOODSPEED and J. N. KENDALL

As pointed out in a number of previous papers, the Fj hybrids
between iV^. sylvestris and N. Tahacum varieties are in practice com-
pletely self-sterile. A small proportion of the ovules borne by these
hybrids are normally matured and capable of fertilization and the
production of viable seeds, and while it is probable that a correspond-
ing proportion of pollen grains are similarly capable of functioning
normally their relative number is so small that attempts to secure self-
pollinated seed have, up to the present time, been unsuccessful. As
a result of this non-success of self-pollination all flowers under bag
are abscissed at various periods following anthesis, and in the case of
unprotected flowers cross-pollination resulting in the maturing of a
very small quantity of viable seed is followed by the retention of less
than 1 per cent of the fruits commonly held upon a plant of one of the
parental species. In a previous communication a description has been
given of efforts, in general unsuccessful, to inhibit this characteristic
abscission of fruits, in which none of or only a very few of the ovules
have been successfully fertilized, and to increase the amount of nor-
mally matured sexual elements (cf. Goodspeed and Ayres, 1916). The
present paper aims to present the results of a considerable series of
preliminary experiments wliich have indicated the mode of abscission

294 University of California Publications in Botany [Vol.5

of flowers and fruits on the F^ species of hybrids and have given
further evidence concerning the relation between successful pollination
and fertilization on the one hand and abscission of flowers and fruits
on the other. The general problem of abscission in the Solanaceae
with particular reference to the genus Nicotiana is being investigated
by one of us and will be the subject of a more extended discussion
later on.

AYe have first to consider the length of time intervening between
anthesis and abscission. In the case of protected flowers of the F^
species hybrids this period is subject to rather extensive variation
(cf. Goodspeed, 1913). The following table indicates the results of
a number of experiments in which tagged flowers were carefully ob-
served from anthesis to fall. Although the hybrid flowers when pro-
tected fall as a result of unsuccessful pollination, the figures given in
the following table are based upon experiments in which botli hybrid
and parental flowers were castrated just prior to anthesis. The influ-
ence of slight mutilations of the flowers in making the castrations is
thus the same in all eases. F^ HI 54 is N. Tabacum var. macrophylla
(U. C. B. G. 22/07) X N. sylvestns (U. C. B. B. 69/07) and F, H179
is iV. Tabacum "Cuba" (U. C. B. G. 200/14) X N. sylvestris.

Number of Days Eetweex Axthesis and Abscission, Average

F, H154 19

F, H179 7

22/07 6

69/07 13

(200/14; cf. Goo<lspee<l, 191.5)

The range for individual plants and their different flowers was
considerably greater. For example, in the case of Fj 11154 seven
different plants gave averages between 9 and 28 days, while the indi-
vidual flovrers on these plants showed variations in the time between
anthesis and abscission of from 6 to 33 days. The statement has been
made in a recent paper (Goodspeed and Clausen, 1916) that F^ H179
holds its flowers in remarkable fashion despite the fact that its pollen
is as non-functional as in the case of the other Tabacum-sylvestris
hybrids. It may thus seem strange that we list this hybrid with the
others in which abscission of almost all flowers and fruits is the rule.
The point here involved demonstrates to what extent the physiological
condition of the plant enters in to effect the abscission problem. Fj
H179 was first grown this past season (1915) and the plants from

1916] Goodspecd-Keudall: Partial Sterility of Nicotiana Hybrids 295

seed exhibited, as noted, an unusnal tendency to hold their fruits to
dehiscence, so that, as they went completely out of bloom late in the
fall, large numbers of capsules were found in place and filled with
apparently phenospermic seed. The fact that from thousands of these
seeds taken from fruits of unprotected flowers less than twenty plants
have been raised demonstrates that successful cross-pollination in the
field was not the cause of non-abscission. The plants of F^ H179 from
which the data given in the above table were taken came up in the
spring of 1916 from their own roots, grew rapidly and flowered two
months before seedling plants were set out into the field. The be-
havior of the flowers was watched during this period of rapid un-
seasonable growth. As the season advanced, more and more flowers
and fruits were retained.

Despite the range of variation in abscission of flowers on individual
plants and the influence of the physiological condition of the plant
upon the situation in general, the above table indicates that there is
a distinct difference in the length of time after castration or non-
pollination during which the parent plants and their hybrids retain
their flowers after anthesis.

In the second place, it is necessary to consider the length of time
involved in the actual process of abscission. In this connection we
are concerned wdth the question whether or not the abscission layer is
performed in the young bud and is capable of functioning at any
period of later development. This is a question which it is difficult
to answer and concerning which it is not easy to obtain trustworthy
evidence. Such histological and experimental evidence as is at hand
seems to indicate that in the abscission of flowers and fruits of
Nicotiana species hybrids an area of cells across the pedicel at its base
is early differentiated and capable of functioning at any later time in
the growth of the flower which it supports. This is indicated, in the
first place, by the observable presence in young flower-buds of a zone
of smaller, isodiametric cells a few millimeters up from the point of
attachment of the pedicel with the main axis of inflorescence. In the
second place, certain species, for example, N. acuminata varieties and
N. glutinosa, shed their open flowers and all buds, even the most
minute, following a sudden change in the temperature conditions to
which the plant is exposed. Further, after fertilization has been
successfully accomplished and the capsule and the seed begins to
mature, abscission practically never takes place under corresponding
environmental conditions. If a demonstrable zone of differentiated

296 University of California Publications in Botany [Vol.5

tissue, through some part of which separation is always seen to take
place, was not present from the early bud stage, or if partially ma-
tured fruits fell as readily as buds and open flowers, it might be con-
ceivable that the formation of the abscission zone occurs only immedi-
ately following the particular "stimulus" or lack of "stimulus" upon
which abscission is dependent.

Returning now to the length of time occupied by the actual process
of abscission, we may note that two types of reaction were investigated.
First, the abscission following non-pollination or unsuccessful polli-
nation, and second, the abscission due to injury, "spontaneous abscis-
sion"; in this case the effect of illuminating gas in the air surrounding
the plant. In the first, the tissues of the pedicels of numerous cas-
trated flowers of all degrees of development were examined histolog-
ically to determine the time of first appearance of loosening or sepa-
ration in the cells of the abscission zone. At least six and apparently
not more than ten hours are necessary for the actual process of ab-
scission caused by non-pollination or unsuccessful pollination. In the
second case above the reaction is much more rapid, taking place in
from one to four hours. These latter figures are based upon direct
observation of the behavior of flowers on a freshly cut shoot placed
in water surrounded by air into which illuminating gas had been
introduced.

The results of a rather extensive histological and cytological inves-
tigation as to the position and condition of the abscission zone and
the nature of the process of abscission proper are summarized below:

1. In N. Tabaciim, N. sylvestris and the F^ hybrids between them
the abscission zone is always to be found at the base of the pedicel.
This is also ti'ue of varieties of N. Langsdorffii, our observations on
this species differing from those of Hannig (1913), who states that
the abscission zone is located at the tip of the pedicel just below the
calyx.

2. A conspicuous grooved ridge or ring of tissue stands out around
the base of the pedicel in Nicotiana species. This grooved ring may
be taken to indicate the position of motor tissue or merely of a node.
The position of the abscission layer is independent of the groove,
although the position of the general abscission zone occurs under it.
The actual abscission layer ordinarily is found from five to seven rows
of cells distal to the groove.

3. The abscission zone is seen in the cortex and pith to be composed
of small isodiametric cells which grade up gradually to the size and

1916] Goodspeed-Kendall: Partial Sterility of Nicotiana Hybrids 297

shape of the cells characteristic of these tissues in the remainder of
the pedicel. The cells of the abscission zone appear to be somewhat
collenchymatous and in many cases contain a greater number of starch
grains than do the neighboring cells without the abscission zone. The
abscission zone extends in a ring completely around the cortex and
across the pith. On the outer or ventral portion of the cortex it is
ordinarily composed of from fifteen to twenty rows of cells, while on
the inner or dorsal side the zone is wider and spreads out into the
considerable area of storage cells found in the axil of the pedicel.

4. Abscission apparently may take place in almost any portion of
the abscission zone distal to the groove. In both cortex and pith the
cells taking part in abscission and most distant from the vascular
cylinder may be from five to ten rows in thickness, but as the vascular
tissues are approached the abscission layer is gradually reduced in
thickness until separation takes place along only one row of cells.
In the cortex this behavior results in a wedge-shaped ring of abscission
cells, the wedge being widest below the epidermis, while in the pith a
circular mass of cells is involved.

5. Abscission starts in the cortical tissues just beneath the epider-
mis on the ventral side and extends around the cortex, taking place
finally on the dorsal side. The first external indication is a bulging
out of the epidermis just above the tissue in which the abscission
process is taking place. This process apparently originates independ-
ently in the pith and simultaneously with the start of abscission in
the cortex. There is no indication of cell division accompanying
abscission in the tissues involved, nor is there evidence of any alter-
ation of the cell walls by the dissolution of the middle lamellae or
elongation and softening of the entire wall. The cells of the abscission
layer become separated one from another over a considerable area or
along only two rows of cells, depending, as noted above, on the prox-
imity to the vascular tissues. This separation appears to be initiated
simply by an increased turgor, as a result of which the cells round up,
intercellular spaces increase in size and the contact points are suc-
cessively reduced. The distention of the epidermis at the start of
abscission, the entire collapse in the pith of all the cells concerned and
the fact that a wilted shoot with less than the normal tur-gidity retains
its flowers following injury but sheds them as soon as turgid — these
facts seem to favor this view. This question as to tlie physiology and
mechanics of cell separation in the abscission zone is still receiving
attention; tlu^ stateiiiciils iiiadi' in the ])receding sentences represent

298 University of California Puhlications in Botany [Vol. 5

the only couclusions that could be drawn from the considerable mass
of data at present available.

7. At the completion of the process of abscission the flower or fruit
is often retained for a short time or until mechanical agencies break
the epidermis and the few tracheal elements still intact. For this
reason a slight tapping of the flowers or fruits is necessarj^ to deter-
mine exactly the time of complete separation in collecting data such
as are presented in the above table. Longitudinal sections of the de-
tached pedicel after abscission show a distinctly convex outline at the
abscission surface with a slight notch at the tip. The surface itself
is composed of the protruding rounded ends of cells, with here and
there a spherical, completely isolated cell mechanically adhering, and
broken ends of tracheal elements. The surface cells, both those in
place and those isolated, are normal in every respect and apparently
do not differ from the cells of the abscission layer prior to separation
nor from the remainder of the cells of corresponding tissues so far
as thickness of wall and size, shape, and character of cell inclusions
are concerned. The exposed, basal, attached portion of the pedicel
corresponds in appearance, except that the abscission surface is flat,
not convex. Soon after separation the cells on this exposed surface
collapse and form a comparatively heavy protective layer.

8. The number of cells actually concerned in the process of ab-
scission is greater in the hybrids mentioned above than in the parental
species. The same is true in the case of ''automatic" as contrasted
with "spontaneous" abscission.

The preliminary nature of this report was indicated at the start.
A full discussion of the literature dealing with and bearing upon ab-
scission, together with the results of more extensive experiments at
present in progress, will be the subject of a more extended commun-
ication.

We take pleasure here in mentioning the obligation under which
Professor F. E. Lloyd has placed us for his many helpful suggestions
in connection with the work reported upon above.

Transmitted September 8, 1916.

1916] Qoodspeed-Kendall: Partial Sterility of Nicotiaua Ilijhrids 299

LITERATURE CITED

GOODSPEED, T. H.

1913. On the partial sterility of Nicotiana hybrids iiia<le with N. syhesiris
as a parent. Univ. Calif. Publ. Bot., vol. 5, no. .5, p. 189.

1915. Parthenogenesis, parthenocarpy and phenospermy in Nicotiana. Ibid.,

vol. 5, no. 8, p. 249.

GooDSPEED, T. H., and Ayres, A. H.

1916. On the partial sterility of Nicotiana hybrids made with N. sylvesti-is

as a parent, II. Ibid., vol. .5, no. 9, p. 273.
GooDSPEED, T. H., and Clausen, R. E.

1916. The nature of the Fi species hybrids between Nicotiana sylvcstris and
varieties of Nicotiana Tabacum, with special reference to the con-
ception of reaction system contracts in heredity. Ibid., vol. 5
(in press).

Hannig, E.

1913. Uutersuchungen iiber das Abstossen von Bliithen, etc. Zeitschr. Bot.,
vol. 5, p. 417.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. II, pp. 301-346, plates 37-48 January 17, 1917

THE NATURE OF THE F: SPECIES HYBRIDS

BETWEEN NICOTIANA SYLVESTRIS AND

VARIETIES OF NICOTIANA TABACUM

WITH SPECIAL REFERENCE TO THE CONCEPTION OF
REACTION SYSTEM CONTRASTS IN HEREDITY

BY

T. H. GOODSPEED and R. E. CLAUSEN

The partially sterile F^ hybrids between Nicotiana sylvestris and
various varieties of N. Tahacum have been a subject of investigation
for a number of years in the University of California Botanical Gar-
den. As stated in a previous paper (cf. Goodsi)eed and Ayres, 1916),
the problems which have arisen in connection with a study of these
hybrids are being attacked from a number of points of view. The
present report is the first which takes up definitely the data bearing
on the genetic aspect of the general problem and, in this particular
connection, it cannot claim to be more than introductory in nature,
while it is equally concerned with providing evidence in support of
a theoretical contention recently advanced (cf. Goodspeed and
Clausen, 1916). In this latter discussion it was pointed out that
hereditary behavior in certain cases may, for a thoroughly consistent
explanation, be looked upon as a result of the interaction of distinct
reaction systems rather than as a result of the expression of specific
factor differences within a common Mendelian system. These two
rather fundanuintally different conceptions may be tlioiiglit of as
applicable to species hybrids and other wide crosses in the first in-
stance and to tlie results of varietal crosses in the second. Thus, one

302 University of California Puhlications in Botany [Vol. 5

may conceive in a varietal cross that the reaction occurs between sets
of factors common to a given system and that the particular type of
behavior exhibited is dependent upon hardly more than a superficial
difference in the case of relatively few of the factors involved. On
the other hand, evidence has been obtained from the results of the
Tahacum-sylvestris hybridizations which indicate that in such wide
crosses there are concerned not contrasts between factors of a com-
mon reaction system, but fundamentally distinct reaction systems
functioning to a certain extent as units in themselves. In presenting
this conception these Nicotian a hybrids were briefly mentioned as
evidence bearing out the suggestions made, and it is the purpose here
to emphasize and amplify in descriptive manner the condition of
affairs elsewhere only touched upon.

The data presented in what follows seem to demonstrate that
when varieties of Nicotiana Tahacum are crossed with .V. sylvestris
the Tahacum reaction system dominates the course of somatogenesis
nearly or quite to the exclusion of the sylvestris reaction system.
In addition to the evidence on this point herein to be presented
we have available a considerable ma&s of quantitative data dealing
with the size and form of vegetative and floral organs (cf. Good-
speed and Clausen, 1915) which, though pertinent and bearing out
our main contention, is not essential to establish the conclusion here
emphasized. An attempt has been made to elaborate and at the
same time cut down the amount of purely descriptive matter by
the inclusion of a considerable number of photographs and draw-
ings of the experimental material. Most of the photographs were
not taken to give evidence in the present connection, and thus it
has not been possible in some cases to secure illustrations of plants
of parent and hybrid in exactly or even approximately the same
stage of development. In the main the photographs of plants or
portions of populations indicate simply the general habit character-
istics of parents and hybrids, while the photographs of flowers and
drawings of leaves give more specific evidence as to the relative
size and form of parent and hybrid organs. All the drawings were
made from fresh material. The leaves drawn in all cases represent
the fourth significant leaf up from the base of the plant, and on a
given plate are all drawn to the same scale.

The following hybrids in F,^ are discussed in this paper. The garden
number in the University of California Botanical Garden is given in
each case.

1^1"] Goodspeed-Claiisen : F^ Species Hybrids in Nicotiana 303

H33— N. sylvestris (U. C. B. G. 69/07 and 107/01; ef. Setchell,
1912, p. 29) X N. Tabaeiim var. macrophylla purpurea
(U. C. B. G. 25/06. ibid., p. 10).

H36— N. (Tabacuin) angustifolia (U. C. B. G. 68/07, ibid., p.
9) X N. sylvestris.

H38— N. Tabaeum var. macrophylla (U. C. B. G. 22/07, ibid., p.
8) X N. sylvestris.

H40— N. Tabacmn var. ealycina (U. C. B. G. 110/05, ibid., p.
6) X N. sylvestris.

H142— N. Tabaeum "Maryland" (U. C. B. G. 78/05, ibid., p.
5) X N. sylvestris.

H179— N. Tabaeum ''Cuba" (U. C. B. G. 200/14, Goodspeed,
1915) X N. sylvestris.

With the exception of the last, these hybrids and their reciprocals
have been remade on numerous occasions during the past tive years
with entirely corresponding results in every case.

A few general statements might be made concerning the above
hybrids and their parents before taking up the more detailed individ-
ual descriptions. In the first place, sylvestris is characterized by a
limited perennial habit, and plants in the garden have come up a
number of years in succession from what appear to be adventitious
buds produced at the base of the stem. In other words, the parts
above ground die down during the winter and entirely new shoots
come up from the surface of the ground in the spring. Such a limited
perennial habit is unusual in the case of an herbaceous tobacco and
is in general peculiar to such arborescent species as N. tnmentosa
and N. glauca. The sylvestris parent is also distinguished from the
Tabaeum varieties by its very slow rate of early growth, as a conse-
quence of which the rosette stage of development is so long maintained
that when sown late the plants in our cultures pass the entire season
in rosette and do not flower until the following growing season.
Finally we may note, as a character distinctly peculiar to sylvestris,
the strikingly pendent habit of the flowers on the dense inflorescences,
a habit maintained from the late bud stage up to or slightly after
anthesis. This sylvestris character is well shown in plate 40, figure 2,
and perhaps more than any other superficial character sets this species
apart from all other species and from the F^ hybrids under consider-
ation liere.

With reference to these more general characters peculiar to syl-
vestris it is to be noted that the Fj hybrids are alike in exhibiting.

304 Uuiversitij of Calif ODiia PubVications in Botany [Vol. 5

first, very rapid early growth relative to their size and, second, an
ability to live over the winter season for a limited number of years.
Their rate of early growth brings them to maturity at approximately
the same date as their respective Tahacum parents, although they are
always somewhat larger than and in some cases twice as large as this
parent. The ability of the F^ hybrids to flower a second and even a
third season on their own roots has previously been taken to represent
a tendency inherited directly from their sylvestris parent. It now
seems probable, however, that this seeming perennial habit should
be looked upon simply as a manifestation or resultant of the greatly
increased vegetative vigor which they exhibit when compared with
their parents. This is in part suggested by the fact that the hybrids
do not die down and come up again from the base of the stem or
from the roots, but the less woody portions of the laterals and main
axis simply die back during the winter and masses of new laterals
from dormant or adventitious buds clothe the framework of the old
plant during the following growing season.

The partial sterility of these Fj species hybrids should also be
briefly mentioned here (cf. Goodspeed and Ayres, 1916). Their flowers
produce only a small proportion of pollen of normal appearance and
it has not been possible to cause this pollen to germinate in its own
stigmatic fluid, in that of its parents, or in artificial germinating fluids.
In other words, the pollen of normal appearance produced by these
hybrids seems to be as strictly functionless as the evidently impotent,
shrunken grains which make up the greater portion of the contents
of the anthers. On the other hand, a few good ovules are produced
in these same flowers and viable seed is matured when they are open-
pollinated or crossed back with the pollen of the corresponding parent.
However, as has been indicated, apparently no seed can be produced
as a result of self-pollination, and indeed selfed F^ flowers fall a short
time after anthesis, due to a lack of successful pollination. In con-
cluding these general remarks it might be noted that reciprocal crosses
in this series of hybrids have always given results identical in every
respect.

F,H36 — N. (Tabacum) angustifolia X N. sylvestris

This hybrid is figured in plates 38, 43, and 46. Plate 38 exhibits
the hybrid placed between the two parents. Tlie plant of sylvestris
on the left is not a representative individual even so far as general
habit is concerned and was taken up from the garden during tho tbii'd

1917] Goodspeed-Clausen : F^ Species Hybrids in Nicotiana 305

year of growth upon its own roots. It is also out of flower. Its
height, as contrasted with that of the hybrid and of angustifolia, is.
however, rather characteristic and in general its distinction from
angustifolia, and thus from the F^ also, is no more striking than is
that of the thorouglily typical plant of sylvestris shown in plate 40,
figure 2. Nicotiana (Tahacum) angustifolia is one of the most con-
spicuous members of the assemblage of Tahacum forms represented
in our cultures. The distinctly petioled leaf is very noticeable, as is
the characteristic drooping habit of the leaves. This latter peculiarity
is emphasized by the occurrence of narrow, strap-like leaves along
the upper third of the laterals, which leaves hang almost straight
down from their point of insertion.

The Fj, as shown in plate 38, represents an expanded expression
of the general angustifolia habit. It is to be noted in this connection
that the rather marked corymbose habit of angustifolia might not
seem to be reproduced in the F^ since the laterals do not overtop and
indeed do not equal the height of the terminal inflorescence. This
situation may, it seems, be taken to represent merely a resultant of
the generally increased vigor of the Fj as compared with either parent,
since particular F^ individuals restricted in growth by cultural con-
ditions have been seen to exhibit a more nearly corymbose habit. The
number of laterals, somewhat greater on the hybrid than on angusti-
folia, has in the same fashion shown itself to be a function of the
amount of vegetative vigor displayed.

Parent and hybrid flowers are shown in plate 43. In general the
infundibuliform corolla of all the Tahacum varieties and of the Fj
species hybrids is in striking contrast to the long, slender-tubed corolla
of sylvestris which, though slightly enlarged somewhat above the
middle of the tube, narrows again as the tube passes out into the limb.
Of all the Tahacum forms here figured, angustifolia is characterized
by the most slender corolla tube and the least inflated infiindibuluni,
and still its corolla tube characters and those of the F^ hybi"ids set it
off sharply from sylvestris. The calyx of sylvestris is also highly
characteristic and is in definite contrast to the various modifications
of tlie Tahacum calyx seen in its several varieties. Thus, the deeply
cleft calyx tube of angustifolia which is clearly apparent though less
ample in the F,, is distinctly different from the smaller calyx tube of
sylvestris with its short, blunt teeth. Finally the configuration of the
corolla limb in sylvestris is distinct from that of any of our Tahacum
varieties. In this case, for example, the deeply divided corolla limb.

306 University of California Publications in Botany [Vol. 5

made up of long, narrow lobes ending in slender lanceolate tips pecu-
liar to angustifolia and the F^, bears no resemblance to the corolla
limb of sylvestris, in which the lobes are broadly triangular and the
lobing rarely extends over one-third the ^vay in from the margin.
The increased size of the F^ flower shown in the photograph, as con-
trasted with the flower of angustifolia to which it otherwise closely
corresponds, may again be assigned to the greatly increased expression
of all organs of the F^ as indicated in plate 38. It is even more sig-
nificant that the relation of length of tube to spread of limb in the
Fj corresponds closely to that displayed by angustifolia as contrasted
with the corresponding relation displayed by sylvestris. Flower color
in angustifolia is a very delicate shade of pink and, as contrasted with
the dead white of sylvestris, the F^ flower is hardly distinguishable
in color from its Tabacum parent.

The domination in FiH3G of the particular Tabacum reaction
system concerned is nowhere more striking than in the case of leaf
characters. This point is brought out in plate 38 and treated spe-
cifically in plate 46. The long-petioled nature of the leaves of
angustifolia distinguishes this form sharply from the sessile-leaved
sylvestris as well as from the other Tabacum varieties, practically all
of which bear sessile, more or less auriculate leaves. The leaves of
angustifolia and of FjHSG in plate 46 were at the time selected to
show the peculiar extensions of the leaf-blade which, in the case of
the majority of the leaves of parent and hybrid, is decurrent along
only the upper half of the petiole. The dominance in the F^ of the
leaf -complex factors introduced by angustifolia is in the drawing too
distinct and comprehensive to require further comment here. One
should note, however, the presence in the F^ leaf of the rather long,
laterally curved point characteristic of angustifolia, for throughout
in the hybrids under discussion here the leaf-tip characters peculiar
to particular Tabacum varieties are remarkably reproduced in addi-
tion to more general characteristics of shape and form of leaf.

F^HSS — N. Tabacum var. macrophylla X N. sylvestris

This hybrid is figured in plate 39, figure 1, in plate 44, figure 1,
and in plate 47. It has throughout been one of the most striking of
the species hybrids under observation in our cultures. Its Tabacum
parent, macrophylla, as we have grown it, exhibits the lowest, most
diminutive habit (two to three feet) of any of the Tabacum varieties,
and thus by comparison F^HSS (six to seven and one-half feet) is

1917] Goodspeed-Claiisen : F^ Species Hyhrids in Nicotiana 307

exceedingly noticeable. The general habit of the F^ corresponds
exactly to that of macrophyUa, not only in the relative number of
laterals and the angle which they make with the main axis, but also
in that this main axis in both cases is short and is overtopped by most
of the larger laterals.

The correspondence of the F^ flower and leaf characters with those
of macrophyUa as shown in plate 44, figure 1, and in plate 47, are,
again, too striking to warrant further comment except with reference
to certain specific points. Thus, the basal portion of the F^ leaf
compares remarkably closely with tliat of macrophyUa in the broad,
clasping base with rounded lobes which can hardly be called auricles.
In other words, the leaf-base characters of macrophyUa are near those
of sylvestris in the sense that they do not include the broad, clasping
auricles which are seen in most of the sessile-leaved Tahacum varieties
and yet no influence of sylvestris is here apparent. The same is as
strikingly true of the leaf-tip characters, since macrophyUa bears a
more bluntly tipped leaf than almost any of the Tahacum group and
is thus very near to sylvestris in regard to this character.

In the case of the floral characters we may note first that the color
in Fj is nearly indistinguishable from that of the Tahacum parent,
being in general of a deep rose-red shade. Further, the triangular,
whitish areas at the bases of the sinuses are seen to correspond in
amount in the two flowers and add to the general color resemblance.
Finally, the nearly pentagonal outline of the limb in macrophyUa is
perfectl}^ reproduced in the F^ flowers. We have seen, in dealing with
FjHSG, that the limb of the angustifolia flower is much more deeply
lobed than that of sylvestris and here we have the macrophyUa flower
with practically no lobing, and thus representing the other extreme,
yet in both cases the F^ flowers reproduce almost exactly the shape
of limb characteristic of the corresponding Tahacum parent.

FiH40 — N. Tabacum var. calycina X N, sylvestris

This hybrid and its parents are shown in plate 39, figure 2, and in
plate 45. Calycina bears an unusual, rather distinctly teratological
flower, types of which are illustrated in plate 45. and possesses an
almost equally unusiud habit in tliat the laterals so much overtop the
terminal inflorescence that the latter is almost obscured. The flowers
of calycina figured in plate 45, figure 2, were selected to exhibit the
extreme expression of the double "hose-iu-hose" character. The

308 University of California l^uhlications in Botany [Vol. 5

flowers of the F^ in plate 45, figure 1, were, on the other hand, picked
out to show the range of expression of the ealycine flower type and to
demonstrate that even those flowers which on superficial examination
appear to be normally developed actually exhibit a trace of the
petaloid abnormality in the calyx. Thus, the calyx of the flower in
the upper right-hand corner of plate 45, figure 1, has an indistinct
streak of light-colored tissue at the point where the pin is seen to
pass through the flower. The two flowers below show increasing
amounts of this petaloid tissue. Now calycina bears many flowers
with only this slight amount of petaloidy of the calyx and figures
1 and 2 of plate 45 might be combined to represent the total range
of floral abnormality in calycina and in the F^ also. However, the
flowers shown in figure 1 are representative of the majority of the
Fj flowers, while those shown in figure 2 are correspondingly repre-
sentative of the majority of the flowers of calycina. A number of
varietal hybrids in which calycina has been crossed with other
Tahacum varieties have been grown through many generations. In
these hybrids the calycine-flower character is recessive to normal
flower. In the species hybrids, on the other hand, the calycine-flower
factor of the dominant Tahacum reaction system which is acting as
a unit permits the otherwise recessive calycine-flower character to be
manifested in Fj. Flower color in calycina and F^ H40 is the same,
and varies from light red to bright pink. The corolla limb proper
is light red and this color may run in streaks down the corolla tube,
while the petaloid calyx may be entirely colored or partially green.
Habit and leaf characters peculiar to calycina are strikingly repro-
duced in the hybrid, as shown in plate 39, figure 2.

F,H142— N. Tabacum "Maryland" X N. sylvestris

This hybrid and its parents are figured in plate 40, plate 41, plate
44, figure 2, and in plate 48. FjH142 is the most vigorous of all
the various hybrids herein descriljed. It overtops both its parents
as must as three feet in many cases, and is correspondingly luxuriant
as to vegetative and floral characters. In general habit "Maryland"
and the F, are remarkably similar in that each shows a pyramidal
or conical shape due to the large spreading basal leaves and the rapid
diminution of leaf size as one passes up the main axis. This habit
is especially well seen in the row of FiH142 in plate 40. figure 1, and
also in plate 41, figure 2, whereas the single plant of "Maryland,"
shown in plate 41, figure 1, is overmature and the large laterals pro-

1917] Goodspeed-ChiKsen : F^ Species Hyhrids in Nicotiana 309

duced late in development mar the characteristic shape of the plant.
The relative height of these laterals is corresponding in the hybrids
when at the same stage of development.

The leaf characters of parents and hybrid are well shown in the
photographs and in the drawings given on plate 48. The long, droop-
ing leaves, rather broad in the center and tapering rapidly to either
end, give to "Maryland" and to the P^ a further distinct and char-
acteristic appearance. The correspondence in shape between the two
is emphasized in plate 48. The broad, clasping auricles of "Mary-
land" and the F, are, however, not too well figured in these drawings
but stand out strikingly in the photographs of plants of parent and
hybrid. The leaf-tip of "Maryland" is very characteristic in its
length and tendency to curve. The tips of the lower leaves of the
plants shown in plate 41, figure 1, have been broken, but the upper
leaves along the lower laterals bring out the character referred to,
while in the plants of the F^ figured both lower and upper leaves show
this leaf-tip peculiarity.

The floral characters of parent and hybrid are shown in plate 44,
figure 2. The color of the flowers of the Tahacum parent and F,
hybrid is in both cases a very light pink that corresponds closely to
that of angustifolia and PjH36, although there is some intangible
difiPerence in shade of color between the two varieties and their hybrids
which is brought out rather sharply by a Lumiere plate. The similar-
ities in configuration of flower between the one parent and the hybrids
need no comment. Attention might be called, however, to the striking
likeness in calyx characters wherein size proportions are correspond-
ing and also to the long, shapely, pointed calyx lobes present in both
flowers.

F,H179— N. Tabacum "Cuba" )< N. sylvestris

This hybrid has been one of unusual interest in connection with
the inheritance of the parthenocarpic tendency exhibited In- its
Tahacum parent (cf. Goodspeed, 1915). As has been mentioned above,
the fact that all the Tabacum-sylvestris hybrids produce no good
pollen results in tlie falling of the vast majority of tlieir flowers,
usually within a day or two following anthesis. "Cuba" has been
shown to mature a fail' jn'oportion of fruits fi'om castrated flowers,
while all the othei" Tahacum varieties lose llieir flowers after castration
about as do the F, hybrids which lack successful pollination. In plate
42, figure 1, is sliown a plant of the F, hybrid made between "Cuba"

310 University of California Publications in Botany [Vol. 5

and sylvestris. No good pollen is produced and thus one would expect
the flowers to fall just as in all these other partially sterile hybrids.
Contrary to this expectation, many of the flowers on F^HITG are
retained finally to mature fruits of normal size containing masses
of small-sized, functionless seed of a type which has been called
"phenospermic." This retention of the fruits is shown in the photo-
graph (plate 42, figure 1) which was taken at the end of the growing
season to illustrate this point. In this connection it must be noted
that, just as the calycine-flower character of calycina is recessive in
varietal crosses and dominant in crosses with sylvestris, so this
partheuocarpic tendency of "Cuba" appears to be recessive in a
varietal cross. "Cuba" crossed with "Maryland" gave an inter-
mediate Fj in general appearance — self-fertile, of course — but follow-
ing a very considerable number of castrations of the F^ flowers only
a very few fruits matured.

This hybrid, in addition to exhibiting the partheuocarpic tendency
of "Cuba," bears out with regard to other characters also the general
contention that the Tahacum reaction system is dominant throughout.
In the case of both parent and hybrid the flower is a greenish to
creamy white and the almost pentagonal corolla limb and slender tube
with slightly SM^ollen infundibulum of "Cuba" is reproduced in the
F^ flower. Leaf characters of hybrid and parent exhibit an equivalent
correspondence, though the two photographs on plate 42 do not
bring out this point satisfactorily since the parent individual is just
coming into flower, whereas the Fj is long past the height of its grow-
ing season. The photographs, however, leave no room for doubt as to
the general similarity in leaf characters.

Of the various Tahacum varieties concerned in these hybrids
"Cuba" is the most vigorous and possesses by far the tallest habit.
The Fi as grown was no taller and indeed did not seem to be quite
as luxuriant vegetatively as "Cuba," a situation brought out in the
two photographs on plate 42. This fact was probably due to a crowd-
ing of the hybrid rows in the field, since they were so close together
that the lower leaves were in almost complete shade after the first
few weeks of the growing season. This latter fact accounts, also, for
the few laterals produced on the hybrid from the central and basal
leaf axils as compared with "Cuba" and other more or less superficial
differences in habit. We have chosen to discuss this ' ' Cubsi" -sylvestris
hybrid even in the absence of as complete illustrative material as has
been included in the case of the other hybrids mentioned, primarily

1917] Goodspeed-Clausen : F^ Species Hybrids in Nicotiana 311

because it illustrates the fact that such an obviously extra-normal
characteristic as parthenocarpy when combined in the Tahacum re-
action system is manifested in the partially sterile hybrid with
sylvestris along with all the other attributes of the reaction system
in which it occurs.

FjH33 — N. sylvestris X N. Tabacum var. macrophylla purpurea

This hybrid is shown with its Tabacum parent in plate 37. It was
made in 1909 by Professor W. A. Setchell, who grew it in 1910 and
has turned over to us his notes upon its general appearance. We are
greatly indebted to Professor Setchell in this regard and also for his
continued interest in and many valuable suggestions concerning the
progress of the experiments dealing with the Tabacum-sylvestris
hybrids. We introduce FiH33 into this discussion with only brief
comment merely as further evidence of the dominance of a reaction
system, the factors within which act together in so remarkably unified
a manner when in contact with a totally different set of factors which
go to make up a totally different reaction system.

The plants of F^H33 seemed when first grown, and still are, re-
markable for their vigor and vegetative luxuriance, although among
the species hybrids more recently made other types of the Tabacum
reaction system crossed with sylvestris have produced plants of equal
size. The photographs in plate 37 emphasize the correspondence
between hybrid and parent both in general habit and in particular
characters. Particular leaf characters are closely similar to those
of the Tabacum parent, but the characteristic, sharply pinched-in leaf-
base of macrophylla purpurea, which is recessive in crosses with
Tabacum varieties having the broad type of leaf-base, is not faithfully
reproduced in the F^ hybrid. Instead, the leaves of the F^ hybrid
exhibit a narrow form of the broad type of leaf-base, an expression
which is intermediate between the broad type of sylvestris nnd the
sharply pinched-in type of macrophylla purpurea.

Flower color in the Tabacum parent and in the hybrid was a deep
red, a somewhat deeper shade of red than that peculiar to the flowers
of macrophylla and FjIISS. The flower of macrophylla piirpnrca is
strictly of the macrophylla type, but considerably larger, and the F,
flowers are identical with the former in shape and in proportion of
tube length to spread of limb, tliough of a somcwliat larger size.

312 University of California Publications in Botany [Vol. 5

DISCUSSION OF EESULTS

The results which have been presented demonstrate that in crosses
involving sylvestris and varieties of Tabacum the F^ hybrids through-
out display the characters of the particular Tabacum variety used
in the cross, but usually on a greatly enlarged scale. The consequences
of the increased growth and vigor of such hybrids must not be lost
sight of in judging as to the completeness of correspondence between
them and their Tabacum parents. This is true because such stimula-
tion may conceivably give rise to variations in proportional effect in
different characters, in such cases disturbing somewhat the ratio re-
lations usual for the character expressions, although fundamentally
the whole series of characters owes its expression entirely to the
directive effect of the Tabacum reaction system. Specifically we have
shown elsewhere (Goodspeed and Clausen, 1915) that under green-
house conditions it is possible to modily somewhat such a compara-
tively constant character complex as flower size, the spread of corolla
decreasing significantly when compared with that found under field
conditions, the length of corolla, on the other hand, increasing
somewhat. It is therefore possible that whatever slight deviations
may be found in these species hybrids of Tabacum with sylvestris,
when compared with tlieir parent Tabacum varieties under similar
conditions, may be largely dependent upon differences in the specific
reactions of certain character complexes to the new set of conditions
obtaining in the F, hybrid.

The results lierein set forth are particularly striking when com-
pared with the type of behavior exhibited by Tabacum in varietal
crosses within the grouj). The Tabacum varieties differ strikingly in
a large number of characters and when crossed give in Fj forms which
are intermediate in their characters. Tliis intermediate condition is in
part undoubtedly due to the fact that each parent contributes a scat-
tered set of factors which display more or less complete dominance, so
that a hybrid is produced the general ty])e of which occupies a position
intermediate between the two parents.^ Much of this intermediacy,
however, is due to a blending in F^ which may be followed by definite,
although often very complex, segregation in subsequent generations.
Very often this segregation is so complex as to indicate the existence

1 A number of character contrasts in Tabacum are known which do display
nearly or quite complete dominance: viz., the petioled condition of the leaf
as opposed to the non-petioled or sessile condition, the normal type of flower
as opposed to the abnormal, calycine type, and the normal fruiting condition
as opposed to the parthenogenetic tendency which obtains in the variety
' ' Cuba. ' '

1917] Goodspeed-Clausen : F^ Species Hyhrids i)i Nicotiana 313

of a number of factor differences even in relatively simple character
contrasts such as colored as against white flowers. Blending inheri-
tance followed by complex, intergrading segregations of this kind is
characteristic particularly of the size and form relations in the various
organs, as for instance in the leaves. The frequent production in
such segregation of extremes lying beyond those exhibited by either
parent is further evidence that this condition may be largely the
expression of the inter-relations of a relatively large number of factors
derived from both parents. It is all the more significant, therefore,
that tliese partially sterile hybrids of sylvestris and varieties of
Tabacum furnish such faithful reproductions of the particular
Tahacum variety concerned in the cross, for it is hardly conceivable
that all the Tahacum factors should be dominant to the corresponding
factors in sylvestris in the same sense that a certain Tahacum factor
is dominant to an allelomorph in the Tabacum series of factors. Thus,
to take a specific instance, when a red-flowered Tahacum, macroph ylla
for example, is crossed with sylvestris the F^ hybrids as grown in the
field show practically the some flower color as the red-flowered
Tahacum parent. There is perhaps a slightly lower intensity of
coloration in the flowers of the F^ hybrid which may well be dependent
upon their larger size. The color changes in fading are remarkably
sinnlar in the two forms. On the other hand, when such a red-flowered
Tahacum is crossed with a white-flowered Tahacum, "Cuba" for ex-
ample, the flowers are strictly intermediate in color. This different
behavior in the two cases might of course be attributed to factor
differences in the two whites used, for as a matter of fact the white
of the flower of sylvestris is distinctly different from the white of
the flower of "Cuba." Nevertheless, when the relations shown by
other character complexes, such as size and form of flower, size and
form of leaf, method of branching, etc., are considered, it appears
more reasonable to interpret the reproduction of the Tahacum flower
color in the F^ hybrid with sylvestris as dependent upon the directive
action of the set of flower-color factors brought in by the Tahacum
parent acting by virtue of their position in the general Tahacum
reaction system. The F^ hybrids, therefore, are to be considered as
depending for their developmental expression upon the Tahacum re-
action system of Mendelian factors acting as a unit in contrast to tlie
sylvestris reaction system which appears to renuiin in a latent con-
dition while the developmental processes are expressing themselves.
The yiodified physiological relations which result from the presence

314 University of California Puhlications in Botany [Vol. 5

of the sylvestris set of factors are apparently responsible for the
increased size and vigor of the hybrids and for slight proportional
variations which may appear in the degree of expression of some of
the Tahacum characters.

The predominating influence of Tahacum in determining the char-
acters of Tahacum-sylvestris hybrids has also been observed by other
investigators. Thus Bellair (1911) has reported that when sylvestris
is crossed with Tahacum the F^ hybrid reproduces the characters of
the Tahacum parent, although the hybrids were larger and more
floriferous than that parent and were almost completely sterile. The
colored plate presented by Baur (1914) illustrates this same condition,
but not in such striking fashion as we have observed it. Unfortunately
this colored plate is not accompanied by any statement as to the type
of Tahacum used in the hybrid, consequently we do not know whether
the Tahacum variety figured is the actual parent of the F, hybrid
of Tahacum X sylvestris illustrated in the plate. The characters of
the sylvestris flower, however, are very faithfully portrayed. East
and Hayes (1912) have also reported results of the hybridization of
sylvestris and Tahacum, but almost wholly from the standpoint of
the increased vegetative vigor of such hybrids. Plate VI of this
article would appear, however, to bear out the contentions which have
been advanced as to the directive action of the Tahacum reaction
system. On the other hand. Brown (1912), who has made a rather
complete study of a hybrid between sylvestris and a variety of
Tahacum which he calls "Havana," has arrived at a different result
and states as a general conclusion that neither parent exercises a uni-
form influence over any particular character of the hybrid or over
the sum total of characters. Since this study was based upon a con-
sideration of hybrids of only one Tahacum variety with sylvestris,
it is not difficult to see how the striking correspondence between
varieties of Tahacum and their F^ hybrids with sylvestris could have
escaped him. Although he finds that the hybrids in the main resemble
the Tahacum parent, he states that in general habit and form of
inflorescence they resemble sylvestris rather closely. These statements
are not, however, very well borne out by the figures he presents, and
such differences as may be noted from the Tahacum variety may
be ascribed to other causes such as we have pointed out above.

On the basis of his study of the external characters of the parents
and of the hybrid between them, Brown assigns to the Tahacum par-
ents an influence of approximately two-thirds and to the sylvestris

1917] Goodspeed-Clausen : F^ Species Hybrids in Nicotiana 315

parent one-third in determining the characters of the hybrid. These
figures are for the most part arrived at from a consideration of meas-
urements of nineteen arbitrarily selected characters. For any par-
ticular character a certain percentage influence is assigned to each
parent and the percentage totals of the set of characters selected are
supposed to represent rather accurately the relative degree of influence
of each parent. This matter, however, is so largely one of arbitrary
interpretation that it necessarily can possess but little value. Particu-
larlj^ is this true in cases in which the hybrid in general surpasses both
parents. It is a well-known horticultural fact that plants in general
may show marked increases in the size of vegetative and even floral
organs due to stimuli furnished by favorable conditions of soil and
climate. Elsewhere (Goodspeed and Clausen, 1915) we have shown
that even such relatively constant characters as those which go to
make up the flower complex may be influenced in definite directions
by external environmental conditions. Conceivably the case may be
similar here, for if the sijlvestris elements be regarded as providing
merely a stimulus for the Tahacum reaction system which is concerned
in directing the course of somatogenesis, then the sylvestris elements,
while in a sense the cause of the increased growth, are not a part of
it. Such a conception is borne out rather strikingly by a consideration
of certain of the measurements given by Brown which appear to fur-
nish a clue to the explanation of this phenomenon. If a comparable
series of measurements dealing with length of leaf, length and spread
of corolla, etc., be examined we find a rather striking proportional
increase over the Tahacum parent throughout, which is not the case
when these measurements are compared with those given for sylvestris.
When particular closely related characters are considered the evidence
is even more strikingly confirmatory. The length of calyx in the
hybrid is about 1.2 times that in the Tahacum parent, and it is 1.6
times that of the sylvestris parent. The corolla tube length of the
hybrid is about 1.3 times that of the Tahacum parent, but only .75 of
that of the sylvestris parent. Corresponding measurements which we
have obtained on parents and hybrids showed practically proportional
increases in corolla spread and length over the Tahacum parent when
the spread of the Tahacum and sylvestris parents was practically the
same, but the length of the corolla tube of sylvestris was about twice
that of tlie Tahacum parent concerned. The same considerations
would appear to apply to the histological features which were studied.
It seems, therefore, reasonable to regard the presence of the sylvestris

316 TJniversity of California Puhlicafio)is in Botany [Vol. 5

elements as furnishing a stimulus for a general increase in size in
the hybrid, but the sylvestris characters are not to be considered as
making up any considerable i^roportion of this increase. This state-
ment is not, however, to be construed as necessitating a denial of any
character influence of sylvestris in the hybrid, but merely as empha-
sizing the general fact that such influence is very slight indeed.

In addition to a study of the Tahacum-sylvestris hybrid, Brown
has made a similar study of the hybrid of Tahacum and N. alata.
This hybrid has been figured by East and Hayes (1912, plate VIII)
and has also been reported upon by Naudin (1863). East and Hayes,
and Brown obtained hybrids which were much weaker than either
parent, but Naudin found the hybrid vigorous but tardy in develop-
ment. The difference may possibly be connected with the fact that
Naudin used N. macrophyUa as the Tahacum parent, whereas East
and Hayes, and Brown used much more vigorous and robust varieties
of Tahacum. The results, however, apparently agree in demonstrating
a striking resemblance between this hybrid and the alata parent.
Brown finds that in this case the alata influence is of about the same
extent as that of Tahacum in the hybrids of Tahacum and sylvestris.
Here the same criticism must apply as that given of the study of the
hybrids of Tahacum and sylvestris. Apparently in this case the alata
reaction system dominates the somatogenic processes, and the Tahacum
instead of stimulating development definitely inhibits it. An interest-
ing indication of the fact that Tahacum does, however, have some
influence beyond that of inhibiting the somatogenic processes is fur-
nished by the fact that the flowers are a very light pink, rather than
wliito as in alata, indicating that although the Tahacum elements are
for the most part incompatible with those of the alata system, never-
theless some of them are able to react slightly with this system and
to give characters which show a slight Tahacum influence.

For other cases of species hybridization in Nicotiana (in addition
to the more recent work) we must consider the investigations of the
older hybridists, Kolreuter, Naudin, and Gartner, all of whom have
conducted extensive investigations of the phenomena following such
hybridization. Ever since Kolreuter (1761) employed the genus
Nicotiana in the classic experiment in which he crossed rustica and
paniculata, it has been a favorite subject for investigations in the
phenomena following hybridization. In spite of the extended period
over which the genus has been under investigation there are still many
uncorrected conti'adictions in the literature which deal with it. Focke

1917] Goodspeed-Clausen : F^ Species Ilijhrids in Nicotiana 817

(1881) has performed a useful service by pointing out a number of
these contradictions, but in many cases they have merely been
pointed out, no subsequent observations having been made to establish
the true state of affairs. In part these contradictions may be due to
confusion in the use of scientific names ; in pai't they apparently are
due to lack of consideration of the varying genetic constitutions of
the individuals employed, a natural consequence of the indefinite
ideas of heredity current before the general recognition of Mendelian
principles. Nevertheless some of the results appear clearly to show
the same general type of behavior as is reported in this paper, one
parent exerting by far the greater influence in the development of
the hybrid.

As an example of conflicting observations concerning the characters
of hybrids, we may take those dealing with the hybrid rustica X
paniculata. Kolreuter (1761) considered that the Fj was exactly
intermediate between the two parents. Gartner (1849, p. 253) be-
lieved that paniculata exerted the greater influence in the hybrid and
as evidence called attention to the resemblance of "Nicot. rustico-
panicidato-panicnlata 5 X rustica J^" to paniculata. Obviously, how-
ever, in the light of modern conceptions this can hardly be considered
proof of the predominating influence of paniculata in the hybrid.
Focke (1881) from his own observations found the hybrids more like
rustica and considered the effect of paniculata as practically confined
to floral characters. Lock (1909) considered his plants of this cross
distinctly nearer to rustica, so much so in the seedling stage that
he was at one time in doubt as to whether they were actually hybrids
or plants from accidental self-pollination of rustica. In the adult
stage, however, he found them intermediate in all characters. Finally
East (1915) reports that the hybrid is intermediate throughout. We
must, therefore, look to the point of view of the investigators them-
selves as a factor in determining their judgment of resemblance to
one or the other parent. This fact is undoubtedly due in part to differ-
ent estimates of the comparative value of resemblances in different
parts of the plant.

We may now consider a few special cases. A^. paniculata X ^^
Langsdorffii is reported by Gartner (pp. 260, 469) to be very nearly
a complete reproduction of Langsdorffii. The resemblance of the
hybrid to Langsdorffii is held to be as great as that existing between
paniculata and plants obtained by crossing back paniculata X rustica
to paniculata for three or four generations. Lock (1909) and East

318 University of California Publications in Botany [A^ol. 5

and Hayes (1912) obtained only weak and stunted plants from this
cross. Lock refrains from making any general statement concerning
the resemblance of the hybrid to one or the other parent, although he
apparently found a predominating influence of paniculata in deter-
mining flower shape and color. All observers are agreed on the total
sterility of the hybrid. According to Lock, fruits were produced which
contained a few seeds but these failed to germinate.

N. glauca X N. Langsdorffii sometimes gives hybrids, but only
with great difficulty (Gartner, p. 144). In one place (p. 222) Gart-
ner describes it as resembling glauca, but in other places (pp. 267,
402) it is listed among infertile hybrids which resemble the male
parent. It is completely sterile (p. 389). Focke (1881) draws the
conclusion that the hybrid resembles glauca, but to us it seems that
Gartner intended to convey the impression that it was more like
Langsdorffii in its characters. In reaching this conclusion we have
been guided by the fact that Gartner's statements as to hybrid and
parental resemblances on p. 222 contain so many other contradictions
to subsequent statements as to make it extremely probable that they
were due to a slip of the pen.

N. suaveolens X N. Langsdorffii is easily obtained, but absolutely
infertile (Gartner, p. 194). In spite of one contrary statement (Gart-
ner, p. 222), we may judge that it strongly resembles suaveolens in
most of its characters. Gartner states on one page (p. 258) that it
resembles the maternal parent so closely that were it not for its total
sterility there might be doubt as to its hybrid nature. In another
place (p. 362) he states that it differs from suaveolens only in it.s ster-
ility, in the separation of the stamen filaments from the tube of the
corolla, and in the bluish color of the anthers.

N. vincaeflora X N. Langsdorffii is listed by Gartner in one place
(p. 222) among those patroclinous in type, but in all others places
its resemblance to vincaeflora is emphasized. On page 258 the re-
semblance to vincaeflora is reported to be just as striking as that of
suaveolens X Langsdorffii to suaveolens. The hybrid is totally sterile
(Gartner, p. 471).

N. glutinosa X N. Tahacum, according to Gartner (p. 471), is
decidedly like the male parent, but the results of Kolreuter and
Naudin appear to establish an intermediate behavior for crosses be-
tween glutinosa and various varieties of Tahacum. Gartner (p. 402)
states that reciprocal crosses of grandiflora X glutinosa and chinensis
X glutinosa reproduce throughout grandiflora and chinensis.

1917J Goodspeed-Clausen: F^ Species Hybrids i)i Nicotiaiia 319

N. suaveolens X N. macrophylla is reported to be so much like
macrophylla that the characters of suaveolens cannot be detected in
the hybrid (Gartner, p. 256). It is a vigorous form (p. 527), and
possesses extraordinary powers of vegetative reproduction (p. 297),
It is also notable for its prolonged period of life (p. 547).

N. quadrivalvis X A^ Tabacum is reported to be decidedly like
the male parent (Gartner, p. 471). On page 401, Gartner includes
macrophylla X quadrivalvis among infertile hybrids resembling the
female parent. Satisfactory conclusions cannot, however, be drawn
from the meager statements concerning the characters of these hybrids.

N. quadrivalvis X glutinosa is listed by Gartner on one page (p.
286) among patroclinous hybrids, and on the next page among those
which are decidedly matroclinous. Focke (1881) has pointed out a
number of inconsistencies in the descriptions of this hybrid and its
reciprocal. It is apparently absolutely sterile (pp. 401, 533), although
the blossoms are held for some time when pollinated with pollen from
the parent forms. On page 559 its dwarf habit is described. The
reciprocal cross, glutinosa X quadrivalvis, is included among those
which are prevailingly patroclinous in type, and there is another note
as to its patroclinous character on page 257. As with quadrivalvis X
glutinosa, the blossoms are abscissed a few days after opening (p.
343). It is a dwarfed and stunted form.

N. rustica X N. quadrivalvis gives a hybi'id resembling the male
parent (Gartner, p. 222), but not so strikingly as do some other
hybrids (pp. 256, 284). It occasionally sets small, shrunken fruits
(p. 367) which appear toward the end of the blooming period and
contain a few seeds (p. 393). The hybrid is difficult to obtain (p. 109)
and the reciprocal apparently cannot be produced.

N. quadrivalvis X N. vincaeflora gives a hybrid in which the type
of quadrivalvis is distinctly discernible (Gartner, p. 256). On page
222, vincaeflora X quadrivalvis is listed among patroclinous hybrids,
and statements as to its patroclinous nature are repeated at other
places (pp. 267, 286, 290, 471). The hybrid is totally sterile.

N. suaveolens X N. glutinosa is stated to be of the paternal type
(p. 267), but it has much enlarged flowers (p. 296). The blossoms
are apparently as deeply colored as those of glutinosa itself (p. 301),
but still present differences in form and color from those of the parents
(pp. 318, 641). On page 404, botli lliis cross and its reciprocal are
listed among infertile hybrids intermediate in characteristics between
the two parents.

320 Vnivcrsitij of California Fuhlicaiions in Botany [Vol. 5

.V. paniculata X -V. vincaeflora may be produced only with great
difficulty (p. 146). It is decidedly like the male parent (p. 256), so
much so that the only influence of paniculata is to be seen in slight
changes in the form and color of flowers and a slight broadening of
the leaves. On page 286 this hybrid is reported to be the most striking
example of hybrids resembling the male parent. It is sterile. The
reciprocal cross, vincaeflora X paniculata, is listed among those in-
fertile hybrids which resemble the maternal parent.

Gartner appears to have been particularly impressed with the
varying degree of influence of one or the other parent in the develop-
ment of the hybrid, and presents the following general discussion of
this problem (p. 255) :

The extent and degree of deviation of the hybrid type from the habit of
the parents and their individual cdiaraoters is very different with different
species of a given genus. With respect to this matter Kolreuter makes the
following assertion: "The greater the differences between two species, the
greater must be the change which occurs iu the hybrid produced by crossing
them; and the less the difference between the two natural species the smaller
and less noticeable will be the change which occurs when they are hybridized."
These two propositions do obtain in many cases, particularly the second; but
in many cases thej- do not, particularly in certain types where iu crossing
the type displays entirely different relations toward the oue or the other
parent form, and the characters are distributed to different parts of the
hybrid in diverse degrees. Very notable in this respect is the behavior of
the hybrids Nicotiana suaveolens and vincaeflora ; for they in their combinations
with N. Langsdorfii retain their own type so completely that they present
differences only in the separation of the filaments from the corolla tube, the
bluish color of the anthers, the greenish coloration of the corolla, and the
curving of the corolla tube; in the hybrid suaveolenti-macropliylla, on the other
hand, suaveolens cannot be detected and macropliylla predominates by far. One
of the most noteworthy examples of such influence is the hybrid Nicotiana
paniculato-vincacflora ; because N. paniculata is so entirely converted into the
type of vincaeflora that only in the smaller greenish blossoms, the rounded, sig-
nificantly smaller, white limb, the partial separation of the filaments from
the tube, which is not crooked, in the somewdiat broader leaves and in the
more delicate branching is a slight difference to be noted from vincaeflora;
for neither in the whole growth and habit of the plant nor in the general form
of the leaves and their wn-inkled surfaces does any notable deviation occur;
whereas, on the other hand, in a combination of this species with N. quaclri-
valvis $ the influence of the latter in the hybrid (N. cpiadrivalvi-viiicaeflora) can-
not be mistaken.

Less striking cases of this kind are furnished by Nicotiana rustico-quadri-
valvis, glutinoso-quadrivalvis, in which the male type predominates, by N.
grandifloro-glutinoso, Altliaea cannabino-officinalis, in which, on the other hand,
the female predominates. In most of the hybrids compounded from mixed
relationships, as in Nicotiana rustico-paniculato-angnMifolia, rustico-paniculato-
glutinosa, and others, the paternal type is so exclusively predominant that these
hybrids might be taken as mere varieties of the jjaternal parents.

1917] Goodspeed-Clausen: F^ Species Hybrids in Nicotiana 321

The above evidence, therefore, although not above reproach, indi-
cates clearly that hybrids between species of Nicotiana often do exhibit
a rather close resemblance to one or the other of the parents involved,
instead of displaying an intermediate behavior. The suggestion has
therefore been made that in such cases distinct hereditary systems
have been contrasted, one of which apparently has gained the ascend-
ancy nearly or quite to the exclusion of the other. This behavior we
have taken merely as a clue to the type of relations which exist in
species crosses. It is not necessary for the sake of the argument that
either species should display a predominating influence in the hybrid,
but in the absence of such effects, it can readily be seen that the
behavior called for upon the assumption of relations dependent upon
system contrasts might be obscured beyond recognition, just as is
Mendelian behavior in experiments which involve a large number of
factor differences.

The data bearing upon inheritance in species hybrids of Tahacum
and sylvcstris are reserved for a forthcoming paper. The present
paper has been designed merely to deal with the resemblances of
Tabacum-sylvestris hybrids to the particular Tahacum variety used
in the crosses.

SUMMARY

1. Crosses between sylvestris and varieties of Tahacum always dis-
play the characters of the particular Tahacum variety used in the
cross, but usually on a greatly enlarged scale.

2. The predominating influence of Tahacum in such crosses is
ascribed to the dominance of the Tahacum reaction system as a unit
when contrasted with the hereditary reaction system of sylvestris.

3. An examination of the literature dealing with species hybrid-
ization shows that the case of varieties of Tahacum- and sylvestris is
not unique, but that in many other crosses one or the other parent
exerts a more or less greatly predominating influence.

Trati.smitfcd June JS, 1916.

322 University of California Publications in Boianij [Vol. 5

LITERATURE CITED
Baur, E.

1914. Eiufiihruug in die experimentelle Yererbungslehie. Berlin.
Bellair, G.

1911. Recroisees entre elles deux espeees qui se sont degagees d'un liybride

n'obeissent plus a la loi Mendelienne de la dominance. IV Conf.
Inter. Genetique, p. 200-213.
Brown, H. B.

1913. Form and structure of certain plant hybrids in comparison with the
form and structure of their parents. Mississippi Agr. Exp. Sta.
Tech. Bull., no. 3.

Clausen, R. E., and Goodspeed, T. H.

1916. Hereditary reaction system relations — An extension of Mendelian
concepts. Proc. Nat. Acad. Sci., vol. 2, pp. 240-244,
East, E. M.

1915. An interpretation of sterility in certain plants. Proc. Amer. Phil.

Soc, vol. 53, pp. 70-72.

East, E. M., and Hayes, H. K.

1912. Heterozygosis in evolution and in ])lant breeding. U. S. Dept. Agr.,

Bur. Plant hid.. Bull. no. 243.
FOCKE, W.

1881. Die Pflanzen Mischlingen. Berlin.
Gartner, C. F.

1849. Versuche und Beobachtungen iiber die Bastanlzeugung im Pflanzen-
reich. Stuttgart.
Goodspeed, T. H., and Ayres, A. H.

1916. On the partial sterility of Nicotituia hybrids made with N. sylvestris
as a parent. Univ. Calif. Publ., Bot., vol. 5, no. 9, pp. 273-292.

Goodspeed, T. H., and Clausen, R. E.

1915a. Variation of flower-size in ]\ icotiaiia. Proc. Nat. Acad. Sci., vol. 1,

pp. 333-338.
1915&. Factors influencing flower-size in Nieotiaiia, with special reference
to questions of inheritance. Amer. Journ. Bot., vol. 2, pp. 332-374.
1916. Mendelian factor differences versus reaction system contrasts in
heredity. Amer. Naturalist (in press).
Kolreuter, J. G.

1761-66. Vorliiufige Nachricht von einigen das Geschleeht der Pflanzen
betreffenden Versuchen und Beobachtungen. Leipzig.
Lock, R. H.

1909. A preliminary survey of species crosses in the genus N^icotiana from
the Mendelian standpoint. Ann. Royal Bot. Gardens, Peradeniya,
vol. 4, pj). 19.5-228.

Naudin, Ch.

1863. Nouvelles recherches sur I'hybridite des vegetaux. Nouv. arch, du
Mus. I.

Setchell, W. a.

1912. Studies in Nirotiana I. Univ. Calif. Publ., Bot., vol. 5, no. 1, pp. 1-86.

PLATE 37

Fig. 1. Nicotiana Tabacvm \nr. macrophylla purpurea (25/06).
Fig. 2. FiH33 — N. sylvestris X N. Tab. var. macrophylla purpurea.

[324]

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED AND CLAUSEN] PLATE 37

FifJ'. \. .\ icdt id iKi 'I'dhiicinii \;ir. iikk ri/pli jilld imrjuirid (2.')/0()).

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED AND CLAUSEN] PLATE 37

^/^')-

'A.

'J. F,U;i3 — A', .sylcv.stri.s X -V. 7'((//. v;ir. niarniiihiilla inirpurea.

PLATE 38.
107/01 — N. sylvestris.

FJI36—N. (Tab.) ungustifoUa X A^ sylvestris.
68/07— .v. (Tab.) august if olia.

[326]

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d

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o

o
en

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m

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PLATE 39.

Fig. 1. The Fi hybrid (H38) .V. Tab. var. maeroplnjUa (22/07) X N. syJves-
tris (107/01) between its two parents.

Fig. 2. The F, hybrid (H40) A". Tab. var. calycinu (110/05) X N. sijlvestris
between its two parents.

[328]

UNIV. CALIF. PUBL, BOT. VOL, 5

[GOODSPEED AND CLAUSEN] PLATE 39

Fiji-. 1

Fiii.

PLATE 40.

Fig. 1. Portion of a row of the plants of the Fi hybrid H142 — N. Tab.
"Maryland" X N. sylvestris.

Fig. 2. Portion of a row of the plants of the hybrid H121 in F,— F^ H33 X
N. sylvestris. In every respect the equivalent of N. sylvestris.

[330]

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CO

TI
—I

m

PLATE 41

Fig. 1. 78/05-A^. Tab. "Maryland."

Pig. 2. Portion of a row of the plants of the hybrid (H142) .V. Tab. "Mary
land" X N. sylvestris.

[332]

c

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o

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PLATE 42

Fig. 1. The Fj hybrid (H179) K. Tab. "Cuba" X N. sylvestris.
Fig. 2. 200/14— 1y. Tab. "Cuba'

) y

[334]

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED AND CLAUSEN] PLATE 42

Fig. 1

Fig. 2

I'LATE 43

Flowers of N. sylvestris (69/07), the Fj hybrid (H36) N. (Tabacum) angusti-
folia X N. sylvestrU) and of N. (Tab.) angmtifolia (68/07).

[;?36]

UNIV. CALIF. PUBL. BOT, VOL. 5

[GOODSPEED AND CLAUSEN] PLATE 43

PLATE 44

Fig. 1. Flowers of N. Tab. var. nuicrophylla ((22/07), the Fj hybrid (H38)
A'. Tub. var. macrophiiUa X N. sylvestris (69/07) and of A". syJvestris.

Fig. 2. Flowers of N. Tab. "Maryland" (78/05), the F, hybrid (H142)
N. Tab. "Maryland" X N. sylvestris, and of N. sylvestris (69/07).

[338]

UNIV. CALIF. PUBL. BOT. VOL. 5 [G00D3PEED AND CLAUSEN] PLATE 44

Fi-. 1

PLATE 45

Fig. 1. Flowers of N. Tab. var. calycina (110/05).

Fig. 2. Flowers of the Fi hybrid (H40) N. Tab. var. calycina X N. syl-
vestris.

[340]

UNIV. CALIF. PUBL. BOT. VOL, 5 [GOODSPEED AND CLAUSEN] PLATE 45

Fio-. 1

PLATE 46

On the left a leaf of the F, hybrid (H36) N. (Tab.) angustifolia X N. syl-
vestris; on the right a leaf of N. (Tab.) angustifolia (68/07).

[342]

UNIV. CALIF. PUBL. BOT. VOL. 5

[GOODSPEED AND CLAUSEN] PLATE 46

/■

k"

PLATE 47

On the left a leaf of N. sylrcsiris (69/07), in the center a leaf of .V. Tab.
A-ar. macrophylla (22/07), and on the right a leaf of the Fj hybrid (H38) N.
Tab. var. macrophylla X A', sylvestri.'i.

•,44]

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PLATE 48

On the left a leaf of the F, hybrid (H142) N. Tah. "Maryland" X A', ^ijh
vestris; on the right a leaf of -Y. Tah. "Maryland" (78/05).

[346]

UNIV. CALIF. PUBL. BOT. VOL. 5 [GOODSPEED AND CLAUSEN] PLATE 48

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 12, pp. 347-428, 10 text figs., plates 49-53 March 6, 1918

ABSCISSION OF FLOWERS AND FRUITS IN

THE SOLANACEAE, WITH SPECIAL

REFERENCE TO NICOTIAN A

BY

JOHN N. KENDALL

CONTENTS

PAGE

L Introduction 348

IL Summary of the literature 350

III. Technique ^ 361

IV. Histology and cytology of the pedicel 363

1. Histological and cytological condition of the mature pedicel 363

2. Development of the separation zone in Nicotiana and Lycoper-
sicum 367

3. Increase in size and development of mechanical tissue in the

pedicel of Nicotiana and Lycopersicum 369

V. The process of abscission 371

1. General description of the process in several genera 371

2. Method of cell separation 376

VI. Abscission of the style and corolla 383

VII. Time of abscission 385

1. Eeaction time 385

2. Abscission time 396

VIII. Experimental induction of abscission 397

1. Induction by illuminating gas 397

2. Action of acids on the separation layer of Nicotiana 404

3. Induction by mechanical injury 406

4. The ability of certain species to throw off pedicels from which
all the floral organs have been removed, as related to the induc-
tion of abscission by mechanical injury 410

IX. Summary 411

X. Conclusion 415

XI. Literature cited 418

XII. Plates 420

■t\?a«-.5:'2'4

348 University of California Publications in Botany VVoiu. 5

INTRODUCTION

Although it is a matter of common observation that many plants
are capable of detaching portions of the body, the underlying cause
and the actual mechanism which bring about such separation are
only slightly understood. The process has often been described as
one of self-pruning by which the plant rids itself of useless portions
of its body. Since abscission is sometimes confused with exfoliation,
it seems desirable here to distinguish definitely between these two
phenomena. It can be said that, in general, exfoliation is preceded
by drying and death of the part to be cast off and that actual separa-
tion of the organ is accomplished by a mechanical break through dry,
dead tissues. Abscission, on the other hand, is usually not preceded
by drying and death of the organ concerned and its detachment is
accomplished by a separation along the plane of the middle lamellae of
active living cells.

Abscission may be either axial or lateral. Axial abscission includes
the abscission of portions of stems, shoots, entire flowers or fruits.
Lateral abscission includes the abscission of leaves, petioles, sepals,
petals or styles. Considerable attention has been given by investi-
gators to the abscission of flowers because of the theoretical detriment
to crops caused by the fall of the flower before the fruit is formed.

The cause of leaf-fall in deciduous species is connected with peri-
odic changes in the physiological condition brought about by changes
in the environment. In the case of some herbaceous plants and occa-
sionally in trees, sudden changes in environmental conditions result-
ing in a loss of physiological equilibrium often cause the throwing
off of leaves, flowers or even small shoots. In certain species, any-
thing which tends to loss or completion of function within or peculiar
to an organ causes the organ to be thrown off. Thus, staminate flow-
ers are commonly throv^ii off soon after anthesis and pistilate flowers
generally fall when fertilization is prevented. Similarly, certain
species — e.g., Impatiens Sultani and Mirahilis Jalapa — throw off por-
tions of their stems which have been rendered useless as a part of the
conducting system because of injury or removal of distal buds or
leaves.

The following definitions of terms, which will be used throughout
this paper, are made necessary because of a notable lack of uniformity
in their usage by various investigators who have dealt with abscission.

1918] Ketidall: Jhscission of Flowers and Fruits in Solanaceae 349

1. Abscission is the detaching of an organ by the separation of
actively living cells at or near its base.

2. The separation layer (Mohl's Trennungschichte) is the layer of
cells the components of which will separate from one another at
abscission.

3. The separation cells or ahsciss cells are the cells that make up
the separation layer.

4. The separation zone is the general region through which abscis-'
sion takes place and usually is largely proximal to the separation layer.

A preliminary account of abscission in F^ species hybrids of Nico-
tiana has already appeared (Goodspeed and Kendall, 1916). The
present study represents an amplification of this investigation and its
extension to other species of the Solanaceae. It is particularly con-
cerned with the following : ( 1 ) the position of the separation layer ;
(2) the origin of the separation layer; (3) the cytology of the separa-
tion layer; (4) the process of abscission, including (a) a description
of the appearance of the separation layer in consecutive stages of the
process and (&) the method of cell separation; (5) the time occupied
by abscission, including (a) the time between the application of the
stimulus and fall (reaction period) and (h) the time involved in the
actual process of cell separation (abscission period) ; (6) experimental
induction of abscission.

Although the investigation reported here is largely a morpholog
ical one, the results of the experiments on the method of cell separa-
tion, the time of abscission and the induction of abscission seem to
have a distinct physiological significance as well.

350 University of California Publiaitions in Botany [Vol. 5

SUMMARY OF THE LITERATURE

Since the literature on abscission is rather voluminous, it seems
best to present the following discussion under several different head-
ings corresponding, to a certain extent, with the six main topics of
interest mentioned in the introduction. The summary below is largely
confined to the literature on axial abscission, although that on lateral
abscission is considered in so far as it has a direct bearing on the most
important aspects of the abscission problem.

1. Histology of the Pedicel

a. POSITION OF THE SEPARATION LAYEE

Hoehnel (1880), discussing the fall of catkins in Populus and
Salix, locates the separation layer at the base of the catkin. The gen-
eral region at the base of the catkin, in the distal part of which the
separation layer is located, he calls the "separation zone." In Salix,
actual separation occurs in the -separation layer, but in Populus it
occurs in the parenchyma entirely outside the separation laj^er.
According to Balls (1911), the separation layer in the cotton flower
is located at the base of the pedicel. The layer is located by Hannig
(1913) at the base of the pedicel in Nicotiana Tahacum, X. rustica,
N. accuminata, N. sylvestris, Datura, and Atropa, and at the tip of
the pedicel in Nicotiana Langsdorffii, Salvia Aloe, Cuphea, and Gasteria.
He finds it occurring at the middle of the pedicel in Impatiens Sultani,
Solanum tuhcrosum, Lycopersicum, Asparagus, and Begonia. Gort-
ner and Harris (1914) and Lloyd (1914&), working on the abscission
of internodes as the result of injury in Impatiens Sultani, locate the
separation layer at the first node below the injury and just above the
axillary bud. Occasionally, according to the latter investigators, ab-
scission may occur at the second or third node below the injury and
in these cases the buds at the first or second nodes seem to be abortive.

The separation layer, according to Hannig (1913), may occur at
the base of the complete inflorescence in Impatiens and Oxyhaphus.
According to Lloyd (1914a), the separation layer occurs at the base
of the pedicel in cotton and at the base of the ripened ovarv' in grape
"shelling." In the abscission of internodes and tendrils in Vitis and
Ampelopsis, Lloyd (1914a) locates the layer near but not exactly at
the base of the internode. A peculiar case illustrating the result of
displacement of the stem on the location of the separation layer is

1918] Kend-all: Abscission of Flowers and Fruits in Solanaceae 351

discussed by Lloyd (1914a) for Ampelopsis and Gossypimn. In the
latter, abscission, in the abnormal case, occurred down the internode
at the base of the pedicel. Tliis is explained as the result of a dis-
placement during growth b}' which part of the pedicel becomes united
to the stem.

Occasionall}', grooves or swellings are noticed at the base of the
organ being abscissed where they correspond more or less exactly to
the general position of the separation layer. Examples are given by
Hannig (1913) for Lycopersicum and Solanum tuberosum and by
Balls (1911) for Gossypium. Abscission may occasionally occur,
according to Lloyd (1914a), above a small bract. According to these
latter investigators, there is more often no external indication of the
layer. Frequently, grooves bear no relation to the layer because in
many cases of this kind (Hannig, 1913, for Bvnnfelsia) separation
occurs a short distance distal to the groove.

From the above brief summary it is evident that in the case of
axial abscission the separation layer is located at or near the base of
an internode. Apparent exceptions are reported by Hannig (1913)
in which it is seemingly located at the middle of an internode. It
seems probable that a more critical re-examination might reveal the
fact that even these exceptions accord with the general rule. In these
cases, for example, the pedicel of the flowers in question might be
composed of two internodes.

h. ORIGIN OF THE SEPARATION LAYER

Kubart (1906) states that the occurrence of the separation layer
in all tyes of abscission may be explained in one of the three following
ways: (a) the separation layer is preformed and represents simply
a portion of the primary meristem which has remained in its original
active state; (&) it represents a secondary meristem; (c) the primary
meristem may function directly as a separation layer. The differ-
ence between a and c is only a difference in time, c being added to
explain the origin of the separation layer in abscission of very j^oung,
embryonic tissues. In a, the separation laj'er is present at the base
of the organ from the start of its development, but in h this layer has
to be formed by a secondary meristem before abscission can occur. In
a, cell divisions are not normally found preceding abscission, but in h
and c they arc. Mohl (1860), working on the fall of the flower in
Aesculus, Pavia, Lagenaria, Cucumis, and Ricinus, states that the
separation layer in these forms is of type h. Throughout his entire

352 University of California Puhlicaiions in Botany [Vol.5

work Mohl gives the general impression that it is necessary for a sep-
aration layer to be formed from a secondary meristem before abscis-
sion can occur. Wiesner (1871), working on leaf -fall in general,
observes that the separation layer is not generally of type h, as Mohl
believes, but more often of type a. According to Becquerel (1907),
the separation layer is formed in the pedicel of Nicotian-a from a sec-
ondary' meristem (type &). In the cotton flower Balls (1911) finds
that the separation layer is of type 1), but according to Lloyd (1914a
and 1916&) there is doubt as to this conclusion, since in the case of
very young cotton flowers in which abscission occurs very suddenty,
he finds only rarely that cell divisions do not precede abscission.
Hannig (1913), for flower-fall in general, states that a separation
layer of type a is always present but in certain species a secondary
layer of type h may also be formed, through which separation may or
may not occur. Hannig, diff'ering from Becquerel (1907), points out
that the separation layer in Nicotimw is of type a. Lloj'd (1914a)
and Loewi (1907) indicate that in general a layer of cells through
which abscission is possible is more often of type a than of type h.
They believe, however, that the separation layer is not a definite
morphological structure but represents merely a physiological con-
dition.

c. CYTOLOGY OF THE SEPAEATION LAYER

Mohl (1860) describes the separation cells in the flower stalk as
young, active, small cells which generally contain no starch. He also
states that in most cases cell divisions are characteristic of the sep-
aration layer, i.e., that the separation layer is meristematic. Hoehnel
(1880) finds that cell divisions are characteristic of the proximal por-
tion of the separation zone in Salix and Populus but in the distal
portion, where the separation layer is developed, these divisions are
not so numerous. In some cases he finds separation taking place in
the parenchyma, entirely outside the "zone" where there had been
no cell divisions. The separation cells in Nicotinna are described by
Becquerel (1907) as small, practically undifferentiated cells with
large nuclei. In Begonia, Fuscliia, Mirahilis, and Impatiens Hannig
(1913) describes the tissue as secondary meristem (type h) with the
cells rectangular in shape and arranged in more or less definite rows.
In contrast to the above observations, he describes the cells as small,
irregularly arranged and spherical in Salvia, Solanum nigrum, and
Nicotianu Tahaciim. In Solanum nigrum the separation layer consists

1918] Kendall: Ahscission of Flowers and Fruits in Solaiiaceae 353

of two or three tiers of cells but in .V. Tahacnni the layer is made up
of ten to fifteen tiers.

Hannig (1913), by means of various microchemical tests, can
detect no chemical difference between the cell walls of the separation
la.yer and those of the cells on either side. Lloyd (1914a), however,
claims that the cell walls of the separation cells break down more
quickly when treated with caustic potash than do the walls of normal
cells. Starch grains are frequently noted by Hannig and Lloj^d
(1916rt) as occurring in the separation cells, especially in the abscis-
sion of internodes by Miradilis JaUipa.

An examination of the literature thus makes it evident that there
has been a great difference noted in the various species in regard to
the character of the separation cells. The one characteristic of these
cells, however, to which there is no exception is that they are in an
actively living condition.

2. The Process of Abscission

a. METHODS OF ABSCISSION

It has been found that in practically all eases of abscission the
detaching of the organ is brought about by the separation of cells
along the plane of the middle lamella. It is the method noted by
Mohl (1860), Wiesner (1871), and Kubart (1906), who call it a pro-
cess of maceration, Correns (1899) calls it a process of "schizolysis. "
Correns, however, in the same work describes a new and different
method of abscission (rhexolysis) which he finds in mosses. In this
latter method, separation is accomplished by a seemingly passive
break of tissues irrespective of the position of cell walls. This may
be the case in the style of cotton (cf. Lloyd. 1914a). This same
method has been reported by Tison (1900) in the leaf of Aristolochiu,
Sipko, although the evidence has been called in question by Lloyd
and Loewi (1907). Still another type of abscission has been described
by Hannig (1913) as a result of experiments on Mirabilis and Oxy-
haphus. In these plants he finds separation being brought about by
a disorganization and dissolving away of a complete tissue. Lloyd
(1916a), on the other hand, states that separation in these species is
accomplished by cell separation and is thus true schizolysis. Hannig
was doubtless confused in this case by the cell elongations which
Lloyd observes and by which the membranes surrounding the proto-
plasts are drawn out exceedingly thin. Loewi (1907), working on

354 TJniversity of California Puhlications in Botany [Vol. 5

several genera, including Cinnamomum and Euonymus, notes and
figures cell elongations similar to those figured by Lloyd (1916a).
These cell elongations he finds so frequent and conspicuous that he
proposes a distinct type of abscission, calling it a " Schlauchzell
mechanismus. ' '

Loewi, on the basis of his studies, seeks to classify the methods of
cell separation in abscission under six different headings, which per-
haps would be more appropriately presented under the next subject
of consideration (the methods of cell separation) ; but since the author
gave them as distinct methods of abscission they will be considered
here. They are: (1) "round cell" mechanism; (2) dissolving of the
middle lamella; (3) maceration; (4) turgescence; (5) cell elonga-
tions; (6) "hard cell" mechanism. They are to be considered merely
as factors which, singly or in combinations, may enter in as a part of
the normal process of cell separation. Loewi also claims that by con-
trolling the temperature, humidity, and various other factors sur-
rounding the plant he can influence it to such an extent as to change
its method of cell separation.

}). METHOD OF CELL SEPARATION

It has been held by various investigators that the cell separation,
almost universally connected with abscission, can be caused either by
(a) chemical alteration and dissolving of the middle lamella or by
(&) increase in cell turgor. This whole matter has received consider-
able attention, although very little direct evidence has been obtained.
Wiesner (1871 and 1905) states that cell separation is caused by the
dissolution of the middle lamella and b}' increased turgor. Kubart
(1906) and Loewi (1907) agree entirely with Wiesner on this point.
Strasburger (1913), Tison (1900), Lee (1911), Hannig (1913), and
Lloyd (1916rt and h) believe that cell separation is accomplished by
the dissolution of the middle lamella. Practically all investigators
have noticed the turgid appearance of the cells after separation,
althougli this of course does not constitute evidence that the separa-
tion is due to increased turgor. Fitting (1911) claims that the sep-
aration is accomplished, at least in some cases, solely by an increased
turgor of the separation cells. He bases his claim on the fact that
abscission is very often too rapid to allow time for the dissolution of
the middle lamella. He also mentions the fact that the separation
cells are very often small, spherical cells, the type of cell which would
respond most readily by an increase in cell turgor. On account of its

1918] Kendall: Absciss^ion of Flowers and Fruits in Solariaceae 355

rapidity and regailarity of reaction, Fitting claims that abscission is
a semi-tropistic phenomenon and suggests the term "Chorismiis" to
designate this type of reaction.

It has been observed by Hannig and Fitting that the presence of
various narcotic vapors in the atmosphere around certain species of
plants causes their flowers or merely the petals to be thrown off.
Various aspects of this general problem of the reaction of plant tissues
to such agencies have been investigated. It has been determined by
various plant physiologists that the presence of narcotic vapors, such
as illuminating or acetylene gas, in the air around certain plant tissues
causes the proportion of soluble carbohydrates within their cells to
increase. This increase in the amount of soluble carbohydrates would
indicate an increase in cell turgor. The question at once arises,
whether or not this increase in turgor can effect complete separation
or maceration of cells without the occurrence of chemical alteration in
the walls. Richter (1908) resting his ease on experimental evidence,
throws some light on this problem. Various kinds of plant tissues
which he subjected to acetylene vapors broke in pieces because of the
maceration and collapse of the living cells within. He finds that in
the case of the cells of tissues which are commonly rich in starch
inclusions, such as the fruit of the snowberry and the potato tuber,
the maceration is most complete. In the potato, for example, 3 to
5 mm. of material on the surface become completely macerated after
being subjected to acetylene gas. According to Richter and Grafe
(1911), the proportion of sugar in starchy seedlings subjected to
acetjdene gas is larger than in seedlings grown under normal condi-
tions. In seedlings from oily seeds, however, the amount of sugar is
decreased and the proportion of glycerine and fatty acids increased.
The conclusion is therefore drawn that the subjection of plant tissues
to narcotic vapors favors the hydrolysing process in the cells involved.
The work of these two investigators goes to show that narcotic vapors
ma}^ cause abscission by acting in either of the most important meth-
ods suggested as responsible for cell separation ; they may increase cell
turgor on the one hand or favor the hydrolysis of the middle lamella
on the other.

Lloyd (1916a) presents evidence of chemical change in the cell
walls of the separation laj'er before abscission. These cell walls stain
in the usual manner with iodine, giving a light brownish color, but
as abscission commences, they give a faint blue color when stained
with iodine and washed out with water. Shortly before cell separa-

356 University of California Publications in Botany [Vol. 5

tion commences, Bismark brown and Ruthenium red fail to stain the
primary and secondary cellulose membranes of the separation cells,
although, when abscission does not occur, the entire cell wall is stained
in the normal manner. The cells when separating seem, furthermore,
to be surrounded only by the thin tertiary membranes. Lloyd, in his
work, figures cells in the process of separation which show the disso-
lution of the primary and secondary membranes of the cell wall.

Various interpretations are given to the repeatedly observed
occurrence of cell divisions preceding and accompanying abscission
Mohl (1860) expresses the opinion that cell divisions are generally
necessary before abscission can occur. Investigators since his time
have disproved the universal occurrence of cell divisions because they
find more and more cases where no cell divisions occur. Lloyd
(1914a) maintains that cell divisions are not of necessity correlated
with abscission, but are merely evidences of renewed growth and
wound responses. As evidence he states that cell divisions are some-
times absent and sometimes present in the same species. He cites
(1916&) the cotton plant as a typical example in which cell divisions
are present in the abscission of older flowers in which the reaction to
stimulus is slow. In young flowers and flower buds abscission may
proceed without cell division. He further notes (1914a) that cell
divisions sometimes precede and at other times follow abscission in a
given species.

c. AGENCIES ACTIVE IN BRINGING ABOUT THE DISSOLUTION

OF THE MIDDLE LAMELLA

Very few theories have been proposed to account for the dissolu-
tion of the middle lamella and practically no evidence of any kind
has been submitted. "Wiesner (1905) claims that in leaf -fall an
organic acid, produced as a result of lessening of cell activity and
stagnation of cell contents, acts on the middle lamella. His evidence
for this statement has to do with obtaining acid reactions with litmus
from cells at the base of the petiole during abscission. Kubart (1906)
also obtains acid reactions at the base of the corolla in Nicotians dur-
ing abscission and, although agreeing with Wiesner that an organic
acid probably causes the dissolution of the middle lamella, he also
admits the possibility that an enzyme plays a part in the process.
Lloyd (1916&) makes the statement that the dissolution of the middle
lamella is a process of hydrolysis and although making no definite
statement on the subject appears to take it for granted that an

1918] Kendall: Abscission of Flowers and Fruits in Solaimceae 357

enzyme of some kind is the active factor. Indeed, since all liydrolys-
ing processes of living cells are now supposed to be due to the action
of enzymes, there is no reason to suppose that the hydrolysis of the
middle lamella does not conform to the general rule. For it is known
that an enzyme, pectosinase, is capable of breaking down the pectose
of which the middle lamella is composed. However, until more is
known concerning the nature of this particular enzjane it remains
impossible to get more definite evidence on this phase of the problem.

3. Abscission of the Corolla

Reiche (1885) gives an account of the fall of the corolla in a
large number of species belonging to about forty-five families of the
monocotyledons and dicotyledons. He finds that the corolla may be
thrown off in one of three different ways : ( 1 ) by the activit}' of a
small-celled separation layer; (2) through decay; (3) through in-
crease in size of the ovarj^ thus tearing off the tissue involved at
the base of the corolla. In many cases of true abscission — case 1
above — Reiche finds that the separation layer is preformed and ready
to function at any moment. This represents a contradiction of
Mohl's observations, according to which the fall of the corolla is
usually due to the action of a separation layer formed shortly before
fall. According to Reiche, the separation layer is very seldom morpho-
logicall}^ differentiated from the neighboring tissue, but in a few cases
he describes the separation layer as consisting of a layer of cells
smaller than the neighboring cells on either side.

Kubart (1906), in his account of abscission of the corolla in sev-
eral different species, describes and figures the process which takes
place in Nicotiana. The separation layer in this genus he finds to be
in no way morphologically differentiated, of indefinite shape, and
located about 1 mm. above the base of the corolla tube. In this gen-
eral region a large number of cells separate from one another, all the
cells in cross-section taking part except the epidermal cells and the
tracheae. Fitting (1911), in his work on the shedding of petals, de-
scribes the process of abscission in several genera, paying particular
attention to Erodium, Geranium, Linum, Helianthemum, Perlagmiium,
and Verhascum. Separation in these cases takes place through a
region of small, spherical cells rich in protoplasm. The separation
layer is not sharply differentiated as compared with the tissues on
either side but is located in a restricted region at the base of the petal.

358 Umversity of California PiiMioations in Botany [Vol.5

He finds no cell divisions preceding or accompanying abscission. The
process in premature abscission he finds differing in no way from
that in normal abscission after fertilization. These conditions, he
states, correspond more or less to those which he finds in the pedicel
during flower-fall.

4. Time of Abscission

The time elapsing between anthesis and flower-fall in partially
sterile F^ species hybrids of Nicotiana and between emasculation at
anthesis and fall in the case of their corresponding parents is dis-
cussed in a previous paper (Goodspeed and Kendall, 1916). It was
there stated that the average time is about nineteen days in F^ H154,
seven in F^ H179, five in .Y. Tahacum var. macrophijlla, and thirteen
in N. sylvestris. When we turn to the question of the reaction time
in premature abscission occurring before the normal time as the result
of sudden changes in external environmental conditions, we find that
this subject has received only slight attention. According to Lloyd
(1914a), the cotton "square" falls in one to twenty-two days after
the weevil lays its eggs, the average time being eight days. In one
experiment in which the ovary was cut transversely, Lloyd was able
to cause one hundred per cent of the young bolls to fall in forty-eight
hours and ninety per cent in twenty-four hours. Larger bolls take a
longer time to respond to injury than do smaller ones, as a result of
the development of the pedicel to a condition in which abscission
meets greater resistance. Cotton ' ' sqviares, ' ' he finds, take a longer time
to respond than young bolls, the former shedding thirty-five to sixty
per cent in thirty-six hours and the latter forty to seventy per cent in
forty-eight hours. On the other hand, he obtains no evidence (1916&)
that the reaction times are any shorter in small buds than in larger
ones. The reaction times in cases where the injury is performed in the
evening seem to be shorter by about twelve hours than in cases where
the injury is performed in the morning. This difference he ascribes
to the increase in turgidity which takes place during the night and
which serves to hasten the reaction. Very severe injuries to the ovary,
he finds, cause fall of young bolls quicker than less severe injuries.
Injuries which are less severe than those mentioned above and per-
formed so as to imitate the injury inflicted on the ovary by insect
larvae caused shedding in three to six days, with most of the fall
occurring on the fifth day. Summing up his entire results, Lloyd

1918] Kc'Hckill : Abscission of Flowers and Fruits in Solanaceae 359

(1916&) states that under field conditions the responses to all kinds
of stimuli conducive to abscission become evident within ten days,
with the maximum frequency below six days.

The actual time involved in the process of abscission (abscission
time) has received even less attention than the problems discussed
above. Fitting (1911) states that abscission time may occasionally
be very short, forty-five seconds to five minutes in the petals of Ver-
hascum and thirty seconds to six minutes in Geranium. Lloyd (1914a
and 1916&) finds abscission after injury of the small cotton-boll taking-
place within four hours, the length of time depending somewhat on
the age of the boll. In a previous paper (Goodspeed and Kendall,
1916) a general estimate of the abscission time was given and it was
stated that normal abscission due to lack of fertilization takes place
in Nicotiana hybrids in four to eight hours and premature abscission
in one to four hours.

5. Experimental Induction of Abscission

According to Hannig and Loewi, abscission may be induced in
two different waj's. First by abnormal external conditions ("spon-
taneous" or premature abscission) and second by normal internal
conditions at the normal time ("automatic" or normal abscission).
We shall consider in the following summary of the literature onlj'
two aspects of induction of the first type.

a. INDUCTION BY NAECOTIC VAPOES

Hannig (1913) reports a comparative stud}- of the behavior of
cut sprigs of different species of plants when subjected to laboratory
air and to illuminating gas. He notes the fact that under either of
the above conditions all the flowers and occasionally a few small
shoots are abscissed. He finds, however, that not all the species in a
given famil}' behave similarly in response to these conditions. We
are particularly interested in the Solanaceae and we may note that
this family contained more species that detached their flowers in
illuminating gas than ^x\y other of the families investigated b}^ Han-
nig. According to Fitting (1911), narcotic vapors such as tobacco
smoke, carbon dioxide, ether, chloroform or illuminating gas fre-
quently cause premature abscission of the corolla. He notices, how-
ever, that ammonia or turpentine vapors fail to cause abscission.
Brown and Escomb (1902) make the statement that Nicotiana, Cu-
curhitn, and Fiichsiu shed flowers and buds in air containing ()nl\-
0.114 per cent carbon dioxide.

360 Ufviversity of Calif arnia Publications in Botany [Vol. 5

h. INDUCTION BY MECHANICAL INJUKY

Becqiierel (1907), in a brief paper on the effect of wounding
flowers of Nicotiana, notes that even after fifteen days flowers without
sepals, anthers, or stigmas do not fall. After the same length of time,
flowers without corollas or flowers in which the corolla or stamens are
only half removed, have fallen. He points out that this result is more
conspicuous in young flowers but did not investigate this point suffi-
ciently to arrive at any definite conclusions. According to Hannig,
removal of various organs of flowers frequently causes abscission but
wounding of the pedicel does not. He concludes, therefore, that in-
jury itself does not cause abscission but only acts indirectly by inter-
fering with important physiological processes in the treated tissues.

According to Lloyd (1914rt), shedding of very young cotton-bolls
can be induced by removal of the styles before pollination, but fall in
this case can be assigned, as Fitting has shown, to lack of fertilization.
It appears that in the cotton flower (Lloyd, 1916&) there is an inhibi-
tion period which starts with the opening of the corolla and during
which premature abscission as the result of sudden stimuli very sel-
dom occurs. Also, cotton-bolls larger than 30 mm. in diameter are
very seldom shed under any conditions. Other results obtained by
Llo3'd on the effect of injury on the abscission of cotton flowers are
discussed above under "Time of Abscission" (page 357). Lloyd
(1914&) also notes the effect of injury on abscission of internodes in
Impatie/ns Sultani. Plants of this species, when a cut is made across
the stem, cast off the remainder of the severed internode. He gives
results of experiments on the eff'ect of different types of injury, noting
that some severe injuries do not cause abscission. Gortner and Harris
(1914) have obtained similar results with the same species. They
find that when the cut is made across the internode, very close to
the separation layer, abscission usually occurs, but occasionally it does
not. The}^ state, as does Lloyd, that the shape and location of the
separation layer may vary slightly according to the type of injurj'.

c. THE DIEECT OE INDIEECT ACTION OF THE EXTEENAL

STIMULUS

In all the above investigations the question naturally arises,
whether the narcotic vapors and injuries or any stimulus conducive
to abscission act indirectly through their influence on the physiolog-
ical condition of the plant or directly, through their action on the
cells of the separation zone. Most investigators, except Wiesner, ex-

1918] K&ndall: Ahscissimi of Flowers and Fruits in Solunaceac 361

press the opinion that atmospheric factors work directly in causing
"spontaneous'' abscission, although offering, so far as I can see, no
evidence for this view. Fitting states that the external influence
acts directly in most cases, but that the indirect action is apparent in
forms which must build a separation layer before fall can occur.
In regard to the action of injury, it seems to be the opinion of most
investigators (Hannig, Bacquerel, Gortner and Harris) that the
stimulus acts indirectly by interfering in some way with such
important physiological processes as transpiration, respiration, or
assimilation. On the other hand, if abscission is sometimes a semi-
tropistic phenomenon, as Fitting has suggested, it is evident that
injury may act directly in causing flower-fall.

TECHNIQUE

The results noted below were obtained largely from the examina-
tion of microscopic preparations made by the paraffin method,
although this method was supplemented by free-hand sections mounted
in water. In investigating the condition of the pedicel in some species
(Datura sp.. Petunia sp. and several species of Nicotiana) only free-
hand sections were examined. For most microchemical studies fairly
thick, free-hand sections are preferable. The material for sectioning
in paraffin was killed and fixed in various concentrations of the
ehromo-acetic series and dehydration and infiltration were, in general,
carried on very slowly. The free-hand sections were mounted in water
without killing.

In cutting longitudinal sections of any kind all the pedicels were
oriented so that the sections were cut parallel to the main stem of the
inflorescence, in the plane formed by the pedicel and stem taken
together. In studying the histology of the pedicel and the cytology
of the separation layer and in studjdng the method of cell separation,
these longitudinal sections were supplemented by cross sections in
series through the base of the pedicel. It was impossible to cut very
thin, longitudinal sections in paraffin without crushing or breaking
the cells ; most of these sections therefore were cut from lOfx. to 15/u, in
thickness. For a similar reason, it was found necessary to cut thick
sections (20)u,to 25ju,) of the pedicels of fruits in which mechanical tissue
had developed. It was possible, however, to cut excellent paraffin
sections from 5^ to 7/x in thickness in cross-section or longitudinally
through the small cells of the separation zone. Since the cells of the

362 University of California Publications in Botany [Vol. 5

separation zone are very small, not much could be determined in
regard to the dissolution of cell walls by means of thick, free-hand
sections. The best results along this line were obtained from the thin
paraffin sections of the separation zone, although in order to show the
cell wall in its normal thickness it was necessary to use the free-hand
sections. As a supplement to these sections, several points of interest
were brought out by washing off the isolated cells from the end of
freshly abscissed pedicels and mounting them for microscopic exam-
ination.

In most of the work the paraffin sections were stained in safranin
and Delafield's haematoxylin. The free-hand sections were generally
mounted in water and stained in iodine. In special instances other
stains were used. Thus, in testing for chemical differences in the cell
walls of the separation cells, several other stains, such as erythrosin,
eosin, Bismark brown, gentian violet and Ruthenium red were used.
It was found that for demonstrating the dissolution of cell walls
aqueous methylene blue was an excellent stain to use. This stain was
allowed to act overnight and the sections destained slightly in alcohol.
Methylene blue was also an excellent stain for the isolated cells ob-
tained as noted above. By fixing these cells to the slide with albumen
fixative and staining with this stain, the thin membranous wall sur-
rounding the protoplast can be distinctly seen.

Various methods, such as subjecting inflorescences to illuminating
gas and mechanical injury, were used to bring about abscission. The
best results were obtained in cases where abscission was induced by
inserting shoots under a bell-jar containing from 1.5 per cent to
3 per cent illuminating gas. By using illuminating gas in this way
and by taking sections of the pedicels at intervals it was possible to
determine just when the first signs of abscission appeared in a certain
percentage of gas. This time was definitely determined for certain
species so that it was possible to get material killed and fixed at any
desired stage in the process of abscission. It was found that the best
results were obtained by killing and fixing the pedicels at about the
time when abscission was known to be commencing.

1918] Kendall: Ahscission of Flowers and Fruits in Sokmaceae 363

HISTOLOGY AND CYTOLOGY OF THE PEDICEL

1. Histological and Cytological Conditions of the

Mature Pedicel

a. NICOTIANA

The vascular system in Nicotians, as in all the other genera
examined, is characterized by intraxylary phloem. Nicotiana differs
slightly from all others in that the xylem seems in cross-section
to be composed of a continuous ring of radial strands of trachea
rather than composed of a broken ring of distinct bundles. When a
branch of the vascular system (fig. 1, a) containing twenty to thirty
xylem strands is given oft' to the pedicel, it assumes the shape of a
crescent in cross-section, with the opening of the crescent on the ven-
tral side. A short distance distal to the groove which marks the sep-
aration zone (tig. 1, &), the crescent closes and throughout the
remainder of the pedicel the vascular system forms a complete cylin-

-■-a

Fig. 1.

a — vascular system.
b — separation zone.
c — pedicel cortex.
sc — stem cortex.
e — epidermis.

Diagram of pedicel of Nicotiana

f — chlorophyllous tissue.
ff — groove.
h — separation layer.
p — pedicel pith.

364 University of California Puhlioations in Botany [Vol. 5

der. The pith and cortex (fig. 1, p and c) are composed of large
parenchyma cells which in the cortex are two or three times as long
as wide, but in the pith are more nearly isodiametric. There is no
mechanical tissue to be found in the floral pedicel but, as will be noted
in more detail later, wood fibres are formed as soon as the fruit begins
to develop. The epidermis of the pedicel (fig. 1, e) is tj^pical but with
ja. poorly developed cuticle, especially in the groove (fig. l,g), where
the cells are also much reduced longitudinally. Beneath the epidermis
is a laj^er of small cells with very large intercellular spaces and an
abundance of chloroplasts (fig. 1,/). This tissue stops a short dis-
tance proximal to the separation zone and does not continue in the
pedicel. The layer of collenchyma which is commonly found in cer-
tain species just beneath this chlorophyl tissue is entirely absent in
Nicotiana, or at least is very poorly developed.

Corresponding with the general region of the groove is an area of
medullary and cortical cells which are smaller than corresponding
cells on either the proximal or distal side of the groove. This region
of small cells is homologous with the separation zone (fig. 1, h) and it
extends across the base of the pedicel. The smallest cells are in the
center of the region, in a plane with the bottom of the groove, and
grade in size to the larger cells of the pith and cortex on either side
(plate 49, fig. 1). The zone of small cells is ten to fifteen tiers of
cells thick on the dorsal side but is wider on the ventral side, where it
spreads out into the large area of storage cells found in the axil of
the pedicel. The separation layer (fig. 1, h) is located five to seven tiers
of cells distal from the bottom of the groove. Hanning reports this
layer as occurring at the tip of the pedicel in Nicotiana Langsdorffii,
but in all my experiments on two varieties of this species I find separa-
tion invariably occurring at the base of the pedicel in the position
described above. All the species and varieties of Nicotiana examined
show a structure of tlie pedicel corresponding with the above descrip-
tion except that in some varieties, as in those of N. Bigelovii, the sep-
aration zone is much thinner on the dorsal side. In such cases it is
also noted that the groove is poorly developed.

The cells of the separation layer are in no way morphologically
differentiated from those making up the remainder of the separation
zone. Indeed, any cell of the zone seems capable of functioning as a
separation cell. The separation cells are smaller than normal cortical
cells and spherical in shape except in the vascular bundles, where they
do not seem to be differentiated in size and are elongated parallel to
the longitudinal axis of the pedicel. The cell walls are slightly thicker

1918J Kendall: Abscission of Flowers and Fruits in Solanac&ae 365

than the walls of normal cortical cells, especiallj' at the corners, thus
giving the tissue a somewhat collenchymatous appearance. The small-
est cells more proximal show this collenchymatous nature more strik-
ingly than do the others. No difference in chemical composition could
be detected, by means of microchemical tests using caustic potash,
sulfuric acid, nitric acid, and various stains, between the cell walls of
the separation cells and walls of other cortical cells. Other tests, how-
ever, indicated a difference in the nature of the cell contents in the
two types of cells. Iodine frequently indicates the presence of starch
in these cells and also colors the protoplasts a darker brown than in
normal cells, showing that the separation cells are rich in protoplasm.
The amount of starch in the cells, however, was found to be extremely
variable, ranging from a total absence of starch to an abundance of
it. Iodine green imparts to the protoplast of the separation cells a
deep blue color in contrast with other cortical cells, which are not
colored by this stain. The blue reaction is most prominent where the
separation layer crosses the phloem. Other cells which react in the
same way to this stain are the sieve tubes and companion cells and
the storage cells in the axil of the pedicel.

b. LYCOPEESICUM

Conditions in Lycopersicnm differ in certain respects from those
existing in Nicotiana. In the former the separation zone (fig. 2, a)

seems to be located at the middle of the pedicel
i, and is marked externally by a swelling, as well
as by the groove of the type already noted as
characteristic of the pedicel of Nicotiana. This
groove in the tomato is very deep (plate 53,
tig. 1), reaching fully half the depth of the
cortex, and is, furthermore, of about the same
depth all the way round, differing in this
respect from Nicotiaiia, where the groove is
absent or poorly developed on the ventral
side. The vascular system in Lycopersicnm
(fig. 2, ft), in contrast with the condition in
Xicotiaiia, is composed of scattered bundles
oi" xylem which in this case do not form a
crescent proximal to the groove but are in the
form of a complete cylinder throughout the
ciitii-c ix'diccl. Ronoath the epidermis (fig.

-9
■f
.b

—c

Fig. 2. Diagram of pedicel
of Lycopersicnm
a — separation zone,
ft^vascular system.
<■ — epidermis.
d — separation layer.
e — pith.
f — chlorophyl-bearing

tissue.
(J — collenchyma

366 University of California Publications in Botany [Vol. 5

2, c) is the chlorophyl-bearing region of the cortex (fig. 2. f), such
as occurs in Nicotiana, but in this case the tissue continues in the
pedicel distal to the groove. Beneath this chlorophyl-bearing tissue
is a layer of well-developed collenchyma (fig. 2, g) which however
does not continue in the pedicel distal to the groove. The separation
layer (fig. 2, d) consists of three to six tiers of cells and is located
in a plane with the groove, differing in this respect from Nicotiana,
where it is located a short distance distal to the groove. Correspond-
ing to the condition in Nicotian-a, the chief characteristic of the separa
tion cells is their small size, spherical outline and active physiological
condition.

c. OTHER GENERA OF THE SOLANACEAE

The condition of the pedicel, so far as the histology of the separa-
tion zone is concerned, was examined in several other species, a list
of which is given below :

Solanum jasminioides Cestrum fasciculatum

8olanum tuberosum lochroma tuberosa

Solanum verbascifolium Datura sangxiineum

Solanum umbelliferum Salpichrora rhomboidea

Solanum nigrum Petunia liybrida

Solanum marginatum Salpiglossis sinuata

Lycium australis

The general condition of the pedicel of Datura sanguineum and
Petunia hybrida is worth describing in some detail. The tissues of
plants of D. sanguineum are more or less herbaceous in nature, large-
celled and somewhat succulent throughout. The chlorophyl-bearing
tissue which, in striking contrast Avith the condition in Nicotiana and
Lycopersicum (figs. 1 and 2). is continuous over the separation zone,
is composed of two rows of small, spherical cells just beneath the
epidermis. Except for a layer of collenchyma, whose much elongated
cells extend the entire length of the pedicel and thus continue the col-
lenchyma through the separation layer, the cortex and pith are com-
posed of more or less isodiametric, thin-walled cells. Floral abscission
is as common in this species as it is in Nicotian-a. The flowers are
very large and furnish excellent material for a study of the cytology
of abscission. Unfortunately not a sufficient number of flowers could
be obtained to make possible any detailed study of this genus. It was
noticed, however, that there is no region of small cells at the base of
the pedicel within which separation occurs and that the separation
cells are identical in size and shape with those on either side among

1918] Kend-all: Abscission of Flowers and Fruits in Solmvacme 367

which separation does not occur. The separation layer here is located
about 8 mm. distal to the base of the pedicel, with absolutely no ex-
ternal indication of its position. Microchemical tests, which in Nico-
tiana gave different reactions in the case of the separation zone and in
the case of normal cortical cells, here fail to show any corresponding-
condition of differentiation.

Abscission has never been found to occur in Petunia or Salpiglossis,
so that it is of interest to examine the histological condition of the
base of the pedicel in these two species. They are practically identical
with regard to the structure of the pedicel, so that the description
given below can be taken as applying to both genera. The cortical
cells of the pedicel pass into those of the stem without any groove or
small-celled region. On the ventral side, however, is the region of
small cells in the axis of the pedicel, which is more or less common to
all flowers. The tissues of Petu7iia are not so soft and succulent as
those of Datura, Nicoiimia, and Lycopersicum. They tend rather to
be dry and tough. The cells in the cortex and pith are also not so
nearly isodiametric as in Datura, but are much elongated in a direc-
tion parallel with the long axis of the pedicel.

The condition in the other species mentioned above will be given
only a general description. Abscission occurs in all the other species
except Salpichrora and Lycium which, however, do not differ, in
respect to the histology of the base of the pedicel, from any of the
others. Solatium tuberosum resembles Lycopersicum. All the other
species are similar in regard to the structure of the separation zone.
There is in every case a general region of small cells extending
across the base of the pedicel where the separation layer occurs.

3. Development of the Separation Zone in Lycopersicum

AND Nicotiana

a. LYCOPERSICUM

The development of the separation zone could be followed better
in Lycopersicum than in Nicotiana because in the former the zone is
not so close to the main axis of inflorescence. The problem here
resolves itself into an effort to determine, by means of longitudinal
sections of very young pedicels, how early in the development of the
flower the groove and the differentiation in cell size of the separation
cells appear. It was found that the development of the separation zone
indicates the method bv which the groove and differentiation in cell

368

University of California Puhlications in Botany [Vol. 5

size originate. The groove is fairly well developed (fig. 5) in young
buds whose corolla is only 3 mm. in length, but is not so deep as in
older buds. The cells of the separation zone at this stage are smaller
than cells on either side, but the difference is not so prominent as in
older flowers. In very small buds whose corolla is only 1 mm. in
length or whose calyx is only 2 mm. long, the groove is just beginning
to appear (fig. 4). In buds below this size (fig. 3) no groove or
differentiation in cell size can be detected. Abscission can occur in
these early stages, before the groove or differentiation in the size of the
separation cells has appeared, as well as at anj' other stage. In these
early stages the radial diameter of the cortex is much less, as com-
pared with that of the pith, than in older flowers. It is evident,
therefore, that the cells of the separation zone are small because they
retain their original small size while the rest of the cortical cells
increase in size. The fact that the groove is formed makes it probable
that there have been few cell division, or none, in the separation zone
of the cortex during the development of the bud. It was observed,
however, that the cells of the separation zone in the pith retain their
meristematic nature for a considerable period during the development

Fig. 3

Fiji. 4

Fig. 5
a — separation zone

1918] Kendall: Abscission of Flowers and Fruits in Solanaceae 369

of the flower. They are at this time rectangular in shape, elongated
perpendicularly to the long diameter of the pedicel, and arranged in
longitudinal rows. In later stages, however, when the flower is at
anthesis, or the fruit is forming, these cells have rounded up and
become irregularly arranged, thus leaving rather large intercellular
spaces.

b. NICOTIAN A
The separation zone develops in Nicotiaua much as it does in
Lycopersicum. It was observed in very young buds — calyx 2 or 3 mm.
or shorter — that no groove was present. In buds larger than these,
the groove and small size of the separation cell is apparent, appearing
first on the dorsal side of the pedicel. It is evident that in both these
genera the groove and area of small cells are explained in the same
way, i.e., by the fact that the normal cortical cells increase in size
faster than do the cells of the separation zone. Since in both genera
abscission can occur even before differentiation of any kind appears at
the base of the pedicel, it is evident that the groove and small-celled
region do not necessarily bear any relation to abscission. This state-
ment is borne out by the fact that in Datura neither the groove nor
the area of small cells is present and in Nicotiana separation occurs a
short distance distal to the groove.

c. CONCLUSIONS FROM THE STUDY OF THE DEVELOPMENT OF

THE SEPARATION ZONE

In view of the above discussion it is clear that the separation layer
in Lycopersicum, Nicotiana, Datura, and probably in the other genera
noted, originates according to the first method, a, proposed by Kubart
(cf. page 350). That is to say, the separation layer represents merely
a portion of the primary meristem which retains its original physi-
ological capacities.

4. Increase in Size and Development of ]Mechanical Tissues in
THE Pedicel of Nicotiana and Lycopersicum

There is a marked increase in the size of the pedicel in both
Nicotiana and Lycopersicum during the development of the fruit. It
was found that during this development the diameter of the pith
remains about the same, the actual increase in size being almost
entirely confined to the cortex (cf. figs, 3, 4, and 5). This increase in
the diameter of the cortex in the pedicel of Nicotiana is due, in the
first place, to an increase in the size of the original cortical cells,

370 University of California Publicutioiis in Botany [Vol. 5

which in average cases measured about 20/i, in diameter in the flower
and about 40/a in the fruit. In the second place, it is due to four or
five divisions of the cambium layer. This second factor in the increase
in size of the pedicel becomes evident when a count is made of the cells
between the phloem and tracheae, the result giving approximately six
cells in the flower and eleven in the fruit.

The increase in size of the pedicel of Lycopersicum, which is much
more prominent than the increase in Nicotiana, can be explained in
the same manner. In the former the increase in size, which in this
case takes place almost entirely distal to the groove, may proceed to
such an extent that the diameter of the pedicel of the fruit is two or
three times that of the flower at anthesis. A measurement of the
cortical cells in cross-section gave on the average 10/x, in the flower and
28/A in the fruit. In this case only two or three divisions of the
cambium occur; the cells resulting immediately show lignification.

The next subject of consideration is the development of mechanical
tissue in the pedicel of Nicotiana and its relation to abscission. It will
be remembered that there w^as no mechanical tissue noted in the
pedicels of buds and flowers. Parallel with the development of the
fruit, however, a continuous ring of mechanical tissue appears in the
xylem of the pedicel. This mechanical tissue is evidently the result
of a gradual lignification of the cells of the cambium and the outside
portion of the xylem parenchyma. There is thus formed a continuous
sheath of what may best be called wood-fibre tissue, in the form of a
c^'linder just outside the tracheal elements. These mechanical elements
first appear in the tissues of the pedicel five or six days after anthesis.
but since the lignification in these more distal tissues is merely the
result of the spreading upwards of the lignification in the older parts
of the plant, this period depends somewhat on the position of the
flower on the inflorescence. It was noticed in Nicotiana that the
wood-fibre tissue develops on both sides of the separation zone before
appearing in the latter, but in time it becomas continuous through
the separation layer. By a lignification of the cells between the two
points of the crescent of wood in the separation zone, there is also
a slight tendency to close this crescent on the ventral side.

Since abscission has not been observed to occur in lignified cells,
the question at once arises whether the tough sheath of lignified cells
which continues through the separation layer could hold the fruit on
the stem even after actual abscission had occurred. Upon looking
over any large number of plants in the field it will at once be evident

1918] Kendall: Ahscission of Flowers and Fruits in Solanaceae 371

that such a condition of affairs very often exists. It will be found in
many cases, especially on older plants, that although abscission has
occurred in the cortex, as evidenced by the presence af a white,
powdery substance at the base of the pedicel, the capsule is yet firm
on the stem. Indeed, in certain hybrid tobaccos it is common to find
most of the capsules in this abscissed condition. The fruit is supported
in these cases by the tough mechanical elements of the wood, which
also prevent the breaking of the tracheae and protect the intraxylary
phloem. In the pith the tissues may be in a somewhat abscissed con-
dition, but since there is no way for these cells to escape through the
sheath of wood they remain for some time in position before finally
collapsing.

The development of mechanical tissues takes place in Lycopersicum
in much the same manner as in Nicotiana but with the distinct differ-
ence that in the former the wood-fibre tissue does not become con-
tinuous through the separation laj^er. That is to say, in the tomato
a break is left in the mechanical tissue in a plane with the bottom of
the groove. It is evident here that abscission would cause fall of the
fruit in any stage of its development, although in this case it happens
that abscission very rarely occurs after two or three days past anthesis.
A condition resembling this one in the tomato was observed in other
berrj'-forming species of the Solanaceae such as Cestrum fasciculatum
and Solanum verhascifolhim, which often drop their immature fruits
by abscission. Abscission, however, very seldom occurs in mature
berries of these species, the fruit generally falling away from the
receptacle above the calyx.

THE PROCESS OF ABSCISSION

1. General Description op the Process in Several Genera

a. NICOTIANA

The process of abscission in all the species of Nicotiana investi-
gated conforms to the usual type involving separation and isolation of
cells. Further details of the process were briefly discussed in a pre-
liminary paper (Goodspeed and Kendall, 1916) for certain F^ species
hybrids of Nicotiana. It was there noted that cell separation starts in
the dorsal side of the pedicel, in the cortex a short distance distal to
the groove (pi. 49, fig. 1) and spreads from this point around to the
ventral side. The first external indication seems to be a bulging of

372 University of California Publications in Botany [Vol. 5

the epidermis (pi. 49, fig. 2) over the tissue in which the process is
taking place. Simultaneously with the start of abscission in the
cortex, the process apparently' originates independently in the pith
(pi. 50, fig. 1). It was further noted that the number of cells con-
cerned in the process, as a general rule, is greater in the hj^brids than
in their parents and also that this is true of ' ' automatic ' ' as compared
with "spontaneous" abscission. Just beneath the epidermis the cells
involved in separation were reported as being from five to ten tiers
thick, but as the process approached the vascular tissue the separation
layer was evidently reduced in thickness to not over one or two tiers
of cells (pi. 52, fig. 1). In the pith a more or less spherical mass of
cells is involved (pi. 50, fig. 1). When the separation is completed
the flower may remain in position for some time, until the epidermis
and tracheal elements are broken bj^ some mechanical agency.

The exposed separation surface of the pedicel was stated to be
convex in outline and slightly notched at the tip. Upon closer exam-
ination the surface itself Avas seen to be composed of the protruding,
rounded ends of cells with here and there completely isolated cells and
broken ends of spiral tracheae. These isolated cells are apparently
normal and do not markedly differ in form, size, or in the nature of
their cell inclusions from the same cells before separation. The
exposed surface of the attached portion of the pedicel is similar in
appearance to that of the detached portion, but is more or less flat
in outline. After separation the cells on this surface collapse and
probably act as a protective layer.

Following the observations recorded above, which had to do largely
with flower-fall in the F^ species hybrids, a number of species have
been investigated in an effort to determine whether or not their mode
of abscission differs from that already described.

It may be noted at the start that no marked exceptions were found
to the previously described condition, although at least two stages in
the procass of abscission have been found to be subject to considerable
variation. The first of these stages has to do with the place of origin
of the abscission process itself. An independent origin in the pith
has been demonstrated to occur in a large number of species and
occasionally it was found that the first evidences of abscission could
be detected here before any similar evidences appeared in the cortex.
Again, it was found in most species that cell separation starts first in
the ventral cortex although other places of origin were found in
several cases. Thus, in Xicotiana Tahacum "^Maryland" and Fj H36.

1918] Kendall: Abscission of Flowers and Fruits in SoUinaceae 373

for example, the process originates on the ventral side and may even
spread through the large area of storage cells in the axil of the pedicel
before reaching the dorsal side. The distance distal from the bottom
of the groove at which separation appears is also subject to variation.
This variation, however, is not typical of certain species, since it may
occur at different times in the same species, evidently as a result of
an abnormal stimulation to abscission.

The second part of the process subject to variation has to do with
the amount of tissue that may be concerned in actual cell separation.
Abscission first becomes complete in a narrow plane between two or
three tiers of cells across the pedicel and the flower can be easily
shaken off at that time. If, however, the flower remains on the stem,
and is kept turgid by the water rising in the unbroken tracheae, cell
separation spreads more and more widely through the tissues of the
pedicel, especially in the pith and cortex. It is the extent to which this
spreading normally proceeds that varies in the different species. When
the process has spread to a considerable extent, a white ring formed
by the isolated masses of cells can be seen with the naked eye at the
base of the pedicel and a casual inspection indicates that the amount
of this white substance varies in the different species. In most
hybrids, except F^ H179, there is more spreading in normal abscission
than in pure species. In Nicotiana quadrivalvis, N. Bigelovii, and
other similar species in which abscission very seldom occurs, no spread-
ing takes place. Spreading, however, occurs to a remarkable extent in
.V. Tahacum "Maryland."

&. LYCOPEBSICUM

We may say that, in general, abscission in Lycopersicmn corre-
sponds to that in Nicotiana and that the main points of distinction
between the two arise only from the original differences in the separ-
ation zones (cf. page 364). In addition, attention must be called to
the fact that quite frequently, in individual plants of the tomato, no
true abscission occurs in normal flower-fall. In these cases the flower
seems to be detached from the plant by a process which compares
closely with that called exfoliation. There is no active cell separation
and the flower simply wilts and dries back to the groove, where it
hangs until broken off by some mechanical agency. The first indica-
tion of the process is the loss of chlorophyl in the pedicel, which
gradually turns yellow, commencing at the tip and spreading proximal
to the separation zone. It is possible that most of the flower-fall

374 University of California Publications in Botany [Vol. 5

noticed by agriculturists is of this type. Quite often, however, true
abscission and this second type of flower-fall may both be found
operative in the same plant or even in the same flower. "Spon-
taneous" flower-fall in the tomato is, of course, of the true abscission
type.

Corresponding with the condition in Nicotiana,' true abscission in
Lycopersicum is seen to originate frequently in the pith. At any rate,
the process goes on here independently of that in the cortex, since the
final break is through the trachei^ and epidermis. Furthermore, separ-
ation takes place in a plane with the bottom of the groove (pi. 53, fig.
2) whereas, in Nicotiana, it takes place a short distance distal to the
groove. Separation may at first take place between only two tiers of
cells (pi. 53, fig. 2). but in time the process may spread until three
or four tiers become involved in separation. However, there is no
spreading of the process to a large number of cells, as is frequently
seen in Nicotiana, so that one very seldom finds the white powdery
substance at the point of separation. Also in contrast with the con-
dition in Nicotiana, there is, as abscission progresses, no bulging of
the epidermis which instead soon breaks in the bottom of the groove.
Separation in the tomato takes place in such a way as to give the
exposed separation surfaces the same general shape after abscission as
in Nicotiana, that of the detached portion of the pedicel being convex
and that of the remaining portion slightly concave.

c. DATUEA

Conditions in Datura differ strikingly from those in the two
species described above. This would be expected when one considers
the great differences in the structure of the separation zones (cf.
page 365). In Datura there is the usual chlorophyl-bearing tissue,
which consists of two rows of small, perfectly isodiametric cells with
large intercellular spaces, just beneath the epidermis. It will be
remembered from the description on page 365 that this tissue in Datura
continues the entire length of the pedicel and therefore, in contrast
with the condition in Nicotiaim and Lycopersicum, extends through
the separation zone. The first sign of abscission is the maceration of
this tissue as indicated by the appearance of a white color under the
epidermis. The latter may as a result become detached from the tissues
of the cortex for a distance of 2 cm. or more along the base of the
pedicel. This is soon followed by a break over the separation layer
and a curling back of the epidermis on either side, with most of the
chlorophyl-bearing cortical tissues still attached to its inner surface.

1918] Kend-all: Abscission of Flowers and Fruits in Solanaceae 375

After the break in the epidermis separation continues in the layer
of collenchyma just beneath. The cells of the collenchyma layer,
which are much elongated parallel to the long axis of the pedicel (five
to eight times as long as wide), separate for a distance of about 0.3
mm. up and down the pedicel, involving only a few tiers of cells. It
is evident that the cells of this tissue separate without dii^culty,
although not by any means as freely as the small spherical cells de-
scribed above. The large, isodiametric, parenchyma cells of the cortex
separate for a distance of 2 or 3 mm., involving many tiers of cells.
The cells of the starch sheath, which are small and spherical, separate
for a distance of 1 cm. or more, thus causing a longitudmal cavity to
be formed just outside of the vascular bundles. In the latter, separa-
tion involves only two or three tiers of cells. Separation originates
and continues in the pith independent of the process in the cortex,
but involves about the same number of cells as in the parenchyma of
the latter tissue. When separation has thus become complete, the
weight of the flower is very often sufficient to break the traches and
cause the flower to fall to the ground.

Several important facts are brought out by this examination of
abscission in Datura. In the first place, it shows that floral abscission
can take place without any structure which might possibly be inter-
preted as a morphologically differentiated separation layer. In the
second place, it indicates that cell separation is possible in several dif-
ferent types of living cells. It also shows that separation takes place
more readily in small cells than in large ones and more readily in
isodiametric cells than in elongated ones. The theory that the separa-
tion layer is not a morphologically differentiated structure, but repre-
sents a physiological condition (Lloyd and Loewi), could certainly be
well applied in this case.

d. OTHER GENERA

The process of abscission in the other species listed on page 365 is
essentially the same throughout. No indications were noted of cell
divisions or elongations accompanying abscission. Separation is
brought about by means of a separation of small and active cells
located in the general region at the base of the pedicel. In all these
forms the separation surface of the pedicel is convex in outline, so
that the separation layer must lie in more or less of a crescent in the
stem at the base of the pedicel. The main difference between these
forms and the three that have been described in detail above is found

376 University of California Puhlications in Botany [Vol. 5

in the fact that in the former, with the exception of Solanum tuber-
osum, separation occurs in the stem at the very base of the pedicel,
whereas in the latter three it occurs through the pedicel a varying
distance from the base.

2. Method of Cell Separation

a. GENERAL EEMAEKS

It will be remembered that two theories have been proposed to
account for the cell separation that is responsible for abscission.
First, it is conceivable that cell separation may be caused by an
increase in cell turgor, which causes the cells to round up and pull
apart without any change taking place in the chemical nature of the
middle lamella. Second, cell separation may be caused by a chemical
dissolution of the middle lamella with or without an increase in cell
turgor. The main difference between the two theories is that the
second, in contrast with the first, maintains that chemical alteration
of the middle lamella is always necessary before abscission can occur.
The first theory gains support from the work of Fitting and the second
from thg work of Hannig. Lee, Strasburger, and Lloyd. Wiesner,
Kubart, and Loewi ])elieve that cell separation takes place by the
action of both factors hut that either factor may at times be the more
important.

b. CYTOLOGICAL CHANGES ACCOMPANYING ABSCISSION

It was stated in a preliminary discussion (Goodspeed and Ken-
dall, 1916) first, that no indication of cell divisions or elongations
were observed accompanying abscission, and, second, that no evidence
of the dissolution of the middle lamella had at that time been obtained.
The first statement has been corroborated in that, during all the later
experiments, no divisions or elongations have been observed in any of
the described species. The dissolution of the primary cell membrane,
however, because of more exact knowledge of the proper time to take
sections and of more successful staining methods, has been fairly well
established.

The main problem here was to determine by the use of various
stains whether or not tlie primary and secondary cell membranes of
the separation cells stain differently in the early stages of abscission
than under normal conditions. This was a point which was found
very difficult to determine, principally because of the fact that the

1918] Kendall: Abscission of Flowers and Fruits in Solanaceae 377

separation cells are, comparatively speaking, very small, but also be
cause of the fact that the walls of these cells fail to show any strati-
fication.

Iodine, Delafield's haematoxylin, Ruthenium red, Bismark brown,
methylene blue, erythrosin, and eosin were used with little success in
most cases. Bj^ using iodine, however, just as abscission is known to be
commencing, a white streak may be seen across the section in the region
of the separation layer. Upon careful examination it was decided
that this white streak was due to the failure of most of the cell walls
in the separation layer to take the stain. Although it is probable
that with more careful examination the other stains mentioned above
would give similar results, it was found that methylene blue was the
only stain with which anything definite could be established. If a
thin longitudinal section cut in paraffin as abscission is known to be
starting, and stained in methylene blue, is examined (cf. page 361), it
will be found that the walls of those cells in which separation is about
to occur have remained almost entirely unstained. The protoplasts in
these cases seem to be surrounded only by the thin tertiary mem-
branes, between which is a streak of colorless material of varying
width (pi. 51). Cell walls where separation is not expected to occur,
however, stain a dark blue throughout in the normal manner.

An examination of freshly isolated cells washed off from the end
of an abscissed pedicel shows that these cells are still turgid and
active. It was impossible to determine whether these cells had in-
creased in size, as compared with the size of similar cells before abscis-
sion, but it is evident that the increase, if any, had not been very
great. The cells still contain their large nuclei, and occasional starch
grains, and show after isolation no signs of degeneration even after
several hours in water. In addition, these isolated cells appear to have
retained their original shape. In the collenchyma of Datura the cells
are from five to eight times as long as wide, and yet these cells retain
their original shape when isolated, as a result of the dissolution of
the middle lamellae. This isolation has evidently not been comj)lete,
since large masses of cells are seen still attached to each other. It is
noticed that in all cases the protoplast is surrounded by an extremely
thin membranous wall (pi. 52, fig. 3). It is also frequently noticed
that the protoplast seems drawn away from the cell wall as if plas-
molysis had occurred. It is possible that this appearance nuiy be due
simply to the gathering together of granules and the denser portion
of the protoplasm in the center of the cell.

378 University of California Publications in Botany [Vol. 5

c. EXPEEIMENTAL EVIDENCE FOR THE DISSOLUTION OF
THE MIDDLE LAMELLA

It is supposed that the middle lamella, or primary cell membrane,
is largely composed of calcium pectate, a calcium salt of pectic acid
which has been given the general name pectose. The secondary cell
membranes probably contain a larger proportion of cellulose with
the pectose than is present in the primary membranes. This pectose,
which is of course insoluble in water, is disorganized by a process of
hydrolysis to form pectin. The pectin, which is a colorless mucilagi-
nous substance, is readily soluble in water but is precipitated along
with the proteids and enzj^mes of the protoplast by the addition of
alcohol. Thus, if a water extract is made from separation zones dur-
ing the first stages of abscission, one would expect to get a solution of
several substances, among which would be the pectin produced by the
dissolution of the pectose in the primary cell membranes. It might
be expected that the amount of precipitate obtained from this extract
with alcohol would be greater, provided the amount of other sub-
stances remained the same, than the amount of precipitate obtained
in a similar manner from separation zones in which there had been
no abscission and in which no pectin had been formed. Whether or
not the increase in the amount of precipitate is due to the added
pectin cannot of course be proven without actual chemical analysis,
and such an anal.ysis would be difficult because of the very small sam-
ples of material obtainable. However this may be, any difference in
the amount of precipitate would be of interest.

This experiment and the two which follow are, as far as I have
been able to determine, the first of their kind. Apart from this fact,
their chief value probably lies in the fact that they suggest a line of
investigation which, if carried on in more detail and with better
facilities, will undoubtedly lead to important conclusions. These
experiments were, however, carried on with as much care as possible
and since the results of duplicate tests are in agreement, they give, as
far as they go, dependable results.

After several experiments indicating the results given below, the
following test experiment was performed:

Experiment 1. — Two water extracts of equal concentration were
made from the lots of material. Lot A contained 200 small pieces of
the pedicel in which the separation zone was located and in which
abscission had started. Lot B contained an equal weight of a similar

1918] Kemdall: Abscission of Flowers and Fruifs in Solanaceae 379

number of pedicels in which no abscission had started. The extracts
were made np to 10 cc. and the precipitate obtained with 60 cc. of
95 per cent alcohol. The precipitate weighed in the two lots :

A 996 mg.

B 903 mg.

One of the preliminary experiments performed with a weaker
alcohol gave results which may or may not be of considerable impor-
tance. In this experiment a light, almost invisible precipitate formed
in A and no precipitate in B. Whether or not the pectins precipitate
in lower percentages of alcohol more readily than the other substances
I have been unable to determine. At any rate, the precipitate in this
case felt slimj- and mucilaginous to the touch and might well have
been the precipitated pectin approximately pure.

d. EVIDENCE FOR INCREASE IN TURGOR

It was stated along with other conclusions in the preliminary paper
(Goodspeed and Kendall, 1916) that from the evidence at that time
available it was probable that cell separation is caused merely by an
increase in cell turgor, and throughout this later work it has been
clear that increased turgor is present during abscission. In view of
the evidence given above, however, it would seem that turgor can
play only a secondar.y role, although the occurrence of increase in
turgor must not be ignored.

The bulging of the epidermis frequently noted as accompanying
abscission is evidence of increased internal pressure. In the pith the
cells next to those which are separating are in a collapsed condition
due to the pressure of the expanding separating cells. By various
experiments it can be shown that humid conditions favor and severe
drought prevents abscission. Richter and others have shown that
narcotic vapors which cause abscission also cause increased turgor by
increasing the proportion of sugar in starch-containing cells. This
increase in cell turgor becomes so great as to cause complete macera-
tion in certain types of tissues. The frequent presence of starch
grains in the separation layer of Nicotiana, part of which are prob-
ably converted into sugar as a result of subjection to illuminating
gas, indicates that there is probably an increase of turgor during
abscission, at any rate when induced by illuminating gas.

On the other hand, a more extensive examination of abscission in
certain plants indicates that all evidences of inci-eased tui'gor may at

380 University of California Publications in Botany [Vol. 5

times be absent. Such cases might be explained by the absence of
any considerable amount of starch in the cells concerned. Indeed,
the starch grains usually noted in tlie separation layer can not at
times be observed. This might also explain the fact that the bulging
of the epidermis and collapse of cells in the pith usually accompany-
ing abscission are sometimes absent. Also, starch grains are rarely
observed in the separation cells of Lycopersiciim and Datura and in
these forms xexy little bulging of the epidermis occurs. Although
humid conditions favor abscission and drought prevents the process,
it has also been observed that drought has to be very severe before it
produces such a result. Other evidences for increased turgor derived
from the turgid appearance of the cells are mostly obtained after
abscission has started and, granting that the cells are isolated by dis-
solution of the middle lamella, more or less expansion due to release
of pressure is to be expected.

A critical examination of the separation cells during abscission
brings out several facts, other . than those mentioned in the above
paragraph, which oi themselves render inadmissible the theory that
cell separation is brought about by increased turgor. These are
as follows: 1. There seems to be no perceptible change in cell
shape or size during separation. 2. The increase in size of the inter-
cellular spaces does not necessarily take place first between the walls
at the /'corners" of the cells, but may appear first as a longitudinal
streak between the lateral walls of the cells (pi. 51). 3. Cell isola-
tion may be incomplete- in large numbers of cells still remaining
attached to each other. 4. Cell separation first becomes complete in
a narrow plane between only two tiers of cells before spreading later
to a larger number of cells. 5. The spreading of cell separation
itself is obviously hard to explain on the basis of the turgor theory.

In view of the facts brought out in this discussion and the positive
evidence for the dissolution of the primary membranes, it should be
clear that increase in turgor, at least in the Solanaceae, is not the
direct cause of cell separation. Undoubtedly there is often great
increase in turgor during abscission, especially in certain types of
cells, but this increase, instead of being the direct initiating factor,
probably serves merely to hasten and facilitate the process.

1918] Kendall: Ahscission of Flowers and Fruits in Solanaceae 381

(. EXPERIMENTS ON THE AMOUNT OF SUGAR IN THE STEM
AND PEDICEL OF NICOTIAN A DURING ABSCISSION

After several experiments, all of which indicated the results ob-
tained below, the following experiment was performed. Experiment
2a was devised to show the change in the amount of sugar which
occurs in the tissues of the pedicel during abscission. Experiment 2&
was intended to show this same difference in a restricted region of the
stem just proximal to the separation layer.

Experiment 2a. Lot A included 200 pedicels of flowers which had
fallen a few minutes before being collected as a result of being sub-
jected to illuminating gas. Lot B included 200 pedicels of flowers
picked at the same time as those making up Lot A, but in which no
abscission was induced. The water extracts made with 10 cc. from
equal weights of the two lots were tested with surplus Fehlings solu-
tion. The precipitates formed upon boiling weighed :

A , 68 mg.

B 95 mg.

Experiment 21). This experiment was carried out in the same man-
ner as experiment 2a, but the precipitates in this case were of such
small quantity that no attempt was made to get actual figures as to
their weights. It was clear, however, merely from an examination of
the filter paper, that there was more precipitate in B than in A — just
the reverse of Experiment 2a. The difference was evidently not as
great as in the latter experiment.

Experiment 2a seems to indicate that during abscission there is a
reduction of nearly one-third the normal amount of sugar in the
pedicel. Other preliminary experiments performed as abscission was
starting showed only a slight reduction in the amount of sugar in the
pedicel. Thus possibly the withdrawal of sugar commences with the
start of abscission. Experiment 21) indicates that there is probably a
slight increase in the amount of sugar in the limited region proximal
to the separation during abscission. It is possible that most of the
withdrawn sugar is used as a source for the energy required in the
active process of cell separation. The slight increase proximal to the
separation layer also shows that there is probably an increase in cell
turgor in the actual tissues which contain the separation layer, due
to the conversion of starch into sugar.

382 University of California Puhlications in Botany [Vol. 5

/. POSSIBLE AGENCY ACTIVE IN THE DISSOLUTION OF
THE MIDDLE LAMELLA

The pectose of the middle lamella may be broken down into the
soluble pectin in three different ways — by the action of an acid,
of an alkali, or of the enzyme pectosinase. Since it is doubtful
whether alkaline reactions in living cells frequently get strong enough
to affect the middle lamella, the probable active agency is limited
to the acid or the enzvme action. Up to the last few vears verv
little has been known about the action of enzymes concerned in
peetic digestion. It has been natural, therefore, for investigators
(cf, Wiesner, 1905, and Kubart, 1906) to consider the acid as prob-
abl}' the active agency. In this connection, it is well to state that I
have obtained distinct acid reactions with litmus from the base of the
corolla of Nicotimia during abscission. This would confirm Kubart,
who, it will be remembered, obtained similar reactions from the corolla
of Nicotiana. But in this case I sometimes obtained acid reactions
from the corolla when in the normal condition. Since these observa-
tions offer no detailed evidence that acidity has increased during
abscission to a degree higher than normal, their significance can well
be doubted.

The tissues of Datura give a distinct acid reaction to litmus in the
normal condition. Experiment 3 below shows a slight increase in
acidit}^ during abscission. No acid reactions of much intensitj' are
given by the base of the pedicel of Nicotiana either in the normal or
abscissed condition.

Experiment 3. Lot A contained the bases of three pedicels cut
while abscission was going on. Lot B contained an equal weight
(6 gm.) of the bases of three pedicels cut in the normal condition.
These were extracted wath water and the extracts made up to 10 cc.
each. By titration with 10 per cent NaOH and phenolphtalein the
following results were obtained :

A 0.75 cc. required to neutralize

B 0.6 cc. required to neutralize

A similar experiment on Nicotiana showed, however, that the nor-
mally low acidity of this genus is slightlj^ reduced during abscission,
as indicated by the following results :

A 0.25 cc. required to neutralize

B 0.37 cc. required to neutralize

1918] Kendall: Ahscission of Floivcrs and Fruits in Solanaceae 383

The normal acidity in Datura is high, but it is doubtful whether
the increase is large enough to account for the dissolution of the
middle lamella. At any rate, it is certain that acidity does not enter
into the problem in the pedicel of Nicotiana. We must, therefore,
fall back upon the enzyme action as probably responsible for the
process of cell separation.

IMost hydrolysiug processes characteristic of living cells are now
supposed to be due to the action of enzymes of different kinds. It
has been definitely claimed (cf. Atkins, 1916) that an enzyme which
has been called pectOvsinase is capable of breaking down the pectose
of which the middle lamella is composed. Add to this the fact that the
action of enzymes has been shown, as has also the process of abscission,
to be very sensitive to all kinds of changes in the external environment,
and it is fairly safe to assume that the method of cell separation is
fundamentally an enzyme problem. Irrefutable proof of this could
be obtained only bj' testing for the activity of pectosinase during the
early stages of abscission and by demonstrating the absence or in-
activity of this enzyme in species where abscission does not occur.

ABSCISSION OF THE STYLE AND COROLLA

Abscission of the corolla in Nicotimia was described by Kubart
and it may be said at once that the observations herein described

agree entirely with his. Abscission of the
corolla is brought about by the separation,
without any previous cell divisions or
elongations, of living cells at the base of
the corolla tube. The separation layer,
which is in no way morphologically differ-
entiated from the neighboring tissue, is
located about 1 mm. from the point of in-
sertion of the corolla on the receptacle. It
thus occurs in the distal part of a region
wliere intergradation of cell shape, between
tlie isodiametric cells of the receptacle
and the more or less elongated cells of the
corolla, is apparent. The separation cells

which are in this region of intergradation
Fig. 6. Longitudinal radial . • t ^ • i i

section of the base of the '^^'^ '^^^^ isodiametric but are more or less

<oiolla tube of Nicotiana, elongated parallel to the long axis of the

showing the method of ab- ^

scission. corolla. All the cells in cross-section of the

384

Unwersity of California Puhlications in Botany [Vol.5

base of the corolla tube at about the level of the separation layer seem
to be involved in the process except the epidermal cells and the
tracheae. The process of cell isolation in this case may spread up and
down for (piite a distance between the epidermis and trachete, thus
involving a large number of cells (fig. 6).

Abscission of the corolla in Datura differs slightly from that in
Nicotiana. As in the latter, there is no differentiated separation
layer, separation occurring in cells which are not visibl}' different
from other cells of the corolla. Cells more or less elongated are in-
volved, as in Nicotiana, but in Datura the region of separating cells
is limited to certain tissues — that is to say, not all the cells across
the base of the corolla tube at about the level of the separation layer
are involved in the process of abscission. The base of the corolla in
Datura is characterized hy distinct longitudinal ridges which alternate
with deep grooves. Thus, a cross-section of a portion of the base of
the corolla appears as in fig. 8. Cell separation fails to occur in the
outside ridges at the level of the separation la^'er, so that, looking at
the base of the corolla tube from the outside during abscission, one
sees separate crescent-shaped regions of macerating cells alternating
with cells which are not separating (fig. 7). This is explained when
a cross-section is taken (fig. 8), which shows that several vascular
bundles, the cells of which do not sep-
arate, are collected in the outside ridges.

Abscission of the style occurs nor-
mally in Nicotiana and Datura a short
time before the corolla has fallen. So
far as it was possible to determine, the
process of abscission is exactly the same
in the style as in the corolla. A separa-
tion of ver^' small, more or less elongated
cells takes place at the base of the stjde
without any external indication such as Fig. 7

frequently occurs in the pedicel of the c — region of separating cells.

a c
Fig. 8

a — vascular bundle.

c — region of cell separation.

& — region of no cell separation.

1918 J Kendall: Abscission of Flowers and Fruiis in Solanaceae 385

flower. As in the case of the corolla, there is no structure which might
be interpreted as a differentiated separation laj^er. Separation occurs
in a region of intergradation in cell shape between the spherical cells
of the ovary and the cells of the style, w^hich are elongated parallel
with the long axis of the style.

TIME OB^ ABSCISSION
1. Reaction Time

a. EEACTION TIME IN NORMAL ABSCISSION

The term "reaction time" is used in referring to two rather dis-
tinct subjects. First, we may have a reaction time represented by
the time intervening between anthesis and normal abscission due to
lack of fertilization. Second, we may have a reaction time which has
to do with the period between the application of the stimulus and
flower-fall in "spontaneous" abscission. The reaction times in normal
abscission were discussed in an earlier communication in the case of
two F^ species hybrids of Nicotiana and their parents. The state-
ments there made have been repeatedly verified and in addition a
considerable amount of data has been accumulated in regard to tlie
time of abscission in other species of Nicotixina and in the genus
Lycopcrsicum. In the case of the former the observations were also
made upon the abscission of the corolla, the effect of pollination on
reaction time, and the reaction time in "spontaneous" abscission.

In determining the abscission times for the hybrid F^ HI 54 (cf.
page 386) , a great variation was noted in the normal reaction time. In
the case of the hybrid F^ H179 (cf. page 386), however, and in other
species or varieties investigated, very little variation in the time of
abscission has been noted. The range of variation in these species
and varieties practically always falls within two or three days and a
large number of observations gives identical times, as far as the number
of days is concerned, in the case of seven to ten flowers. There is a cer-
tain variation in the length of the reaction times in different flowers on
the same plant, but the plants of a species do not differ from one an-
other in their average reaction times. It was noticed that the figures
were approximately the same whether the averages were based on the
records of four or five fiowers or of a considerably larger number ;
thus the results given in the following table may be considered con-
clusive. Where the number of flowers involved is less than four.

386

University of California Puhlications in Botany L^^ol. 5

however, the results serve merelj' as approximate estimate of the
abscission reaction time.

In obtaining the records tabulated below a separate tag was sup-
plied for each flower. This tag was put on the flower at the begin-
ning of the observation, the plant visited twice a day thereafter and
records kept on the tags, which were left on the flower until the close
of the observation. If a flower fell upon being tapped or shaken,
abscission was considered to have occurred and the date was recorded
on the tag, which was then collected. Similarly, in the case of the
records for abscission of the corolla, a slight pull had to be applied
before it could be determined whether abscission had occurred. As a
means of preventing fertilization, the stigma was cut away in addi-

TABLE 1

I

Time from
bud' to
anthesis

II

Time from
pollination to
mature fruit

III

Time from

pollination to

abscission of

IV

Time from

anthesis to

abscission of

V

Time from

anthesis to

normal flower^

Designation of
species or variety

!

corolla

corolla,
uupollinated

fall

No.
flowers

Avg.
No.
days

No.
flowers

Avg.
No.

days

No.
flowers

Avg.

No.
days

No.
flowers

Avg.

No.
days

No.

flowers

Avg.

No.

days

F, H38

10

18

Pi H179

{

4

8

4

14

15

3

23

82

6
6

20

7

Fi H36

7

4

3

6

N. sylvestris

{

10

11

6

4

9

42

6
6

9

15

N. Tabacum

3

12

0

4

2

6

3

5

"Maryland"

N. Bigelovii

5

10

5

3

5

5

8

17

var. Wallacei

N. Bifjelovii

5

19

5

2

G

5

6

no fall

"Porno"

N. Bigelovii

{

2

16

var. typica
N. Bifjelovii

4

21

1

4

2

8

3

no fall

(hybrid?)
N. multivalvis

3

18

2

4

2

no fall

N. quadrivalvis

5

20

5

7

5

2

6

no fall

N. suaveolens

1

8

8

8

8

7

13

N. Sanderae

15

15

5

4

5

6

6

9

N. rustica var.

3

4

4

6

brasilia

N. rustica

7

6

7

3

4

4

(Winnebago)
N. rustica var.?

4

15

4

2

5

3

6

5

Lyeopersicum
esculentum

4

6

4

3

4

8

17

9

^ The buds recorded here were of such size that the corolla and calyx were of the
same length.

^ Sterile pollen applied to the stigma.

* By normal flower-fall is meant fall due to lack of fertilization.

1918] Kendall: Abscission of Flowers and Fniifs in Solanaceac 387

tioii to removing tiie anthers before anthesis. Various experiments
liad shown that such an operation on the flower does not induce
abscission or affect its normal physiological condition to any great
extent.

F^ H154 is Nicotiana Tabacum vai". niacropJiylla (U. C. B. G.
22/07) X N. sylvestris (U. C. B. G. 69/07). F, H179 is N. Tabacum
"Cuba" (U. C. B. G. 200/14) X N. sijlvestris. F, H36 is .V. sijlvestris
X N. Tabacum var. angustifolia (U. C. G. B. 68/07).

The results given in table 1 indicate, in the first place, that the
different species differ considerably in all the types of abscission
reaction times considered, and, in the second place, that on the aver-
age, application of a fertile pollen to the stigma tends to shorten
the time between anthesis and abscission of the corolla by two days.
The one apparent exception to this statement is Nicotiana suaveolens,
but in this case the i)ollinated flowers • fell five or six days later
than the corolla, indicating that growth of the pollen had not pro-
ceeded very far. Records on F^ H179 and N. sylvestris indicate that
sterile pollen does not have the same effect on abscission that fertile
pollen does. This would seem to show that here the effect of pollina-
tion upon the postfloration phenomena is not due, as Fitting (1909)
has found in orchids, to mere mechanical or chemical stimulation of
the stigma by the pollen. This much being certain, the question still
remains whether the results obtained depend upon fertilization or are
due to the growth of the pollen tubes down through the style.

According to East (1915), working on self-sterility in Nicotiana
hybrids, the pollen tubes reach the ovary, in cases of cross-pollination,
three or four days after application of pollen to the stigma. Since in
all cases recorded above cross-pollination was carried on and since in
most cases the corolla was not thrown off until three or four days
after application of pollen to the stigma, it is possible that fertiliza-
tion is the important factor in shortening the time between anthesis
and abscission of the corolla. In N. quadrivalvi-s, however, the corolla
was thrown off within eighteen hours after pollination, whereas, when
pollination is prevented, the corolla may remain on the flower for
fifty-seven hours. If East's conclusions are correct, this would seem
to indicate that the shortening of the reaction time in abscission of
the corolla is due to some stimulation of the stjde by the pollen tubes
and not to fertilization. This conclusion, however, could be doubted
even here, because the style of N. quadriimlvis is very short, so that
the pollen tubes might reach the ovary in a much shorter time than is

388 TJnvversity of California PuhJications in Botany [Vol. 5

required in larger flowers. Au attempt was made to get further data
on this point b}^ removing the style several hours after application of
pollen before the pollen tubes could possibly have reached the ovary.
This operation occasionally causes the whole flower to fall, and since
in such cases abscission in the pedicel occurs before fall of the corolla,
no results in regard to the latter organ are obtained. The possible
effect of the operation on the abscission of the corolla was checked
by control tests of unpollinated flowers in which the styles had also
been removed. This can also be checked hj a comparison with the
periods of time given in table 1, column III.

It was found in three flowers of F^ H179 that, when the style was
removed three daj'S after pollination, the corolla was, on the average,
thrown off three days after anthesis. The control test for this experi-
ment gave in three flowers an average of five days. Where the stjde
was removed two daj's after* anthesis, four flowers gave an average of
three days. Where the style was removed one day after pollination,
the corolla was abscissed in five flowers an average of three days after
anthesis. A control test gave in this case an average of five days for
five flowers. Finally, the style was removed in seven flowers seventeen
hours after pollination. The seven flowers gave in this case an average
of four days for the time betw^een anthesis and fall of the corolla. A
control test for this last case gave for five flowers an average of five
davs.

These experiments were repeated with N. sylvestris. In one case
where the style was removed in three flowers two daj^s after pollina-
tion, the corolla was thrown off on an average of four days after
anthesis. A control test of this ease gave an average of six days for
three flowers. In another case the style was removed in three flowers
one day after pollination. In this case the corolla was abscissed on
an average of three days after anthesis.

The results given in the above paragraphs indicate definitely that
it is the stimulation of stylar tissues caused by the growth of the
pollen tubes which shortens the time between anthesis and abscission
of the corolla. They also show that the removal of the style has no
appreciable effect on the abscission of the corolla. It is evident from
the results given that the influence of the pollen is seen as early as
seventeen hours after pollination, and it is possible that the effect may
be manifested even earlier. It is significant that the period given in
the case where the style was removed seventeen hours after pollina-
tion is one day longer than in the ease where the style was removed

1918] Kendall: Ahscksion of Flowers and Fruits in Solanaceae 389

twentj'-four hours after pollination. This may possibly indicate that
in the first case the influence of the pollen tubes has diminished, be-
cause of the shortening of the period which they have had for growth.
If this is the case, it is reasonable to suppose that the influence of the
growing pollen tvibe increases up to twenty-four hours after pollina-
tion as the pollen tube lengthens. Thus, at six hours after pollination
it is possible that no effect of the pollen tubes would be noticeable,
while twenty-four hours after pollination the entire influence of the
growing pollen tube has been exerted.

The effect of pollination on the time between anthesis and flower-
fall was tested by experiments similar to those described above.
Results in such experiments are difficult to obtain because removal of
the style frequently causes the premature fall of the flower. If the
flower fell before abscission of the corolla, the fall was considered
premature, as the result of the removal of the style, and the record of
that particular flower not considered. Since under ordinary condi-
tions pollinated flowers remain on the plant, it is to be expected that
the stimulation of the stylar tissues by the pollen tubes, if it has any
influence at all, would increase the length of time between anthesis
and flower-fall. Granting the truth of this assumption, any reduction
in time between anthesis and fall can be considered as the result of
removal of the style. '

In one test on ten flowers of F^ H179, where the style was removed
two days after pollination, flower-fall occurred on an average of seven
days after anthesis. A control test in this case also gave seven days
for ten flowers. This time is approximately the same (the actual
average calculated to the tenth of a day was 6.7) as those given in
table 1, column V, for the time between anthesis and normal flower-
fall due to lack of fertilization. A similar test on six flowers of N. syl-
vesiris, where the style was removed two days after pollination, gave
an average of thirteen days. The time for this species in table 1,
column V, is fifteen days.

These two records indicate that the stimulation of the stylar tissues
by the growing pollen tubes has no effect on the time between anthesis
and flower-fall. In the second case above, and also perhaps in the
first, the stimulation of the style seems to have shortened the time
somewhat, but in this case the result can be explained by the effect
of the later removal of the stvle.

390 University of California Puhliaxtions i}i Botany [Vol.5

b. REACTION TIME IN "SPONTANEOUS" ABSCISSION

Exact data in regard to the reaction time can be given only in
two definite eases. Tlie observations in these cases were made on
small shoots of the plant to be considered, which were placed in water
and inserted under a bell-jar containing- 1.5 per cent illuminating-
gas. After several hours, the material was shaken every fifteen min-
utes to determine when the first flower fell. F^ H179 and N. Tahaciim
"Maryland" were selected as material for the experiments because
these forms were found most sensitive and thus react regularly and
quickly to stimuli. Abscission occurs in the pedicel of F^ H179 seven
hours after insertion into 1.5 per cent illuminating- gas at a tempera-
ture of approximately 19° C. The smaller buds begin to fall first,
but are followed in a short time by the open flowers. Abscission
occurs in A. Tabacum "Maryland" in eight hours under the above
conditions.

The remainder of the data having- to do with the reaction time in
spontaneous abscission is in the form of approximate estimates derived
from the results of experiments on the induction of abscission. In
the case of abscission induced by illuminating gas most species which
shed their flowers in 1.5 per cent illuminating gas do so after ten or
fifteen hours at room temperature.

There remains now to be considered the reaction time in cases of
flower-fall due to mechanical injury-. The results along this line are
largely derived from tables 2, 3, 4, and 5, which, however, were
arranged to show more particularly the comparative effect of different
t^'pes of injury, as causing or not causing abscission in flowers of
various ages. These tables might as well be presented under the
heading "Experimental Induction of Abscission by Mechanical In-
jury" (page 405), but since it is necessary to draw certain conclusions
from them in regard to the time of abscission they are presented and
explained at this time.

Tables 2, 3, 4, and 5, which follow, serve to record the results of
a number and varietj' of experiments all designed to show the relation
of mechanical injury to abscission. It was very soon discovered while
carrying on the experiments that the effect of injury depends to a
large extent upon the age of the flower. Now the age of the flower
can be most conveniently measured by determining the increase in
size of growing parts such as the corolla and ovary. Thus it was
necessary in each case to record the size of the flower — size being a

1918] Kendall: Abscission of Flowers and Fruits in Solanaceae 391

criterion of age — upon which the test was being made. This was done
by noting on the tag which ^v^as supplied for each flower (cf. page 385)
the length of the corolla in millimeters, the condition of the corolla,
or any other condition of the flower which would serve to indicate its
age. The period of development of the flower and fruit is divided
into several arbitrary- stages, each of which is designated by a Roman
numeral in the second column of the tables. Where the number of
flowers designated in the first column are nearly in the same stage
of development only one numeral appears in the table, but where the
range in size of the flowers is quite extensive two numerals appear,
representing the range in size within which the flowers were found at
the time of the experiment. The stages of floral development which
each Roman numeral represents are given below.

Bud

I corolla 2 mm. to -j mm. in lengili

II corolla 6 mm. to 10 mm. in length

III corolla 11 mm. to 15 mm. in length

IV corolla 16 mm. to 20 mm. in length

V corolla 21 mm. to 30 mm. in length

VI corolla 31 mm. to 40 mm. in length

VIT corolla 41 mm. to 50 mm. in length

VIII - corolla opening

IX anthesis

X 2 days after anthesis

XI corolla withering

Fruit

Immature

XII fruit 5 mm. to 8 mm. in length

XIII fruit 9 mm. to 10 mm. in length

Mature
XIV fruit 11 mm. to 12 mm. in length

The operation of injuring the flower consisted largely in removing,
by cutting away with a sharp safety razor blade, entire floral organs
or parts of them. In some cases, however, organs were only slit longi-
tudinally with a sharp knife or merely punctured with the point of a
pair of forceps.

Several types of injury that remove the style, stigma or stamens
before pollination may cause fall by preventing fertilization. It is
evident, therefore, that fall occurring after such an operation per-
formed on the flower before anthesis may be due to lack of fertiliza-
tion and not to the injury. If, however, the fall occurs within the
minimum time elapsing between anthesis and normal flower-fall due

392

University of Calif urnia Puhlications in Botany [Vol. 5

to lack of fertilization, it can be safely concluded that the fall is due
to the effect of the injury. This minimum time is about seven days
for iV. Laiigsdorffii. It can be safely said, therefore, that any fall
occurring in less than seven days after injury to the flower near
anthesis is due directly to the effect of the injury. In cases where the
stamens or style are removed in flowers younger than those at anthesis.

TABLE 2

Effect of Different Types of Injury in Causing Flower fall in

N. Langsdorffii var. grandiflora

Avg. No.

No.

Size or

Injury to

days before

flowers

coiulition
of flowers

fall of

'

•

remaining

Calyx

Corolla

Stamens

Pistil

Pedicel

organs

rio

10

II-VII

all cut

all cut

all cut

all cut

1

a-

VII -XI

( (

<(

((

( 1

2

10

XII-XIII

i i

11

((

"

3

2

XIV

1 1

t (

n

i (

no fall

' 4

I-II

i cut

1 cut

{ i

style cut

7

3

III-VII

i i

1 (

i«

( (

7

3

VIII-IX

i i

< I

(<

i i

7

b^

5

XI -XII

I i

I i

( 1

i •

no fall

2

XI-XII

i i

i I

((

style and

5

part of

ovary cut

3

XIII -XIV

i 1

(>

( (

i'l

4

r 5

V-VII

i cut

((

1 style cut

7

o J

5

VIII-IX

( (

( (

•<4

6

e

2

XI

i i

<t

( (

9

3

XII

( i

i i

( 1

no fall

r 4

I

all cut

3

d-

1

L12

II

III-XII

1 i

no fall

2

V-VII

slit on sides
to base

2 slit on
2 sides
to base

7

e-

8

III-XI

1 (

no fall

3

II

( t

ovarv slit i

3

3

V-VII

t i

( (

5

3

IX

a

((

2

o

XII

> (

"

5

' 5

IX

anthers

10

f-

all cut

2

V-VII

all cut

7

. 3

VII -X

i i

9

' 4

VIII

stigma cut

9

g-

')

L 2

V-VII
VII-X

style cut

1 1

7
10

4

XIV

all cut

all cut

no fall

h-

XIII

i cut

i cut

2

2

L 4

XIV

1 i

((

no fall

XIII -XIV

slit to base

slit to base

L i

rio

II

slit to base

i I

3

IX

1 1

ii

i

6

I -VIII

1 cut

a

i through

8

II-XII

2 cuts

t i

i through

1918] Ke^iclall: Abscission of Flowers and Fruits in Solanaceae 393

allowance must be made for the approximate number of days preced-
ing anthesis. Thus, if a flower of the above species is injured three
daA-s before anthesis, the fall can not be assigned to the injury unless
it occurs before ten days have elapsed. The minimum time for
Fj H179 is about five days; thus, any time of five days or more recorded
on a flower, injured near anthesis, was considered as "no fall." The
minimum time for Lycopersicum is about six days.

Finally, it is necessary to state that tlie process of reaction to the
diiferent types of injury recorded in the following tables was by no
means impeded by low temperaturas. Xicotiana Langsdorffii was
tested out in a greenhouse where the average temperature approxi-
mated 75° F. The tests on F^ H179 and Lycopersicum were per-
formed in the botanical garden of the University during July and
August, when the temperature was also comparatively high.

The following statement of results is derived in great part but not
entirely from the foregoing tables. It has been noticed that cutting
off the freshly opened flower at the tip of the pedicel causes the
remainder of the pedicel to be thrown off in from ten to fifteen hours,
but after the same operation on developed capsules the pedicel re-
mains ' firm from thirty-six to ninetj'-six hours after the injury.
Removal of the calyx causes the fall of buds in two or three days,
depending upon the age of the bud. Removal of half the calyx
together with two-thirds of the corolla and all the stamens causes
fall in one to four days, depending upon the age of the flower. A

TABLE 3

Effect of Pollination of Flowers of N. Lanr/sdorffii var. grandiflora ox

Reaction to Injury

No.
flowers

Avg. No.

Pollination

Injury

days before
fall

^{l

pollinated when injured

calyx and stamens cut

no fall

not pollinated

< <

10

Ht

pollinated when injured

calvx " i corolla cut

no fall

not pollinated

(I

8

No. days after pollination when

injured

r 2

1

all organs cut at tip of pedicel

2

1 2

2-6

1 1

2

f-{ 2

7-8

1 1

2

1 3

2

i calyx, I corolla, stamens,

4

I

style cut

;}

4-.1

( I

5

1

6-7

1 1

2

9

( <

3

9

I <

no fall

394

University of California Piihliaiti-ons in Botany [Vol. 5

transverse cut through the entire flower which passes through the
middle of the ovary causes fall in one to two days. A similar oper-
ation in the case of maturing fruits changes the date of fall to
four to eight days. Removal of half the corolla and all the stamens
causes fall of buds in one day and the fall of 3'oung flowers in two to
three days. Removal of the stamens or stA'le in buds causes fall in

TABLE 4
Effect of Different Types of Injury in Causing Flower fall in FiH179

Avg. No.

No.
flowers

Size or

Injury to

days before

eoudition
of flowers

fall of

remaining

Calyx

Corolla

Stamens

Pistil

Pedicel

organs

>(^

II-VIII
XI -XV

i cut

1 cut

all cut

style cut

1

no fall

K.?

III -VII

i cut

i t

1

VIII -IX

i i

i (

no fall

c 10

V-VIII

a

1 1

r 9

I

all cut

2

7

II

i 4

2

3

II

1 <

no 'fall

d-

4

III-IV

i i

3

6

III -IV

( i

no fall

1

V

i t

2

4

V-VII

i i

no fall

2

IX

1 (

( 1

' 7

III-IV

i i

2

1

V

1 1

5

e -

3
6

V

( (

no fall

VI -VII

i I

1 (

'■

r 5

II-VIII

i t

2

L 4

VII -VIII

i (

no fall

' 1

II

1 slit on 2

sides to

base

1 slit on 2

sidos to

base

5

1

II

( i

i t

no fall

9

IV- VII

i 1

1 i

( 1

g-

9

2

II

II-IV

2 slits on 2

sides to

base

2 slits on 2

sides to

base

1
4

5

V-VII

( (

< i

no fall

5

II-V

punctured

on both

sides

punctured

on both

sides

ovary
punctured,
small hole

2

h-

3

VI -VII

1 1

( i

i 4

no fall

3

VII -XI

I i

i i

i (

2

3

Il-III

i (

i i

i i

2

3

VI -X

( i

t(

i i

2

15

III-XII

■

1 slit to
base

no fall

i-

5

punctur'd

1

l

many

times

' 6

XIV

i cut

capsule

4

n

i cut

. 3

XIV

( i

t i

no fall

1918] Kendall: Ahscission of Flowers and Fruits in Solanaceae 395

two to four days. Severe iiijurj^ of an}- kind to the ovary causes fall
in one to two days.

The figures given above for the reaction time in cases of abscission
following mechanical injury, together with a more detailed considera-
tion of the tables, indicate that the reaction time, in general, does not
depend so much on the type of injury as on the age of the flower
concerned. What connection there is between the type of injurj- and
the reaction time seems to be based, except in cases of injury to the
ovarv, on the relation of the amount of material removed to the
amount remaining. Thus, cutting off the flower at the tip of the
pedicel causes abscission of the remaining pedicel more quickly than
any other type of injury. One exception to this statement is seen, as

TABLE o

Effect op Different Types of Injury in Causing Flower fall in

Lycopersicum esculentum

Avg. No.

No.
flowers

Size or

njury to

days before

condition
of flowers

fail of

remaining

Calyx

Corolla

Stamens

Pistil Pedicel

organs

r 4

I

all cut

no fall

a^ 4

II -VIII

< (

( i

6

XII

( (

k i

^ 3

XII

entire
ovary cut

2

3

XIII-XIV

ovary
punctured
4 times on

no fall

1)-

1
4

3

XII
XII

XIV

top

((

ovary

punctured

4 times on

side

3
2

no fall

r 4

II

punctured
at base

punctured

ovary
punctured

9

c-

once on
side

l 4

VIII

( 1

1 1

1 (

4

r 4

II -VIII

i cut

i cut

no fall

1 4

VIII-IX

"

i i

((

5

(IJ :i

I-II

i i

ovary i cut

1

I 2

VIII

i i

i i

( I

3

IX

a

i i

< (

2

e i)

I-IX

i I

all cut

no fall

'(;!

VIII

style cut

,1

X-XI

i i

no fall

« s

VIII-XIV

slit

i i

r 3

VIII

all cut

( (

4

( 1

1 1

no fall

4

II-VIII

( 1

396 University of California PuMications in Botany [Vol.5

z

indicated above, in the case of injury to the ovary in which this organ
may be merely punctured, without necessarily removing any material,
yet abscission occurs in one to two days after the injury.

It has, on the other hand, been evident throughout all the abscis-
sion experiments that age of flower is the important factor in deter-
mining the reaction time, older flowers nearly alwaj's responding more
slowly to stimulation by injury than younger ones. It will be seen,
however, from the tables that there are occasionally individual excep-
tions to the general rule. These exceptions might be explained in a
number of ways. For example, it is possible in the case of older flow-
ers that the ovary, having increased in size, was accidentally cut in
the operation of injury, thus adding the extra factor of stimulation
of the ovarj' which in younger flowers would not be present. In gen-
eral, such exceptions to the general rule indicate to what extent the
normal or abnormal physiological conditions of the plant enter into
the problem.

2. Abscission Time

The abscission time, or the actual time involved in the process of
cell separation, was considered in a preliminary paper (Goodspeed and
Kendall, 1916) wherein the minimum time in which abscission was
known to have occurred w^as stated to be from four to eight hours in
normal abscission and from one to four hours in "spontaneous"
abscission. A few additional data are now at hand in the case of
F^ H179 and Nicotiana Tahacum " ^Maryland. " These two forms,
as has already been noted, are a little more sensitive than most
Nicotiana varieties and normal abscission was found to take place in
from three to six hours.

The time of cell separation in "spontaneous"' abscission can be
more exactly determined than that in normal abscission because of
the regularity with which the plants respond to certain conditions of
injury or to the presence of narcotic vapors. Data on this point were
obtained in the follow'ing manner. Flowering shoots with flowers of
different sizes were cut, placed in water and inserted under a bell-jar.
Enough illuminating gas was then introduced under the jar to make
1.5 per cent approximately. The temperature during the experiment
was practically constant at 19° C, After the shoot had been left in
this abnormal atmosphere for five hours a few flowers were picked off
at fifteen-minute intervals and free-hand sections made of their
pedicels until flowers about the size of those which were being sec-

1918] Kendall: Abscission of Flotvers and Fruits in Solanaceae 397

tioned began to fall. It was found that signs of abscission hardly
ever appeared until thirty to forty minutes before actual fall occurred.
This indicates that the actual process of cell separation in F^ H179
takes place in from thirty to forty minutes. Experiments carried on
in the same manner with X. Tahacum "Maryland" indicate that
abscission here takes place in from forty-five to sixty minutes.

Both the reaction time of abscission and the actual abscission time
are profoundly influenced by temperature and by humidity. Varia-
tion in the intensity of the illumination, however, seems to have no
direct influence upon abscission. In comparing the effect of changes
in temperature and humidity it was found that the results of experi-
ments intended to show the time of abscission are far more dependent
upon temperature than upon humidity. This is not because changes
in humidity have little influence upon abscission but because such
changes have to be very great indeed before bringing about any appre-
ciable effect. Very slight changes in temperature, on the other hand,
often influence abscission to a marked degree. Abscission goes on
very actively under high temperatures and conversely very slowly
under low temperatures. It starts in the case of F^ H179 about seven
hours after insertion in 1.5 per cent ilhiminating gas at a temperature
of 19° C. If the same experiment be repeated in a temperature of
approximateh' 9° C. abscission may not occur for fifteen to twenty-
four hours.

Drought has to be quite severe before retarding abscission. There
is no doubt, however, that wilted shoots will not drop flowers as
quickh^ as fresh ones and if the wilting proceeds far enough no abscis-
sion will occur. This effect is all the more noticeable if the air around
the wilted shoot is kept free from moisture.

EXPERIMENTAL INDUCTION OF ABSCISSION

1. Induction by Illuminating Gas

The first subject to be considered under tliis heading is the com-
parative effect of illuminating gas in causing abscission in several
species of the Solanaceae. The method of determining this consisted
largely in placing flowering shoots of the different species in water
under bell-jars and introducing enough illuminating gas under the
jars to make the percentage of narcotic vapors in the air around the
plant 1.5. The temperature during the experiments was eompara-

398 University of California Puhlicatiwis in Botany [Vol. 5

tively high, ranging from 15° to 20° C. The results, which were
recorded approximately fifteen hours after subjection to the gas. are
given in the following table :

TABLE 6

Species, variety, or Amount of abscission, expressed almost entirely

hybrid in terms of size of flowers thrown off

X. Tabacum var. macrophylla all buds up to anthesis.

X. Tabacum ' ' Maryland ' ' all flowers up to 4 or 5 days past anthesis.

F, H154 all buds uj) to opening of corolla.

Fi H36 all buds and flowers.

FiH179 all buds and flowers.

N. glauca young buds.

X. rustica var.? buds up to anthesis.

X. rustica var.? buds, flowers, and fruits.

X. Bigelovii var. Wallacei no abscission.

X. Bigelovii "Pomo" no abscission.

X. quadrivalvis no abscission.

X. multivalvis no abscission.

X. Sanderae buds up to anthesis.

X. suaveolens buds up to anthesis.

X. plumbaginifolia buds up to opening of the corolla.

Solanuni unibelliferum ^ small buds.

S. jasminioides buds and flowers.

S. verbascifolium no abscission.

S. nigrum small buds.

Tochroma tuberosa no abscission.

Oestrum fasciculatum buds and flowers.

Lycopersicum esculentum var.

pyriforme no abscission.

L. esculentum var. vulgare small buds and occasional flowers.

Petunia hybrida no abscission.

Salpiglossis sinuata ,no abscission.

Datura sanguineum buds and flowers.

Salpichrora rhomboidea no abscission.

Lycium australis - no abscission.

As might be expected, most of these varieties react to laboratory
air in the same manner that they do to illuminating gas. In the case
of laboratory air a longer time and liigher temperature is generally
required before the reaction occurs. All the species, with the excep-
tion of those which throw off only young buds, detach most of their
flowers when left in laboratory air overnight. If a window or two is
left open, allowing fresh aid to enter and at the same time lowering
tlie temperature, no abscission occurs.

It was found that several of the species recorded above, in which
no abscission or very little abscission occurred, detached more flowers
when a larger percentage of gas was used or when subjected to 1.5
per cent gas for a longer time. Thus, both varieties of Lycopersicum

1918] Kendall: Ahscissio)! of Flowers and Fruits in 8ola,imce<ie 399

esculent um, lochrorna tuherosa, Solanum nigrum, and *8^. verhasci-
foliuni, upon subjection to 3 per cent illuminating gas for twenty
liours, throw off all flowers up to those two or three days past anthesis.
No abscission occurred, however, in any concentration of gas, in
Nicotiana Bigelovii, N. quadrivalvis, y . multivalvis, Lycium australis,
Petunia hyhrida, Salpiglossis stinuata, or Salpichrora rhomhoidea.

A peculiar condition exists in Solanum umhelliferum, Avhich throws
off buds in the illuminating gas but never under any conditions, in-
eluding temperature or the presence of narcotic vapors, throws off
flowers in which the corolla has fully opened. A corresponding con-
dition seems to exist in Nicotiana Tahacum var. macropliylla, FiHlSi,
iV. Sanderae, N. rustica var. hrasilia, and in one other variety of N.
rustica, all of which seldom under any conditions detach fully opened
flowers, although flowers up to that stage are freely abscissed. Thus
there seems to be, in certain species and at about the time of the open-
ing of the corolla, a sudden increase in resistance to the external
stimulus which is causing abscission. In other species this sudden
increase in resistance does not take place, abscission commonly occur-
ring at any stage in the development of the flower or fruit and the
increase in resistance taking place very gradually. In addition, there
seems to be an intergradation of forms between those in which the
increase in resistance takes place suddenly and those in which it takes
place gradually.

The next subject to be taken up is a consideration of experiments
5, 6, 7. 8, and 9 on the induction of abscission in small isolated pieces
of the pedicel. The main purpose of devising these experiments was to
throw some light, if possible, on the direct or indirect action of the
external factor in causing "spontaneous" abscission. The pedicel of
F^ H17n was again chosen as material for the following experiments,

Fij.'. !)

400

University of California PiiNications in Botany [Vol. 5

largely because of the ease aud regularity with which abscission is
induced in this hybrid bj^ sudden changes in the external environment.

Experiment 5. — This experiment was devised to discover the effect
of reducing the volume of material proximal to the separation layer
on the abscission of flowers of Nicoiiana as induced by illuminating
gas. Two series of flowers were cut as in figure 9. In the last two
flowers represented on the right the cut was made less than 0.5 mm.
from the separation layer. These flowers were then rolled in damp
filter paper and left in 1.5 per cent illuminating gas overnight. After
fifteen hours, abscission had occurred in all the flowers except the one
represented on the extreme right in the figure. Abscission had
occurred in one flower in which the cut had been made less than
0.5 mm. from the separation layer. The control to this experiment
showed that abscission does not occur for several days in a series of
flowers cut as in figure 9 and kept under normal conditions.

Experiment 6. — This experiment was devised to show the effect
upon abscission of reducing the volume of material distal as well as
proximal to the separation layer. In this case the flowei*s were cut off
at varj'ing distances from the separation layer, making the series
shown in figure 10. The last two pieces on the right in this series
were cut less than 0.5 mm. on each side of the separation layer so
that the total length of the pieces was not much above 1 mm. In this
experiment and in similar ones which follow it was necessary to keep

^

Fig. 10

1918J Kendall : Ahscission of Flowers and Fruits in Solanacme 401

the material moist. This was accomplished in various ways, but the
best method was found to eouvsist in placing the pieces on a long strip
of filter paper one end of which rested in water. In this experiment
abscission occurred after ten hours subjection to 1.5 per cent illum-
inating gas in all except the two pieces represented in the extreme
right of figure 10. Abscission here took place in several pieces rang-
ing from 1 mm. to 2 mm. in length. A microscopic examination of the
separation surfaces indicated that the process of abscission corre-
sponded entirely with normal abscission as it occurs in plants in the
field. Experiments made in a similar manner upon A. Tahacum
"^Maryland" and Lycopersicum gave similar results. In the control,
which consisted in keeping pieces of the pedicel as shown in figure 10
under normal atmospheric conditions, abscission occurred after about
twenty hours, evidently as the result of no other stimulus than that
caused through cutting off the flower by severing the pedicel. The
reaction in the control, however, is much slower than in the case in
which the added effect of the illuminating gas is operative, indicating
that the latter factor, although it here serves merely to hasten the
abscission process, has an effect of some kind on the tissues at the
base of the pedicel.

Following these two experiments, a number of attempts were made
in the same way to induce abscission in longitudinal free-hand sections
of the pedicel cut for microscopical examination. It was soon discovered
that the abscission process could be induced in the separation zone in
thick longitudinal sections of the pedicel by subjecting them to high
percentage (5 to 7 per cent) of illuminating gas. Cell separation in
cross-sections through the separation zone could not be induced by any
means at hand. The following experiments give more detailed results
in this connection.

Experiment 7. — In this experiment, median, longitudinal sections
of varying thickness were cut through the pedicels so that the plane
of the sections corresponded with the plane formed by both the
pedicel and the main axis of the inflorescence. These sections were
subjected to 7 per cent illuminating gas, care being taken to keej) them
moist, but not submerged, throughout the entire experiment. The
best arrangement was found to be one in which the sections rested in
a thin film of water on one side but were exposed to the air on the
other. After several hours in the 7 per cent illuminating gas, abscis-
sion started in the thicker sections but not in the thinner ones. The
extent to which abscission proceeded depended upon th(> thickness of

402 University of Calif or nia Publications in Botany [Vol.5

the section. Abscission became complete in sections 0.3 mm. or more
in thickness, the separation taking- place in such a way that a slight
bending or pulling motion sufficient to break the tracheae divided the
section into equal halves. In thinner sections, ranging from 0.3 mm.
to 0.17 mm., abscission starts in the normal position but does not pro-
ceed to completion, the extent to which the process takes place depend-
ing, as has been said, upon the thickness of the section. In sections
much below 0.17 mm. no signs of abscission appear. Also, if the
thicker sections are shortened in length to any considerable extent by
cutting off portions of the tissues from either side of the separation
laj^er, abscission will not occur.

The process of abscission as it occurs in these sections corresponds
exactly to the process in an entire pedicel. Cell separation starts
independently in the pith and in the cortex, appearing first in that
part of the cortex corresponding to the ventral region of the pedicel
where, it will be remembered, abscission starts in the entire flower.
When mounting the sections on an object slide for microscopical
examination, the isolated cells in the pith lie in position but can be
easily washed out with a small jet of water. In the cortex a break
soon appears in the epidermis as the result of manipulation in mount-
ing and a cavity is formed at that point as the result of the isolated
cells of the cortex floating out in the water.

Experiment 7 was repeated in the case of Datura with similar
results, except that in this case abscission was more active since it
involved more cells, a situation which one might be led to expect
because of the differences between the two species in the normal abscis-
sion of entire flowers. It will be remembered that the separation cells
of the cortex in Datura are in no way distinguishable from other
cortical cells ; yet even in these sections separation occurs in a definitely
predetermined position corresponding entirely Avith the position in
abscission of the entire flower. It was even noticed that abscission
started in these sections in the same tissues and in the same manner
as in normal floral abscission.

After the thickness of the sections best adapted to obtaining results
liad been determined, the following experiment was performed on
sections cut from different x^arts of the pedicel.

Experiment 8. — In this experiment a series of longitudinal sections
of the pedicel were cut so that the plane of the sections was at right
angles to that of the sections cut in Experiment 7. The first section
was tangential, on the ventral side of the pedicel, and contained only
the epidermis and a few tiers of cortical cells. Section 2 was also

1918] KendaU: Al)scisslo)i of Flowers and Fruits in Solamiccae 403

tangential but contained a few tracheae on one surface. Section 3 was
more or less radial, containing two strands of vascular tissue on either
side. Sections 4 and 5 were similar to sections 1 and 2. On subject-
ing these sections to illuminating gas it was noticed that abscission
started first in sections 1, 2, and 3, appearing last in sections 4 and 5.
This result is exactly parallel with the process as it occurs in normal
abscission, where the process starts fir.st in the ventral cortex and in
the pith.

In passing, mention might be made of the peculiar reaction of the
tangential sections 2 and 4, which were made up almost entirely of
cortical cells with a few vascular elements on one side. AVhen abscis-
sion occurred in these sections, a bending or bowing of the section was
always noticed. This bending was always such that the tracheal tissue
was on the concave side, as if the cells of the cortex had undergone
considerable expansion while the cells of the vascular tissue retained
their original size. From the work of Richter and others, it may be
expected that subjection of portions of plant tissues to illuminating
gas would cause an increase in turgor in the cells concerned. Thus, it
is probable that the bending of the sections, as described above, is due
to the increase in turgor of the cortical cells caused by the narcotic
effect of the illuminating gas. The extent of the bending was such
that most of the cells in the cortex as well as the separation cells must
have been involved in the process. On repeating the above experiment
with Datura, a similar bending of the tangential sections was even
more pronounced than in Nicotiana.

Experiment 9. — As mentioned above, efforts to induce abscission
failed in thin sections. The sections in Experiment 9 were cut so that
they were thin in the separation layer but thick on either side. Both
surfaces of these sections were thus cut slightly concave so that the
sections were thickest at the ends and thinnest in the middle, where
the separation zone was located. The sections were then subjected to
7 per cent illuminating gas as in Experiment 7. It was not possible
to cut very thin free-hand sections of the shape described, but it was
demonstrated without a doubt that abscission occurred in sections of
this peculiar shape which were thinner in the separation zone than
those in Experiment 7 where abscission had failed to occur.

Certain conclusions which can l)e drawn from experiments 5, 6, 7.
8, and 9 are given below.

]. Abscission can be induced by aHowing the external factor to act
directly upon the cells in tlic vicinity of tlic separation zone (Expts.
6. 7. and 8).

404 University of California fuhlications in Botany [Vol. 5

2. Abscission induced by the above methods in isolated pieces must
be independent of transportation of material from the rCvSt of the plant.

3. The fact that abscission cannot be induced in thick cross-sections
of the separation zone shows that cell separation cannot be induced
by the action of the external factor directly on the separation cells.

4. It is necessary that a certain proportion of the tissues of the
pedicel be in intercellular connection with the cells of the separation
zone before cell separation will occur, but this proportion is surpris-
ingly small (Expts. 7, 8, and 9).

5. There is evidently increase in turgor in all the cortical cells of
the pedicel during abscission induced by the above method (Expt. 8).

2. Action op Acids on the Separation Cells op Nicotiana

Under this heading a description will be given of the effect of
mineral acids on small isolated pieces such as were used in experiments
6, 7, 8, and 9. It was stated above (page 364) that by the use of two
mineral acids together with several stains, no chemical difference could
be detected between the cell walls of the separation cells and those of
normal cortical cells. The present work represents an attempt to
determine, by experimental means and by watching through the micro-
scope the action of acids on cell walls, whether the c(41 membranes
of the separation cells are more subject to hydrolysis than those of
normal cortical cells.

Experiment 10. — Small pieces of the pedicel were prepared as in
figure 10. These pieces were boiled for one or two minutes in 4 per
cent hydrochloric acid and then washed in water. I^pon examination
it was found that the pieces could be separated into halves through
the separation zone by a slight pulling or bending motion. Microscopic
examination of the separation surfaces showed that the break through
the cells of the separation zone had taken place along the plane of the
middle lamellae of their walls. This same type of separation was
brought about without boiling when 10 per cent nitric or hydrochloric
acid was allowed to act on the pedicels for approximately five minutes.
"When longitudinal sections are used in place of entire pedicles, the
same results are obtained but much more rapidly. It was also noticed
that separation under these latter conditions takes place more quickly
in younger pedicels than in older ones. In the pedicels of fully
developed fruits no separation could be induced, but in those of

1918] Kendall: Abscission of Flowers and, Fruits in Solanaceae 405

immature fruits separation oeeurred in the cortex but failed to take
place within the vascular cylinder.

Experiment 10 at first glance would seem to indicate that the cell
walls of the separation cells are more subject to hydrolysis than normal
cortical cells. Another interpretation is possible, however. Actual
separation which takes place through the separation zone may be due
to the fact that the cells in this zone are small and have a tendency
to be isodiametric, whereas the remaining cells of the cortex are larger
and are elongated parallel to the long axis of the pedicel. Hydrolysis
of the cell walls may go on with equal rapidity in all the cortical cells
at the base of the pedicel, yet upon bending or pulling separation may
take place through the region of isodiametric cells because of the inter-
locking of the elongated cells in the rest of the cortex. An attempt
was made to gain further evidence on this point by observing through
the microscope the action of acids on the cell walls of the tissues con-
cerned. When the action of the acids is thus observed, the walls are
seen to soften and to swell to two or three times their normal thick-
ness. This effect is all the more noticeable if the walls initially are
comparatively thick. Now, since the cells of the separation zone are
small and somewhat collenchymatous, or at least have thicker walls
than normal cortical cells, the process of swelling in the cell wall is
most conspicuous in that region. Indeed, hardly anj"^ swelling can be
perceived as a result of the acid treatment in the cell walls of normal
parenchyma cells of the cortex. However, when a form such as
Lycopersicum is examined in which there is a distinct layer of col-
lenchyma beneath the epidermis for the entire length of the pedicel,
this collenchyma appears to be affected at the same time and in the
same manner as the cells of the separation zone of Nicotiana. Also
in Nicotiana there seems to be a certain amount of similarity in
reaction to acids between the smaller cells of the cortex just beneath
the epidermis and those of the separation zone. The conclusion can
thus be drawn that the cell walls of the separation cells are no more
readily hydrolyzed than those of normal collenchymatous tissues. Of
course, the fact still remains that the collenchyma of the cortex may
be more subject to hydrolysis than the cortical parenchyma. Now
the small cells of the separation zone not only extend across the base
of the pedicel but also spread throughout the general region at the
base of that organ; it was therefore noticed that the swelling of cell
walls was by no means confined to cells of the separation layer but
was more or less prominent throughout the whole general region at
the base of the pedicel.

406 University of California Puhlications in Botany [Vol.5

The general results of these observations are in a sense negative
and seem to indicate that the walls of the separation cells are no more
subject to hydrolysis than the walls on either side. This, of course,
does not preclude the possibility that a difference exists which is too
slight to be detected. It appears, however, that the general region
at the base of the pedicel may be more subject to hydrolysis than the
more distant portions.

3. Induction by ^Mechanical Injury

The results of experiments on the induction of abscission by mechan-
ical injury are recorded in tables 2, 3, 4, and 5, which have already
been considered under the heading, "Time of Abscission" (page 384).
Several facts of interest brought out by table 2. which deals with
Xicofiana Langsdorffii var. grandi/Jora, are summarized below.

1. It appears that removal of or injury to the capsule does not
cause abscission in mature fruits (table 2, a, h, and h; table 3, c and
d) . The same types of injury generally do cause abscission in im-
mature fruits.

2. It seems that a transverse cut comi)letely through the flower at
the distal end of the calyx causes abscission only in buds or flowers
near anthesis (table 2, c). It appears, however, that such a cut
proximal to the distal end of the calyx causes abscission in flowers
several days past anthesis as well as in buds (table 2, a, h).

3. Removal of the entire calyx causes fall in very young buds only
(table 2, d) .

4. It seems that slitting both the corolla and calyx longitudinally
on both sides from tip to base does not induce abscission even in young
buds (table 2, e).

5. Entire removal of the style or stamens causes fall only in young
Imds (table 2, / and g) .

6. It appears that injuries to the pedicel do not cause abscission,
provided the flower is not entirely cut away (table 2, i). Just here it
is worth mentioning that two of the pedicels cut transversely as
recorded in table 2, i, were cut so deep that the flowers bent over
and hung only by a few vascular strands and cortical cells. The
wound healed over, however, and the two flowers matured with the rest.

7. It is evident that injuries which reach the ovary are much more
elfective in causing abscission than injuries affecting the other parts
of the flower (table 2. h and ( ).

1918] Kendall: Abscission of Flowprs and Frnifs in Sola'naceae 407

8. Fertilization has no intluenee whatever in preventing abscission
when the latter is induced by a transverse cut completely through tlie
flower at the base or middle of the cah'x (table 3, c and d).

9. Certain types of injury, such as entire removal of the calyx and
stamens or removal of the entire calyx and half the corolla, evidently
cause abscission only by preventing fertilization (table 3, a and h).

Taking up now the results given in table 4. which dealt with
Fj H179. it will be seen that this hybrid is more sensitive to injury
than is N. Langsdorffli. Nevertheless, it is very plain that the general
conclusions announced above for this latter species hold for F^ H179
also. There follows a partial summary of the results in table 4 and
a comparison of these results with those obtained in the experiments
on N. Langsdorffli.

1. It seems that removal of the calyx causes fall of much larger
buds than in X. Langsdorffli (table 4, d).

2. F^ H179 is evidently much more sensitive in its abscission re-
action to a transverse cut through the flower at the middle of the calyx
than N. Langsdorffli (table 4, a).

3. It would seem that slitting the calyx and corolla even to the
extent of dividing these organs into four longitudinal strips does not,
as a general rule, cause abscission. Such an injury does cause abscis-
sion only in extremely small buds (table 4. gr).

4. It appears that puncturing the calyx, corolla and ovary so
that a hole is formed about 2 ram. in diameter in the latter organ
causes fall in flowers of all sizes up to two or three days past anthesis
(table 4. h) . Since it is evident that such a hole through the calyx
and corolla alone would not cause abscission (table 4, ^). abscission
in this case must be induced by injury to the ovary.

5. It is evident that a slit completely through the pedicel for its
entire length fails to cause fall in buds or open flowers, but where an
effort is made to destroy completely the connection between the flower
and stem abscission will occur (table 4, i).

(i. Removal of the style or stamens, as a general rule, causes fall
only in young buds, but removal of the former organ is probably more
eft'ective in causing flower-fall than removal of the stamens (table 4. e
and /). On the other hand, where half the corolla is removed along
with the stamens fall occurs in larger buds than where only the latter
organs are removed (table 4, ?>).

7. Removal of only half the corolla apparently does not induce
abscission (table 4, c).

408 Universitij of California Publications in Botany [Vol. 5

8. ^Mature capsules of F^ H179 are apparently more sensitive to
injury than those of X. Langsdorffii (table 4, j).

The table dealing with the experiments on Lycopersicum indicates
that flowers of this genus are remarkably resistant to injury, fall
occurring only as the result of stimulation when the ovary is injured
(table 5, c and d) . Since a large number of tomato flowers are nor-
mally abscissed from the different inflorescences on a plant, the sev-
eral exceptions to the above statement noted in the table probably
demonstrate to what extent the normal physiological condition of the
plant affects the matter. It seems to be the opinion of most gardeners
who are familiar with the tomato plant that floral abscission in this
species is more dependent upon soil conditions than upon injury or
sudden changes in climatic conditions. It would seem, however, that
injuries to very young fruits normally cause fall, but in this case a
stage of development is soon reached at which injury to the berry has
no effect in inducing abscission (table 5, /).

Taking the general results of all the experiments into consideration,
it is seen, in the first place, that wOiere injurs* of a certain type causes
fall, a stage of development of the flower is soon reached beyond which
the injury no longer causes fall. The increase in resistance to the
stimulus of mechanical injury takes place gradually in the species
investigated, but some of the species are much more resistant than
others. In the second place, injuries to the ovary generally cause
flower-fall. Thirdly, whether or not flower-fall occurs as a result of
injury to other flower parts depends in some way upon the quantity
of material removed. Fourthly, injury to the pedicel does not cause
abscission unless it breaks entirely the cellular connection between
flower and stem. Lastly, it is improbable that fall induced by injury
is due to checking the transpiration stream, since injury to the ovary
could have no such effect. Also, a cut across the pedicel so that the
flower hangs by only a few tracheie must check transpiration from the
flower considerably, yet in this case no abscission occurs.

It was suggested by Bequerel that injury might cause abscission
by checking the transpiration stream which passes up through the
pedicel. Considerable doubt has already been cast on this point in the
above discussion. In order to throw more light on this question the
following experiment was performed in an effort to determine whether
checking the transpiration stream of itself and unaccompanied by
mechanical injury would cause abscission.

Experiment 12. — As a means of checking transpiration from the
flower a coating of paraffin seemed desirable because it hardens

1918] Kendall: Abscission of Floivcrs and Fruits in Solunaceae 409

quickly, thus permitting several coats to be applied. It was doubtful
whether other substances, such as lard, cocoa butter or vaseline, which
might have been used, would not have been prevented from completely
covering the tiower in one coating by the presence of numerous hairs
and glandular fluid on the calyx. In this experiment flowers were
immersed in melted paraffin to within a millimeter of the separation
zone and allowed to stand in water under normal atmospheric condi-
tions. As a test for abscission, the shoot was shaken or individual
flowers tapped from time to time. It was found that several Nicotiana
varieties and hybrids differed in their reaction to this treatment as
they did in their reaction to illuminating gas. In .V. Tahacum "i\Iary-
land, " for example, paraffining the flowers failed to cause abscission
for six days, at the end of which time the flowers began to fall, as did
those of the control. Some varieties, however, under such treatment,
throw off buds at the end of twenty-four hours, but open flowers of
the same varieties are never shed. "Whether or not the buds fell in
these varieties depended largely on the temperature, at lower tempera-
tures no fall occurring. Also, in cases where abscission of buds did
occur it was evident that something was actually impeding the pro-
cess ; none of the white substance formed by the isolated cells was seen
at the base of the pedicel and the buds had to be shaken or tapped
quite severely before they fell.

The results of Experiment 12 and the various observations on the
induction of abscission by mechanical injury render it extremely
unlikely that checking the transpiration stream is ever a direct cause
of abscission. The few cases recorded above in which such a condition
seems to cause abscission can be better explained by the action of some
other factor than that of interference with transpiration.

In connection with these experiments upon the effect of checking
transpiration the results of Lloyd and Balls on the effect of root
pruning, etc., in cotton must be mentioned. It was found that a pre-
mature shedding of flowers and young bolls followed root pruning
and further that, in general, there is a relation between boll-shedding
and the rise and fall of the water-table. Proof positive is not sup-
I)lied that root pruning causes fall of flowers by reducing the water
supply of the plant body, and any number of other factors may enter
in after such mutilation to bring about, in part at least, such a result.
Experiments reported in the present paper seem to leave no doubt
that, in Nicotiana at least, temperature is a more important factor in
controlling abscission than water supply.

410 University of California Fnhlic-ations in Boianij [Vol.5

4. The Ability of Certain Species to Throw off Pedicels

PROM which All the Floral Organs Have Been

Kemoved, as Related to the Induction op

Abscission by Mechanical Injury

It was soon noticed in the experiments that all plants of a species
in which floral abscission occurs throw off the remains of the pedicel
when this organ is severed at any point distal to the separation layer.
If after such an operation no abscission occurs, it can lie safely con-
cluded that floral abscission never occurs in that species. Petnnia
hyhrida, Salpiglossis sinuata, Salpichrora rhonihoidea, and Lycium
australis are the only species of the list in table 6 which do not absciss
flowerless pedicels in this way. Nicotiana Bigelovii, N. quadrivalvis,
and iV. niidtivalvis occasionalh^ do not throw off pedicels under such
conditions. The reaction time in cases where the last three species do
absciss severed pedicels is very slow (four to fourteen days).

Turning now to the relation of these observations to the induction
of abscission b}^ mechanical injury, it is first necessary to recall the
controls used in Experiments 5 and 6 (cf. pages 399 and 400). A fur-
ther consideration of the reaction of these controls will suggest that
mechanical injury can induce abscission by the action of the stimulus
directly on the cells in the vicinity of the separation zone. The con-
trol used in Experiment 5, it will be remembered, showed that abscis-
sion does not occur under normal conditions in a series of flowers cut
as in figure 9. From the control used in Experiment 6 it is evident
that merely cutting off the flower at varying distances from the sep-
aration laj'er, forming pieces as represented in figure 10, causes ab-
scission to occur, evidently as the result of no other stimulus than
that of severing the pedicel. Now, if the cut be made through the
pedicel at a point approximately 1 mm. distal to the separation layer
in flowers, as represented on the extreme right of figure 9, abscission
will occur in the remaining piece, which is now scarcely 2 mm. in
length. It is evident that the stimulus caused by severing the pedicel
must act directly on the cells in close proximity to the separation
zone. Practicall}^ the same results are obtained when the transverse
cut is made through the base or middle of the calyx. There is no
reason to suppose that the stimulus set up by cutting through the
flower near the base or middle of the calyx differs in any fashion from
that offered by a cut severing only the pedicel.

1918] Kendall: Abscission of Flowers and Ft^uits in Solaiutceae 411

Several interesting conclusions are brought out by an examination
of the above facts. In the first place, the abscission of the remains of
severed pedicels is probably independent of the transportation of
materials from the rest of the plant to the separation zone. It may
result from the action of the stimulus directly on the cells in the
vicinity of the separation layer and is, therefore, largely independent
of such phj'siological processes as transpiration which might conceiv-
ably enter in. In the second place, abscission induced by mechanical
injur}' is probably of the same nature as that of severed pedicels and
therefore probably results from the action of the stimulus directly on
the cells in immediate proximity to the separation layer.

SUMMARY '

The final summary of results given below is presented under
several headings corresponding to those of the main body of the
paper. Unless otherwise stated, the results given may be taken as
applying to all the species of the Solanaceae in which abscission was
found to occur. First is presented a complete list of the species which
were investigated, indicating by 1 those in which floral abscission
never occurs, by 2 those in which it very seldom occurs, and by 3
those which were actually examined microscopically to determine the
histological structure of the separation zone and the method of
abscission.

3 N. Tabacum var. maciophylla

3 N. sylvestris

3 N. Tabacum "Maryland"

3 FiHlo4 (N. sylvestris X N. Tab.

var. maerophylla)
3 F,H179 (N. sylvestris X N. Ta-
bacum "Cuba")
3 F,H36 (N. sylvestris X N. Tab. var.
angTistifolia)
N. glauca
3 N. rustica (2 varieties — not bra-

silia)
2,3 N. Bigelovii (3 varieties)
2 N. quadrivalvis (2 varieties)
2 N. multivalvis
X. Sanderae
N. rustica var. brasilia
X. suaveolens

3 Solanum umbelliferum

S. tuberosum

S. jasminioides
3 S. verbascifolium

S. nigrum
2, 3 loehroma tuljerosa
3 Oestrum fasciculatum

Lycopersicum esculentum var. vul-
gare
3 L. esculentum var. pyriforme
1, 3 Petunia hybrida
1, 3 Salpiglossis sinuata
3 Datura sanguineum
1 Salpiclirora rhomboidea
1 Lycium australis

412 University of California Puhlications in Botany [Vol.5

Histology and Cytology of the Pedicel

1. The separation layer arises in all the species listed above, except
Lycopersicum and Solanum tuberosum, at or near the base of the
pedicel. In the latter two species the layer is located near the middle
of the pedicel, but even in these cases, if one considers the pedicel to
be composed of two internodes, the layer occurs at the base of the
most distal internode.

2. The separation layer is preformed, ready to function at any
stage in the development of the flower and represents (cf. Kubart's
first type, page 350) a portion of the primary meristem which has
retained some of its originally active condition.

3. In all the species except Datura the separation cells are char-
acterized by their small size, isodiametric shape, large amount of
protoplasm and somewhat collenchymatous appearance. A study of
the early histological development of the pedicel indicates that the
small size of the separation cells does not necessarily bear anj' relation
to abscission. This statement is supported by the fact that in Datura
there is absolutely no visible difference between the separation cells
and any other cells of the pedicel.

4. Various tests with stains, acids, and alkalis fail to indicate any
chemical difference between the cell walls of the separation cells and
the walls of neighboring cortical cells which do not separate. How-
ever, the middle lamellae of cell walls in the general region at the
base of the pedicel seem somewhat more easily hydrolysed by acids
than in the more distal portions,

5. A stud}' of the early histological development of the pedicel in
Nicotiana and Lycopersicum shows that the grooves near which the
separation zone arises do not necessarily bear an}' relation to abscis-
sion. The grooves are formed because, in the development of the
pedicel, certain cells do not increase in size so fast as the neighboring
cells on either the proximal or distal side.

6. The development of mechanical tissue in the pedicel of Nicoti-ana
continues through the separation layer, thus frequently holding the
fruit on the plant in spite of the fact that abscission commonly occurs
in the cortex. In most of the berry-forming species of the Solanaceae
this mechanical tissue does not become continuous through the separa-
tion layer and thus offers no impediment to fall when abscission occurs
in that region.

1918] Kendall: Abscission of Flowers and Fruils In Solanaccac 413

The Process of Abscission

1. The process of abscission conforms to the usual type, which
involves the separation of cells along the plane of the middle lamella
of the cell wall separating them.

2. No cell divisions or elongations were observed to accompany
abscission.

3. All the cells across the pedicel in the region of the separation
layer take part in separation except the tracheae and cuticle, which
must be broken mechanicall.y. The total number of cells which may
be involved is greater in some species than in others. This number
may also yaxy in the same species because of changes in the external
conditions.

4. Cell separation is brought about by the hydrolysis and conse-
quent dissolution of the middle lamella (primary cell membrane) or
perhaps both the primary and, in part, secondary cell membranes.
The agency active in the hydrolysis of the cell membranes is probably
an enzyme.

5. An increase in cell turgor frequently occurs during abscission,
but probably serves merely to hasten and facilitate the process. Most
of the frequently observed expansion and the turgid appearance of
the separation cells during abscission are probably due to the natural
release of pressure caused hy the dissolution of the middle lamellae.

6: Abscission of the style and corolla in Nicotiana and Datura
resembles, to a large extent, abscission of the flower.

Time of Abscission

1. The length of time between anthesis and normal flower-fall due
to lack of fertilization differs among the varieties of Nicotiana. This
variation was found to range between an average of five to eighteen
days in some fifteen species and varieties of Nicotiana. A much
smaller range of variation (0.7 to four days, with the largest fre-
quency in the three day group) was noted for the time between an-
thesis and fall of the corolla after pollination.

2. The stimulation of the stylar tissues by the growth of the pollen
tubes tends to shorten the time between anthesis and fall of the
corolla, this effect being independent of fertilization. Such stimula-
tion of the stylar tissues has no appreciable effect upon floral ab-
scission.

3. Floral abscission occurs in F^ H179 seven hours after subjecting
shoots of the plant to 1.5 per cent illuminating gas at a temperature

414 University of California Publications i)i Botany [Vol. o

of 19° C. It occurs in Xicotia}ia Tahacum "^larylaiid" in eight hours
under the same conditions. The actual time involved in the process of
cell separation in the above-mentioned cases lies within thirty to forty
minutes in the hybrid and within forty-five to sixty minutes in the
Tahacum variety. Normal abscission in these forms is much slower

4. The length of the reaction time in cases of flower-fall due to
mechanical injur}' shows that this length of time depends more on
the age of the flower than on the type of injurv'.

5. Temperature is the most important conditioning factor in esti-
mates of the time of abscission.

Experimental Induction of Abscission

1. Floral abscission is induced, in a large number of the species
investigated, by illuminating gas or laboratory air. The increase in
resistance to abscission stimulated in this manner takes place suddenly
in some species, since abscission will not occur after the opening of
the corolla. In other species this condition does not exist.

2. It is possible to induce the process of abscission with illuminat-
ing gas in small isolated pieces of the pedicels or in longitudinal sec-
tions of the pedicel cut free-hand from fresh material.

3. Abscission in Nicotiana and Lycopersicum is induced by certain
types of severe injury and not by others. Injurv" to the ovary seems
more effective in causing abscission than injurv^ to other parts of the
flower. In the case of these other flower parts, it seems necessary that
a certain amount of tissue be actually removed or destroyed before
fall occurs. Injurj^ to the pedicel does not cause abscission unless it
breaks entirely the connection between floral organs and stem.
Flower-fall in Lycopersicum is not readily induced by injury. Floral
abscission in this genus is more dependent upon physiological condi-
tions brought on by abnormal soil conditions.

4. Experiments on the induction of abscission in small isolated
pieces and in flowers with only a small portion of the stem proximal
to the separation layer attached indicate that the stimulus produced
by the action of external factors such as illuminating gas and mechan-
ical injury can cause abscission by acting directly on the cells in close
proximity to the separation zone. The action of external factors is
thus largely independent of such physiological processes as transpira-
tion which might enter in. This statement is supported bj' experi-
ments which show that abscission is not necessarily induced by
checking transpiration from the flower.

1918] Kendall: Abscission of Flowers (uiel Fruits in Solanaceac 415

CONCLUSION

It is proposed in what follows to take up consideration of such
phenomena in connection with abscission as are still but slightly
understood. One of the most perplexing of these is undoubtedly the
definitely predetermined location of the separation layer when no
morphological and sometimes no physiological (Datura) difference can
be detected between the cells that separate and those that do not.
There need be no doubt, however, that such a difference does exist
and that a sufficient refinement of technique will serve to detect it.

In considering this matter further it may be recalled that the
separation layer in axial abscission is located at or near the base of an
internode. There is undoubtedly some connection between this fact
and the fact that the cells most active physiologically are often found
in this region. The growth of an internode may be brought about by
the action of an intercalary meristem located at the base of the organ
and a meristem so located in some cases retains its original activity
in the mature internode. Now it is well known that the walls of young
active cells are more readily subject to hydrolysis than the walls of
older cells, because of the fact that the former contain more water.
If we assume, then, that the internode is a metabolic gradient with
the most active cells at the base, it would be expected that the walls
of these cells would be more subject to hydrolysis than any other cells
of the internode. If some hydrolysing agency becomes active
throughout the pedicel, it might be expected that the walls of the
cells at the base of the internode would react first, causing their sep-
aration and thus cutting off the flower or internode. By assuming
in this wa}^ that separation always takes place through the most
active cells of the internode it seems possible to explain the predeter-
mined location of the separation layer.

There is undoubtedly some connection between the above problem
and the fact that some plants must perfect a separation layer before
detachment can take place. In such cases the tissues at the base of
the organ are too old for separation. The same stimulus which causes
abscission in some species causes a renewal of activity at the basal
region of an organ, resulting in cell divisions and new cells. These
new cells may, under a continuation of the stimulus, separate one
from another.

Another perplexing problem, which also includes many subsidiary
problems, relates to the exact course taken by the stimuli in causing

416 University of California Publications in Botany [Vol. 5

abscission. Experiments described in the present paper have indi-
cated that this course may be direct as well as indirect. Assuming for
the present that some of the factors bringing about abscission always
act directly while others act indirectly, we might classify the general
factors operative in the case of the Solanaceae as follows :

Direct 1. Narcotic vapors.

2. Injury to floral organs.

3. Sudden rise in temperature.

4. Lack of fertilization.
Indirect 5. Clianges in soil conditions.

6. Factors evident in normal physiological development.

The direct factors act directly on the cells at the base of the pedicel
and consequently the reaction time must be comparatively rapid. The
indirect factors act indirectly through the general physiological con-
dition, which in turn furnishes the direct stimulus for cell separation.
In the latter case the reaction time must, as a general nile, be slow.
The nature of factors under 6 are most difficult to understand. An
example of the action of these factors would be given in those cases
where most of the flowers of an inflorescence are normally abscissed
leaving only one or two to continue development, and in those species
which absciss male flowers after anthesis.

A further analysis of the course of the abscission reaction intro-
duces another unsettled problem — the nature of the agency which is
directly responsible for the dissolution of the middle lamella. It has
been pointed out before that an enzymatic body of some kind is prob-
ably involved. The following discussion brings out certain facts
which it is necessary to take into consideration when speculating as
to the nature of this supposed enzyme. The activity of the enzymatic
bod}'" must be subject to both internal and external conditions. The
enzj-matic material must also be extremely sensitive to slight changes
in the normal enviroiunent. It must be continually present in the
cells of the separation zone and ready at any moment to react to such
changes in the enviroiunent. A comparison of several species in
regard to their abscission reactions to the factors listed above indicates
that this supposed enz^Tiie must be more sensitive in some species
than in others. Indeed, in certain species in which no abscission
occurs the enzyme must be absent from the region of the separation
zone or entirely inactive. Finally, it seems necessary to assume that
in certain species the action of the enzyme is suddenly inhibited at
about the time of the opening of the corolla.

1918] Kendall: Abscission of Flowers and Fruils in Solanaceae 417

r

It has been noticed in all the experiments detailed above that
older flowers are less subject to "spontaneous" abscission than
younger ones. The transition line as to size or age beyond which
no abscission occurs can not in most cases be definitely drawn ; that
is to sa}^ the development of a resistance to stimidi takes place grad-
ually. This is probably explained by the fact that cell walls gradually
become less subject to hydrolj'sis with age. The celluloses and pec-
toses lose water with age and it is well known that these compounds are
subject to hydrolysis in proportion to the amount of water they con-
tain. In those cases where the increase in resistance to stimuli takes
place suddenly it is necessary, as suggested above, to assume some
kind of inhibitor of the enzj^piatic action.

The effect that pollination has in hastening abscission of the
corolla is a subject which is related to the phenomena described by
Fitting (1909) for orchids. The phenomena are as yet only slightly
understood. The explanation seems to involve some relaying of
stimulus from cell to cell. This is also involved in the explanation of
floral abscission induced bj- injury to the ovary. These two cases
and others indicate that in some instances, at least, abscission responses
are related to tropistic responses as Fitting (1911) has suggested.

Finally, attention may be called to the fact that the most pressing-
need in connection with all the problems mentioned above is, in the
first place, to establish by some experimental means a definite connec-
tion between some enzymatic body and the process of abscission and,
in the second place, more definite knowledge as to the role which cell
turgor plays in cell separation. Taking all the facts into considera-
tion, it is evident that abscission is fundamentally a physiological
problem, the crux of which lies, as in all such problems, in the bio-
chemistry of the cell.

The studies reported upon above were carried on under the direc-
tion and supervision of Professor T. H. Goodspeed and I am under
deep obligation to Professor F. E. Lloyd for many valuable sugges-
tions both throughout the course of the experiments and during the
preparation of this report of them.

418 University of California P uhUcations in Botany [Vol.5

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1918] Kendall : Abscission of Flowers and Fruits in Solaimcear 419

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wiss. Bot., vol. 16, p. 630.

ElCHTER, O.

1908. Ueber Turgorsteigerung in der Atmosplier von Narkotica. Lotos,

vol. 56, p. 105.

RiCHTEE, O., and Grafe, V.

1911. Ueber den Eiufluss der Narkotika auf die chemische Zusammensetzung
von Pflanzen. S.-B. Akad. Wien, Math-nat. KL, vol. 120.1, p. 1187.

Strasburger, E.

1913. Das botanische Praktikum, p. 349.
TisoN, A. (quoted from Lloyd 1914a).

1900. Recherehes sur la chute des feuilles chez les dieotyledones. Mem. Soc.
Linn. Normandie, vol. 20, p. 125. Quoted from Lloyd (1914a).

WiESNER, J.

1871. Untersuchung liber die herbstliche Entblatterung der Holzgewaehse.

S.-B. Akad. Wien, Math-nat. Kl., vol. 64, p. 456.
1905. Ueber Frostlaubfall. Ber. Deutsch. Bot. Ges., vol. 23, p. 49.

PLATE 49

Fig. 1. Base of pedicel of NicoUana bud showing groove, separation zone,
and process of abscission well under way in dorsal cortex.

Fig. 2. Portion of cortex in the separation layer of Nicotiana showing the
bulging of the epidermis, one of the first signs of abscission.

[420 ]

UNIV. CALIF, PUBL. BOT. VOL. 5

[KENDALL] PLATE 49

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*

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^^^

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.4-

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•t?

^

Fi"-. 1

/^'i^ "A

(<

Fit

PLATE r>{)

Fig. 1. Portion of the base of the pedicel of ^Jicotiana at a late stage in
the process of abscission showing the independent origin of the process in the
pith.

Fig. 2. Portion of the cortex in" the separation layer of Nicotiann showing
separating cells next to the vascular system.

[422]

UNIV. CALIF. PUBL. BOT. VOL, 5

[KENDALL] PLATE 50

s

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/

^ 1

'^'^

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'S?

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PLATE 51

Portion of the separation layer of Nicotiana showing cells iu the process of
separation in the upper part of the section.

[424]

UNIV. CALIF. PUBL. BOT, VOL. 5

[KENDALL] PLATE 51

4%

PLATE 52

Fig. 3. Purticui uf dorsal cortex near the grooxe in the pedicel of Xicotiana,
showing the abscission process well under way.

Fig. 2. (J roup of isolated cells washed off from end of a freshly abscissed
pedicel of Nicotiana.

Fig. 3. Single isolated cell showing the thinness of the remaining cell
membrane.

[ 426

UNIV, CALIF. PUBL, BOT. VOL. 5

[KENDALL] PLATE

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PLATE 53

Fig. 1. Portion of pedicel of Lycopersicum, showing groove and separation
zone.

Fig. 2. Portion of cortex of pedicel of Lycopcrsicvm, showing groove and
abscission process fairly well along; cell sei)aration first takes place between
only two tiers of cells before sjireading to others.

428

UNIV. CALIF. PUBL. BOT. VOL. 5

[KENDALL] PLATE 53

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UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 13, pp. 429-434 August 10, 1918

CONTROLLED POLLINATION IN NICOTIAN A

BY

THOMAS HARPER GOODSPEED and PIRIE DAVIDSON

In the course of the breeding experiments with Nicotiana carried on
in the Botanical Garden of the University of California the question
has arisen on a number of occasions and in a variety of connections as
to the relation in this genus between the number of pollen grains
applied to the stigma, the number of fertilizations accomplished and,
finally, the number of seeds resulting. In the case of the F^ Tabacum-
sylvestris hybrids, for example, it has been shown that a few ovules
capable of fertilization and the production of viable seeds are matured,
and it has seemed possible that at least a corresponding percentage of
normal pollen grains are produced. In field practice it is impossible,
however, to obtain selfed seed of these hybrids even when the stigmas
are artificially close, or self-pollinated with a considerable excess of
pollen ; the flowers thus treated falling after some days just as those
allowed to pollinate themselves naturally under bag. In this connec-
tion it would be of interest to know whether in self-fertile species a
relatively large excess of normal pollen is necessary to accomplish the
fertilization of a relatively small number of ovules and whether the
fertilization of three or four ovules is sufficient to inhibit the abscission
which follows entire absence of pollination. Again, branching pollen
tubes have been observed in a number of species of Nicotiana when
the pollen was grown in artificial germinating media. If such
branching occurs in the style and is accompanied by a division of
male nuclei with the result that more than one ovule is fertilized by
a single pollen grain, it would obviously be of importance in the
interpretation of F, ratios, etc.^ With these and other points in mind

1 A cytological examination of a number of the branching pollen tubes gave
some evidence that at least chromatin fragments were present in two or more
of the branches. This fact might suggest that the abnormal germinating fluid
of the pollen cultures was alone responsible for the branching and further
resulted in a fragmentation of the initial nuclear material.

430 University of California Publications in Botany [Vol. 5

•

it was our intention to carry out an extensive series of experiments on
a number of pure lines and hybrids of Nicotiana in which the number
of pollen grains involved in each pollination was accurately known.
Limitation of time and the lack of adequate greenhouse facilities have
made it impossible to carry out our original plans. However, the
results which have already been obtained seem of sufficient interest to
warrant their publication at this time.

The particular results which are the subject of this paper were
obtained in experiments upon six plants of Nicotiana Langsdorffii var.
grandiflora (U. C. B. G. 107/08w). The pollination experiments were
carried on in a greenhouse the average temperature of which was 30° C.
It was known that the species used did not exhibit any traces of a
parthenogenetic nature.

Flowering laterals were trimmed to a large bud and all leaves were
removed. After careful castration these buds were bagged. When
fully receptive a pre%aously determined number of pollen grains was
applied to the stigma and all pertinent data recorded on the copper
wured pot-label which served to attach the bag to the plant. The
paraffin bags were removed about two weeks after pollination.

The number of pollen grains used in the various pollinations was
controlled in the following manner. A few grains were placed in the
depression of a hanging-drop slide. Their number was determined
and the preparation was covered with a cover slip and sealed with
water. In the greenhouse the corolla of the flower was turned back,
the cover slip removed, the slide carefully turned over and the pollen
allowed to come into contact with the stigmatic surface covered with
stigmatic secretion. Another count of the pollen grains remaining on
the slide was then made to determine the number that had become
attached to the stigma. Obviously defective grains were not considered
in the pollen counts. The sources of error in any such method are
obvious. However, the results given in the following table indicate
that this method of obtaining controlled pollinations is approximately
accurate. Other methods were tried but proved in every way less
satisfactory than the one described above.

At maturity the ripened seed capsules were gathered and the
number of seeds counted. It was possible in a few cases to determine
the position of the seeds on the placental surfaces. None of the seed
was tested as to its viability, but microscopic examination demonstrated
the presence of normal embryos and endosperms. The results of some
twenty-one controlled pollinations are given in the following table.

1918] Goodspeed-Davidson: Controlled Pollination in Nicotiana 431

Tabulated Results of Controlled Pollinations in Nicotiana Langsdorfjfii
VAR. grandiflora (U. C. B. G. 107/08w)

Plant 17 was used as the pollen parent in each case.

Position of seeds

Experi-
ment
number

107/08W

plant

number

Number of
pollen
grains

Number

of

seeds

1

11

20

13

2

14

50

12

3

14

50

26

4

14

60

12

5

14

30

26

6

25

60

10

7

25

40

16

8

25

40

11

9

25

50

38

10

25

15

2

11

43

10

2

12

43

10

4

13

43

5

1

14

43

2

0

15

48

15

6

16

48

18

2

17

48

5

0

18

48

8

2

19

48

5

3

20

48

14

7

One seed in each cell ; one at top and one in

middle.
Four close together near top of one cell.

Middle.

Three in one cell, one at bottom and two in
middle; four in the other cell, two at bottom
and two in middle.
21 48 3 3 One at bottom of one cell ; two in middle of

the other cell.

A number of points of interest which might repay further study
suggest themselves in connection with the results noted in the above
table. The present data is too fragmentary to make possible any
specific conclusions of general applicability. Such conclusions must
wait upon a greater accumulation of evidence to allow of statistical
treatment of the results. However, certain points brought out in the
above table bear directly upon the question of the total sterility of
the pollen of the Fj Tabacum-sylvestris hybrids and upon the general
abscission problem in Nicotiana.

It is evident that fertilization of an extremely small percentage of
the ovules capable of fertilization- is sufficient to cause the flower to
be held upon the plant rather than to be abscissed. We have for some
time suspected that some such delicate balance existed between fer-
tilization and the activation or formation of the separation layer. In

2 Over two hunrlred viable seeds are produced by close pollination in
Nicotiana Langsdorfjii var. grandiflora.

432 University of California Publications in Botany [Vol. 5

this connection we may consider the three following possibilities in
the ease of the species under consideration. In the first place we may
think of a ripe ovary containing at least two hundred ovules, each one
properly matured and capable of the production of a viable seed fol-
lowing self-fertilization. After such fertilization and under normal
conditions the seed capsule is retained on the plant up to and follow-
ing the shedding of the ripe seed. On the other hand, another ripe
ovary of the same plant in which no ovules are fertilized falls from
the plant along with the other flower parts and a portion of the pedicel
a few days after such maturity. Finally, in the case of a third ripened
ovary on the same plant the fertilization of two or three ovules is
sufficient to inhibit flower-fall. The fact that in experiments 14
and 17 in the above table but two and five ovules respectively could
have been fertilized^ is evidence in this connection. Additional evi-
dence is found in the way in which the fruits of the F^ Tahaciim-
sylvestris hybrids remain upon the plant when only a very few seeds
are finally matured in them. In this case cytological examination of
ripe ovaries showed that but a very small number of the six or seven
hundred embryo-sacs are normal and capable of fertilization. When
the viable 'pollen of either of the parent species is placed on the
stigmas, the majority of the flowers thus pollinated remain attached
to the plant and a few seeds are fully or partially matured in each
ovary. We have here a case in which normally all the flowers on the
plant fall as a result of lack of pollination with viable pollen and in
which it is actually impossible for more than a very few ovules to be
fertilized, yet when these few fertilizations are accomplished abscission
does not take place.

Throughout the above discussion we have emphasized fertilization
as contrasted with final formation of viable seed as the determining
factor in the abscission of the flower. This has been done advisedly
with the following facts in mind. In the F^ Tabacum-sylvestris
hybrids ripe seed capsules retained on the plant often contain nothing
but a few empty seed cases. In other words it would seem that the
fertilization of all or a number of the normally matured embryo-sacs
provided the stimulus necessary to inhibit the activation of the separa-
tion layer, the question as to whether or not any of these fertilizations
resulted in the formation of viable seeds being non-essential. Further,
the results of experiments 14 and 17 in the above table indicate that

3 The results in general indicate that branched pollen tubes with the neces-
sary sexual elements do not occur in the style and thus that only one ovule is
fertilized by a single pollen grain.

1918] Goodspeed-Davidson: Controlled Pollination in Nicotiana 433

only the fertilization of an extremely small percentage of the normally
matured ovules and possibly the completion of the earlier stages in
embryo and endosperm development are necessary to make abscission
impossible. The question of the inhibitory stimulus provided by the
passage of pollen tubes down the style is still an open one. The fact
that premature pollination in tobacco* has been shown to cause abscis-
sion lends support to the supposition that stylar penetration is im-
portant. In this connection the delicacy of the balance between
stylar penetration or fertilization and abscission is again emphasized
in that before the normal maturation of the female sexual elements
pollination causes abscission, whereas at their complete maturity stylar
penetration by a few pollen grains or fertilization of a few embryo-
sacs is sufficient to inhibit such abscission.

In our experience there is in Nicotiana a certain stage of develop-
ment of the seed capsule beyond which automatic abscission does not
take place and spontaneous abscission cannot be induced. The
explanation of this situation is found in the fact that mechanical
tissue is rapidly developed in the pedicel of the flower somewhat after
anthesis. A flower has only to pass the dangerous period when after
cell separation (abscission) there is not sufficient mechanical tissue to
hold it in position, to be retained permanently upon the plant. It is
a question in such cases as experiments 14 and 17 above if abscission,
induced by lack of normal seed development, may not occur after its
normal time of occurrence. If it does so occur the unbroken cuticle
and the more or less unaffected vascular bundle tissue both supported
by the mechanical cylinder, may, on the one hand, prevent the drying
out of the living but separated cells of the separation layer and, on
the other, furnish the necessary supplies of water and metabolic
ingredients to the developing seed capsule.

The results obtained in these experiments on controlled pollination
appear finally to prove that no normal pollen is produced by the F^
Tahacum-sylvestris hybrids. As noted above the flowers of such
hybrids (with the exception of the parthenocarpic Tahacum "Cuba"
hybrids) always fall when allowed to self -pollinate under bag. Many
attempts extending over a number of years have been made to secure
successful self-pollination artificially. A considerable excess of pollen
has been applied in a single and in a number of successive pollinations,
the stigma has been irritated with foreign substances prior to self-

4 Hartley, C. P., Injurious effects of premature pollination, U. S. Dept. Agr.,
Bur. PI. Tnd., vol. 22, 1902.

434 University of California Publications in Botany [Vol. 5

pollination, artificial stigmatic fluids have been used, etc. In all eases
the flowers have fallen. The results of microscopical examinations and
pollen cultures have always indicated that no normal pollen was pro-
duced. Still it has always seemed possible that there might be a very
few normal pollen grains corresponding to the percentage of normal
ovules. That there is no such good pollen seems finally proved by the
above results which show that two to five stylar penetrations or fer-
tilizations are sufficient to inhibit flower-fall. If even one-half of one
per cent of the thousands of pollen grains applied to the stigma were
normally matured the flowers should have been retained upon the
plant. Genetic incompatibility seemingly need not be considered in
connection with this abscission evidence as to the pollen condition of
these hybrids because it should not be expected to interfere with pollen
tube growi;h and probably not with fertilization itself.

In the table data are given in a few instances as to the position on
the placentae of the mature seeds. Thus some fragmentary evidence
is given on the question of "selective" fertilization. Hartley {loc.
cit.) states "That there is a close relation between the pollination of
one half of the stigma and the setting of seeds in the corresponding
half of the ovary is certain . . . ." No data are, however, given by
Hartley as to the position of the seeds resulting in his experiments in
w^hich small amounts of pollen were used. Our results indicate that
there is no selective fertilization from the point of view of position on
the placentae and that the particular embryo-sacs reached by the pollen
tubes is a matter of chance.

Transmitted May S, 1918.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 14, pp. 435-437, plate 54, 1 figure in text September 25, 1918

AN APPARATUS FOR FLOWER MEASUREMENT

BY

T. IT. GOODSPEED axd E. E. CLAUSEN

For a number of years we have been collecting data concerning
the inheritance of flower size in hybrids between two varieties of
Nicotiana Langsdorffii. It was early seen to be impracticable to
attempt any measurements of fresh flowers in the field. For reasons
disciLssed elsewhere^ it seemed advisable to measure the first twenty-
five flowers produced by each plant, and when from four hundred to
eight hundred plants are involved this can be accomplished only by
picking the flowers each day from every plant and preserving them
in fluid (2% formalin) to be measured in the laboratory. For making
these measurements the machine described below was devised. A
description of it is given at this time because the results of our experi-
ments cannot for the present be published, and it seems possible that
others may be able to employ the apparatus, or some modification of it,
in similar investigations. The original suggestion which led to the
perfecting of the apparatus described was given to us by Dr. R. Gold-
schmidt, to whom our thanks are due. We are indebted to Mr. V.
Arntzen of the Department of Civil Engineering of the University
of California, who constructed the machine under our direction, for
his helpful interest.

The accompanying drawing (pi. 54) is self-explanatory, and it is
only necessary to describe the way in which the apparatus is used in
making the flower mea-surements. The flowers of N. Langsdorffii are
slender tubed, with a spreading limb provided with shallow and round-
pointed lobes. The flowers are taken from the formalin solution,
washed in water and the calyces removed. They are then cut with

1 Goodspeefl, T. TT., and Clausen, E. E., Amer. Jour. Bot., vol. 2, pp. 3.32-374,
1915.

436

University of California Publications in Botany [Vol. 5

scissors at the point of union of limb and tube. This operation is
simplified by the soft condition of the tissues after being immersed in
formalin for some weeks, which causes the whole flower to straighten
out when drawn from the washing water. The point at which the cut
should be made is indicated by a slight groove occurring at the point
of union of tube and limb. The limb and tube thus separated are
placed in a dish of water so that the former may flatter out normally.
It is then drawn up onto a piece of glass and transferred thus flattened
to a large glass plate. The tube is then picked out of the water and
placed beside the limb on the glass plate. This plate is cut approxi-
mately ten and one-fourth by twelve inches to fit into the frame of the
measuring apparatus, where it is held firmly by the set screws gg
(pi. 54).

Figure 1

Parallel to the long axis of the glass plate two or three lines from
two to three inches apart are drawn with a diamond. The cut ends of
the tubes and one lobe of the limbs are brought to touch one of these
lines. The arrangement is diagrammatically illustrated in figure 1.
The size of the flowers will, obviously, determine the number which
can be thus arranged on a single glass plate.

The flowers arranged as shown in figure 1 on the glass plate are
put into the machine. The operator faces the circular disc (pi. 54, a)
and the knurled head j (pi. 54) is turned to the right or left until the
line n, marked on the movable bar m, is directly under the first of the
lines scratched on the plate glass. By loosening the set screw h (pi. 54)
the circular disc is swung around until the zero point is directly behind
the indicator I. The set screw /( is then tightened and the knurled
head j is turned to the right until the line n, which is visible through
the glass plate, is directly on a line with the corolla lobes h, c (fig. 1).

UNIV. CALIF. PUBL, BOT. VOL. 5 [GOODSPEED AND CLAUSEN] PLATE 54

;^

Jfn^

4 racH

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Uv/i/^Rj/rr Of California

Dlpartmeint or Botany

Flower Mca3uring Apparatus

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Top Va

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438 University of California Publications in Botany [Vol. 5

The diameter of the limb (fig. 1, e) is then read off in millimeters on
the scale on the circular disc (pi. 54, a). The knurled head is now
turned still more to the right until the line n is under the end of the
tube (fig. 1, d). The length of the tube (fig. 1, /) is then read off.
The bar m (pi. 54) is next turned back to the left to get the diameter
of the second limb (fig. 1, g) and then moved to the right to obtain
the length of the second tube and so on.

This apparatus or some modification of it would seem useful in
measuring a wide variety of objects. Leaves, especially, can be
measured on it very successfully.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 15, pp. 439-450

December 28, 1918

NOTE ON THE EFFECTS OF ILLUMINATING

GAS AND ITS CONSTITUENTS IN CAUSING

ABSCISSION OF FLOWERS IN

NICOTIAN A AND CITRUS

BY

T. H. GOODSPEED, J. M. McGEE and E. W. HODGSON

I. INTEODUCTION

In our laboratories considerable attention has recently been given
to the abscission problem. It came to the attention of one of us in con-
nection with an investigation of the partially sterile F^ hybrids between
Nicotiana Tabacum varieties (cf. Setchell, 1912) and N. sylvestris}
A preliminary study of the mode of abscission in these hybrids was
reported upon some time ago (Goodspeed and Kendall, 1916). As a
continuation of this work, abscission of flowers and fruits in the
Solanaceae and particularly in Nicotiana has recently been investigated
(Kendall, 1918) . Some studies have been made by one of us regarding
the relation of the environmental complex to the occurrence of abscission
and with reference to the mode of foliar abscission in Citrus (Hodgson,
1917, 1918). More recently attention has been called to the delicacy
of the balance between fertilization and floral abscission (Goodspeed
and Davidson, 1918). The present paper reports the results of experi-
ments upon the effects of illuminating gas and its pure constituents
in causing flower-fall, which represent a continuation of similar experi-
ments by Kendall (loc. cit.) on Nicotiana, together with a report on
experiments of the same type on the genus Citrus. The data sub-
mitted were considered preliminary at the time they were gathered.
Their interest and the fact that other more important matters have
put a stop indefinitely to any further accumulation of evidence make
it seem desirable to present them at this time.

NEW \ou
QAKDKbi

1 Cf. various papers in Univ. Calif. Publ. Bot., vol. 5.

440 University of California Piihlications in Botany [Vol. 5

II. METHODS

The illuminating gas supplied to the laboratories of the University
of California has the following composition by volume.

Nitrogen 4.10%

Oxygen 0.10

Hydrogen 55.00

Methane 26.30

Ethylene 5.00

Carbon dioxide 1.80

Carbon monoxide 7.70

In the experiments with Nicotiana the apparatus for subjecting the
flowers to certain percentages of illuminating gas and its constituents
consisted of five-litre bell- jars. In one case the bell- jar was fitted with
a ground-glass stopper and stopcock and was set in a large crystallizing-
dish so that the mouth of the bell-jar could be closed with a water seal.
Part of the air in the jar was then drawn off and the jar partly filled
wnth water, the volume of air Avas noted and the desired amount of gas
being experimented with was introduced through the stopcock. In
the other case a bell-jar was fitted with a ground-glass plate which
sealed up the open end completely, the seal being made air-tight with
vaseline. This bell-jar was fitted with two stopcocks and the gas being
experimented with could thus be easily introduced and an equal
volume of air simultaneously drawn off. In each of the experiments
a portion of the terminal or lateral inflorescence upon which were
seed capsules, open flowers and unopened buds was cut carefully from
the plant and the cut end of the stem placed as quickly as possible in
w^ater in a 250 c.c. Erlenmeyer flask and the whole placed under the
bell-jar. For each experiment a control was also kept in the open air.
During the course of the experiments the flowers were shaken at
frequent intervals to see if abscission had occurred. Flowering laterals
from one plant of Nicotiana Tahacum var. macrophylla purpurea
(U. C. B. G. 25/06) were used throughout.

In the experiments to determine the comparative effects of the con-
stituents of illuminating gas upon floral abscission in this species of
Nicotiana the gases were prepared as follows:

(a) Carbon dioxide — action of dilute c. p. sulfuric acid on pure
sodium bicarbonate.

(6) Carbon monoxide — treating c. p. sodium formate with pure
cone, sulfuric acid and washing by bubbling through strong sodium
hydroxide solution.

1918] Goodspeed^McGee-Uodgson: Effects of Illuminating Gas 441

(c) Hydrogen — electrolytically by electrolysis of distilled water
containing sodium hydroxide, then passing through a tube containing
soda lime and fused calcium chloride.

(d) Methane — treating sodium acetate with soda lime and washing
by bubbling through strong sodium hydroxide solution.

(e) Ethylene — dropping ethyl alcohol (95%) into cone. c. p. phos-
phoric acid which was kept at a temperature of 210° to 220° C and
washing by bubbling through cold cone, sulfuric acid and finally pass-
ing through a large U-tube filled with soda lime.

In the experiments with Citrus large dessicating dishes with ground-
glass covers were used. In these containers flower-bearing shoots were
placed and illuminating gas introduced. The reported percentages of
gas used in this case (cf. table 1) are only approximations and were
not quantitatively correct as in the corresponding experiments with
Nicotiana. The controls were run in large moist chambers. Citrus
sinensis varieties Washington navel and Valencia and Citrus limonia
var. Eureka, growing in the greenhouses of the University of Cali-
fornia, were employed in the experiments.

III. EESULTS
The results of the experiments to determine the effect of various
percentages of illuminating gas in causing flower-fall in Nicotiana and
Citrus are summarized in the following table.

Table 1

Effects of Various Percentages op Illuminating Gas in Causing Flower-
fall IN Nicotiana and Citrus
The figures given represent the times in hours between the start of
the experiment and the fall of the first flower

Experi-

Per cent

Nicot

iana Tabacum

Citrus sinensis

ment

illuminating

var

. macrophylla

var. Washing-

C.

sinensis

C.

limonia

number

gas

purpurea

ton navel

var

. Valencia

var. Eureka

1

1.5
Control

22
44

2

3.0
Control

30
48

60
72

120
144

3

10.0

24

4

1 0.0 (dry

atmosphere

Control

0

48
44

5

20.0

23

42

72

144

Control

43

72

96

150

6

50.0

22

42

50

130

Control

42

70

96

140

7

75.0
Control

40
66

66
100

150
180

442 University of California Publications in Botany [Vol. 5

The effects of the pure constituents of illuminating gas were investi-
gated only in the case of Nicotiana. Table 2, which follows, summarizes
the results of these experiments.

Table 2

Effects of the Pure Constituents of Illuminating Gas in Causing

Flower-fall in N. Tahacum var. macropliylla pxirpurea

The figures given represent the times in hours between the start of

the experiment and the fall of the first flower

Experiment
number

Gas
used

CO,

Per cent
of gas

10

Time
in hours

17

Control

34

CO

10

15

Control

28

H,

10

30

Control

30

H,

2.5

34

Control

34

0114

10

48

Control

48

c^n.

5

13

C3H4

5 (dry

Control

atmosphere)

14
20

6

7

In two experiments (table 1, experiment 4, and table 2, experi-
ment 7) the material was subjected to the gases in a dry atmosphere.
The bell-jar already described as fitted with a ground-glass plate sealed
with vaseline was used in these experiments with a large amount of
fused calcium chloride scattered over this ground-glass bottom. In
all the other experiments with 25/06 water-sealed bell-jars were used.

In an additional experiment a lateral branch of 25/06 was exposed
in an atmosphere containing 5% by volume of ethylene, but no
abscission of the leaves could be induced, even after a considerable
period had elapsed. In Nicotiana Tahacum there seems to be no direct
leaf-fall in the sense that leaf bases are cleanly detached from the stem
by the death or separation of cells. The dead, dry leaves remain
attached to the plant often for months until the blades are broken
away by the wind or other agencies. Thereafter the torn, dry leaf
base may or may not come away cleanly from the stem. It seems
apparent, however, that there is no abscission mechanism present in
the leaf base, at least there is none which may be stimulated to
activity by ethylene. Further investigation in this connection would
appear to be profitable and necessary.

1918] Goodspeecl^McGee-Hodgson: Effects of Illuminating Gas 443

IV. DISCUSSION

Kendall (1918, p. 397) investigated the effects of 1.5 vol. % illumi-
nating gas upon the abscission of flowers in fifteen species, varieties
and hybrids of Nicotiwiia and in thirteen other genera and species of
the Solanaceae. Flowering laterals were placed under the influence
of the gas and air mixtures for fifteen hours, at the end of which time
the amount and extent of abscission was noted. So far as Nicotiana
is concerned he found that in four forms (cf. p. 398, table 6) neither
buds, young flowers, flowers at anthesis, nor seed capsules were
abscissed. In one case young buds only fell. In four cases all buds
up to anthesis fell, but no older flowers nor seed capsules. In one
form all flowers up to four or five days past anthesis were abscissed,
and in three cases all buds and flowers fell. Finally, in one case it is
recorded that buds, flowers and fruits w^ere abscissed. Kendall also
noted that when 3 vol. % of illuminating gas was used, or when the
material was subjected to the 1.5 vol. % of gas for more than fifteen
hours, some of the species previously found to be unaffected abscissed
their flowers. His results in general indicated that there might be a
more or less definite relation between the concentration of poisonous
gases in the atmosphere surrounding the plant and the reaction time
in spontaneous abscission.

With these results of Kendall's in mind, interest centered in sub-
jecting the same material which he used to varying concentrations of
illuminating gas and its constituents. The similar experiments upon
induced flower-fall in Citrus varieties seemed of interest from a number
of points of view. It has been frequently observed that in fumigating
citrus trees with hydrocyanic acid in California there is a heavy leaf-
fall, especially when certain weather conditions prevail. Apparently
no observations have been made upon the effect of poisonous gases in
causing flower-fall in this genus. The results here also serve as a
check upon the data gathered from the similar experiments with
Nicotiana.

From the results given in table 1, it is clear that the reaction time
in spontaneous abscission is not appreciably hastened by increasing
the percentage of illuminating gas surrounding the material under
investigation. This fact is emphasized particularly in the case of
Nicotiana, where the variations in reaction time both in the controls
and in tlic material subjected to the gas are relatively slight. Miss
Doubt (1917) has recently made a detailed study of tlie responses

444 University of California Publications in Botany [Vol. 5

of plants to illuminating gas. Flower-fall was not reported upon, but
the response so far as leaf-fall is concerned received attention. A
large number of species was placed in atmospheres containing various
concentrations of illuminating gas and some of its constituents. A
striking relation was found to exist between the concentration of the
gas and the extent of leaf-fall. Thus, to take a few examples, in Salvia
splendens 1000 p.p.m caused the oldest leaves at the base of the stem
to fall, while 5 p.p.m. caused less shedding; in Datura stramonium
4000 p.p.m. caused the fall of all leaves except the youngest, whereas
with 5000 p.p.m. only the oldest leaves fell, and in Hibiscus rosa-
sinensis the same results were obtained when 4000 and 1000 p.p.m.
were used. In this connection it is interesting to note that in the case
of Citrus the opposite relation was foiuid to hold, namely, that the
youngest leaves were the first to be shed. Thus, in the case of a potted
seedling subjected to an atmo.sphere containing illuminating gas,
shedding began with the terminal leaves at thirty hours and gradually
extended down the stem until all the leaves had fallen at fifty-four
hours.

The distinction between flower and leaf abscission is emphasized
in the relation, pointed out by IMiss Doubt, between the age of the leaf
and the readiness with which abscission is induced. She found that
the older the plant, the less gas was required to cause the older leaves
to fall; the younger leaves in all cases being least affected (cf. Lloyd,
1914, p. 69 and 1916, p. 57). This situation might be explained by
the fact that in the case of the decidedly deciduous species the period
during which the older leaves would normally be attached to the
plant was less than that of the younger leaves and that thus the
abscission layer was already partially formed or more readily activated.
In the absence of controls further speculation on this point is useless.
In contrast to these responses of younger and older leaves, we have the
following situation in the case of floral abscission, at least so far as
Nicotiana is concerned. Here the period preceding the partial matur-
ing of the fruit is, almost without exception, the only one in which
flower-fall can take place, since the rapid development of mechanical
tissue makes fall nearly impossible thereafter, even if a separation
layer is found among the cortical cells which remain undifferentiated.
Thus buds, young flowers, and partially matured seed capsules alone
are shed — and the latter only rarely. To take one example, it is a
common experience in the field to find that as a result of low tempera-
ture there is a progressive fall of the smallest buds and then larger

1918] Goodspeedr-McGee-Hodgson: Effects of Illuminating Gas 445

ones, while open flowers just before anthesis and older flowers are
apparently not at all affected.

Miss Doubt mentions the fact that some species would give no
visible response during or immediately following the period of ex-
posure to illuminating gas, but that a number of days after the end
of the treatment more or less heavy leaf-fall would occur. This is an
interesting point, especially when one considers its implications with
regard to the factors actually responsible for initiating cell separation.
Further, a specific effect of different gases which bring about spon-
taneous abscission is suggested in view of the fact that, as contrasted
with Miss Doubt's results with illuminating gas, jMoore and Willaman
(1917) found that fumigation with hydrocyanic acid causes an increase
in permeability of the leaf septa, which is followed by a wilting, etc.,
from which, however, the treated plants after a time appear to recover
completely. It may be noted in this general connection that Hannig-
(Lloyd, 1914, p. 68) states that 0.00002 vol. % of illuminating gas
caused flower-fall in Mirahilis, etc., while high concentrations em-
ployed for fourteen hours did not give the same result directly but
did give it indirectly somewhat after the end of the treatment. Lloyd
(1916, p. 58) states that cotton bolls "may be shed when one or two
days old in relatively high frequences, in response to stimuli applied
before anthesis, provided the stimuli applied are severe enough."

In the case of the experiments with Citrus the controls show a
rather wide variation which is sufficient to account for the variation
in reaction time shown by the material subjected to gas. It will also
be remembered that the percentages of gas stated in table 1 were not
so quantitatively correct as in the similar experiments with Nicotiana.
Except in the case of variety Washington navel the effect of illumi-
nating gas is very slight and for C. limonia one might almost be led
to suspect from the results given that gas has no effect in accelerating
reaction time. It seems possible that with the exception of variety
Washington navel there is a type of rigor effect in the case of the
higlier percentages of illuminating gas which inhibits all normal
response. Fitting (1911), who showed that laboratory air, carbon
dioxide, tobacco smoke, ether, etc., cause premature fall of corolla,
also found that rigor induced by heat effects and lack of oxygen tend
to inhibit the injurious effects of poisonous gases. Of interest in con-
nection with this whole question of the influence of poisonous and
anesthetizing gases is the work of Hempel (1911), who has shown that

2 We have not liad access to the original of TIannig's article.

446 University of California Publications in Botany [Vol. 5

ether effects are dependent upon its concentration. Normal destruc-
tion of proteins in the germination of Pisuni and Lupinus was retarded
by doses up to approximately 0.01% by volume, but the process was
accelerated in strong doses. Also Johannsen (1896) found that certain
concentrations of ether and chloroform caused an increase in soluble
sugars and in the decomposition of proteins in bulbs of Crocus and
seeds of barley and pea, while very weak doses gave the reverse effects,
i.e., favored starch and protein synthesis.

The definite response of variety "Washington navel as compared
with the other Citrus material is quite in keeping with the normal
reaction of these plants whereby under certain conditions of tempera-
ture and humidity they drop their immature fruits, while correspond-
ing environmental conditions have a much less corresponding effect
upon other species of Citrus. In this connection attention must be
called to the differences in the average reaction times for the controls,
in that flowers of variety '^N'ashington navel fall in respectively two-
thirds and one-half the time that is necessary for flower-fall in the
other two forms. This gradient is rather remarkable from a number
of points of view and our results should be confirmed and extended
and similar determinations made for other Citrus varieties.

The experiments in which tlie pure constituents of illuminating gas
were employed were marred by our inability to maintain constant
temperatures during their course. The influence of variations in
atmospheric temperature in such abscission experiments was apparent
from the start and some preliminary efforts were made to determine
it. One of a series of the moist chambers, noted above as employed for
the controls in the experiments with Citrus, was placed in an incubator
and run for some time at approximately ten degrees above room
temperature. Foliar abscission under such conditions appeared at the
end of thirty hours, while the control run at room temperature showed
the first leaf-fall at fifty-six hours. The variation in the reaction time
of the controls given in table 2 is rather great, but the results of
experiments 3, 4, and 5 in this table show that this variation does not
need to be given too much weight in connection with the effects of the
various gases in causing abscission. This variation, however, appears
to be indicative of changes and instability in the general physiological
condition of the plants under investigation. The experiments listed
in table 2 were carried on at practically the end of the normal growing
period of the plants used and ordinary experience and the results of
other workers Avould suggest that this fact might influence to some
extent reactions to specific stimuli (cf. Lloyd, loc. cit., p. 69).

1918] Goodspeed-McGee-Hodgson : Effects of Illmninating Gas 447

In experiments 3, 4, and 5 (table 2) the material was placed in
contact with 10 vol. % and 25 vol. % of hydrogen and 10 vol. % of
methane, respectively. The time required for the first flower to fall was
the same in the treated material as in the controls. The results of the
experiments in which hydrogen was employed are included primarily
to emphasize the point mentioned in the paragraph above, as there is
no reason to suppose that this gas would be effective in initiating
abscission.

The result of experiment 5, in which 10 vol. % of methane was
used, shows that this gas has nothing to do with the flower-fall caused
by illuminating gas. Knight and Crocker (1913) in studies of toxicity
of tobacco smoke found that methane in 0.00001% concentration was
not toxic to the etiolated hypocotyl of the sweet pea, carbon dioxide
when washed out of the smoke in no wise decreased its toxicity, and
that the toxicity of ethylene is so extreme that 1 part in 10,000,000
has a marked effect.

As will be noted in table 2, relatively high concentrations of carbon
dioxide, carbon monoxide, and ethylene are effective in bringing about
flower-fall in decidedly less than the normal time. The effect of
ethylene was to have been anticipated in view of the evidence furnished
by a number of investigations which indicate that this gas not only
is able to produce marked physiological changes in the plant, but also
that to its presence in illuminating gas is attributable the responses
which plants give when subjected to small amounts of that substance
The results of Knight and Crocker already referred to emphasize this
point. Harvey (1913) found for the seedling castor oil bean that the
cotyledons fell or the abscission layer was formed after exposing the
plants to 1 p.p.m. of ethylene or to 25 p. p.m. of illuminating gas (in
this case equal to 1 p.p.m. of ethylene). Doubt {loc. cit.) showed that
in various species 5 to 8 p.p.m. of ethylene caused leaf-fall. In at least
two cases it is worthy of note that no leaf-fall was reported after
treatment with 8 p.p.m. of ethylene, although fall occurred when
4000 p.p.m. illuminating gas was used. Undoubtedly fall would have
occurred if the concentration of ethylene had more nearly approached
that in which it was present in the concentration of illuminating gas
which did cause fall.

Our experiments upon the effectiveness of the constituents of
illuminating gas in causing flower-fall are of value mainly in so far as
they indicate that carbon monoxide and carbon dioxide are effective.
As mentioned above Knight and Crocker {loc. cit.) found that carbon

448 University of California Publications in Botany [Vol. 5

dioxide was not a toxic constituent of tobacco smoke and Miss Doubt
{loc. cit.) states that carbon monoxide had no effect in bringing about
leaf -fall. Carbon dioxide, in Fitting's (1911) experiments, caused
shedding of the corolla prematurely. Brown and Escombe (1902)
found for a number of species that in 11.4 parts in 10,000 inflorescence
was almost totally inhibited, while in Nicotiana a/finis and N. sylvestris
the small flower buds which began to form were all shed long before
anthesis. Hannig (1913) found that carbon dioxide was not effective
in causing premature floral abscission.

As will be noted in the case of experiments 3 and 4 in table 1. the
flowers fell at the end of forty-eight hours in a dry atmosphere con-
taining 10 vol. % of illuminating gas and after approximately the
same length of time in the case of the control, whereas in a moist
atmosphere containing the same per cent of illuminating gas the
flowers fell in twenty-four hours. This situation emphasizes the fact
that there is a definite moisture requirement for the abscission process.
It has been apparent throughout our field experience with Nicotiana
that severe floral abscission often follows sudden changes in tempera-
ture, especially when such changes are accompanied by rain or great
atmospheric humidity. The role and significance of turgor in the
abscission process has been fully dealt with elsewhere (cf. Goodspeed
and Kendall, 1916 and Kendall, 1918). The conditions obtaining in
experiments 6 and 7 in table 2 were the same as in the experiments last
referred to, except that 5 vol. % ethylene in place of 10 vol. % illumi-
nating gas was employed. Here, however, the reaction time in the
dry and the moist atmospheres was approximately the same, while the
first flower in the control fell after a considerably longer period.
This may simply be another illustration of the extreme toxicity of
ethylene or may possibly be due to the fact that this experiment was
performed late in the normal growing season of the plant, with a
consequent greater instability of many of the vital physiological
processes.

Our data are in general too fragmentary to permit the drawing of
any conclusions as to the basic cause of abscissional responses to
poisonous gases. It seems probable that these phenomena will finally
be proved to be due to modifications in the normal water relations of
the plants concerned. There is abundant evidence that such modifica-
tions caused by natural or artificial reduction of the absorbing sur-
faces or by increased transpiration under conditions of high tempera-
ture and low humidity will bring about abscission. Poisonous gases

1918] Goodspeed-McGee-JIodgson: Effects of Illuminating Gas 449

may be thought of as bringing about disturbances in normal water
relations by increasing the permeability of the leaf septa to favor
abnormally high water loss or by a paralysis of the stomatal apparatus
with corresponding results. On the other hand, it is at least con-
ceivable that a shock effect resulting in a rather complete disturbance
of physiological equilibria may be the basic cause of the observed
abscission response of plants subjected to poisonous gases.

V. SUMMAEY
The experiments reported upon in detail above were performed to
give evidence as to the effect of various concentrations of illuminating
gas and of its constituents upon the abscission of flowers of Nicotiana
Tahacum var. macrophyUa purpurea, Citrus sinensis varieties Wash-
ington navel and Valencia and C. limonia var. Eureka.

1. In N. Tab. var. macrophyUa purpurea the presence of illumi-
nating gas in the atmosphere surrounding flowering laterals caused
the first flowers to fall in approximately one-half the normal time.
The reaction time was approximately the same in all concentrations of
illuminating gas.

2. Of the constituents of illuminating gas, carbon monoxide, carbon
dioxide and ethylene caused premature abscission.

3. All the experiments with the exception of two were carried on
in a moist atmosphere. In these two cases the effect of a dry atmos-
phere containing in the first case 10 vol. % illuminating gas and in
the second 5 vol. % ethylene was observed. In the first, abscission was
so retarded that the first flower fell after approximately the same
length of time as the control. In the second, the first flower fell almost
as soon in the dry as in the moist atmosphere, and in both cases con-
siderably earlier than in the control.

4. In the case of C. sinensis, variety Washington navel exhibited a
marked abscissional response to illuminating gas and did so irrespec-
tive of its concentration. In illuminating gas C. sinensis variety
Valencia and C. limonia variety Eureka showed little or no increase in
the reaction time of the abscission process.

LITERATURE CITED
Balls, W. L.

1912. The cotton plant in Egypt. London.

Brown, H. T., and Escombe, F.

1902. The influence of varying amounts of carbon dioxide in the air on
photosynthetic process of leaves and the mode of growth. Proc.
Roy. Soc. London, vol. 70, p. 397.

450 University of California Publications in Botany [Vol. 5

Doubt, Sarah L.

1917. The response of plants to illuminating gas. Bot. Gaz., vol. 63, p. 209,

Fitting, H.

1911. Untersuchungen iiber der vorzeitige Entblatterung von Bliiten. Jahrb.
f. wiss. Bot, vol. 49, p. 187.

GOODSPEED, T. H., AND KENDALL, J, N.

1916. On the partial sterility of Nicotiana hybrids made with N. sylvestris

as a parent, III. An account of the mode of floral abscission in the
Fi species hybrids. Univ. Calif. Publ. Bot., vol. 5, no. 10, p. 293,

GOODSPEED, T. H., AND DAVIDSON, P.

1918. Controlled pollination in Nicotiana. Univ. Calif. Publ. Bot., vol. 5,

no. 13, p. 429.
Hannig, E.

1913. Untersuchungen iiber das Abstossen von Bliiten u.s.w. Zeitschr. Bot.,
vol. 5, p. 417.

Harvey, E. M.

1913. The castor bean plant and laboratory air. Bot. Gaz., vol. 56, p. 439.

1915. Some effects of ethylene on the metabolism of plants. Bot. Gaz., vol.

60, p. 193.
Hempel, J.

1911. Researches into the effect of etherization on plant metabolism. Kgl.

Danske. Vidensk. Selsk. Skrift., vol. 7, p. 215.

Hodgson, R. W.

1917. Some abnormal water relations in citrus trees of the arid Southwest

and their possible significance. Univ. Calif. Publ. Agr. Sci., vol. 3,
no. 3, p. 37.

1918. An account of the mode of foliar abscission in Citrus. Univ. Calif.

Publ. Bot., vol. 6, no. 15, p. 417. *

JOHANNSEN, W.

1896. Aether-und Chloroform-Narkose und deren Nachwirkung. Bot. Cen-
tralbl., vol. 68, p. 337.

Kendall, J. N.

1918. Abscission of flowers and fruits in the Solanaceae, with special refer-
ence to Nicotiana. Univ. Calif. Publ. Bot., vol. 5, no. 12, p. 347.

Knight, L. I., and Crocker, Wm.

1918. Toxicity of Smoke. Bot. Gaz., vol. 55, p. 337.

Lloyd, F. E.

1914. Abscission. Ottawa Nat., vol. 28, p. 41.

1916. The abscission of flower buds and fruits in Gossypium, and its rela-

tion to environmental changes. Trans. Roy. Soc. Canada, 3rd Series,
vol. 10, sec. 4, p. 55.

Moore, W., and Willaman, J. J.

1917. Studies in greenhouse fumigation with hydrocyanic acid: physiological

effects on the plant. Jour. Agric. Res., vol. 11, no. 7, p. 319.

OSTERHOUT, W. J. V.

1913. The effect of anesthetics upon permeability. Science, n.s., vol. 37,
p. 111.

Setchell, W. a.

1912. Studies in Nicotiana, I. Univ. Calif. Publ. Bot., vol. 5, no. 1, p. 1.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 16, pp. 451-455 April 3, 1919

NOTES ON THE GERMINATION OF TOBACCO

SEED III

NOTE ON THE RELATION OF LIGHT AND DARKNESS TO

GERMINATION

BY

T. HARPER GOODSPEED

The recent paper of Honing^ reopens the question of the light
requirements for germination in Nicotiana. For a number of years
the writer has been convinced that the seed of the great majority of
species of Nicotiana would germinate in darkness and that the
numerous statements to the contrary were based upon experiments
not accurately controlled. An examination of the voluminous liter-
ature dealing with the influence of varying amounts of illumination
upon the germination of seeds leaves no doubt that temperature and
moisture effects are contributing factors in the results obtained, and
that the stage of maturity of the seed employed is a matter to be
carefully determined. Finally, when one considers that from the
strictly physiological point of view the influence of light upon germin-
ation corresponds to that of light upon growth phenomena in general
as an initiating stimulus and a source of energy, the need for the
most exact methods of experimentation is indicated.

The following results dealing with the influence of light and
darkness upon the germination of five varieties of Nicotiana Tahacum
and five of N. riistica were obtained from experiments wliich are looked
upon as preliminary to a more thorough and better controlled investi-
gation. Since the results listed are so definite and since the larger
investigation contemplated must wait upon the completion of more
important matters, it seems well to present briefly the data at hand.

»— . 1 Honing, J. A., The influence of light on the germination of the seeds of

cr> different varieties of Nicotiana Tahacum, Bull. Deli Proefstat., December, 1916.

QC

452 University of California Piiblications in Botanxj [Vol. 5

A thorough review of and commentary upon the literature dealing
with the light requirements for germination in general appeals to
the writer as important in view of the divergent results obtained by
different investigators. Such a review is in progress and in the present
report no attempt will be made to correlate the results listed with
those of other workers.

I am indebted to Miss E. E. Keith for valuable assistance in set-
ting up the experiments and recording the germinations.

The following list of varieties of N. Tahacum and N. rustica with
their numbers in the University of California Botanical Garden
(U. C. B. G.)- will serve to identify the individuals included in the
table and discussion below.

12/07 — Nicotiana rustica var. asiatica.

13/07 — N. rustica var. brasilia.

14/07 — N. rustica var. humilis.

15/07 — N. rustica var. jamnicensis.

16/07 — N. rustica var. scabra.

22/07 — N. Tabacum var. viacropht/Ua.

25/06 — N. Tabacum var. macrophylla purpurea.

71/05— N. Tabacum "Brazilian."

72/05— iV. Tabacum "Cavala."

78/05— iV. Tabacum "Maryland."

The seed was prepared for germination as described in previous
papers.^ For certain of the experiments (cf. table, note 2) a glass-
sided germinating case was provided. In this germinating case a
40-watt tungsten electric light bulb was hung and the ventilation so
regulated that the temperature was approximately' constant at 30 °C.
The seeds to be subjected to continuous darkness were placed in paper
collar-boxes and the boxes put into the germinating case. The dupli-
cates were placed in the germinating case exposed to the light of the
electric bulb day and night. In the remaining experiments no attempt
was made to regulate the temperature, and the seeds in collar-boxes
and undarkened were placed near a window but at no time in direct
sunlight. For an^' two sets of the same seed — one in darkness and
one in diffuse light — the range of temperature variation was the same
when the germination took place out of the germinating case, as in
all such cases the two tests were set up on the same day. The tests
were examined on the davs indicated in the table below and the

2 Cf. Setchell, W. A., Studies in Xicotiana I, Univ. Calif. Publ. Bot., vol. 5.
no. 1, pp. 1-86, 1912.

3 Goodspeed. T. H., Notes on the germination of tobacco seed, Univ. Calif.
Publ. Bot., vol. 5, no. 5, pp. 199-222, 1913; idem, ibid., vol. 5, no. 7, pp. 233-2-18,
1915.

1919]

Goodspcecl: Germination of Tobacco Seed

453

g-ermiiiated seeds picked out. The criterion of germination was the
same as that noted in a previous paper.

The breeding experiments with Nicotiana conducted in the Univer-
sity of California Botanical Garden cover a considerable number of
years ; thus we will be able to investigate the light requirements for
germination in the case of seed of various ages. Attention might
again be called to the fact that the seed used in our experiments is
pedigreed seed representing in each ease the product of individual
plants of species and varieties of Nicotiana grown in the pure line.
The writer's previous reports have indicated the remarkable viability
of old tobacco seed. In the table below it will be noted that in the
case of the N. Tahacnm varieties seed varying in age from nine to twelve

o

c
o

"S.Sf

Number of seeds that germinated on the days indicated

C c

<.5

c
0

[ Day of maxi-
1 mum germina-
1 tion

7

8

9

10

11

12

13

14

15

16

17

18

19

20

20 +

1

1916

12/07

80

9

89

2

3

7

2

1916

12/07

631

19

3

"5

90

2

7

3

1916

13/07

50

30

4

"5

89

2

4

7

4

1916

13/07

54

24

1

3

82

2

7

5

1916

14/07

88

5

....

9^

2

ri

7

6

1916

14/07

21

30

....

51

2

—

10

7

1916

15/07

94

9i

2

7

8

1916

15/07

95

95

2

+

7

9

1916

16/07

4«<2

36

"8

92

2

7

10

1918

16/07

73

21

94

2

+

7

11

1909

22/07

(36

9

75

9

10

12

1909

22/07

67

13

6

86

9

+

13

13

1916

22/07

80

7

87

2

7

14

1916

22/07

73

73

2

_

7

15

1906

25/06

19

10

■3

"6

3

"4

....

45

12

12

16

1906

25/06

22

11

15

6

7

4

65

12

-1-

12

17

1907

25/06

21

24

22

4

"i

1

73

11

13

18

1907

25/06

34

17

11

11

2

75

11

+

12

19

1909

25/06

85

90

9

8

20

1909

25/06

59

3

6

68

9

—

8

21

1911

25/08

17

38

1

24

80

7

16

22

1911

25/06

"l

3

5

40

25

74

7

=

17

23

1912

25/06

4.3

25

2

11

81

6

11

24

1912

25/06

46

8

13

6

5

2

80

6

=

11

25

1916

25/06

92

2

94

2

8

26

1916

25/06

78

5

83

2

=

8

27

1909

71/05

52

9

99

9

8

28

1909

71/05

66

14

i

81

9

=

11

29

1916

71/05

84

"5

2

91

2

8

30

1916

71/05

82

13

95

2

+

8

31

1909

72/05

SO

"4

"1

85

9

12

32

1909

72/05

60

16

1

78

9

=

12

33

1916

72/05

86

2

88

2

8

34

1916

72/05

55

29

6

90

2

+

8

35

1909

7S/05

5

55

25

85

9

16

36

1909

78/05

57

57

9

—

20 +

37

1916

78/05

10

8

10

"7

"5

9

49

2

13

38

1916

78/05

8

20

10

13

3

7

61

2

+

12

^ The figures in bold face type refer to seed germinated in continuous darkness.

' TTp to this point the figures in ordinary type refer to seed gennination in continuous
light, the source of light being a 40-watt tungsten electric light bulb. The remaining figures
in ordinary type refer to seed germinated under diurnal illumination.

■■ "-)-" indicates that the per cent of seeds germinated in darkness e.xceeded the per cent
germinated under continuous or diurnal illumination.

■• " = " indicates that germination under the two conditions was the same, a difference
of less than ten seeds being the criterion.

° " — " indicates that germination in darkness was decidedly less than under continuous
or diurnal illumination.

454 University of California Publications in Botany [Vol. 5

years was available. In the majority of cases the germination in
light and in darkness of nine year old as compared with two year old
seed was tested. For 25/06 (tests 15 to 26) the germination under the
two conditions of twelve, eleven, nine, seven, six, and two year old seed
was investigated. Two year old seed only of five N. rustioa varieties
was employed. As will be seen in the table the older seed germinated
with a good or fair percentage, although the germination is scattering
and the period of maximum germination is later than in the case of
younger seed of the same pedigree.

Various points are brought out in the table above which deserve
further investigation. Thus, for example, the poor germination of
two year old seed (tests 37 and 38) as compared with nine year old
seed (tests 35 and 36) of 78/05 is unusual and may indicate a lessened
viability due to continued inbreeding. This matter is especially inter-
esting in view of the fact that two year old seed of 78/05 germinated
much more heavily in darkness than in light. Again, the heavy
germination of the nine year old seed of 71/05 (tests 27 and 29) is
worth}^ of notice.

The notation used in the seventh column of the table to indicate
the relation between the germination of seed of the same year in
light and in darkness is merely one of convenience and has no particu-
lar significance. Thus the " _j_ " sign is employed simply to emphasize
the fact that the per cent of germination of the seed in darkness was
actually greater than that of the corresponding seed subjected to
continuous illumination or under diurnal illumination. In reality
practically all those pairs of tests marked "-|-" fall into the " = "
section since germination in darkness rarely exceeded germination in
light by more than ten seeds.

There is no doubt that the seed of five representative types of
N. Tahanim and of five varieties of N. rustica will germinate readily
in darkness. These five varieties of N. Tahacum represent a large
proportion of the basic types from which the commercial strains of
American tobacco, with which Honing worked, have been derived.
Honing {loc. cit., p. 14) found that of twenty-one strains of N.
Tahacum received by him under trade names from the United States
Department of Agriculture and germinated in darkness more than
fifteen germinated only 20 per cent or less and that none of the
twenty-one germinated over 50 per cent. I am at a loss to explain
this result of Honing or a number of the others which he reports.
Since the germinations listed in the above table indicate that germina-

1919] Goodspeed: Germination of Tohacco Seed 455

tion in darkness may be slow and scattering, Honing's conclusions
might have been different had he followed the progress of his germin-
ations in darkness over a longer period.

In addition to the general conclusion that N. rustica and N.
Tahactcm varieties will germinate in darkness, another point of inter-
est is suggested by the results given in the above table. Thus it will
be noted that old and new seed will germinate equally well in darkness.
Of nine tests of seed from six to twelve years old only two showed a
smaller per cent of germination in darkness than in light. Similarly
of ten tests of two year old seed, eight are marked ''-(-" or "=. " A
confirmation of this apparent phenomenon and any attempt to com-
ment upon its significance must wait upon a more detailed investi-
gation.

NEW foiik

■OT A NJil,. ••",■:

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 17, pp. 457-582, 2 figures in text, plates 55-85 April 14, 1922

INHERITANCE IN NICOTIANA TABACUM

I

A REPORT ON THE RESULTS OF CROSSING CERTAIN

VARIETIES

BY

WILLIAM ALBERT SETOHELL, THOMAS HARPER GOODSPEED,
AND ROY EL WOOD CLAUSEN

CONTENTS PAGE

I. Introductory : 458

II. Plan of the work ; 460

III. Angustifolia-7nacrophylla series 462

1. Parents oi the angustifolia-macrophylla series 463

2. Fi of the angustifolia-macrophylla series ;., 467

3. F2 of the angustifolia-macrophylla series 469

4. F3 and subsequent generations of the angustifolia-macrophylla series 472

a. Stenophylla derivatives 475

h. Latifolia derivatives 476

c. Lanceolata derivatives 478

d. Loriifolia derivatives 478

e. AuRicuLATA derivatives 479

/. Sessilifolia derivatives 480

5. Summary of flower color observations in F2 and subsequent generations 482

6. Later sowings of F2 and F3 of the angustifolia-macrophylla series 483

7. Crosses of derivatives with the parents 487

8. Discussion of results of the angustifolia-macrophylla series 490

IV. Cahjcina-virginica series ., 494

1. Parents of the calycina-virginica series 494

2. Fi of the calycina-virginica series 496

3. F2 of the calycina-virginica series '. 497

4. F3 and subsequent generations of the caZ?yana-?;i>^imca series 499

5. Discussion of results of the calycina-virginica series 504

V. Alha-macrophylla series .- 504

L Parents of the alha-macrophylla series ; 504

2. F) of the alha-macrophylla series 505

3. ¥2 oi the alha-macrophjiUa series 505

4. F3 and subsequent generations of the alha-macrophylla series 507

5. Discussion of results of the alha-macrophylla series. 510

458 University of California Publications in Botany [Vol. 5

PAGE

VI. General Conclusions 510

1. Origin and interrelationships of varieties of Tabacum 510

2. Methodology of Mendelian analysis in Tabacum 513

3. Mendelian heredity in Tabacum 516

VII. Summary 520

Literature cited 520

Explanation of plates 522

I. INTRODUCTORY

The inception of the work on the various species of Nicotiana
grown and bred in the University of California Botanical Garden
has already been sketched in a previous number of this series (cf.
Setchell, 1912). As stated there, the original intention was to assemble
a collection of tobacco plants simply as a portion of the outfit of the
Botanical Garden for general instruction and display. So great was
the variety and evident misapplication of the names under which the
seeds were received, however, that it seemed advisable to attempt to
determine, as definitely as possible, the status of each plant.

In this connection, the work of Comes, in particular, came under
consideration and especially his views as to the origin and interrela-
tionships of the various cultivated forms belonging to the Tabacum
group. Comes (1899, p. 4 and elsewhere) regards the numerous culti-
vated forms of tobacco as having originated in various ways from
certain fundamental varieties. He estimated that there are six of
these fundamental varieties of Tahacum, and he supposed the large
number of various and seemingly more or less intergrading forms to
have arisen through the influence of the forces of acclimatization,
adaptation, hybridization, and selection. Of these, undoubtedly, the
greater variations have been produced and perpetuated, according to
the ideas of Comes, through hybridization and selection. In his mono-
graph (1899) and in his later more exhaustive treatise (1905), Comes
has attempted to estimate just which of his six fundamental varieties
of Tahacum have cooperated in producing each one of the cultivated
"races" so far as known to him.

The statements of Comes as regards the constitution of his various
races seem to have been based on the results of morphological study
rather than upon breeding analysis. The advisability occurred to the
senior author of attempting to test Comes' hypothesis by selecting
varieties seemingly fundamental in type, and through hybridization

1922] Setchell-Goodspeed-Clausen : Nicotiana Tahacum 459

and selection attempting to secure constant races exhibiting various
recombinations of the parental characters. The work thus conceived
has been carried out in detail in a certain few but seemingly charac-
teristic cases. Several different crosses were made in 1909, the first
filial generations were grown in 1910, and each year since that time
has seen successive filial generations in the field.

Although the Nicotiana investigations were originally designed to
attack experimentally a comparatively simple and definite problem,
they have since been greatly amplified in scope. At the present time
three rather distinct lines of investigation are actively in progress, viz.,

1. Mendelian inheritance in N. Tahacum.

2. Inheritance of quantitative characters.

3. Studies of interspecific hybrids.

The recent appearance of bud variations in hybrid lines favorable for
an analytic study of that phenomenon has resulted in the addition
of another research project. Now it has been found that, although
seemingly distinct, progress in these separate lines of investigation is
more or less interdependent. In particular it has been found that
certain of the phenomena exhibited in interspecific hybrid populations
from crosses between N. sylvestris and varieties of N. Tahacum require
for satisfactory analysis and explanation an accurate and detailed
knowledge of the Mendelian differences which exist among the par-
ticular varieties of N. Tahacum that have been used in those investi-
gations. Accordingly in later years these studies of hybrids between
varieties of N. Tahacum, originally designed merely to test experi-
mentally the interrelationships existing among such varieties, have
been directed toward a specific Mendelian analysis of the germinal
differences existing in a selected set of varieties.

With this change in emphasis has come a full appreciation of the
difficulties of Mendelian studies in N. Tahacum. It has been very
evident that, for the most part, the character differences among varie-
ties of N. Tahacum do not rest upon a simple genetic basis; on the
contrary, they often depend upon very complex and involved Men-
delian differences ; so that in segregating populations it is often im-
possible to demonstrate the existence of definite, discontinuous char-
acter classes. Not uncommonly the members of such populations maj''
be arranged in series connecting by imperceptible differences the most
extreme character expressions in the population.

But although complex intergrading segregation has often been
observed in F2, it has not been found that such complex segregation

460 University of California Publications in Botany [Vol.5

persists in subsequent generations in the hybrid lines. On the con-
trary, it has been found, as will become evident in a study of the ex-
perimental material communicated herewith, that a great simplification
occurs in the segregation in F, and subsequent generations, and that
continuous segregation gives way to discontinuous just as might be
expected from Mendelian theory. By observing the segregation in
the consecutive generations of hybrid lines which have become homo-
zygous in most of their loci through self-fertilization, it is possible to
obtain some idea of the Mendelian factor pairs involved iii the char-
acter contrasts and of their relations to one another. It has also proved
possible by a few years of self-fertilization to establish stable lines
representing recombinations of parental characters. By investigating
the interrelations among such stable derivative lines, which obviously
should differ in fewer factors from one another and from the original
parental varieties than the parental varieties differ from each other,
it would seem possible to develop an indirect mode of attack by which
the Mendelian analysis could be refined to any desired extent. The
original plan of the investigation, therefore, having as its purpose a
demonstration of the possibility of securing by hybridization stable
derivative lines representing recombinatons of characters contained in
the parents and comparable to the numerous existing varieties of N.
Tahacum, has been diverted into a detailed study of Mendelian differ-
ences among a typical set of N. Tahacum varieties.

II. PLAN OF THE WORK

In the introductory paper the senior author has discussed the fun-
damental types of N. Tahacum, and as indicated there, has expressed
a preference for selecting some five fundamental varieties, or species,
as representing the basal morphological elements found, or seemingly
to be detected, in cultivated races of N. Tabacuni. There is no neces-
sity for discussing further, at present, the reasons for preferring the
particular types selected by us as against those of either Comes or
Anastasia (1906), since the fundamental conceptions agree sufficiently
well and the important thing has been to make a beginning in experi-
mentation by using varieties which present seemingly fundamentally
different character complexes in most characteristic form in plants
breeding true to type in the pure line. Certain reasons for selecting
a particular type or types will be discussed in connection with the

^^-2] Setchell-Goodspeed'Claiiscn: Nicotiana Tabacum 461

consideration of the various crosses. Besides the ' ' fundamental ' ' types,
there have been selected for crossing certain other types, possibly
fundamental, or in some cases derivative, which have been employed
for testing the inheritance of some particular character or group of
characters. All of these have been described in the first paper of this
volume.

The taxouomic problems in N. Tahacum do not appear to differ
from those presented by many other species of cultivated plants.
Barley, maize, oats, rice, wheat, among others, exhibit a similar diver-
sity of forms with more or less obvious class distinctions. In these
as in N. Tabacum it appears to be an easy task to shuffle and recombine
characters indefinitely. Clearly there can be no segregation of forms
into distinct species on genetic grounds; the basis of speciation, if any,
must depend either upon convenience merely or what amounts to
practically the same thing, upon elevation of certain Mendelian char-
acter contrasts to a higher rank in classification than others. Since
the taxonomic problem, therefore, is not strictly a genetic one, it seems
best to follow general usage in this respect, referring all the poly-
morphic assemblage of forms to the one species N. Tabacum, and re-
garding the several races included thereunder as varieties of equal
rank.

The varieties employed in this series of investigations are : N.
Tabacum var. alba, U. C. B. G. 30/06, previously described by Setchell
as "White" Tobacco; N. Tabacum var. angustifolia, U. C. B. G. 68/07,
previously described by Setchell as N. angustifolia; N. Tabacum var.
calycina, U. C. B. G. 110/05 ; N. Tabacum var. macrophylla, U. C. B. G.
22/07 ; and N. Tabacum var. virginica, U. C. B. G. 78/05, previously
described by Setchell as N. Tabacum "Maryland." In each instance
the University of California Botanical Garden (U. C. B. G.) number
contains in the numerator the accession number of the year given in
the denominator. The varieties have in the majority of cases been
grown in pure lines from the date of their receipt. In order to avoid
needlessly encumbering the text with scientific names, the varieties
mentioned above will be referred to by their varietal designations
only, and when reference is made to the whole group the species name
Tabacum will be used alone.

Three series of cultures are described in the present article: the
angustifolia-macrophylla series, which has been derived from reciprocal
crosses of angustifolia and macrophylla; the calycina-virginica series,
derived in the same way from calycina and virginica; and the alba-

462 University of California Publications in Botany [Vol. 5

macrophylla series, from alha and macrophylla. In the course of the
investigations other crosses were made between different varieties of
Tabacum and to a limited extent between other species of Nicotiana;
but the principal attention has been paid to the three crosses noted
above, and they and their progenies alone will be considered in the
present paper. It may be said at this point that the different varieties
of Tabacum cross readily with one another, giving an abundance of
good viable seed. The hybrids are uniformly self-fertile.

The methods of hybridization used need not be considered here,
because they have been described in detail by Goodspeed (1912) else-
where in this series. The particular refinements of technique which
must be employed in sowing the seed, on account of its very small size,
have also been there described. It might be well to state, however,
that the most refined methods doubtless will not prevent the occasional
appearance of a stray plant in the cultures. The danger of contami-
nation arises not only during the sowing of the seed, but also when the
bags are placed over the unopened buds. It is very easy to include a
few stray seeds under the bag, for their small size makes it almost
impossible to detect them in the coarse, sticky indumentum of the
plant. In spite of these obvious difficulties, however, the number of
plants that have certainly been strays has been very small. Their
rare occurrence indicates clearly that the technique employed has been
very successful.

III. ANGUSTIFOLIA-MACROPHYLLA SERIES

This series has received the most attention since the parents are
so distinctly different, and the results have consequently been more
complex than those which have followed the crossing of any other pair
of Tabacum varieties. As will be demonstrated below, F, seemed at
first hopeless in its variety of segregation. Later generations, however,
exhibited so much less, or so little variety in their segregation products
that it was easy to obtain new permanent combinations of characters
or "fixations." Certain of its segregants have been followed out to
F., and have also been crossed back on the parents which they most
closely resembled.

Six successful crosses were made. Of these H^^ and Hg had macro-
phylla for the male and angustifolia for the female parent, while H^,
Hg, Hi5, and H^g were reciprocal crosses. As a matter of convenience

1922] Setchell-Goodspeed-Clausen: Nicotiana Tahacum 463

the generations later than F^ were grown only from Ha and H^, the
larger number from H^. The predominance of H^ in the later families
selected for the continuation of the work was not, however, due to any
especially different behavior evidenced in that particular series.

1. PARENTS OF THE ANGUSTIFOLIA-MACEOPHYLLA SERIES

By selecting angustifoUa and niacrophylla for crossing, two varie-
ties were obtained which resemble each other in height and general
habit, but Avhich differ strikingly in leaf and flower characters. The
differences are sufficiently great to lead one to regard them as belong-
ing to different species ; in fact, all five Tabacum varieties selected by
us as possibly fundamental differ sufficiently among themselves to be
regarded as species in the Tahacum section rather than as varieties.
It is not our intention, however, to emphasize this point, since any
discussion would of necessity lead to a general survey of all the known
varieties and races at present included under Tahacum. If, however,
these five, viz., angustifoUa, macrophylla, "Cavala," Maryland, and
"Brazilian" (cf. Setchell, loc. cit.) could be considered by themselves
as wild plants, it seems to us that any taxonomist of the present day
would certainly award to each of them the rank of a separate species.
These considerations should be borne in mind in estimating the signifi-
cance of the results obtained through crossing.

AngustifoUa, U. C. B. G. 68/07, is a variety which has long been
known and which is represented in our breeding experiments by a
pure line very closely approximating the type. It has been figured
and discussed by one of us (Setchell, loc. cit., p. 9, pi. 7). The photo-
graph given there is of a young plant just coming into flower and
consequently does not represent the habit of the plant in full blossom
or in fruit, after the full number of laterals is developed. A plant
in the height of its vigor is represented in plate 55, figure 1. In
stature angustifoUa belongs to the low corymbose group of Tahacum
varieties, which also includes the forms bred in the University of Cali-
fornia Botanical Garden under the names calycina and macrophylla,
and which is in decided contrast to the tall, more "racemose" (al-
though these may be "corymbose" at the top) forms such as alha and
virginica.

In height angustifoUa varies from 75 to 120 cm. The central axis
develops its corymbose panicle of short racemes first, but it is usually
soon overtopped by the successive laterals developed basipetally, each

464 University of California PuhUcations in Botany [Vol.5

lateral, in turn, developing a corymbose cluster of racemes, rising
more or less above its predecessors. The result is tbat the whole plant
has the short corymbose habit mentioned above. The stems and
branches of angiistifolia are comparatively slender, being much more
slender than those of macrophylla, or those of any other of the Tdbacum
varieties except those of calycina, which are very similar.

The leaves of angustifolia are alternate and distinctly and moder-
ately long petiolate. The blade of the lower leaves is ovate-lanceolate,
tapering above to a long, curved point, more or less conduplicate below
and with the rounded bases unequal. Above, the leaves are less con-
duplicate, more so even at the base, with the petiole shorter, while the
uppermost (bracts) become almost sessile and narrowly lanceolate even
to almost linear in outline. The normal petiole is naked at the base
and in the middle portion, but the base of the blade is slightly and
narrowly decurrent along the upper portion. Occasionally a petiole
shows a narrow wing throughout its length and at times the petioles
of all the leaves on certain plants are more or less winged, but the
majority of the plants have naked petioles (cf. also Goodspeed and
Clausen, 1917, p. 306, pi. 46, right-hand figure). The leaves of angus-
tifolia have also a very characteristic drooping habit, much more pro-
nounced than in any other Tabacum variety except calycina. In older
plants, after capsule formation has well advanced, all the leaves are
hanging obliquely downwards.

The flower of angustifolia is distinctive and differs in details of
shape and color from that of any other Tahacum variety, and especially
from that of macrophylla. The general shape of the flower is that of
all the Tahacum section, but the corolla is much more slender and more
gradually infundibuliform than that of any of the other varieties re-
ported here. The calyx is broadly campanulate, prolonged above into
5 long, but unequal, linear-lanceolate, pointed lobes, of which one is
longer than the remaining four and gives the calyx a zygomorphic
appearance. The corolla is narrow and tubular below the middle,
expanding rather gradually and evenly above into a conical infundi-
bulum which bears the spreading, deeply 5-lobed limb at its summit.
The length of the tube of the corolla is about 6 cm. and its greatest
diameter about 7 mm. The limb of the corolla, at first erect (opening
bud), then horizontal, finally becomes somewhat deflexed and measures
about 3 or 3.5 cm. across. It is divided almost to the tube into 5 lobes
which are ovate-lanceolate with long, narrow, tapering tips. The lobes
of angustifolia are much longer and have narrower tapering tips than

1922] Setchell-Goodspeed-Clausen : Nicotiana Tahacum 465

those of any other Tahacum variety, and in this respect are in direct
contrast to those of macrophylla. The lobes are unequal and give a
slight suggestion of zygomorphism to the corolla. The stamens are
inserted on the lower portion of the tube and are usually slightly ex-
serted in anthesis. The pistil possesses the usual 2-celled ovary, long,
slender style, and thick, slightly bilobed stigma, more or less exserted
in late anthesis, characteristic of the genus Nicotiana. The color of
the corolla is a light, though lively, pink, much lighter than the red of
macrophylla. The capsule at maturity is slightly flattened longitud-
inally, is broadly lanceolate in profile, tapers above into an acuminate
apex, and is about 25 mm. high and 8 to 9 mm. thick. It is the most
slender of all the capsules borne by the various Tahacum varieties
and in decided contrast to the stout capsule of macrophylla.

In plate 55, figure 1, is illustrated a plant of angustifolia at the
height of its blooming period. Typical features of the plant are shown
in the line drawings of plate 56. Photographs of typical leaves are
shown in plate 58, where they may be compared with photographs of
the leaves of macrophylla. Photographs of the flowers are reproduced
in plate 60, where they may be compared with those of macrophylla
and of the hybrids between these two varieties.

Macrophylla, U. C. B. G. 22/07, has already been discussed and
figured by one of us (cf. Setchell, loc. cit.). The original seed was
obtained from Comes, but the plants do not correspond to his figures
(cf. Comes, 1899, pi. VIII) either as to habit or shape of leaf. They
differ also from his description in these same respects. The flower,
however, agrees, and it seems best to retain for it the name under which
we have cultivated it.

The habit and height of macrophylla are both very similar to those
of angustifolia. The habit is low corymbose, the central axis bearing
a panicle of corymbose racemes and the laterals arising one after the
other bearing similar inflorescences and equaling or overtopping the
central axis. The stems and branches are stouter than those of angus-
tifolia, however, and this, together with the broader, more solid looking
leaves which do not droop so much as those of angustifolia, give a
mature plant of macrophylla a much more robust appearance than is
the case Math a mature plant of angustifolia. The plant figured in the
first number of this volume (pi. 6) was young. An older plant shown
herewith on plate 55, figure 2, is in full blossom and beginning to ripen
its capsules, and gives a better idea of the habit of a well grown plant.

466 University of California Puhlications in Botany [Vol.5

The leaves of macrophylla are sessile by a partially clasping base
and possess two basal lobes partially clasping the stem. The general
shape is obovate, the widest portion being above the middle. The
leaves taper gradually to the broad clasping base below and abruptly
to a narrow more or less acuminate tip above. The surfaces show the
secondary veins branching at a more obtuse angle than do those of the
leaves of angustifolia. The color of the leaves is a dark green in
macrophylla and more of a yellowish green in angustifolia . In every
way, then, the leaves of the two parents differ from each other as much,
in fact, as do the leaves of many species.

The flowers of macrophylla, while of the same general type as those
of angustifolia, differ in details of shape and color. The flowers of
macrophylla are about 4 cm. long. The calyx is broadly ovate in pro-
file, deeply cut into 5 broad and somewhat unequal lobes. The corolla
tube is stout cylindrical (about 5 mm. in diameter) below, broaden-
ing suddenly into a stout infundibulum above (about 10 mm. in diam-
eter). The limb is at right angles to the tube, is about 23 mm. across,
and is more or less pentagonal with 5 shallow sinuses. The color of
the corolla is deep red fading to an almost lilac tint after anthesis.
On the limb are 5 triangular lighter areas, one having the narrow
apex at each sinus and the broad base at the top of the tube. In the
much darker color, in the broader tube and stouter infundibulum, and
in the barely appreciable lobing of the limb, the corolla of macrophylla
is the antithesis of that of angustifolia. In stamens and pistil, the
flower of macrophylla shows little variation from that of angustifolia.

The capsule of macrophylla is broadly ovate, tapering abruptly to
a mucronate tip. It is about 2 cm. high and about 1.5 cm. in diameter,
contrasting very decidedly with the comparatively slender capsule of
angustifolia.

A typical plant of macrophylla is shown iu plate 55, figure 2.
Typical features of the plant are shown in line drawings in plate 57.
Photographs of leaves are reproduced in plate 58, where they may
be compared directly with those of angustifolia. In plate 60 its flowers
may be compared directly with those of angustifolia and with those of
the hybrids.

It has seemed best to call attention to the characters of and differ-
ences between these two varieties, parents in the first set of crosses to
be discussed, in order that the behavior of their hybrid progeny may
be clear. In height and habit there is a close agreement, but in leaf,
flower, and fruit there are sufficient differences to mark them as sep-
arate species.

1^--] Seichell-Goodspced-Clausen: Nicotiana Tahacum 467

2. Fi OF THE ANGUSTIFOLIA-MACROPHYLLA SERIES

In late July of 1909, some 7 crosses were made between angusti-
folia and macrophylla, 6 of which, as stated above, were successful.
Hj, H^, and H,, as they were designated, involved angustifolia as the
female plant, while H4, H5, H15, and H^g were reciprocals. No seed was
obtained from H^, but all the other 6 crosses gave a fair yield. The
usual care (cf. Goodspeed, loc. cit., pp. 129-131) was taken in cleaning
and sowing the seed. This was done in the spring of 1910, germination
was good in all cases, and 337 plants, distributed as follows, came to
maturity and seed bearing. The family of H„ had 56, H3 had 60, H^
had 47, H^ had 58, H^j had 55, and Hig had 61 plants.

A survey of all these plants showed in general a remarkable uni-
formity in habit. A certain amount of difference was to be detected
on careful scrutiny, but little if any greater than that which is ex-
hibited among a large number of individuals of one or the other parent.
In height, F^ showed exactly the same variation as the parent, the
central axes varying from 65 to 145 cm., but largely varying from 90
to 120 cm., while the laterals rose to 150 cm. Some rows showed uni-
formly higher, others uniformly lower plants, the differences probably
being due to different soil and water conditions. The habit (see pi. 61)
was low corymbose and the general appearance as to stoutness seemed
more or less intermediate between the two parents. The leaves in
shape, size, etc., very closely resembled those of angustifolia. There
was some appreciable variation in the leaves, however, and often con-
siderable variation on the same plant, a characteristic of angustifolia
which has already been mentioned. Plate 59 reproduces photographs
of different types of leaves obtained from F^ plants. The blade is
broadly elliptical ovate with the lateral veins at an obtuse angle, much
as in macrophylla. The base is rounded, or even slightly cordate in
some leaves, while the tip is more blunt. These characters seem, at
least, to' indicate an influence of macrophylla. The leaf, however, is
distinctly petiolate, but the petiole is not so long as in angustifolia.

The petiole is definitely winged and the wings are expanded at the
base into auricles, which are often triangularly decurrent along the
internode of the stem. This wing is usually present in all the plants
of Fj, but some leaf or leaves on a plant may lack it, and in some
plants it is only slightly developed, or at least, is without auricles.
The wing was from 5 to 7 mm. wide on some leaves.

The leaf of lOF^Hi^P^ represented in plate 62 even more closely
resembles the typical leaf of angustifolia. The wing along the mar-

468 University of California Publications in Botany [Vol.5

gins (or edges) of the petiole is narrow and is prolonged as a slight
ridge to the internode and is decurrent (?) or can be traced as it bends
sharply downwards. Such wings are, at times, found in pure bred
angustifolia plants. This leaf, then, resembles the angustifolia leaf
fairly closely, but differs from its ordinary expression in the more
tapering base, in being less distinctlj^ conduplicate, in tapering more
abruptly toward the tip, in having shorter petioles and in having more
of a wing on the margins of the petiole.

The flower of F^ (see pi. 60) resembles that of angustifolia more
than that of macrophylla. The color is deep pink, decidedly of a
deeper shade than is the flower of angustifolia, yet far from the red
of macropliylla and in a way intermediate between the two. There
is no trace, on the limb of the corolla of F^, of the 5 -white triangle-
shaped areas so characteristic of the limb of the corolla of macrophylla.
The infundibulum. while possibly slightly stouter t-han that of the
flower of angustifolia, is not so stout as that of the flower of macro-
phylla. In length the flower of F^ averages about 4 to 4.5 cm. as
against an average of 6 cm. in angustifolia, and of 4 cm. in macro-
phylla. The tube averages about 3.5 to 5 mm. in diameter below, as
contrasted with 2.5 to 3 mm. as an average in angustifolia and 5 mm.
in macrophylla. The infundibulum in the corolla of F^, while neither
abrupt nor so stout as that of the flower of macrophylla, is noticeably
more abruptly enlarged and stouter than that of angustifolia. The
limb of the corolla in F^ averages 2.5 to 3.25 cm. in greatest diameter,
while that of angustifolia averages 3 to 3.5 cm. and that of macrophylla
averages about 2.3 cm. in greatest diameter. The lobes of the corolla
in Fj are about half the width of the limb from tube margin to extreme
tip of lobe, while in angustifolia they are about two-thirds of this and
in macrophylla they are only one-third or even less. The lobes, also,
are decidedly broad at the base, particularly so as compared with their
length. In general, then, the corolla of F^, while closer to that of
angustifolia, shows by its stouter tube, more abrupt and more swollen
infundibulum, intermediate spread of limb, less deep lobing, shorter
and broader lobes, and deeper shade of pink, definite influences of
macrophylla also.

The capsule of F^ is broader than that of angustifolia, but nar-
rower than that of macrophylla. There is greater variability in hori-
zontal diameter in the capsule of F^, The flower and fruit of F^,
then, although no careful biometric study has been made, are inter-
mediate between those of the two parents, yet incline more toward
angustifolia than toward macrophylla.

19--] Setchell-Goodspeed-Clausen : Nicotiana Tahacum 469

In general, then, a survey of F^ shows throughout a series of ten
different families a uniformity of individuals as great as that exhib-
ited in either of the parents. Some few slight differences exist among
individuals both of F^ and of the parents which may possibly be re-
ferred to lack of a completely homozygous conditon in the parents.
In characters in which the two parents differ, whether in color of
flower, quantitative corolla character complexes, capsule character com-
plexes, or leaf character complexes, the F^ hybrid exhibited through-
out a character expression intermediate between that of the two
parents.

3. r, OF THE ANGUSTIFOLIA-MACKOPHYLLA SERIES

In 1911, there were selected as parents for the F^ 13 plants from
Ho and 12 from H^. Twenty-one families of approximately 50 plants
each were set out in the field. On account of the great diversity shown
in these populations, it was found impossible to study individually
each of the thousand plants grown ; consequently particular attention
was paid to only 5 families from each hybrid. The other families wore
gone over carefully, but nothing notably different w^as found in their
behavior. All fifty plants survived in each family except in the last,
viz., llFoH^P^g, where only 48 came to maturit3^ There were then
498 plants of Fo under more careful observation, representing both
the cross and its reciprocal, with about 550 remaining for only casual
examination.

As might have been expected, there was a great variety of plants
resulting and segregation as to differences in combination of characters
of flower, fruit, and leaf was little short of bewildering. An attempt
was made to study and arrange these combinations, but it was found
to be impossible. A careful survey, however, was made of the popu-
lations and a tabulation of characters was attempted. Some 16 fairly
readily separable types, based on leaf characters, were distinguished,
but between these closely approaching types others were to be found
of intermediate and overlapping character. One each of the types
selected was drawn, and these drawings are reproduced in plates 63
to 78.

A glance at these plates, which were carefully drawn to scale, will
show something of the nature of the combinations of characters of the
two original parents. Type 1 (pi. 63) shows a close approximation,
yet not an absolute reproduction, of angustifolia, while type 16 (pi. 78)
in a similar way is a close approximation to macro pkylla. The other

470 University of California Puhlications in Botany [Vol.5

14 types (pis. 64 to 77) are clearly intermediates approaching one
parent more than the other, but types 12, 13, and 14 (pis. 74 to 77,
inclusive) are decidedly different from either as to leaf, at least, and
type 10 (pi. 72) is of another altogether different form, although all
of these leaf shapes are connected to a greater or less extent into one
series of more or less gently intergrading forms.

As to the shape and dimensions of the corolla there is to be found
a similar series of intergrading forms from the slender corolla tube
with gradually expanding and slightly swollen infundibulum and
deeply lobed limb of type 1 (pi. 63) to the corolla with stout tube,
abruptly and considerably swollen infundibulum with slightly lobed
limb of type 16 (pi. 78). In color the corollas vary from the light
pink of angustifolia to the red of macrophylla and three shades are
at times fairly readily distinguishable, the light pink of angustifolia,
the deep pink of F^, and the several nuances of the red of macrophylla.

The capsules also show various combinations from the slender
gradually attenuated capsules of angustifolia to the stout, swollen,
abruptly upwardly attenuated capsules of macrophylla. Both cap-
sules and corollas approaching one parent may be found with leaves
more closely approaching the other parent. In stature and habit the
plants of all the 21 families were reasonably uniform and agreed in
general in these respects with the parents and Fj, there certainly being
no greater amplitude of variation in these respects than was to be
found in the parental types.

Among the great variations, two characters seemed to stand out
fairly clearly for rough statistical enumeration, viz., color of the
corolla and the possession, or lack, of a petiole. Numerical data for
these characters are given in table 1. Some care was taken to obtain
a careful census of the families as regards each of the characters. As
regards colors, it was, as noted before, possible to distinguish three
shades, or sets of shades, which were designated as light pink, pink, and
red. In practice, however, it was usually difficult to distinguish the
two shades of pink from each other. The red gave very little trouble.

In attempting to classify the plants of F, with respect to type of
leaf base, more difficulty was experienced because of the variety of
forms which were produced and the degree of intergradation w^hich
existed between forms. In judging the presence or absence of petiole,
therefore, in these populations, the classification is faulty because of
lack of knowledge of the genetic constitution of the various distinct
forms and those which grade into them. In table 1 the plants are

19221

SetcheU-Goodspeed-Clausen : Nicotiaua Tahacum

471

thrown into the petiolate class if they were distinctly narrowed at the
base, and whether naked or winged.

In Fo, then, there appears to be simple Mendelian inheritance in
only one pair of the original character contrasts of the parents, namely,
red versus pink corolla color. Here the hybrid is intermediate
and Fo segregates sharply into pink and red in the ratio 3 pink : 1 red.
Within the pink class there is a more or less evident segregation into
2 pink : 1 light pink, but the shades intergrade so that no distinct line
of demarcation exists between the classes. As respects leaf base char-
acters, the segregation is so complex that no reasonable genetic analysis
is possible. The numerical data for this latter character presented in
table 1 are of value only in that they indicate a close agreement in
segregation among Fo families, thereby furnishing a rough statistical
demonstration of the equivalence of the several families. The more
definite data on leaf base characters are derived from generations
subsequent to F2.

TABLE 1

CLASSIFICATION OF F2 PLANTS OF THE ANGUSTIFOLIA-MACROPHYLLA SERIES
ACCORDING TO COROLLA COLOR AND LEAF BASE CHARACTERS.

Family

Garden
Numbers

Corolla Color

Leaf Base

Designations

red

pink

light pink

petiolate

non-petiolate

A

IIF2H2P2

12

23

14

42

7

B

IIF2H2P3

14

25

10

30

20

C

IIF2H2P6

13

21

15

34

14

D

IIF2H2P7

7

21

22

35

15

E

IIF2H2P13

15

20

14

30

20

F

IIF2H4P2

13

28

7

32

17

G

IIF2H4P35

12

29

8

35

14

H

IIF2H4P40

13

15

22

32

18

J

IIF2H4P41

8

31

10

31

17

K

IIF2H4P43

6

27

15

38

10

Totals

113

240

137

339

152

472 University of California Puhlications in Botany [^'or..

4. F3 AND SUBSEQUENT GENEEATIONS OF THE ANGUSTIFOLIA-

MACROPHYLLA SERIES

From F, of Ho and H„ 20 plants were selected for further ex-
perimentation and families of 25 were determined upon as the unit.
In all except four, the families of 25 each were successfully raised.
Of one of the four only 14 plants were obtained, which were all that
germinated, while in each of the other three families 24 plants were
reared to maturity. Altogether, then, 486 plants were raised of the
Fg during the season of 1912. It was the intention to grow from each
of the selected types, as drawn for illustration. Fifteen of the families
from the type parents were successfully reared, but, in some way or
other, the seed of type 4 (lOFoHoP^Pig) was not to be found, and,
unfortunately, no note had been made as to whether or not any seed
was produced. No complete sterility, however, Avas noticed in any
members of F, of either Ho or H^, and the presumption is that Fo seed
of type 4 must have been lost in harvesting.

The variation within each family was decidedly less than that of
the families of Fo. Of the 20 families reared wholly or in part, 4
families were very nearly uniform, varying in minor details only.
Five families segregated only in corolla color, 4 segregated only in
leaf base characters, and the remaining 7 segregated both in corolla
color and leaf base characters. In table 2 are summarized the data
as to gro.ss behavior of these families of F3. In those families grown
in F^ and subsequent generations, a definite attempt was made to fix
the original characters of the Fo type selection in a pure line. The
genealogical relation of these selected lines to each other is shown in
the chart reproduced herewith. The letters. A, B, C, etc., correspond
to the Fo family designations noted in table 1, and the numbers refer
to type selection numbers corresponding to the type illustrations in
plate 63 to 78, or, in the case of types 17 to 21, corresponding to those
types as described in the succeeding accounts of the later generations.

1922]

Sctchdl-Goodspeed-Clausen : Nicotiana Tabacum

473

TABLE 2

Fa FAMILIES OF THE ANGUSTIFOLIA-MACROPHYLLA SERIES.

Type
Nos.

Garden
Numbers

No. of
plants
in fam-
ilies

Results in F3

1

IIF2H2P7P49

25

Segregated both as to leaf and flower color

2

IIF2H2P3P30

25

Segregated both as to leaf and flower color

3

IIF2H2P3P14

14

Segregated only as to leaf

5

IIF2H4P41P14

24

Segregated both as to leaf and flower color

6

11F2H4P2P,8

25

Uniform except as to length and development of
wing of petiole

7

IIF2H2P13P48

25

Uniform both as to leaf and flower color

8

IIF2H2P3P4.

25

Segregated as to leaf only

9

IIF2H4P41P8

25

Segregated both as to leaf and flower color

10

IIF2H4P41P17

24

Segregated only as to flower color

11

IIF2H4P41P9

25

Segregated only as to flower color

12

IIF2H4P41P12

25

Segregated only as to flower color

13

.IIF2H2P3P44

25

Segregated only as to flower color

14

IIF2H2P3P38

25

Segregated both as to leaf and flower color

15

IIF2H2P3P1O

25

Uniform, slight variation in tint and lobing of corolla

16

IIF2H2P3P8

24

Segregated only as to leaf

17

IIF2H4P35P27

25

Segregated only as to flower color

18

IIF2H4P35P38

25

Segregated both as to leaf and flower color

19

IIF2H4P35P43

25

Segregated both as to leaf and flower color

20

IIF2H4P40P44

25

Uniform, close to macrophylla

21

IIF2H4P41P29

25

Uniform, close to angustifolia

474

University of Calif &rma Puhlications in Botany [Vol. 5

In F, primary selection for parents of subsequent generations was
based upon the type of leaf borne by the plant, flower color being
followed as a secondary matter. In order to systematize the discussion
concerning Fg and subsequent generations, six general types have been
selected and named and the discussion of the families has been grouped

Pi 1909

ANCUST

FniiAl

fifl

MA

CROPHYLL

1

rULIAJ

L*J

WA

\

Fi 1910

J- r^ r^

Hi H2 Ha

T

ffl

4

r^ ^ An

Hs His [He

h 1911

A

I

9 C D

: F c
r 6 17 18 19 ;
^ 6 ^A ;

^ 6 6a 1
r 6 ^ 20

US%, 20

V

LI
i[5

f

20a
2Qa

J K

Fa 1912
h 1913
Fs 1914
Fs 1915
h I9i6

il

1 ,
8

3 14 5 16 i
5

_

_

9

J II 12 21
2 2
2I2a2
2I2a2
2 12a 2

Fig. 1. — Chart showing the relationships of the various families of the angusti-
foUa-macrophylla series. The different Fi hybrids are connected with their female
parents; no seed was secured from Hj. The Fj family designations correspond to
those given in table 1, and the numbers in later generations are the type numbers
under which the populations are described in the text. F« and F5 of type 12a were
grown in 1914 and 1915 respectively.

under these headings. The six general types selected and the names
given them are as follows:

a. Stenophylla derivatives. As a series these approximate very
closely in leaf shape to angustifolia. The distinguishing feature of
this series is the possession of a distinct, long petiole.

h. Latifolia derivatives, which are characterized by the possession
of a broad leaf with a petiole shorter than that of angustifolia. The
petiole in these types is more or less winged.

c. Lanceolata derivatives, which are characterized by the posses-
sion of a lanceolate leaf like that of type 13, illustrated in plate 75.
This is a non-petiolate form.

d. LoRirpoLiA derivatives, characterized by possession of long leaves
with very narrow blades. The type specimen, type 12, is illustrated
in plate 74. This also is a non-petiolate form resembling the lanceo-
lata derivatives, from which it differs in the extreme narrowing of the
blade.

^'*--] Setchell-Goodspeed-Clausen : Nicotiana Tahacum 475

e. AuRicuLATA derivatives. The typical form of leaf is that of
type 10, illustrated in plate 72. The leaf blade of this form is char-
acterized by an abrupt contraction of the blade at the base, nearly, if
not quite, to the midrib. Clasping auricles, from which the name is
derived, are usually present in this form.

/. Sessilifolia derivatives, of which the leaf of macrophylla may
be taken as the type. These derivatives are non-petiolate, as the name
indicates.

a. Stenophylla derivatives

Type 1, as may be seen from the drawing of Fo (cf. pi. 63), seems
very close to angiistifolia, and had light pink flowers. There were 25
plants of 12F3H.P-P4g, the leaves of which were carefully noted; but
one passed its flowering stage too early to be judged, so that the colors
of the flowers of 24 only are known. Sixteen plants had stenophylla
leaves very nearly of type 1, but the extent of the wing structure varied
somewliat. The remaining 9 had lanceolata leaves of type 14. In
flower color the segregation ratio noted was 5 red : 19 pink. No further
generations of this line were grown.

Type 17 was not selected for illustration in Fo, but was a plant
very close to angustifolia. It had, however, somewhat narrower leaves
and deep pink flowers. The 25 plants of I2F3II4P3-P07 were uniform
and like the F^ parent except as to flower color ; 3 were red and 22 w^ere
deeper or lighter pink. This line was not grown through further
generations.

Type 21, also, was not selected for illustration of the Fg plant, but
was chosen later for perpetuation because of its extremely close agree-
ment with angustifolia. The F3, I2F3H4P4P09, consisted of 25 vigorous
plants which seemed to be uniform to the finest detail and agreed in
every respect with plants of angustifolia. There were noticed in the
plants of this family peculiar fimbriae attached to the corolla, or split
corollas, or, in one instance, a split hose-in-hose flower such as occurs
at times also in pure angustifolia. This type seemed to be a pure
recombination of the characters of angustifolia.

Type 21 was continued through to the seventh generation and
found to be constant in the uniformity of the individuals in the several
families. In 1913, 94 plants of F4 were grown ; in 1914, 85 plants of
F,,; in 1915, 10 plants of F^ ; and in 1916, 8 plants of F,. All these
populations closely resembled one another as to individuals as well
as those of the F3 and the F^ parent. They are all so close to angus-

476 University of California Publications in Botany [Vol.5

tifolia as to be practically indistinguishable from it. This line may
be regarded, therefore, as a stable derivative very closely approxi-
mating angustifolia in all its characters.

h. Latifolli derivatives

Type 2 (cf. pi. 64) approached in F, fairly near to some of the
variations of F^ (cf. pi. 62). It might be regarded as a stenophylla
derivative possessing an unusuallj^ luxuriant development of the wing
of the petiole, but it seems more reasonable to classify it as a latifolia
derivative exhibiting marked narrowing at the base of the lamina, such
as is shown in laKceolata derivatives. The flower was designated as
light pink in the notes taken at the time of flowering. The leaves of
F3 showed segregation through a considerable range, 6 being close to
the LATIFOLIA type of Fj, 6 to the latifolia type of its F^ parent
(type 2), 8 were sessilifolia leaves approaching in type those of mac-
rophylla, and 4 were auriculata leaves of type 10. In 13 the flowers
were noted as light pink, in 11 as pink, and in 1 as red. No subsequent
generations of this population were grown.

Type 3, in F,, had (cf. pi. 65) a distinctly ovate lanceolate leaf
with a short fairly broadly margined petiole. The flowers were light
pink. F3, I2F3H2P3P14, amounted to 14 germinations, all of which
developed, although slovdy, into healthy, normal appearing plants.
The flowers were all the light pink color of the F^ parent, agreeing
with those of angustifolia, but varying somcAvhat in shape and size.
The leaves were of various shapes, 4 were distinctly petiolate, while
10 were sessile. Of the 4 petiolate plants the petiole of 1 was naked
and of 3 more or less winged. Of the 10 sessilifolia plants, 9 were
very similar to type 11, but 1 was rather longer and narrower, although
otherwise approaching the same general shape. No further generations
from this line were grown.

Type 5 in F, (cf. pi. 67) resembled F^ most nearly, but the winged
petiole was short and the corolla tube slightly stouter. The flower
color was pink. Of 12F3pl4P^iPi4, 24 plants were grown. Of these
23 had leaves almost exactly like those of the Fg parent, but 1 had
leaves more nearly like auriculata of type 8 (cf. pi. 70). Of the 24
plants, 16 had flowers of various shades of pink while 8 had red flowers.
This line was not groAvn in subsequent generations.

Type 6 was represented in F2 by a plant which resembled F^ in
having a M'inged petiole to the leaf and a pink flower. It is well repre-

1922] Setchell-Goodspccd-Clauscn: Nicotiana Tabacum 477

sented on plate 68. In the 25 plants of 12F3H,PoPi8, the height,
habit, flower shape, and flower color were close to, if not identical with,
those of the Fo parent. As respects leaf base characters, li were
LATiFOLiA of type 6, 4 had long, naked petioles, 3 had short, naked
petioles, 1 had a long, winged petiole, and 4 were auriculata plants
nearly of type 10. This seems like a considerable segregation, but the
leaves are of only two generic types, viz., petiolate and non-petiolate.
In subsequent generations selection was made in one line for latifolia
leaves of type 6, and in the other for auriculata leaves of type 10,
called type 6a to indicate its derivation.

Of type 6 as thus established 100 plants of F^ were grown in 1914;
100 plants of F,- (50 each from 2 different parents) in 1915; 20 plants
of Fg in 1915; and 20 of F^ in 1916. All the individuals thus grown
were constant to latifolia of type 6 as originally selected.

Of auriculata of type 6a, similarly, 100 plants of F^^ were grown
in 1913 ; 94 of F^ in 1914 ; 20 of F„ in 1915 ; and 20 of F, in 1916. All
these plants were uniform and true to auriculata of type 6a, very
close to AURICULATA of type 10. In both these types we have definitely
obtained stable recombinations of germinal elements exhibiting char-
acters different from those of the parents.

F3 of type 7, I2F3H2P13P48 (cf. pi. 69), consisted of a family of
25 plants, all vigorous except one (P17), which was set out in the field
later and developed into a "runt," as often happens with such later
plantings. All the plants agreed well with one another in height and
habit except the "filler," and all agreed in inflorescence, flowers, and
leaves. There were some variations in size and lobing of the limb of
the corolla, indicating possibly minor segregation, but in all general
characters there was uniformity to a large degree. The plants agreed
well in all characters with the Fo parent, and also with the F^ parent.
The color of the flower was light pink, the petioles of the leaves varied
somewhat in length, were distinctly and more or less broadly winged,
and the blade was heart-shaped, at least at the base in the lower leaves.
In all respects these characters were no more variable than they were
found to be in F^.

Type 7 continued to breed true in subsequent generations. It was
grown in 1913 (100 plants, FJ, 1914 (2 families of 50 plants each,
F,), 1915 (10 plants, F J, and 1916 (10 plants, F,). All were uni-
form as to leaf and flower color. Type 7 is very close to the type of
Fj and to type 6 described above. It, too, evidently represents a stable
recombination of germinal elements derived from both parents.

478 University of California Publications in Botany [Vol. 5

Type 9 resembles type 5, but had in Fg a very short winged
petiole and elliptical lanceolate blade. It also had pink flowers. F..,
12F3H^P4iPs, consisted of 25 plants, 18 of which showed latifolia
leaves of type 9, but 7 had sessilifolia leaves of type 14 (cf. pi. 76).
Twenty-one had pink (or light pink) flowers and 4 had red. No
further generations of this line were grown.

Type 19 was an F, plant of which no drawing was made, but it
resembled F^ (cf. pi. 62), having broadly ovate leaves with a long
and broadly winged petiole and pink flowers. Fg, I2F3H4P35P43, con-
sisted of 25 plants, 6 of which had sessilifolia leaves of type 16 (cf.
pi, 78) or nearer, perhaps, to those of macrophylla, while 19 had
latifolia leaves of type 19. In 5 plants the flowers were a somewhat
darker red than they were in the other 20. This line was not followed
further.

c. Lanceolata derivatives

Type 13 is similar to type 12 described below, but the leaves of the
Fo plant were more lanceolate and broader and the flowers were lighter
pink. The 25 plants of I2F3H2P3P44 were uniform and like Fo except
in flower color. Four were red, 19 decidedly pink, and 2 inclined to
light pink. The line was not grown in subsequent generations.

d. Lariifolia derivatives

Type 12, as shown in plate 74, differed very decidedly in leaf shape
from either parent. The long linear-lanceolate leaf had the long taper-
ing curved tip of angustifolia, but the blade tapered below, making
practically a new type. The flowers were like those of angustifolia
in shape but were pink. The 25 plants of F,, I2F3H4P41P12, were
exact duplicates of F, as to habit, leaf, and flower shape, but 10 had
red and 15 had pink flowers of various shades, mostly dark. None
seemed as light pink as angustifolia.

This is the most interesting of the types carried tlirough subse-
quent generations, representing, apparently, a new combination of leaf
characters. One of the pink flowering F, plants was chosen for seed
and the designation, t.ype 12, retained for this and its progeny, while
the designation, 12a, was given to one of the red flowering F., plants
also chosen for seed.

Type 12, as thus limited to the pink flowered plant, gave scanty
germination and few plants for F4 in 1913. Apparently it was still
varying slightly in color within the pink shades, although fairly uni-

1922] Setchell-Goodspeed-Clausen : Nicotiana Tahaeum 479

form except for one aberrant ( ?) plant of a decidedly lighter shade.
Two "normal" parents of F^ gave 88 and 100 plants of F.^ in 1914,
which were uniform and of a bright pink color. In 1915 Fg showed
10 plants, and in 1916 F. also showed 10 plants, still uniform and pink.

Type 12a on being segregated in the second growing of Fg in the
season of 1913 yielded 100 plants of F^ in 1914, uniform and of deep
red flower color. Fj, of 10 plants in 1915, and also Fg, of 10 plants in
1916, produced uniform individuals of deep red flower color.

We find, then, in types 12 and 12a definite fixations of the lorii-
FOLiA type, one with uniformly pink flowers and one with uniformly
deep red flowers.

e. AuRicuLATA derivatives

Type 8 is represented in F. by a plant which had a leaf with an
extremely constricted base (cf. pi. 70) and deep red flowers. It is
not a typical auriculata derivative, but is included under this heading
because it resembles the members of this class more closely than those
of any other. Fg, 12F3H2P3P^i, consisted of 25 plants which were
uniform in height, habit, and flower color, and in agreement with Fo
in these respects. The leaves, however, were of two distinct types, 16
AURICULATA of type 8 and 7 sessilifolia of type 16 (cf. pi. 78), the
latter being near to the type of macrophylla. No further generations
of this line were grown.

Type 10, as shown by the drawing (pi. 72), had a peculiar leaf,
near to the macrophylla type, yet deeply constricted at the base into a
narrow and extremely abbreviated structure which may resemble a
petiole or only a deeply constricted blade. There were, however,
auricles partially clasping the stem and slightly decurrent. The leaf
form was that characteristic of N. Tabacum var. macrophylla purpurea
(cf. Setchell, loc. cit.). All 24 plants of Fg had the same type of leaf
as F2, but the flowers were of three fairly readily distinguishable
shades ; 3 were red, 16 pink, and 5 light pink. Fo had very dark pink
flowers. The line was not grown in further generations.

Type 6a is a true auriculata derivative which segregated in Fg
from an F, latipolia selection. Its occurrence and behavior are de-
scribed in connection with the account of type 6, the latipolia type
from which it segregated. Grown in the pure line for five generations
it has remained constant for the auriculata type of leaf.

480 University of California Fuhlications in Botany [Vol. 5

/. Sessilifolia derivatives

Type 11 (cf. pi. 73) in F, gave 25 plants in 12F3H,P,iPn, all
vigorous except one, but that one showed the same characters of leaf
and flower as the others. All 25 plants possessed a sessilipollv type
of leaf very close to the Fo parent and uniform among themselves.
There were two distinct shades of color of the flowers, 9 red and 16
pink. No further generations of this line were grown.

Type 14 (cf. pi. 76), so far as F, is concerned, was one of those
having sessile leaves of a broadly lanceolate type and pink flowers.
There were 25 plants in I2F3H0P3P3S, 24 had sessilifolia leaves of
type 14, while one (a "filler") had auriculata leaves like type 8; 19
had pink (or light pink) flowers, while 6 had red flowers. This line
was not followed through subsequent generations.

Type 15 (cf. pi. 77) was represented in F,, 12¥ JIJ' ^Y ^^, by 25
vigorous plants which seemed surprisingly uniform and approached
macrophylla very closely as to leaf and color of the flower. In the
flower, however, the color seemed even darker than that of macrophylla,
there were only slight traces of the white triangular markings on the
limb, the limb was much more deeply lobed, and the tube less stout
and with the infundibulum much less abruptly swollen. These differ-
ences seem to indicate that type 15, which all the F3 plants closely
resemble, is not an exact recombination representing macrophylla.

Type 15 was represented in 1913 by two families, F, of 10 plants
and F4 of 100 plants. Both families were uniform as to individuals,
and agreed with the F, population grown in 1912 as well as with the
F2 ancestor of the season of 1911. As this line seemed to be constant
and very close to, although not absolutely identical with, macrophylla,
differing in flower shape and leaf shape to some extent, type 15 was
considered to be a fixation and no further cultivation of it was made.

Type 16 (cf. pi. 78), which in F. approached macrophylla very
closely in leaf, flower shape, and flower color, was represented in F3,
I2F3H0P3P8, by 25 plants. These were all alike and closely resembled
the F2 parent in all respects except in leaf shape. Fifteen had sessili-
folia leaves of type 16 while 8 had auriculata leaves approaching
those of type 10 (cf. pi. 72). This line was not grown in further
generations.

Type 18 is the designation given to an F^ plant, of which no draw-
ing was made. It seemed close to macrophylla, but the flower color

1922] Setchell-Goodspeed-Clausen: Nicotiana Tahacum 481

was pink and the leaves were more slightly attenuate at the base.
F.J, 12F3H^P33P3s, gave 25 plants, 13 of which had the sessilifolia
leaf of type 18 ; 7, auriculata of type 10 ; and 5, auriculata of type 8.
In flower color. 17 were some shade of pink and 8 red. The line was
not grown in further generations.

Type 20 was not selected for illustration in F,, but was a plant
chosen because of its very close resemblance to macrophylla, coming
even closer than type 16. The F3, I2F3H4P40P44) consisted of 25 vig-
orous plants of remarkable uniformity. In height, habit, inflorescence,
flower, color, shape, fruit, etc., the details follow those of macrophylla
so closely as to be indistinguishable unless possibly by careful and labor-
ious biometric study. This type may represent a practically pure
recombination equivalent to macrophylla, and is to be compared and
contrasted with type 15.

In 1913 two families of F^, one of 21 plants and the other of 100
plants, were uniform, as were 3 families of 50 plants each of F- in
1914. ■ In 1914, however, a surprising thing happened. A fourth
family of Fg, consisting of 50 plants, was uniform except one plant
which had pink (instead of red) flowers and an auriculata leaf ap-
proximating type 8 or 10. It seems certain that this plant must have
been an intruder, but its seed was saved under bag and grown and is
noted below and on the pedigree chart as type 20a. The other 3 plants
of F5 whose seed was sown in 1915 gave type 20 in Fg in families of
10, 9, and 8 respectively, and in turn the seed of 4 individuals of
"pure" type 20 gave, in 1916, uniformity in families of 10 each.

Type 20a, which originated or intruded in 1914, in one plant of
F5 of type 20 gave in Fq, in 1915, 10 plants segregating for flower
color and probably also for leaf characters, although the notes taken
are inconclusive on the latter point. In 1916 F. of 10 good plants
showed uniformly red flowers, but 7 had sessilifolia leaves, 4 of which
were decidedly contracted at the base and 3 had very short winged
petioles (auriculata of type 8 or type 10). On the whole it seems
most likely that the single plant in the F^ family was an intruder,
since all other families of the line have been constant since F,. A stray
seed somewhere along the processes of culture would explain it and
its appearance is all the more incomprehensible as a matter of inclu-
sion in the pedigree of type 20, as it is so close to macrophylla as to
seem practically identical with it.

482

University of California Puhlications in Botany [Vol.5

5. SUMMARY OF FLOWER COLOR OBSERVATIONS IN F^ AND
SUBSEQUENT GENERATIONS

In tables 3 and 4 we have summarized the numerical data with
respect to flower color inheritance in Fg and in the subsequent popu-
lations. In table 3 are assembled data with respect to the behavior
of red flowering selections from populations segregating for red and
pink. It will be noted that all the five selections which were made
bred true for red flower color in the succeeding generations. In table

TABLE 3

INHERITANCE OF RED FLOWER COLOR IN Fa, et seq.

Type Numbers

Garden Numbers

Flower color of population

8

I2F3H2P3P4,

25 red

12a

I4F4H4P41P12P,

100 red

15

I2F3H2P3P10

25 red

16

I2F3H2P3P8

24 red

20

I2F3H4P40P44

25 red

TABLE 4
POPULATIONS FROM PINK FLOWERING SELECTIONS OF ALL SHADES IN Fa et seq.

Flower

color classification

Type

Garden Numbers

Parent
Color

Num-

bers

red

pink

light pink

3

I2F3H2P3P14

light pink

14

6

I2F3H4P2P18

pink

25

7

12F3H2P,3P48

light pink

25

12

I3F4H4P41P12P8

pink

88

12

I3F4H4P41P12P9

pink

100

• •-•

21

I2F3H4P4P29

light pink

25

1

I2F3H2P7P49

light pink

5

19

(or light pink)

2

12F3HiP3P30

light pink

1

24

(13 light pink)

5

12F3H4P4lP,4

pink

8

16

(or light pink)

9

I2F2H4P4.P8

pink

4

21

(or light pink)

10

I2F3H4P41P17

pink

3

21

(5 light pink)

11

I2F3H4P41P9

pink

9

16

(0 light pink)

12

I2F3H4P41P12

pink

10

15

(0 light pink)

13

I2F3H2P3P44

pink

4

21

(2 light pink)

14

I2F3H2P3P38

pink

6

19

17

12F3H,P4P35P27

pink

3

22

18

I2F3H4P35P38

pink

8

17

19

I2F3H4P35P43

pink

25

(5 darker red)

Tot

als of segregating popula

tions

60

187

(Types 2 and 19
excluded)

1922] Setchell-Goodspeed-Clausen : Nicotiana Tahacum 483

4 are assembled the data from pink flowering selections from popu-
lations which showed segregation into red and pink. In this table the
populations which bred true for pink are assembled in the upper
portion of the table, and those which showed further segregation into
red and pink are assembled in the lower portion. Of the 18 selections
made, 7 bred true for pink (or light pink), and 10 gave segregation
in the succeeding generation in about the ratio of 3 pink : 1 red. The
total figures for the 10 populations — 187 pink : 60 red — are in very-
satisfactory agreement with the simple Mendelian ratio. The family
of type 19 behaved in an anomalous fashion, which may indicate mis-
classification of the Fg parent ; and the family of type 2, which showed
only one red plant has been included among those which bred true for
pink. Strictly light pink selections should have given only light pink
flowers in subsequent generations ; the pink ones should all have given
segregating populations. The evidence indicates that this result would
be obtained if segregation occurred for only one pair of allelomorphs.
The difiiculty, in part at least, appears to be the result of segregation
of modifying factors in the populations. These factors apparently
have an effect on flower color sufficient to obscure segregation into
pink and light pink, but not enough to obscure the segregation into
red and pink. The actual results indicate an approximate agreement
with expectation, but the breeding test clearly is necessary in order
to determine the actual distribution of the pink individuals into their
genetic classes.

6. LATER SOWINGS OF F^ AND F3 OF THE ANGUSTIFOLIA-
MACROPHYLLA SERIES

In 1916 and 1917 certain families of F2 and F3 of H, were grown
in order to reexamine them in the light of data previously collected
and to determine whether or not any more definite classifications could
be made than those stated in the preceding pages. The populations
grown are described briefly below.

I6F2H2P0, as the population number would indicate, was a sowing
of seed of lOFiHoPg from the original F^ population of H.. As in
previous cases, the segregation as regards leaf shape was so complex
as to preclude definite classification. The types previously noted for
second generation populations were all in evidence and along with
them practically every sort of intermediate. The height of plants
and general habit likewise agreed with the description previously
given.

484 University of California Puhlications in Botany [Vol.5

It was possible as in previous instances to segregate the plants into
definite flower color classes. In order to make this segregation as
accurate and free from bias as possible a special method of classifica-
tion was adopted. At the height of the blooming season, single typical
flowers were collected from each plant of a population and placed in
vials correspondingly numbered. These specimens were then taken
into the laboratory, where they could be classified under optimum light
conditions. The specimens so collected could then be shifted around
into their phenotypic classes and properly compared with each other
and with the parent colors. The color classification thus obtained
M^as individually recorded, and later the population was checked over
in the field to insure correction of any errors of classification. The
surprising feature of this population was a sharp, three-class segre-
gation into red, pink, and light pink ; the reds the shade of macro-
phylla, the light pinks almost exactly that of angustifolia, and the
pinks intermediate between the two. Within the classes there ap-
peared to be no significant differences in depth of shade. Two plants
bore no flowers. The ratio obtained was 15 red : 23 pink : 10 light
pink.

IGFoHoPiT was likewise a sowing of the seed of one of the original
F^ plants, in this instance of IOF1H2P17. As respects habit, height,
and leaf shape, there was a strict resemblance throughout of this
population to the one described above. Flower color was studied in
the same manner and with substantially the same results. However,
in this population there was a shading off from pink to light pink,
such that it was impossible to draw a sharp line between these two
classes as was done in the previous population. The shading off was
abrupt, but there were, nevertheless, a few plants on the border line.
The observed ratio was 16 red : 34 pink and light pink.

In 1917 six F3 populations, each containing approximately 100
plants, were grown in order to make further studies of the inheritance
of leaf shape. It was impossible, however, to study these plants as
thoroughly as might have been desired on account of conditons ob-
taining during 1917. However, specimens of leaves from each plant
were pressed and preserved and these were studied and classified in
the summer of 1919. A brief account of each population follows :

I7F3H2P17P6 was a sowing from IGF.HoPi-Pe, a stenophylla
selection. With respect to leaf base characters the segregation was
roughly but rather obviously into two types, a long petioled steno-
phylla class approximating type 1 in appearance, and an auriculata

1922] Setchell-Goodspeed-Clausen: Nicotiana Tahaciim 485

class approximating type 10. Within the stenophylla class there
was a variation in the amount of "wing" on the petiole and in the
type of blade base, some having the abrupt base of type 1, whereas
others had an attenuated type of blade which gradually drew in to
the petiole. In the auriculata class there was also a variation from
the strict form of type 10 to a type which lacked the flaring auricle
typical for that form, and had a very short naked petiole. In addition
to this variation in the amount of "wing" of the constricted class
there was also a difference in the presence or absence of attenuation
noted for the stenophylla class, some plants having leaves abruptly
drawn in to the midrib, whereas others were very markedly attenu-
ated. The difference in this respect appeared to be equivalent in the
two distinct classes, i.e., it was independent of any difference in the
' ' petioled " or " constricted ' ' condition. With respect to stenophylla
vs. AURICULATA the Segregation was 66 stenophylla : 32 auriculata.

I7F3II2P17P8 was a sowing from I6F0II0P17P8, another steno-
phylla selection. The leaf classes obtained here were two, steno-
phylla (type 1) and sessilifollv (type 15). The segregation into
the two classes was distinct, but, as in other populations, there was a
great deal of variability in each class. There was attenuation of the
kind previously noted in both classes. Some of the petioled individuals
had distinct wings, but the larger number were naked. Some few
individuals had very short petioles. The segregation ratio was 76
stenophylla : 24 sessilifolia.

ITF.H^Pi^PiQ was a sowing from 16F„H2Pi7Pin, a stenophylla
selection. The population was remarkably uniform in leaf shape,
which closely approximated angustif olia with minor differences. The
straplike leaves which are a characteristic feature of the upper por-
tions of plants of angustifolia were lacking in this population, and
the leaf tip and distal portion of the leaf blade did not narrow so
gradually in this population as in angustifolia. Otherwise, the char-
^ acters of the plants throughout were closely similar to angustifolia:

I7F3H2P17P22 was a sowing of seed of I6F2H2P17P02, a stenophylla
selection. Of the six F^j populations studied, this one exhibited the
greatest diversity in segregation. With respect to leaf base characters,
there were two outstanding classes, stenophylla and sessilifolia (type
15), which could be separated readily. Within the stenophylla class,
however, most of the individuals exhibited a more or less winged con-
dition. Within the sessilifolia class, on the other hand, most of the
individuals exhibited more or less narrowing of the leaf ba.se, like

486 University of Calif oryiia Publications in Botany [Vol. 5

type 14. A few of the sessile individuals, instead of exhibiting gradual
and uniform narrowing toward the base of the leaf, were constricted
to a degree intermediate between aubiculata of type 10 and sessili-
FOLiA of type 15. With respect to stenophylla versus sessilifolia
the observed segregation was 67 stenophylla : 32 sessilifolia.

I7F3H2P17P3 was a sowing of seed of I6F2H2P17P3, an F. sessili-
folia selection. The leaves throughout had the sessile type of leaf
base characteristic of macrophylla, but there were many modifications
of it in the population. A rough classification with respect to these
modifications of the macrophylla type of leaf base gave the following
results :

On 59 plants, the leaf bases were very nearly the form typical for

macrophylla.
On 22 plants, the leaf bases were gradually attenuated toward the
base, resembling lanceolata of type 13 as a mean. This at-
tenuated form of the sessile leaf was a very striking feature of
this population.
On 10 plants, the leaf bases were intermediate in type between

lanceolata of type 13 and the typical macrophylla form.
On 2 plants, the base of the leaf immediately above the point of
attachment was noticeably constricted, the leaf base thus formed
being intermediate between the macrophylla type and auricu-
LATA of type 10.
On 2 plants, the leaves were intermediate in constriction of the
leaf base between the strict macrophylla type and that of the
two plants described immediately above.
The classification here given is presented only to show that the
sessile type of leaf base characteristic of macrophylla is subject to a
number of very definite modifications which probably account for some
of the complex types of segregation observed in other populations.

I7F3H0P17P10 was a sowing from I6F0H0P1-P12, a sessilifolia
selection. With respect to leaf base segregation there were two dis-
tinct classes, sessilifolia (type 15) and auriculata (type 10). There
was here also a marked degree of variation within the classes. Within
the sessile class the variation was in amount and kind of narrowing
of the leaf blade toward the base. A few plants showed a condition
approaching the auriculata type in this respect, whereas others
showed a gradual attenuated form of narrowing such as has been
noted before in other populations. Within the auriculata class most
of the individuals instead of possessing the slight wing and flaring

1922] Setchell-Goodspeed-Clausen: Nicotiana Tahacum .487

auricles of type 10 had short naked petioles. A few were strictly of
type 10. The following segregation ratio was noted : 61 sessilipolia :

27 AURICULATA.

7. CROSSES OF DERIVATIVES WITH THE PARENTS

In the preceding account we have pointed out that by growing
definite hybrid selections in the pure line through a number of gener-
ations it has been possible to establish a certain number of stable
derivatives which represent more or less obvious recombinations of
characters of the original parents. In a Mendelian sense, they repre-
sent stable reorganized germinal complexes containing hereditary ele-
ments that have been derived from both parents. Obviously such
recombinations of Mendelian units must differ in fewer units from
either parental type than did the parental types from each other. To
test some of these derivatives we have crossed them with the original
parents, usually with the one to which they bore the closest resem-
blance, in order to observe how complex a type of segregation the
hybrids thus obtained would exhibit as compared with that of the
original angustifolia-macrophylla hybrids. In so far as they have been
studied to date, a description of these hybrids and their progenies
follows :

SESSiiiiFOhiAxmacrophylla. Fg sessilifolia of type 20 was crossed
with macrophylla giving H-^ = type 20$ x macrophylla(^ and H-^ =
reciprocal thereof. The derivative parent here very closely resembles
macrophylla throughout in flower color and shape, habit, leaf shape,
etc. ISF^Hjo and ISF^H-i, two families of 50 plants each, were equiv-
alent in every respect. The plants were very close indeed to macro-
phylla, as is also the sessilifolia parent. The only difference readily
observed was some variation in the amplitude of the corolla. In Hgi,
a plant with a larger and one with a smaller corolla were selected for
pure seed. In Fo, grown in 1916, one family of Hjo and two families
of Hgi, of 50 plants each were grown. The flower color in the F,
populations was throughout that of macrophylla and the leaf charac-
ters also were those of macrophylla. All three families were remark-
ably uniform, not only agreeing with one another but uniform as to
indivduals. They all resembled closely the macrophylla type and there
was no definite segregation of any kind in them. The three popula-
tions appeared to be replicas of macrophylla throughout except that
they were slightly more robust.

488 University of California Publications in Botany [Vol.5

Latifolia X angustifolia. Fg latipolia of type 6 was crossed with
angustifolia giving H-2 = type Q^xangustifolia(^ and H53, its recip-
rocal. The derivative parent possessed the short winged petiole char-
acteristic of LATiFOLL\ of type 6. In F^ 50 plants of each cross were
grown. They exhibited the long naked petiole characteristic of angus-
tifolia.

In Fo two populations of 50 plants each were grown. In color of
flowers the two populations were light pink throughout, closely cor-
responding in this respect to angustifolia. In leaf shape the segre-
gation was sharply into two classes: the stenophylla type of leaf
base (long, naked petiole) and the latifolia type (shorter, winged
petiole). There was some variation in the stenophylla class sug-
gesting intermediacy between angustifolia and latifolia, but the forms
exhibiting it showed a graded series from strict stenophylla to inter-
mediate. The LATIFOLIA class was very uniform and sharply set off
from the other class. The segregation ratios observed were as follows :

Stenophylla

Latifolia

■2H.„Pl6

42

8

2H53P30

36

14

Totals 78 22

AuRicuLATA X niacroph ylUi. F. auriculata of type 6a was crossed
with macrophylla giving H,,^ and H-^ ^ F- type 6a'^ x macrophyllac^
and H-- and H-„, their reciprocals. It should be observed that type
6a is an early segregant from the latifolia of type 6 of H-, and H.,,.
In Fi 50 plants were grown of each of the four parents. All four
populations were equivalent in every respect. All the plants had pink
flowers, although one plant had flowers of a lighter shade than the
others, and leaves of a shape somewhat intermediate between the two
parents, i.e., they were more contracted at the base than macrophylla,
but much less so than those of type 6a. One plant of H-,^, namely
15FiH,5Pi,3, showed larger corollas than any of the other F^ plants
of any famil}^ and was selected for further breeding.

In Fo four families were raised and they proved to be equivalent
in all respects, except as noted. There was sharp segregation for leaf
shape into the sessilifolia and the sharply constricted auriculata type.
In the sessilifolia class there were a number of obvious intermedi-
ates, as might be expected from the characters exhibited by F^, but
they formed a continuous series with the strict sessilifolia forms.
The auriculata class did not intergrade with the dominant class.

1922]

Setchell-Goodspeed-Clausen: Nicotiana Tabacum

489

Segregation for flower color was studied by the method described above.
The color distinction between red and pink was sharp and easily drawn.
In the pinks, however, there was a continuous series of shades from
the deep rose pink characteristic of F^ to the light pink typical for
angustifolia. Numerical data are given in table 5.

TABLE 5

Fj SEGREGATION OF PINK AURICULATA X RED SESSILIFOLIA.

Garden Numbers

Pink

sessilifolia

Red
sessilifolia

Pink
auriculata

Red
auriculata

16FoH5,P7

32

6

9

3

16F2H55P16

23

11

11

5

16F2H55P29

26

13

7

4

16F2H5SP26

26

11

7

2

16F2H,9aP35

26

12

6

2

Totals

133

53

40

16

Expected

136

45

45

15

In 1918 in connection with flower size studies three more popula-
tions of FoHj, were grown. Leaves were collected from each plant
and pressed, and leaf shape studies were made on these preserved
specimens. The studies were not so satisfactory as those made in the
field, where it is possible to examine all the leaves on a given plant ;
nevertheless, the data derived from the studies agreed substantially
with those obtained in 1916 from field studies. It was noted in these
studies that there was a distinct class of "attenuated" leaves similar
to those which have been described in previous populations. Both
attenuation and constriction were observed to occur in the leaves of
some individuals, and this gave rise to some difficulty in classification.
Numerical data are given in table 6.

TABLE 6

F2 SEGREGATION OF SESSILIFOLIA X AURICULATA.

Garden Numbers

Sessilifolia

ACRICULATA

I8F2H65P40
I8F2H55P41
I8F2H55P48

67
79
79

28
18
17

Totals

225

63

490 University of California Publications in Botany [Vol. 5

Stenophylla X angusti folia. Reciprocal crosses were made between
F-, STENOPHYLLA of type 21 and angustifolia; H-6=^F5 type 21$ x
angustifoUa(^ and Hj-, its reciprocal. Stenophylla of type 21 has been
described previously as a stable derivative closely approximating
angiistifoUa in all its characters. F^^ families of 50 plants of each
hybrid were raised in 1915. They were uniform throughout and so
close to angustifolia in all characters as to be indistinguishable from
it. One plant seemed to be of a slightly darker pink corolla color.
ISFsHjeaPii was the only ¥<, family raised. The flower color of this
population was about the shade of angustifolia and uniform through-
out the population. The family showed only a slight variation in the
base of the blade such as is also seen in populations of angustifolia.

8. DISCUSSION OF EESULTS OF THE AXGUSTIFOLIA-MACROPHYLLA

SERIES OF INVESTIGATIONS

Obviously the outstanding result of this series of investigations of
hybrids between angustifolia and niacrophylldi is a demonstration of
the complexity of the germinal differences which exist between the
two varieties with respect to practically every character contrast which
may be made between them. Only in one instance, the contrast be-
tween the light pink flower color of angustifolia and the red of macro-
phylla, is a simple Mendelian formulation possible. Here evidently
the main flower color difference is dependent upon a simple allelo-
morphic contrast. Red x light pink gives F^ intermediate pink, and Fo
1 red : 2 intermediate pink : 1 light pink. The red segregants breed
true for red, the light pinks for light pink, and pink continues to
segregate in the typical mono-hybrid fashion. Inasmuch as the inter-
mediate pinks and light pinks form an intergrading series, it is con-
venient to look upon red as the recessive color. Accordingly we give
this pair of factors the designation, Rr, following the mnemonic system
advocated by Morgan, and shall so refer to it in what follows. The
difficulty among the pinks appears to be due not only to phenotypie
variation but also to the existence of modifying factors which have a
relatively slight effect upon flower color expression. These less strik-
ing modifications of flower color we are seeking to analyze further.

In the leaf shape investigations, the complexity of the results is
plainly evident from an examination of the data presented in the fore-
going pages. Although the behavior here is complex, in every feature
it parallels the Mendelian expectation for complex factor relations.

1922] SetcheU-Goodspeed-Claiisen: Nicotiana Tahacum 491

I,n Fo the variety of leaf shapes encountered was nothing short of
bewildering and series could be built up from them showing complete
intergradation from one type to another. Selection of phenotypes
from Fo, however, gave F3 populations in which the complexity of
segregation was usually reduced in a very definite fashion. Most of
the populations exhibited fewer classes than Fj, and the selection of
Fo phenotypes held the expression of F3 within very definite limits.
Thus selection of sessilifolia forms gave in F3 either all sessilitolia
or approximately 3 sessilifolia : 1 auriculata. In no case did such
selections give F3 populations with stenophylla or latifolia leaf
types. A summary in detail of the type of populations produced is
as follows.

Stenophylla selections may segregate in a variety of ways. Thus,
type 1 showed approximate segregation into 3 stenophylla : 1 sessi-
lifolia. Type 21 bred true to the stenophylla characters. Among
STENOPHYLLA selections grown in 1917, population ITF.HoP^.Pg,
showed approximate segregation into 3 stenophylla : 1 auriculata;
ITFgHoPiTPgj 3 STENOPHYLLA :1 SESSILIFOLIA; ITF^HoPi^Po bred true
for STENOPHYLLA, and I7F3H2P17P22 gave a rather indefinite segrega-
tion of approximately 3 stenophylla : 1 sessilifolia. Latifolia
derivatives crossed with angustifoUa gave F^ stenophylla and F^
approximately 3 stenophylla : 1 latifolia.

Latifolia selections also segregate in perplexing fashion. The F^
population of angustifoUa x macrophylla is typically latifolia in its
characters. Latifolia under certain conditions therefore is a very
complex hybrid expression. Recurrence of complex segregation of a
latifolia selection is shown in F3 of type 2. F3 of type 3 exhibited
a rather anomalous segregation ratio of petioled and sessile forms.
Type 5 apparently bred true, although there was one anomalous plant
in the population. Type 6 exhibited complex segregation, with an
indication of a ratio of 3 latifolia : 1 auriculata ; with subsequent
establishment of both latifolia and auriculata in constant races.
Type 7 bred true for a type of leaf like F^ ; and type 9 gave approxi-
mate segregation of 3 latifolia : 1 sessilifolia.

Loriifolia and lanceolata derivatives are really variations of the
sessilifolia type. They were both produced in constant races. Their
genetic relation to the other forms is, however, not well established
by this series of investigations. Although these two are really ({uan-
titative variations from the strict sessilifolia type, nevertheless, cer-
tain of our data indicate discontinuous inheritance of these contrasts.

492 University of California Fuhlications in Botany [Vol. 5

The same quantitative factors that differentiate the narrow-leaved f orm^
of SESSiLiFOLiA from the typical broad-leaved forms may apparently
differentiate narrow-leaved stenophylla, latifolia, and auriculata
forms from the more typical broad-leaved ones. It is of interest in
this connection to note that loriifolia derivatives have much narrower
leaves than either of the original parents.

We have been especially interested in these loriifolia derivatives
because they are somewhat like the narrow-leaved forms that Hassel-
bring (1912) found among Cuban tobaccos, and which are so well
recognized among Cuban growers as to have received the specific desig-
nation of lengua de vaca or "cow's tongue." Our results indicate
that it is possible for such forms to arise by segregation from crosses
between broader leaved forms. The lengua de vaca of the Cuban
growers is, therefore, probably a segregation product which could
easily be eliminated by the adoption of proper pure line methods of
breeding,

Auriculata forms appear to breed true whenever segregated. The
exception is type 8, which requires further investigation. It may be
a leaf type shnilar to auriculata but of different genetic constitution.
Auriculata of type 10 bred true in F,. The auriculata form 6a,
which segregated from type 6 bred true thereafter. Auricuuvta
crossed with macrophylla, H54, Hgg, H-^, and H-g, gave SESSiiiiFOLiA in
Fi and in F2 3 sessilifolia : 1 auriculata.

Sessilifolia forms have broad sessile leaves, the distinguishing
feature being merely their sessile mode of attachment. Of such selec-
tions from the original ¥n populations, four, with the exception of one
anomalous plant, bred true for sessilifolia. Each of the other three
populations segregated into sessilifolia and auriculata in about the
ratio of 3 sessilifolia : 1 auriculata. Two sessilifolia selections
were grown in 1917. One of these bred true to sessilifolia ; the other
gave 3 sessilifolia : 1 auriculata. The behavior of sessilifolia in
relation to stenophylla and latifolia is explained above.

On the basis of these results we may distinguish certain definite
allelomorphic pairs of factors as follows

Ss, stenophylla versus sessilifolia : SS being long petioled like
angustifolia, and ss broadly sessile like macrophylla. The heterozygote
may possibly approach an intermediate condition similar to latifolia.

LI, stenophylla versus latifolia: LL being long petioled like
angustifolia, and 11 short petioled like latifolia and with a distinct
but not broad wing. The contrast is really one of SSLL, stenophylla

1922]

Setchell-Goodspeed-Clausen : Nicotiana Tahacum

493

versus SSU, latifolia. Both ssLL and ssU are probably typical sessi-
LiFOLiA forms. Here again the heterozygote prolwibly shows an indis-
tinct type of intermediacy.

Aa, SESSiLiFOLiA versiis auriculata : AA having the broad clasp-
ing leaf base characteristic of niacropliylla, and aa the deeply con-
stricted leaf bases with flaring auricles characteristic of auriculata.
The contrast here is really one of ssAA, sessilifolia versus ssaa, auri-
culata, for these factors are evidently latent when in combination with
SS or Ss.

Fig. 2. Leaf base types of the angustifolia-macropliyUa series. Left to right:

STENOPHYLLA, LATIFOLIA, SESSILIFOLIA, and AURICULATA.

Some of the possible genotypes, their phenotypic expression, and
genetic behavior are included in table 7. Here only monohybrid segre-
gation is considered because it is doubtful, on account of the various
types of intermediacy shown by heterozygotes, M'hether it would be
possible to classify dihybrid and trihybrid populations satisfactorily.

TABLE 7

GENETIC BEHAVIOR OF VARIOUS LEAF TYPE GENOTYPES.

Genotype

Phenotype

Genetic

behavior

SST.T.AA

STENOPHYLLA

Breeds true

SsLLAA

STENOPHYLLA

3 STENOPHYLLA

: 1 SESSILIFOLIA

SSLIAA

STENOPHYLLA

3 STENOPHYLLA

: 1 LATIFOLIA

SSLLAa

STENOPHYLLA

Breeds true

SsLLaa

STENOPHYLLA

3 STENOPHYLLA

: 1 AURICULATA

SSllAA

LATIFOLIA

Breeds true

SsllAA

LATIFOLIA

3 LATIFOLIA

: 1 SESSILIFOLIA

SsUaa

LATIFOLIA

3 LATIFOLIA

: 1 AURICULATA

ssT.LAA

SESSILIFOLIA

Breeds true

ssllAA

SESSILIFOLIA

Breeds true

ssUAa

SESSILIFOLIA

3, SESSILIFOLIA

: I AURICULATA

ssllaa

AURICULATA

Breeds true

494 Universitij of California Puhlicatious in Botany ['^'ol. o

Although intermediaey of the heterozygote appears to be the normal
thing in these leaf shape contrasts, it is proper to state that this inter-
mediaey may depend to some extent upon the effect of modifying
factors rather than upon the heterozygous conditon of a pair of allelo-
morphs. Thus the intermediate conditon between stenophylla and
AURICULATA is met with in populations which do not contain auricu-
LATA segregation products. There are so many modifying factors in
this series of investigations that it is probably impossible for us to
declare definitely that in any one instance our observed segregation
was wholly the result of segregation of one pair of allelomorphs.
Further investigations are in progress, the purpose of which is to
isolate and evaluate, if possible, certain of these subsidiary factors.
For the present we can only state our certain knowledge of their
existence, and our belief as to their various effects.

IV. CALYCINA-YIRGINICA SERIES

The calycina-virginica series of hybrids and derivatives has received
much less attention than has been given to the previous series ; partly
because the differences between the parents are less striking and the
diversity of segregation products was not so great. Two hybridizations
were made : H^g which had calycina for the female and virginica for
the male parent and Hoq which was the reciprocal cross.

1. PAKENTS OF THE CALYCINA-VIRGINICA SERIES

Elsewhere Setchell has given descriptions of calycina and virginica
("Maryland"). Like angustifolia and macropJiylla, these two varie-
ties possess distinct sets of characters which set them apart from the
other Tabacum varieties that have been grown in the University of
California Botanical Garden.

Calycina is represented in our cultures by a variety, U. C. B. G.
110/05, which was originally received from the Botanical Gardens of
Cambridge University. The figure previously published (cf. Setchell,
loc. cit., pi. 4) well represents the general habit and type of the plant.
The particular features of the characteristic teratological flower of
calycina are better shown in plate 79, in which the leaf shape is also
illustrated in more characteristic fashion. For illustrations of some
of the variations which occur in the expression of the split hose-in-hose
flowers the reader is referred to Goodspeed and Clausen, 1917, plate 45.
The legends to the two figures of this plate should be reversed as indi-
cated in the references to the plate in the text of this earlier article.

19--] Sctchell-Goodspeed-Clausen: Nicotiana Tahacum 495

In stature, as previously mentioned, calycina belongs to the low
corymbose group of Tahacum forms. In height the central axis usually
varies between 60 and 75 cm. The laterals, however, which develop
later from the base, overtop the central axis and reach a height of
120 to 135 cm. Like macrophylla, central axis and laterals bear close
panicles of corymbose racemes, the laterals developing successively
from the base. The stems and branches are stouter than those of
angustifolia and the leaves do not droop so considerably. In these
respects calycina occupies an intermediate position between angusti-
folia and macrophylla.

The leaves of calycina, as plate 79 will show, are sessile, but they
are distinctly different from those of either angustifolia or macro-
phylla. Curiously enough, however, they do rather closely approxi-
mate certain of the derivatives of the an g ustifolia-macrophylla series,
as, for example, the lanceolata and loriifolia leaves of types 13 and
14 respectively, illustrated in plates 75 and 76. The leaves vary from
broadly to narrowly lanceolate, tapering toward both base and apex,
and usually with a long curved tip. The broader leaves are borne at
the base of the plant, those above them becoming successively narrower
in a continuous series until the linear leaves or straplike bracts of the
inflorescence are reached. There are no auricles at the base of the leaf.

The inflorescence is in the form of a very close panicle of racemes,
the secondary axes of which are mostly patent, and more or less re-
curved or bent back. The flower as a whole is of a very characteristic
split hose-in-hose type. The corolla is usually split on one side, some-
times twice split, and more or less curved. The characteristic split-
ting of the corolla is seen even in very young buds and often the pistil
protrudes from them. Typically the calyx has an elongated whitish
green tube, with 3 to 5 of its tips more or less petaloid. Sometimes
strips of petaloid tissue extend down the entire length of the calyx.
The pod is ovoid oblong in shape. As it enlarges it splits the calyx,
which then withers and drops off like the corolla, leaving a naked,
whitish green capsule. The flower color is red fading to bluish purple,
apparently the same as that of macrophylla.

Virginica is represented by U. C. B. G. 78/05, a strain received
from the United States Department of Agriculture under the identi-
fication number "205-20-7." It is figured by Setchell, plate 3, and
by Goodspeed and Clausen, plate 41, figure 1. The typical leaf and
flower characters are well represented in plate 80 herewith.

In stature virginica. belongs to the moderate pyramidal group of
Tahacum varioti(>s. It is coiispicnously taller tlian calycina, the ceii-

496 University of California Publications in Botany [Vol. 5

tral axis reaching a height of 150 to 175 em. While strong laterals
develop they do not originate at the base of the plant as in calycina.
and they do not overtop the central axis. These characteristics to-
gether with the broad spreading basal leaves give the plant its pyra-
midal or conical shape. The leaves are very close in general shape to
those of calycina, but they taper less abruptly to either end. The apex
is prolonged into a fairly long point curved to one side, and the base
is expanded into two broad, partially clasping auricles.

The inflorescence consists of a more ample panicle than that of
calycina. The flowers are light pink in color, identical in this respect
wdth those of angustifolia. The tube and infundibulum are narrow,
gradually increasing in diameter from below in a funnel-shaped
fashion. The corolla lobes are broad at the base, but have long,
slender incurved points. Capsule and calyx present no very charac-
teristic features, although the calyx is persistent in contrast to the
deciduous calyx of calycina.

It will be seen from the foregoing descriptions that there are a
number of distinct character contrasts between calycina and virginica,
a brief note of which may well be made at this point. In flower color,
red of calycina is contrasted with light pink of virginica, the same
contrast which existed in the angustif olia-macropliylla series. Simi-
larly the split hose-in-hose flower of calycina is contrasted with the
normal one of virginica; low stature with tall ; and a less decided
contrast in leaf shape exists, depending upon the presence or absence
of auricles at the base of the leaf.

2. P, OP THE CALYCINA-VIRGINICA SERIES

In the season of 1910, 55 plants of lOF^His and 58 of IOF^Hoq were
grown. In the season of 1911, 10 plants were grown of each of
llFjHis and llFiH^^.

Like other hybrids which have been grown, these populations were
uniform and equivalent throughout. It was thought that lOFjHoo
showed a more distinctly pronounced trace of calycina characters than
did lOF^H^g, but the populations of the same seed grown in !1911
showed no appreciable difference in this respect.

In general appearance the F^ plants resembled virginica more than
they did calycina. The plants were somewhat shorter than virginica,
running up to 135 em. In these plants it was noted that some of the
laterals overtopped the central axis as they do in calycina. The in-
florescence was in general of the ample type characteristic of calycina.

1922

SctchcU-Goodspccd-Clausen : Nicotiana Tahacum

497

The flower color was a deep pink intermediate between the two
parents. The flower shape was normal throughout save that on every
plant there was a small percentage of calyces with one or more pink
and somewhat broadened calyx tips, or with a streak of white on one
side. Sometimes these partially petaloid calyces were partly decid-
uous. In shape of flower the hybrid closely resembled virgimca except
that the corolla lobes were longer and more decidedly mucronate.
Calyx and capsule w^ere almost identical with those of virginica, the
calyx being typically persistent and accrescent. The leaves were some-
what broader proportionately than those of virginica, but they pos-
sessed the pronounced auricles of that parent. The usual gradation
in leaf shape on each plant from the broad basal leaves to the linear
bracts of the inflorescence was in evidence.

The main features of Hjg and H^o are well illustrated in the draw-
ings of lOF^HisPn shown in plate 81. The general habit and charac-
ters are illustrated in the photograph of lOFiHigP^^ which is repro-
duced in plate 83, figure 1.

3. Fo OF THE CALYCINA-VIRGINICA SERIES
In the season of 1911 four Fo families of the calycina-virginica
series were grown, viz., llFoHi^Pa,.,, llFjHigPin, llF-.H^oPv, ^^^
llF,H,,P,e.

As in the angustifoUa-macrophylla series, the segregation exhibited
in those four families, comprising 97 plants, was nothing short of be-
wildering, and in most cases an intergrading series of forms connected
one character expression with another. However, an attempt was
made to classify the plants into categories suggested by the four pairs
of character contrasts existing between the parents. The results of
this classification are given in table 8.

TABLE 8

NUMERICAL DATA FROM F2 POPULATIONS OF THE CALYCINA-VIRGINICA SERIES.

Corolla color

Corolla shape

stature

Leaf width

Garden Numbers

a
'a

a
'a

0

1

a
'Z

S

Is

e
0

a

0

S

3

■5
B

13

-a

0

83

c

11F2H,8P25
11F2H,8P49
IIF2H20P7
1 1 F2H20P26

6
7
5
5

11

14

9

10

6

4

11

8

6
12

7
10

8
4
8
6

9

9

10

7

17
19
11
12

2
3
6
5

5
3

8
6

17
14
21
15

7

11

4

8

Totals

23

44

29

35

26

35

59

16

22

67

30

498

University of California Publications in Botany [Vol. 5

In this cross, corolla color behaved in exactly the same manner as
it did in the angustifolia-macrophylla series. The same remarks as
to sharpness of segregation apply here as in that series. Red was
nearly always readily distinguishable, but pink and light pink formed
a more or less completely intergrading series. Taking the results in
this way, we obtain 23 red ; 73 pink and light pink, which is substan-
tially in accord with Mendelian expectations.

TABLE 9

F2 SEGREGATION IN CALYCINA-VIRGINICA SERIES.

Garden numbers

Pink
normal

Pink
hose-in-hose

Red
normal

Red
hose-in-hose

I6F2H18P25
I6F2H18P49
I6F2H20P7
I6F2H20P38

24
2.5
29
30

14

8
6

8

8
14
10
11

3
3
4
1

Totals

108

36

43

11

Expected

112

37

37

12

With respect to corolla form some difficulty was encountered be-
cause the expression of the hose-in-hose character in the segregants
did not seem to be so extreme as it was in the parent, and a large
number of the plants showed slight traces of it, but sometimes in a
more pronounced form than in the F^ hybrids. Accordingly the classi-
fication of corolla form in table 8 is not a wholly satisfactory one.

The classification for stature and leaf width is subject to similar
remarks as to its definiteness. Here there was also a more or less
completely intergrading series of forms and no accurate measurements
were taken. However, there is no doubt that there was segregation
with respect to these characters, and a range of forms was obtained
which completely bridged the gap between the parents. The behavior
of these characters is to be considered in the light of their segregation
in subsequent generations.

In 1916 four additional Fo populations of the calycina-virginica
series w^ere grown in order to reexamine populations for the segrega-
tion of normal versus hose-in-hose flowers, and red versus pink flower
color. The method of classifying the flowers was that used in studies
of 1916 populations previously mentioned. The results of these studies
are given in table 9.

1922] Setchell-Goodspeed-Clauseu: Nicotiana Tahacum 499

In the segregation the same grading as before of the pinks into
two intergrading classes in the proportion of approximately 2 inter-
mediate pink : 1 light pink was observed, but it was even more difficult
to draw a line between light pink and intermediate pink because of
the effect of the hose-in-hose conditon on flower color expression in
those plants which bore teratological flowers. In the matter of segre-
gation into normal and hose-in-hose flowers, some difficulty was ex-
perienced because some otherwise normal flowering plants bore some
flowers which showed a tendency for the calyx to become petaloid,
and others bore flowers which showed a very slight hose-in-hose ten-
dency. A correspondingly slight hose-in-hose tendency is also present
in Fj plants. These plants were classified as normal. Here again it
can be seen that the segregation ratios of 144 pink : 54 red and 151
normal : 47 hose-in-hose are in substantial agreement with Mendelian
expectation for contrasts in a single pair of allelomorphs in each case.
Moreover, the dihybrid ratio is substantially in agreement with that
expected for independent segregation of the members of these two pairs
of allelomorphs.

4. F3 AND SUBSEQUENT GENEEATIONS OF THE CALYCINA-VIRGINICA

SERIES

In 1912 twelve F3 families of Hjg and five of Ho,, were grown. They
will be grouped for consideration according to the characters which

TABLE 10

Fa BEHAVIOR OF RED SEGREGANTS. »

Garden numbers

Red

12F3Hl8P25Pll

25

12F3H18P25P19

25

12F3H,8P49P,2

25

I2F3H18P49P24

25

12F3H2C)P26P25

25

the F, parent exhibited. In table 10 the data with respect to the be-
havior of F3 populations from red flowering F2 plants are collected.
Five such populations gave nothing but red flowering plants, indicating
clearly that red segregants breed true. In table 11 the data from pink
flowering plants are similarly collected. The reader will not fail to
notice that some pink flowering selections were not heterozygous for

500

University of California Puhlications in Botany [Vol.5

red. This bears out our statements as to the difficulty of classifying
pink and liglit pink. In the seven populations which produced red
flowering plants 38 plants had red flowers and 134 pink or pinkish
flowers; again in substantial agreement with the behavior of flower
color in the angustifolia-macrophyUa series. The behavior of segre-
gants classified as light pink is shown in table 12. Of the four popu-
lations from which data w^ere gathered only one bred true to light

TABLE 11

Fs BEH.A.VIOR OF PINK SEGREGANTS.

Garden numbers

Red

Pink

Light pink

I2F3H18P25P7

5

16

4

I2F3H18P20P21

21

4

12F3H„P25P2.5

6

19

I2F3H1SP49P9

4

20

I2F3H18P49P1O

11

13

I2F3H18P49P25

4

16

5

I2F3H20P26P6

4

20

I2F3H20P26P1I

4

21

Totals for segregat-

ing populations

38

134

TABLE 12

Fa BEHAVIOR OF LIGHT PINK SEGREGANTS.

Garden numbers

Red

Pink

Light pink

12F3H,8P25P2»
12F3H,8P49P22
I2F3H20P7P9
I2F3H20P26P5

8

6

12
15
25

23
5
4

pink, one of the others bred true for pink, possibly a slightly darker
shade than true light pink, and two segregated for all three colors;
they must therefore have been pink heterozygotes.

In F4 two populations each of Hj^ and of H.„ were grown. Popu-
lation ISF^Hj^Po-.P^Pn from an F^ population breeding true for red
gave in F4 100 plants all red flowering. Population ISF^Hj.^Po.PuP^
from the same F., population gave 97 plants all red flowering like
calycina. Population 13F4H.^nP2pP-Ps, w^hich bred true for pink in
F3, gave in F4 96 plants, all pink flowering. These three populations
were grown to F. without showing further evident segregation. The

1922]

Setchell-Goodspeed-Clausen: Nicotiana Tabacum

501

pink of the pink flowering derivative was at first considered somewhat
darker in shade than the light pink of virginica, but this line also
showed the hose-in-hose flower character, which sometimes makes it
difficult to determine flower color accurately. In later generations of
this line its color was noted as equivalent to the light pink of virginica.

TABLE 13

Fa BEHAVIOR OF HOSE-IN-HOSE SEGREGANTS.

Garden numbers

Hose-in-hose

12F3Hi8P25P21

25

*12F3Hl8P25P24

23

I2F3H18P49P9

24

*12F3H,8P49P.2

25

12F3H,8P49P24

25

I2F3H20P26P6

24

I2F3H20P26PU

25

* Apparently not so extreme as calycina.

TABLE 14
Fs BEHAVIOR OF NORMAL SEGREGANTS.

Garden numbers

Hose-in-hose

Partial

Normal

12F3H,8P25P7
I2F3H18P25P..
r2F3Hl8P26Pl9
I2F3H18P25P25
*12F3H,8P49PlO
I2F3H18P49P22
I2F3H18P49P25
I2F3H20P7P9
I2F3H20P26P5
I2F3H20P26P25

9
4
5
3

4
5

7
10

4
20

4

21

20

3

16

17

22
20
25

15
15

Totals

47

153

Taking up corolla form next, we may deal with the different popu-
lations in the same manner as was done in the case of flower color.
F3 populations from F^ hose-in-hose segregants are recorded in table
13. Seven populations were grown, all of which bred true to the
hose-in-hose character, although curiously enough two ])opulations,
12F;jn,sP2-P._,^ "J'<1 12F,.,HisP49Pio did not appear to exliibit so ex-
treme character expressions as calycina.

Only one partially hose-in-hose plant was grown in F.,. For the
sake of economy of space it is included in table 14, where it is marked

502

University of California Puhlications in Botany [Vol. 5

with an asterisk. Strangely enough, it was one of the two in the table
which did not throw hose-in-hose flowers. The other normal selections
all threw hose-in-hose flowering plants in the proportion of about 3
normal to 1 hose-in-hose.

In subsequent generations only the three families which were pre-
viously considered under flower color were grown. Normal flower
selections from 12¥ Jl^^ ^r^ ^^ gave two populations, one of 100 and one
of 97 plants. The plants all bore normal flowers. In ISF^HisPasPuPi.,
it was noted that some flowers were split, but there was not even a
suggestion of approach to the true hose-in-hose condition. The other
population ISF^HooPoePsPs was from a hose-in-hose selection in the

TABLE 15

Fs BEHAVIOR OF TALL SEGREGANTS.

Garden numbers

Tall

Short

I2F3H18P25P7

12F3H,8P25P24
I2F3H20P7P9

19
1

6

6
24
19

TABLE 16

F3 BEHAVIOR OF MEDIUM SEGREGANTS.

Garden numbers

Tall

Short

I2F3H18P49P12
I2F3H13P49P22

1

23
24

corresponding F3 population. Ninety-four plants were grown to ma-
turity, all of which were strictly hose-in-hose. In subsequent gener-
ations these three populations bred true to type save for the sporadic
appearance of hose-in-hose flowers on plants which otherwise bore
nothing but normal flowers. This, however, is not an unusual phe-
nomenon even in pure line cultures of normal flowering varieties of
Tdbacum, and it is extremely doubtful whether the hybrid derivation
of these plants had anything to do with the production of occasional
split flowers.

As respects height of plants the F3 data are given in tables 15, 16,
and 17, which give the behavior of tall, medium, and short F2 segre-
gants respectively. The behavior here is not very convincing. Prob-
ably the difficulty in judging the character and the influence of
variation in soil condition had something to do with it.

1922]

Setchell-Goodspeed-Clausen: Nicotiana Tdbacum

503

In the subsequent generations the behavior was, however, more
definite. ISF^HigPosPuPg was grown from a tall F3 plant. No defi-
nite notes were taken as to height, but the population was noted as
varying. In Fg and subsequent generations the line bred true to tall.
ISF^HjsPo-iPiiPia was grown from a short Fg plant. The ninety-seven
plants were all of low stature and in subsequent generations the line
bred true for low stature. I3F4H20P26P5P8 was grown from a tall
F3 plant. Ninety-four plants, although variable in height, all be-
longed in the tall class and in subsequent generations the line bred
true for tall stature. Nothing but a careful biometrical study under

TABLE 17

Fs BEHAVIOR OF SHORT SEGREGANTS.

Garden numbers

Tall

Short

I2F3H18P26P11

10

15

I2F3H18P25P19

16

9

I2F3H18P25P21

25

I2F3H18P25P25

5

20

I2F3H18P49P9

1

24

I2F3H1SP49P10

24

I2F3H18P49P24

7

18

I2F3H18P49P25

9

16

I2F3H20P26P6

8

16

I2F3H2UP26P6

5

19

I2F3H20P26P11

25

Totals

68

129

well controlled cultural conditions, however, would yield results capa-
ble of strict Mendelian analysis. However, it can be said that none
of the results here recorded preclude the possibility of such an analysis,
although it evidently can not be done in any simple qualitative manner.

As respects leaf width it was found impossible to make even such
a rough classification as was attempted in the case of stature. Here
again nothing short of a strict biometrical analysis would furnish the
basis for a Mendelian formulation.

As has been indicated above, three separate lines of this series
were carried out to the seventh hybrid generation. Of these, one was
a recombination of cliaracters from both parents exhibiting the tall
stature and normal flower of virginica with tlie red flower color of
calycina. One exhibited a stature intermediate between that of caly-
cina and virginica in combination witli llie normal flower shape of

504 UniversUij of California Puhlicatians in Bodnty L^oi-. 5

virginica and tlie red flower color of cahjcina. The third had the tall
stature of virginica and red flower color, in association with the hose-
in-hose flower form of colycina. These tliree lines apparently bred
true for all their characters,

5. DISCUSSION OF RESULTS OF THE CALYCINA-VIRGINICA SERIES

No extended discussion of results is indicated in connection with
the calycina-virginica series of hybrids because particular attention
was given to so few characters. Just as in the case of angusUfoUa-
macrophylla, so in this series of hybrids the character differences
proved to tiepend upon complex genotypic differences. Apparently
the flower color contrast in these two varieties was the same as that in
the angustifolia-macropliylla series, and the same relations with respect
to dominance and segregation were found to hold for it. Without
doubt we are dealing here with the Rr ])air of allelomorphs as in the
previous instance. The demonstration of tlie simple factor relations
in the inheritance of th(> split hose-in-hose form of flower adds to our
series another pair of allelomorphs which we may call Cc (calycine).
In this case the dominance of normal over split hose-in-hose appears
to be nearly, if not quite, complete. The sporadic appearance of split
hose-in-hose flowers on otherwise normal plants does not even seem to
be clearly associated with the heterozygous genotype, Cc. The data
for height are not of sufficient accuracy or extent to warrant an at-
tempt at Mendelian formulation. It was again found possible vei-y
easily to shuffle and recombine the characters occurring in the parent
varieties and to esta])lish recombination derivatives in pure lines.

V. ALBA-MACROPHYLLA SERIES

1. PARENTS OF THE ALBA-MACROPHYLLA SERIES

Alba, which is one of the parents of the alha-macropliylla series,
is the "White" tobacco, U. C. B. G. 30/06, described by Setchell. It
is one of the taller forms of Tahacuni, ranging in height from 165 to
220 em. Typically aJha is unbranched below; above, it has flowering
branches corymbosely arranged in succession from above downward.
The leaves are sessile, more, ample, more rugose, and more velvety than
those of macrophyUa. They are narrowed suddenly above the ex-
panded, somewhat aurieled and partially clasping base. The leaves

1922] Setchcll-Goodspecd-Clausot : Nicotmna Tabacum 505

resemble those of macrophylla in shape but differ from them particu-
larly in the basal portion. The corollas are white with a yellowish
tinge ; but in shape, size, and general proportions they are very similar
to those of macrophylla. Line drawings of typical features of alha
are reproduced in plate 82. The reproductions of photographs of the
leaf of alba and of the Fj hybrid of the alha-macrophylla series are
shown in plate 84.

Macrophylla, U. C. B. G. 22/07, has been described above.

In these two varieties there are definite character contrasts in color
of flowers, macrophylla being red and alha white ; and in stature,
macrophylla being low of stature and alba distinctly taller. Other
contrasts also exist, although they are not so definite, in the style of
branching and in the shape and texture of the leaves. Like those
which have been considered above, this is a hybrid series in which
the contrasts between the parent forms are of a distinctly complex
character.

2. F, OF THE ALBA-MACROPHYLLA SERIES

The crosses between alba and macropyhlla were made in July, 1909.
The cross was successful in both directions, and seed was secured from
alba^ X macrophylla^, which was given the number Hoo, and from the
reciprocal which was given the number H24.

When mature the F^ plants were tall, 100 to 200 cm., averaging 130
to 160 cm. Habit and leaf shape were in general those of alba. The
corolla was deep pink of about the same shade as that of the F^ of
the angustifolia-macrophylla series. The variation in height in these
populations possibly indicates a lack of constancy in the alba parent
in this respect. In plate 83, figure 2, is shown an F^ plant of lOFiH.^.

3. F, OF THE ALBA-MACROPHYLLA SERIES

In 1911 four F. populations were grown, viz., 25 plants each of
llF,H,3Pi;„ llF,H,3P,i, and llF.IL.Pe, and 23 plants of 11F,H,,P.,,.
The four populations, although small, proved to be equivalent in every
respect. The type of segregation was very complex. That of differ-
ences in types of leaves, especially, presented such a series of inter-
gradations as to defy any definite classification. Likewise in height,
there was a continuous series of forms from the tallest to the shortest,
A rough classification was, however, made for purposes of reference
into tall, medium, and short. An excellent illustration of the segre-
gation for this character is shown in plate 85, figure 1, which shows

506

University of California Puhlicaiions in Botany [Vol. 5

two adjacent plants of IIF0H24P34, one tall and of the general habit
of alha, and the other short and of the general habit of macrophylla.
The classification for height is given in table 18. Obviously no satis-
factory Mendelian formulation can be deduced from these data.

As regards flower color, however, the classification is more definite.
Four more or less distinct shades were distinguishable, viz., red, pink,
light pink, and white. The pink and light pink shades merged into
each other, consequently they have not been separately recorded in
table 18. Bearing in mind the previous behavior of red and pink, as
shown in the angustifolia-macrophylla and calycina-virginica series,

TABLE 18

¥2 SEGREGATION IN THE ALBA-MACROPHYLLA SERIES.

Stature

Flower Color

Garden numbers

tall

medium

short

red

pink

white

IIF2H23P13
IIF2H23P31
IIF2H24P6
IIF2H24P34

11

13

7
6

6

6

10

8

8
6
8
9

3

4
3
6

14
12
15
13

8
9

7
3

Totals

37

39

31

16

54

27

it would appear that we are here dealing with dihybrid populations
in which a pair of allelomorphs for color versus white is concerned in
addition to that pair upon which the contrast of pink versus red was
found to depend. The pair of allelomorphs for the pink versus red
contrast has been represented by R and r, respectively. If we repre-
sent the contrast of color versus white by W and w, respectively, the
two parents in this series would possess the following genotypes :

Alia = RRww

Macrophylla = rrWW

The light pinks of the previous series would then be RRWW, and the
factor R might be regarded as a dominant diluter. According to this
formulation, F^ of the alha-macrophylla series would be RrWw, pink,
and Fo should segregate in the ratio 3 red : 9 pink : 4 white. The
expected result in the classification of ninety-seven plants in whole
numbers is 18 red : 55 pink : 24 white. Agreement is thus fairly close.
A check on the results above noted for the 1911 sowings of the Fo
population was made by growing in 1916, five additional Fo popula-

1922]

Setchell-Goodspeed-Clausen : Nicotiana Tahacum

507

tions of the same series, viz., I6F2H03P5 ; I6F2H23P30 ; I6F2H03P34 ;
I6F0H04P28 ; and I6F2H24P33. The segregation in the resulting popu-
lations is recorded in table 19.

The method of studying these flowers was the more accurate one
previously described in connection with later generations of the
(Uigustifolia-macrophyUa series. In the classification of flowers it was
noted that reds and whites were sharply distinguishable from pinks.
The pinks were of many different shades ; some very light, others rela-
tively dark, corresponding to the range obtained in the angustifoUa-
macrophylla series. However, in these populations the range of vari-

TABLE 19

F2 SEGREGATION IN 1916 SOWINGS OF ALBA-MACROPHYLLA SERIES.

Garden numbers

Red

Pink

White

Totals

I6F2H23P5

11

18

11

40

I6F2H23P32

12

19

11

42

I6F2H23P34

8

24

9

41

I6F2H24P28

5

34

11

50

I6F2H24P33

7

29

14

50

Observed

43

124

5G

223

Expected

42

125

56

223

ation of pink appeared to be greater and the intergradations more
gradual than in that series. In the whites there was also evidence of
differentiation into classes depending upon the amount of yellow or
creaminess in the flowers. Some of the whites appeared to belong to
a clear white albino class, but most of them had a distinctly creamy
tinge. The observed segregation in these populations was in almost
exact agreement with the formulation advanced above.

4. F3 AND SUBSEQUENT GENERATIONS OF THE ALBA-MACROPHYLLA

SERIES

In table 20 we have summarized the behavior of the F3 populations
as respects color of flowers and height of plant. Of the five red F2
plants from which F3 populations were grown, three proved to be
homozygous for red and one proved to be a heterozygote of the genetic
constitution rrWw. Of this latter selection two sowings were made,
one in 1912 and another in 1913. The combined results from these
two sowings, .35 red: 14 white, are in fair agreement with Mendelian

508

University of California Publications in Botany [Vol.5

expectation. The other population exhibited an anomalous type of
segregation, and gave 2 red : 23 white. It is unfortunate that this
line was not investigated further, but the results probably are due to
an experimental error.

TABLE 20

Fs SOWINGS OF THE ALBA-MACROPHYLLA SERIES.

F2 Phenotypes

Garden
Xumbers

Flower Color

Stature

Flower
Color

Stature

Red

pink

white

short

tall (or
medium)

Tall (or M)

I2F3H23P13P3

19

6

25

Short

I2F3H23P31P1

22

—

22

Red

Sh't(orM)

I2F3H23P3.P17

25

4

21

Tall

I2F3H23P31P22

24

4

20

Tall

I2F3H23P31P25

2

23

1

24

Tall

I6F3H23P13P3

16

8

Tall

I2F3H23P13P13

2

14

6

8 .

10

Medium

I2F3H23P13P25

6

12

/

22

Tall

I2F3H23P3.P7

6

14

5

25

Tall

I2F3H23P31P19

10

9

4

23

Pink

Medium

I2F3H23P31P20

6

12

0

4

19

Tall

I2F3H24P6P0

3

22

25

Short

I2F3H24P34P18

5

13

7

24

1

Tall

I2F3H24P34P20

20

0

25

Tall

I6F3H24P34P20

13

4

TaU

I2F3H23P13P14

25

25

Tall

12F3H23Pl3Pl5

25

25

Short

I2F3H23P13P24

25

25

TMiite

Tall

I2F3H24P6P2 •

24

24

Short

I2F3H24P6P3

25

4

21

Tall

I2F3H24P6P4

23

23

Short

I2F3H24P34P23

1

23

25

Short

I3F3H23P13P24

10

10

Short

I3F3H24P34P23

10

10

Eight families of Fo plants were grown from pink F^'s. Of these
F, plants six proved to belong to the RrWw genotype. The totals
from these six populations, viz., 35 red : 74 pink : 34 white, are in fair
agreement with the dihybrid ratio 3 red : 9 pink : 4 white. One of
the other populations gave 3 red : 22 pink. It was probably the result
of sowing seed from an Fo plant of the genetic constitution RrWW
which should give 3 pink : 1 red. The observed segregation ratio is
not good, but the numbers are small. Two sowings of F3H24P.-,4P2o
gave totals of 33 pink : 9 white. The F. plants in this case must have
been of the genetic constitution RRWw; in which case expectation
would be 3 pink : 1 white. No selection was observed to breed true

1922] Setchell-Goodspeed-Clausen: Nicotmna Tahacum 509

for pink in F,. This, however, is not inexplicable, for only one in
nine among the F, pinks should belong to the RRWW genotype.

Sowings were made from seven white F^ plants. Among 190 plants
so produced there was one pink flowering individual. It surely rep-
resents some kind of experimental error. We may say, therefore, that
for flower color the formulation advanced to account for the Fo segre-
gation ratio, also accounts for the behavior observed in the various F3
populations.

We have reported the data on height in table 20, largely in order
to show that this character, although obviously dependent on factor
differences, is so complex as not to permit of a simple qualitative
treatment. Thirteen F,, sowings from tall F^ plants gave ten popu-
lations showing only tall plants. Two of the remaining populations
showed segregation into 31 tall (and medium) : 13 short. One popu-
lation consisted entirely of short plants. The classification of the Fg
parent of this plant as "tall" was noted as doubtful at the time, the
note ''or medium" being appended. Two populations were grown
from Fo plants of medium height. One of these populations was uni-
formly of low stature; the other showed segregation into 19 tall (and
medium) : 4 short. Six populations were grown from F^ parents,
four of which apparently bred true for low stature, the other two
showed segregation into tall (and medium) or short in the ratio 42 : 8.
It is interesting to note that at the time of classification the parents
of these two later populations were classified as short (or medium),
indicating a doubt as to proper classification. More definite data will
be necessary before a satisfactory formulation of these height differ-
ences can be made, but certain of our results seem to indicate that
there is one allelomorphic pair which has a rather marked effect on
stature, and that there are other subsidiary pairs of factors which
have less marked effects.

Only one line in this alba-macrophylla series was carried out to
subsequent generations to demonstrate the possibility of fixing char-
acter complexes from a hybrid. It was a low stature white flowering
line. In F4, 100 plants of 13F,Ho4P34P23P2 bred true to low stature
and white flower color. The population was uniform, the plants ex-
hibited the general habit of macrophylla rather than that of alba; and
the leaves were the same shape as those of macrophylla, but they were
slightly rugose, although not so much so as those of alha. In F,.„ two
populations of 25 plants each were grown, viz., 14F-H24P34P2.!P2P4t
and 14F-H.4P34P2..,P.2P83. No differences were detectable between these
two populations, and the characters exhibited were those we have noted

510 University of California Publications in Botany [Vol.5

for F4. In Fe 10 plants each of 15F^B.._^^,^^F^,F^F^,F, and ISF^H.,
P3,P23P2P83Pi2 and in F, 10 plants each of leF.Hs.Pa.P.gP^Ps^PioPs
and I6F-H24P34P23P2P47P5P8 were grown. In both cases the parallel
populations were equivalent and the characters exhibited and described
in F4 remained constant. Plate 85, figure 2, is a good illustration of
the type of this family as fixed. A photograph of the original F,
plant, from which tlie family descended, is reproduced in plate 85,
figure 1. It will be noted that the derivative represents a fixation of
the characters of the original F2 selection, and that no important seg-
regation occurred in it either in F3 or in subsequent generations.

5. DISCUSSIOX OF EESULTS OF THE ALBA-MACROPHYLLA SERIES

Here again, as in the calycina-virginica series, no extended discus-
sion of results is necessary. Obviously the differences separating the
two varieties are of a complex nature genetically as in the two previous
cases. The series demonstrates the existence of another pair of allelo-
morphs for flower color in this group of Tahacum varieties, viz., Ww,
and the part played by it in the production of both red and light pink
flower color has been determined. The height contrast again proves
to be too complex for qualitative Mendelian formulation. As in the
previous cases, the establishment of stable recombination derivatives
proved to be a simple task.

VI. GENERAL CONCLUSIONS

We shall limit the discussion of these results to three main topics
upon which these investigations seem to have thrown some light: (1)
the origin and interrelationships of varieties of Tahacum; (2) the
methodology of Mendelian analysis in Tahacum; and (3) Mendelian
heredity in Tahacum.

1. ORIGIN AXD INTERRELATIONSHIPS OF VARIETIES OF TABACUM

As a result of extensive studies of a considerable assemblage of
Tahacum varieties. Comes (1905) came to the conclusion that the
species Tahacum could be subdivided into six fundamental varieties :

a. var. fructicosa Hook.

h. var. lancifolia (W.) Comes.

c. var. virginica (Agdh.) Comes.

d. var. hrasiliensis Comes.

e. var. havanensis (Lag.) Comes.
/. var. macrophylla Shrank.

1922] Setchell-Goodspeed-Clausen: Nicotiana Tahacum 511

Inasmuch as practically every Tahacum variety shows combinations
of characters of two or more of these fundamental varieties, Comes
assumed them to have been derived mostly through hybridization be-
tween the fundamental varieties, and he proceeded from purely morph-
ological studies to classify the different commercial varieties on the
basis of their supposed hybrid derivation. Anastasia (1906), who
has criticized this scheme of Comes very severely, reduced the number
of fundamental varieties to four, striking out fructicosa and lancifolia
from Comes' list, and substituting purpurea for macrophylla. Al-
though disagreeing as to the fundamental varieties, Comes and Ana-
stasia seem to agree in referring existing varieties to derivation, mostly
through hybridization, from a relatively small number of fundamental
varieties.

The Howards (1912) object to the mode of classification of Comes
and Anastasia, and point out as a result of their studies of types of
Indian tobaccos that no attempt at classification based on derivation
can be considered seriously unless supported by actual experimental
studies. In her later paper in particular Miss Howard (1913) shows
that segregation products may be obtained through hybridization
which transcend the limits set by the parents. The Howards propose
a scheme of classification based primarily upon leaf and habit char-
acters, and they adopted this morphological system purely as a pro-
visional means for facilitating identification and reference among the
numerous forms of Indian tobaccos.

Our results agree with those stated by the Howards, and we raise
the same objection to schemes of classification such as Comes and
Anastasia have advocated. Any scheme of classification based on
morphological considerations alone cannot well meet with the approval
of geneticists, for it does not take into account genotypic differences
which exist among forms of similar morphological appearance. Thus
it is possible, as Miss Howard points out, by crossing different mem-
bers of a given group to obtain segregation products which belong in
an entirely different morphological group in the scheme of classifica-
tion. In particular she points out that "petiolate" forms have been
produced as segregation products from two "sessile" parents, yet
"petiolate" and "sessile" have been used as primary indexes for
classification of tobaccos into groups.

The difficulty from the genetic point of view with any classification
of Tahacum varieties is the same as that which is met with in tlie
classification of varieties of other polymorphic species. Taking the
species as a whole and viewing the entire assemblage of its varieties,

512 Umversity of California Publications in Botany [Vol.5

there is evidently in Tahacuni, to those who accept current interpre-
tations of heredity, a series of allelomorphic contrasts, the number of
which cannot even be guessed, but which need not perhaps be more nu-
merous or striking than those which have been discovered in Drosophila.
But whereas in Drosophila the factors have been kept in stocks in-
volving for the most part single factor differences from a common wild
type, in Tahacum, and in other cultivated crop plants such as barley,
maize, oats, rice, wheat, etc., these factor differences have been shuffled
about through long periods of cultivation until existing varieties are
no longer related clearly to a common form or to each other. In some
instances in such groups certain factor differences have a more strik-
ing visible effect than in others. In such instances we have an obvious
mode of classification based not upon number of factor differences so
much as upon the striking character differences which arise from
certain factor contrasts. Thus in barley we have the classification of
varieties advocated by Harlan (1918) based upon recognition of a
number of major morphological distinctions, some of which at least
have been clearly analyzed in Mendelian fashion ; and the same prin-
ciple has been recognized in the classification of varieties of maize,
where it has led to the absurdity of erection of a heterozygous form,
podded maize (vide Collins), as one of the primary group distinctions.
In some instances, doubtless, the sorting of factors may give rise to
certain recombinations which are more favorable to life processes than
others, as Muller has pointed out in another connection, and such
genotypes may act as centers around which groups of varieties may
be built up, thus giving rise to more or less obvious grouping of varie-
ties. The attempt to base a system of classification upon reference to
certain fundamental types does not, however, promise much simpli-
fication of the difficulty ; moreover, such an attempt rests upon the
rather naive assumption that it is unnecessary to account for the
fundamental types.

From a genetic standpoint, therefore, it w^ould appear that in
attacking the problem of classification and interrelations of varieties
in a polymorphic species the major premise should be a recognition
of the fundamental equivalence of every homozj^gous genotype. Start-
ing from this premise a system of dichotomy beginning with those
factor contrasts which produce the most striking, visible effects and
proceeding to those of lesser effect might be set in operation. Such a
system obviously would in certain cases separate some similar varie-
ties into separate groups, and would lead to recognition of group
differences without obvious morphological distinctions, but the system

1922] Setchell-Goodspeed-Clausen: NicoUana Tahacum 513

would have a real significance, and the relationships indicated by it
would be fundamental ones. It is, however, necessary to have a much
more extensive knowledge of Mendelian heredity in Tahacum than we
have at present before such a system can be formulated.

2. METHODOLOGY OF MENDELIAN ANALYSIS IN TABACUM

From the Mendelian side there are certain obvious facts associated
with Tahacum as a species. In the first place, as we have stated before,
the species is highly polymorphic. A large and striking assemblage
of varieties exists, the most extreme of which hybridize readily and
give fully fertile hybrids and full fertility in their derivatives. A
few teratological forms are known in which fertility is somewhat re-
duced, but the above generalization does not far overstate the facts.
The species is, moreover, so highly polymorphic that with respect to
any given character a representative collection of varieties may be
arranged in a series connecting the most extreme expressions of that
character by imperceptible steps. Thus in flower color we have repre-
sented in the collection of varieties of the University of California
Botanical Garden dark red, red, light pink, pinkish, and white, and
descriptions occur in the literature which indicate the existence of
further shades of red connecting these. Now flower color is a rather
definite character, comparatively speaking, for it appears to be little
affected by ordinary environmental conditions. In many polymorphic
forms, such for example as maize, there are a large number of such
definite characters, and as a consequence studies of inheritance in
these forms have resulted in definite Mendelian analysis of many char-
acter differences. But in Tahacum unfortunately most of the char-
acters involve quantitative elements, and these with few exceptions
depend so largely for their particular expression upon environmental
conditions that it becomes a difficult matter in a segregating population
to distinguish between those differences which are inherent and refer-
able to the genotype and those which have come about through the
action of extrinsic forces. And yet our assemblage of tobacco varie-
ties indicates clearly that there are genotypes which give rise to all
possible expressions in these characters. Here we find the reason for
the present backward state of knowledge of inheritance in Tahacum,
for while there have been numerous investigations which indicate
clearly that the Mendelian mode of transmission may be followed in
all these character differences, yet there are very few investigations
which have resulted in the precise type of factor analysis characteristic

514 University of California Publications in Botany [Vol. 5

of investigations with other forms, specific mention of which is un-
necessary.

The general features of inheritance in Tahacum varietal crosses
are plain enough. The results of our investigations in this connection
agree throughout with the conclusions which Miss Howard drew from
her studies. When we are dealing with complex differences, the F^
is commonly intermediate in character expression between the two
parents. Not only is this true as respects the F^ plant as a whole but
it is also true for individual characters. The F, commonly consists
of a varied assemblage of forms covering the range between the two
parents, or even not uncommonly presenting products not included
in the range between the two parents. So many and of such variety
are the forms obtained that accurate classification is entirely out of
the question. But in Fg and in subsequent generations segregation,
even for characters commonly regarded as quantitative, sometimes
occurs in distinct discontinuous classes in marked contrast to the inter-
grading series of forms obtained in F,. This is shown particularly
well in our analysis of leaf base factors, for in this case we have been
able to adopt a qualitative mode of attack on one of the features w^hich
contributes to leaf shape. If such an analysis proves successful in
one instance, there seems to be little reason why it should not be ex-
tended to others. There is, therefore, additional evidence in this suc-
cessful application of the mode of qualitative analysis to quantitative
characters in support of the oft repeated contentions of East (1913),
Hayes (1912), Hayes, East, and Beinhart (1913), Miss Howard
(1913), and others that fundamentally the same mode of inheritance
holds for quantitative characters in tobacco as for qualitative ones.
The distinction between the two classes of characters is purely an
artificial one erected for the purpose of convenience in formal treat-
ment, and at most depending merely upon an increase in complexity
of the factor relations involved and on the greater fluctuation of the
characters in response to environmental differences.

The question remains to be discussed whether semiquantitative
characters admit of a qualitative mode of analysis, and if so, how?
Miss Howard (1913) as a result of her extensive studies of inheritance
in Indian tobaccos concludes that the easiest way to determine the
principles underlying inheritance in these forms is to establish as
many extracted homozygous intermediate forms as possible. The estab-
lishment of such forms in themselves, however, is only a step in the
Mendelian anah'sis of the differences. Such forms are, as might have
been expected on theoretical grounds alone, less different from one

1922] Setchell-Gaodspeed-Clausen: Nicotiana Tahacum 515

another and from the parents than the original parents are from each
other. Moreover, our experiments show that as a result of simplifi-
cation of the factor differences the derivative strains crossed with each
other or with the parents give Fo progenies which often exhibit clear-
cut segregation in characters which showed intergrading series in the
original F, population. In other populations, however, from crosses
between derivatives, the populations still exhibit perplexing com-
plexities which make classification difficult and uncertain. In such
cases we could again resort to the method of establishing intermediate
derivatives from them ; but if the number of factors concerned in a
given character is even moderately large, as is certainly the case with
many of these quantitative characters, the number of genotypically
different derivatives which may be secured becomes so great as to make
the method impracticable.

Our experience indicates that the successful factor analysis of these
quantitative character differences depends not only upon getting what
Castle (1919) has called the residual heredity equivalent throughout
the population, but also in establishing the proper kind of residuum
which will most emphasize the character differences associated with
the pair of factors or pairs of factors under investigation. The prob-
lem may be illustrated crudely by considering the pair of flower color
factors Rr. If the residuum should contain PP, the effect of which
is described below, segregation would give PPRR, PPRr, and PPrr.
In character expressions these three different genotypes would doubt-
less all be of various shades of dark red, difficult or impossible of ac-
curate separation. With such a residuum, therefore, it would be im-
possible to investigate satisfactorily inheritance in the factor pair Rr.
But if we should substitute pp for PP in the residuum, the segregation
products would be ppRR and ppRr, which would be pink, and pprr,
which would be red. Here the segregation would be sharp and dis-
tinct, and there would be practically no difficulty in classification.
How complex such interrelations can be has been shown most clearly
by Bridges (1919) in his account of specific modifiers of eosin in
DrosopJiila. As Bridges shows it would easily be possible to obtain
populations of Drosophila defying classification, but by keeping the
factors separate and studying their character effects with known
residual genotypes, it has been possible to determine and locate the
factors involved. Doubtless much of the extraordinary success of
Mendelian analysis in Drosophila has been due to the fact that factor
differences arose under conditions such that the residual genotype
gave no difficulty ; whereas in crop plants, the geneticist starts with

516 University of California Publications in Botany [A'^ol. 5

long established diverse types, evidently related to one another in
fundamentally the same manner as are the various Drosophila mutants,
but more complexly, and from these complex assemblages he must
unravel the tangled skein of heredity.

There are, however, other and perhaps quicker ways of establishing
a uniform and favorable residual heredity than that of securing and
testing homozygous extractives, and these may be employed in certain
special cases. Thus, if it be desired to study the relationship of the
pair of factors Ss for the petioled versus sessile condition, it should
be possible to proceed by crossing back the F^ of angustifolia x macro-
pJiylla, for example, to macrophylla, selecting the petioled forms from
the back cross for again crossing back to macrophylla, and continuing
the process until clear-cut segregation was obtained. Such a mode
of procedure should establish a residual genotype equivalent to that
of macrophylla itself, and should thereby enable the student event-
ually to study the effect of substituting SS for ss in the macrophylla
genotype. In tobaccos technical details make it particularly easy to
adopt such a procedure, but it is useless to speculate further upon its
results until it shall have been attempted.

3. MENDELIAN HEREDITY IN TABACUM

From the standpoint of factor analysis, we have demonstrated
clearly in the foregoing pages, the existence of a number of distinct
pairs of factors. Two of these affect flower color, one flower form,
and three affect the character of the leaf base. The particular effects
of the opposing members of these pairs of factors and the interrela-
tions which they exhibit so far as these have been investigated have
been set forth in the discussions which follow the description of each
of the three series of hybrids. Although evidently many other factor
differences were concerned in these studies, and remain for further
investigation, the results which we have described make a beginning
tow^ard a more accurate knowledge of Mendelian heredity in Tabacum.

So far as our results furnish any data on the question, the six
pairs of factors isolated exhibit no linkage relations. The data here
are far from complete, but the results are in accordance w'ith theory.
According to White (1912), there are twenty-four pairs of chromo-
somes in Nicotiana. Assuming for the sake of discussion that each
of these pairs of chromosomes bears a set of factors comparable in
numbers to any other pair, then the chances of finding linkage when
only six pairs of factors are studied is very slight. This large number

i^--l Setckell-Gaodspeed-Clausen: Nicotiana Tabacum 517

of pairs of chromosomes may account for the ease with which recom-
bination pure lines were established. Even with a large number of
factor differences, such as evidently distinguish these Tabacum varie-'
ties, the chances are slight with so many pairs of chromosomes that
linkage will enter in as a factor to cause the continued preservation
of a heterozygous condition as a consequence of selection for a certain
set of characters.

It remains to consider those portions of the Nicotiana literature
which deal specifically with the Mendelian inheritance of the charac-
ters which we have investigated, and to harmonize our results with
those which have been reported previously. Unfortunately there have
not been many investigations in Tabacum which have been prosecuted
far enough to arrive at a definite factor analysis of the differences
under consideration. The investigations of Miss Howard (1913),
" promise of the continuation of which has not thus far been fulfilled,
in general confirm those which we have presented in this paper. On
the strictly analytic side, however, Miss Howard did not carry her
work very far. This doubtless was due to the difficulty of making a
factor analysis of the characters which she selected for study, viz.,
(1) time of flowering, (2) height of stem, (3) arrangement of the
leaves on the stem, (4) length of the decurrent portion of the lamina,
(5) venation of the leaf, (6) leaf shape, and (7) undulation of the
surface and margin of the leaf. For most of these characters she
demonstrates, by the presentation of numerical data in some cases
as far as F^, the probability of the character differences in ques-
tion depending upon multiple factor differences. In the case of height
certain of her cultures strongly suggest the existence of a pair of
allelomorphs, which has a relatively great effect, for in some of her
cultures there are definite discontinuous height differences. For the
inheritance of length of the decurrent portion of the lamina Miss
Howard postulates the existence of at least three or four distinct pairs
of factors. As respects leaf base, she records the synthesis of petiolate
types from sessile parents, observing in two cases a simple 1 :2 :1 segre-
gation into petiolate : intermediate : sessile. As respects corolla color,
she records one Fj population from pink x very pale pink fading into
white which consisted of 72 pinks of various shades to 45 whites, but
some of the palest pinks were indistinguishable from Avhite. She found
evidence of grouping among the pinks, and postulates the existence
of two factor differences to account for it. The investigations which
we have reported do not throw light upon the factor constitution of
the very pale pink varieties with which Miss Howard worked. Our

518 University of California Publications in Botany [Vol. 5

varieties angustifolia and virginica have lively pink flowers. Of the
paler pinks or "pinkish" forms we have a representative in our A".
Tahacum var. Cavala, U. C. B. G. 12/05, which has flowers distinctly
lighter in color than those of angustifolia or virginica. Our petiolate
forms also seem to be of different constitution from those with which
Miss Howard worked, for she presents evidence to show that hers are
combinations of recessive factors and that they breed true whenever
they occur as segregation products, whereas our petiolate forms often
gave plants with sessile leaves as segregation products. We have,
however, secured evidence that some distinctly short petiolate forms
arise from sessile ones, perhaps by modifications of the auriculata
leaf type in the direction of stripping the auricle and lower portion
of the lamina from such leaves, but our results are not yet definite
enough to permit of rigid formulation. Further investigation of the
relationships of the various petiolate forms is necessary.

As respects flower color Allard (1919) has presented some inter-
esting data which at first sight appear to contradict those which we
have presented. Allard found that carmine x pink gave F^ carmine and
Fo 3 carmine : 1 pink. The back crosses gave consistent data. Thus
F^ carmine x carmine parent gave all carmine, and F^ carmine x pink
parent gave 1 carmine : 1 pink. In F, pink segregants bred true for
pink, and carmine either bred true for carmine or gave again 3 carmine
:1 pink. The difficulty here is that our red is not genetically identical
with Allard 's carmine. Our flowers of macrophylla and calycina at
full expansion show a color lying between rose red and pomegranate
purple of the Ridgway color scale. This color, which we have called
red for the sake of brevity, is very close to carmine, but we have an-
other flower color, which we call dark red, represented by N. Tahacum
var. mucrophylla purpurea, which is probably identical with the Giant
Red flowering tobacco which Allard used in his experiments.

We have made some preliminary tests of this dark red, and find
that it behaves differently from red. Crossed with our white it gives
dark red in F^, instead of pink as was obtained from red x white.
Since our white carries the factor R, which is responsible for the
production of pink flower color, dark red must differ from pink in a
dominant factor. If %ve call this factor pair Pp, then our various
colors of tobacco would have the following genotypes :

Dark red WWRRPP

Red WWrrpp

Pink WWRRpp

White ww^RRpp

19--] Setchell-Goodspeed-Clausen: Nicotiana Tahacum 519

Obviously this formulation would account for AUard's results with-
out contradicting those which we have presented, but inasmuch as our
experimental evidence is not yet complete we refrain from any further
discussion of the consequences of this scheme save one. Allard presents
certain data for a cross of carmine x white which gave in F^ light
carmine, and in F, 3 colored : 1 white, the colored being various shades
of carmine and pink. Allard 's discussion of this case is somewhat
mixed, but he evidently erroneously expected a simple monohybrid
segregation of the 1:2:1 kind. That more than one factor is con-
cerned in the cross is clearly shown by the results of crossing some of
the extracted whites with pink varieties. The results of three such
crosses gave :

1. Pink (Maryland Mammoth) x Extracted white 36 carmine : 18 pink

2. Extracted white x Pink (Maryland Mammoth) 20 carmine : 23 pink

3. Pink (Conn. Broadleaf) x Extracted white 12 carmine : 39 pink

Totals 68 carmine : 70 pink

In (1) above we have combined in the carmine class 17 carmine and
19 somewhat lighter than carm;ine.

If we consider a cross of dark red x white according to the genetic
formulation given above, the F^ should be dark red, and Fg should
consist of 9 dark red : 3 pink : 4 M^hite. Doubtless the pinks and the
dark reds would exhibit various shades, but the three classes should
be distinct. If we combine "carmine" and "lighter than carmine"
to form a carmine class and dark and light pink to form a pink class,
Allard 's F, data reduce to the following form :

149 carmine : 64 pink : 65 white.
This ratio compares very favorably with a 9 : 3 : 4 expectation, viz. :

157 dark red : 52 pink : 69 white.
No F3 results from sowings from colored F, plants are given, but the
single F2 white, which gave when crossed with pink approximately
equal numbers of carmine and pink flowering plants, is accountable
for as of the genotype wwRRPp. Further investigations are in pro-
gress for the purpose of determining precisely the relation of dark
red and pinkish to the red, light pink, and white colors reported upon
in this paper.

There are other references in the literature to Mendelian inherit-
ance in Tahacum., but inasmuch as these do not bear upon the
characters which we have attempted to analyze it does not appear
necessary to discuss them at this point.

520 University of California Publications in Botany [Vol. 5

VII. SUMMARY

Studies of three intervarietal crosses in Tahacum demonstrate that :

1. All the differences between varieties of Tahacum can be analyzed
in a Mendelian fashion, if sufficient refinement in methods be intro-
duced.

2. Stable recombinations of parental characters can readily be
obtained with three or four generations of self-fertilization.

3. Characters outside the range between the parents are sometimes
produced following hybridization, and these may be readily established
in stable lines by self-fertilization.

4. The petioled leaf base of angustifolia and the sessile leaf base
of macrophylla differ in at least three pairs of factors.

5. A single factor difference exists between normal and split hose-
in-hose flowers.

6. Two pairs of factors account for the relation existing between
red, light pink, and white flower color. A third pair of factors is
necessary to account for dark red.

On the theoretical side it has been pointed out that :

1. Derivation of relationships and erection of systems of classifi-
cation after the manner of Comes and Anastasia cannot be relied upon
unless supported by experimental evidence.

2. An adequate scheme of classification should be based upon iden-
tities and dissimilarities in the genotypes, irrespective of the derivation
of the forms in question.

3. Mendelian analysis in Tahacum requires that special attention
be paid to residual portions of the genotype, so that the factor differ-
ences under consideration act in a stable residuum most favorable for
emphasis of the character differences under investigation.

LITERATURE CITED

Allard, H. a.

1919. Some studies in blossom color inheritance in tobacco, with special
reference to A'^. sylvestris and N. Tabacum. Am. Nat., vol. 53, pp.
79-84.

Anastasia, G. E.

1906. Le varieta tipiche della Nicotiana Tabacum L. Scafati.
Bridges, C. B.

1919. Specific modifiers of eosin eye color in Brosophila melanogastcr. Jour.
Exp. Zool., vol. 28, pp. 337-384.

1922] Sctchell-Goodspeed-Clausen: Nicatiana Tahacum 521

Castle, W. C.

1919. Piebald rats and the theory of genes. Proe. Nat. Acad. Sci., vol. 4,
pp. 126-130.

Collins, G. N.

1917. Hybrids of Zea ramosa and Zea tunicata. Jour. Agric. Ees., vol. 9,
pp. 383-396.
Comes, O.

1899. Monographie du genre Nicotiana eomprenaut le classement botanique
des tabacs industriels. Atti del E. Institute d 'Incoraggiamento di
Napoli, ser. V, vol. 1.
1905. Dello razze dei tabacehi filogenesi, qualita ed uso. Ibid., vol. 57.

East, E. M.

1913. Inheritance of flower size in crosses between Nicotiana species. Bot.
Gaz., vol. 55, pp. 177-188.

GOODSPEED, T. H.

1912. Quantitative studies of inheritance in Nicotiana hybrids. Univ. Calif.
Publ. Bot., vol. 5, pp. 87-168.
GooDSPEED, T. H., and Clausen, E. E.

1917. The nature of the Fi species hybrids between Nicotiana sylvestris and

varieties of N. Tahacum. Univ. Calif. Publ. Bot., vol. 5, pp. 301-348.

Harlan, H. V.

1918. The identification of varieties of barley. U. S. Dept. of Agric, Bull.

622, pp. 1-32.
Hayes, H. K.

1912. Correlation and inheritance in Nicotiana Tahacum. Conn. Agric. Exp.

Station, Bull. 171, pp. 1-45.

Hayes, H. K., East, E. M., and Beinhart, E. G.

1913. Tobacco breeding in Connecticut. Conn. Agric. Exp. Station, Bull.

176, pp. 1-68.

Hasselbring, H.

1912. Types of Cuban tobacco. Bot. Gaz., vol. 53, pp. 113-126.
Howard, A., and Howard, Gabrielle L. C.

1910. Studies in Indian tobaccos. No. 2, The types of Nicotiana Tahacum L.
Mem. India Dept. Agric. Bot. Series, vol. 3, pp. 59-176.

Howard, Gabrielle L. C.

1913. Studies in Indian tobaccos. No. 3, The inheritance of characters in

Nicotiana Tahacum L. Ihid., vol. 6, pp. 25-114.

MULLER, H. J.

1918. Genetic variability, twin hybrids, and constant hybrids in a case of
balanced lethal factors. Genetics, vol. 3, pp. 422-499.

EiDGWAY, Egbert

1912. Color standards and color nomenclature.

Setchell, W. a.

1912. Studies in Nicotiana, 1. Univ. Calif. Publ. Bot., vol. 5, ])]). 1-86.
White, O. E.

1913. Bearing of teratological development in Nicotiana on theories of

heredity. Am. Nat., vol. 47, pp. 206-229.

1914. The history of Nicotiana, II. An account of the heredity and envi-

ronirient of a family of tobacco plants. Brooklyn Bot. Garden
Loaflots, Series 2, No. 12.

EXPLANATION OF PLATES

A special note is due the illustrations in this paper. The line drawings were
made by Miss Anna Hamilton and Miss Helen M. Gilkey. Special attention was
paid to accuracy in proportions and details. No attempt, however, was made
to represent the characteristic Nicotiana pubescence. The photographs require
no special mention save that sometimes the garden number given in the legend
does not correspond with that given on the label in the photograph. The dif-
ference is due to a change in system of numbering used in F3 and in subsequent
populations. In this paper, in order to avoid confusion, garden numbers from
the beginning have been made to conform to this change. The legends of
all the plates have been made more complete than is usual in order to facilitate
cross-reference and to enable the reader to grasp their essential significance more
readily.

PLATE 55

Fig. 1. Nicotiana Tabacum var. angustifoUa, U. C. B. G. 68/07. A typical
plant of angustifoUa at the height of its blooming period. The laterals over-
topping the central axis and the long-petioled stenophyUa form of leaf are
especially to be noted. The drooping of the leaves is very characteristic of this
variety.

Fig. 2. Nicotiana Tahacum var. macrophylla, U. C. B. G. 22/07. A typical
plant of macrophylla at the height of its blooming period. Note especially the
stout laterals overtopping the central axis and the sessiUfolia type of leaf.

[522]

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PLATE 56

Nicotiana Tabacum var. nnf/mtifoUa, U. C. B. G. 68/07. Line drawings of
typical details of angustifoUa. In the upper right-hand corner the characteristic
straplike sessile leaf or bract of the inflorescence. Upper left, details of bud,
flower, and capsule. Lower right, details of pistil and stamens. Lower left, the
typical long-petioled stenophylla leaf of angustifoUa. Leaves X %; flowers and
capsules natural size.

[524]

UNIV. CALIF. PUBL. BOX. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 56

PLATE 57

Nicotiana Tdbacum var. macrophyUa, V. C. B. G. 22/07. Liue drawings of
typical details of a plant of macrophyUa, showing floral details and the extreme
variations in leaf size and shape on the plant. Leaves X %; flowers and cap-
sules natural size.

[526]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 57

PLATE 58

Fig. 1. Nicotiana Tahacum var. angustifolia, U. C. B. G. 68/07. Typical leaves
of angustifolia of the stenophyUa type showing the range of variation on a single
plant.

Fig. 2. Nicotiana Tahacum var. macrophylla, U. C. B. G. 22/07. Typical leaves
of macrophylla of the sessilifolia type showing the range of variation on a single
plant.

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PLATE 59
AngnstifoUa-macrophylla series, F, leaves.

Fig. 1. Typical leaf of lOFiHoP^o, an Fi of the angustifolia-macrophyUa
series. Note the short, winged petiole and the clasping auricles.

Fig. 2. Typical leaf of IOF1H3P58, a variation from the usual latifolia type
of the F, leaf. Note the shorter petiole, less conspicuously winged condition,
and the almost total lack of auricles.

Fig. 3. Typical leaf of 10F,H4P;5. The petiole is somewhat longer than that
normal for the F,.

Fig. 4. Typical leaf of lOFiH^P-o. The petiole here is shorter than that
normal for the F,.

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PLATE 60

Portions of inflorescences of iV. Tabacum var. macro phylhi, N. Tabacum var.
angustifolia and the Fj hybrid between them.

Fig. 1. Left, portion of inflorescence of macrophylla, middle, of the F,, and
right, of angustifolia.

Fig. 2. Left, portion of the inflorescence of macrophylla. middle, two of the
F„ and right, of angustifolia.

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PLATE 61
Angustifolia-macroj^hyUa'seTies, F, plants.

Fig. 1. Photograph of 10F,H;P,c, the Fi plant from which the leaf shown
in plate 59, figure 1, was taken.

Fig. 2. Photograph of 10F,H;P.,6, the F, plant from which the leaf shown
in plate 59, figure 4, was taken.

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PLATE 62

AngiistifoUa-macrophyUa series, line drawings of Fj.

Line drawings showing morpliological details of the typical Fj plant of the
aiuj ustifolia-macrophylla series. The garden number of the plant was IOF1H15P7.
Leaves X V2; flowers and capsules natural size.

[536]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN 1 PLATE 62

PLATE 63

AngustifoUa-macrophyUa series. tyj)e ].

Line drawings of mori)ho]ogifal details of F^ of type 1. The garden number
was IIFoH^PtPj^. Note particularly the stenophylla type of leaf. Leaves X % ;
flowers and capsules natural size.

The F;. progeny of this jilant consisted of 16 stenophylla of type 1 and 9 Jcuice-
ohita of type 14.

[538]

UNIV. CALIF. PUBL. BOT, VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 63

PLATE 64
Angustifolia-macrophylla series, type 2.

Line drawings of morphological details of F.^ of type 2. The garden number
was llF,H,P:,P3o. The leaf is of the Jafifolia type. Leaves X %; flowers and
capsules natural size.

The Fg progeny of this plant consisted of 12 latifoUa, 8 sessilifolia, and 4
auriculata.

[540]

UNIV. CALIF. PUBL. B07, VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ) PLATE 64

PLATE 65
AngustifoIia-inacrophyUii series, type o

Line drawings of morphological details of F2 of type 3. The garden number
was llFoHsPaPn. The leaf is of the latifoJia tyjie. Leaves X %; flowers and
capsules natural size.

The F;; progeny of this plant consisted of -4 latifolia and 10 sessilifolia.

542]

UNIV. CALIF, PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 65

PLATE 6(3
AngustifoUa-7nacroij]iyUa series, type 4.

Line drawings of the morphological details of type 4. The garden number
was llFoHaPyPis. The leaf is an extreme form of the latifolia type. Leaves
X %; flowers and capsules natural size.

No progeny was grown from this plant.

[544]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN J PLATE 66

PLATE 67
AngustifoUa-macrophyUa series, type 5.

Liue drawings of morphological details of type 5. The garden number was
llFoH4P4iP,4. The leaf is of the laiifolia type. Leaves X %; flowers and cap-
sules natural size. ,

The F3 progeny of this ]dant consisted of 24 laiifolia and 1 anriculata.

[546]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 67

PLATE 68
AngustifoUa-macrophylla series, type 6.

Line drawings of morphological details of F. of type 6. The garden number
was llFjH^P.Pis. The leaf is of the latifolia type. Leaves X %; flowers and
capsules natural size.

The Fa progeny of this plant consisted of 5 stenophyUa, 17 latifolia, and 4
auricnJata plants, but the segregation was not distinct.

[54S]

UNIV. CALIF. PUBL. BOT. VOL. 5 | SETCHZLL-GOODSP^ED-CLAUS :N 1 PLATE 68

PLATE 69
Angustifolia-macrophylla series, type 7.

Line drawings of morphological details of Fo of type 7. The garden iiuinbor
was llF.H.PiiP^s- The leaf is of the hififalia type. Leaves X V:\; flowers and
capsules natural size.

The F;, progeny of this plant was uniformly of the same type as the parent,
and the line bred true in subsequent generations.

[550]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 69

PLATE 70

AnquHtifoUa-macrophyUa series, type 8.

Line drawings of morphological details of F^ of tyi)e 8. The garden number
was llFoHjPiiPj,. The leaf a])])roached the uuricuUita type. Leaves X %;
flowers and capsules natural size.

The F3 progeny of this plant consisted of 16 .sessilifolia and 8 auriculata,
indicating that the F-, plant was an extreme variant of tiie heterozygous sessiHfoUa-
auriculata condition.

[552]

UNIV. CALIF: PUBL. BOX. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 70

PLATE 71

AngustifoUa-macrophylla series, type 9.

Line drawings of morphological details of F, of type 9. The garden number
was IIF2H4P41P8. The leaf is of the latifolia type. Leaves X %; flowers aud
capsules natural size.

The F3 progeny of this plant consisted of 18 latifolia and 7 sessilifolia.

[554]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN | PLATE 71

PLATE 72
Angustifolia-macrophyUa series, type 10.

Line drawings of morphological details of F, of type 10. The garden number
was llFoHiP^Piv. The leaf was of the auriculata type. Leaves X M?; flowers
and capsules natural size.

The F3 progeny of this plant consisted uniformly of auriculaia plants.

[556]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 72

PLATE 73
AngustifoJia-macrophylla series, type 11.

Line drawings of morphological details of F, of type 11. The garden number
was llFaHJ'jiPa. The leaf is of the scssilifoUa type. Leaves X %; flowers and
capsules natural size.

The Fj progeny of this plant was uniformly of the same sessilifolia type.

[558]

UNIV. CALIF. PUBL. BOT. VOL. 5 ( SETCHELL-GOODSPEED-CLAUSEN ] PLATE 73

PLATE 74

Angustifolia-macrophyUa series, type 12.

Line drawings of morphological details of F, of type 12. The garden number
was IIF2H4P41P12. The leaf is of the loriifolia type. Leaves X %; flowers and
capsules natural size.

The F3 progeny of this plant was uniformly of the same loriifolia type, and
two constant races, one with red and one with light pink flowers, were obtained
from it.

[560]

UNIV. CALIF, PUBL. BOT. VOL. 5 I SETCHELL-GOODSPEED-CLAUSEN J PLATE 74

PLATE 75

Angustifolia-macrophyUa series, type 13.

Line drawings of morphological details of Fo of type 13. The garden number
was llFoHoPsPj^. The leaf is of the Innceolata type. Leaves X %; flowers and
capsules natural size.

The F;; progeny of this plant was uniformly of the same lanceolata type.

[562]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCH ELL-GOODSPEED-CLAUSEN J PLATE 75

PLATE 76

Angustifolia-macrojjJiyUa series, type 14.

Line drawings of morphological details of F^ of type 14. The garden number
was IIF2H2P3P38. The leaf was classified as sessilifolia, although strictly it is
intermediate between sessilifolia and lanceolata. Leaves X Mi', flowers and
capsules natural size.

The F..J progeny of this plant consisted of 24 plants of the same sessilifolia
tyi)e and 1 "filler," which had leaves more like auriculata of type 8.

[564]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN 1 PLATE 76

PLATE 77
Angustifolia-macrophylla series, type 15.

Line drawings of morphological details of F„ of type 15. The garden number
was llFjHoPaPio. The leaf is of the sessilifolia type. Leaves X Vs; flowers and
capsules natural size.

The F3 progeny of this plant was uniformly of the same leaf type.

[566]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 77

PLATE 78
AngustifoUa-macrophyUa series, type 16.

Line drawings of morphological details of F™ of type 16. The garden number
was llFoHjPsPso- Tlie leaf is of the sessilifolia type. Leaves X %; flowers and
capsules natural size.

The Fs progeny of this plant consisted of 15 sessilifolia and 8 auriculata.

[568]

UNIV. CALIF. PUBL. BOX. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ) PLATE 78

PLATE 79

Nicotiana Tabacum var. calycina, U. C. B. G. 110/05.

Line drawings of morphological details of leaf and flower of calycina. The
leaf is of the lanceoJata type, and the flowers are of the conspicuously teratolog-
ical, split hose-in -hose form. Leaves X %; flowers and capsules natural size.

[570]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 79

PLATE 80

Nicotiana Tabacum var. virginica, U. C. B. G. 78/05.

Line drawings of morphological details of leaf and flower of virginica. Con-
trast the normal flowers and auricled leaves with the corresponding details of
calycina, shown in plate 79. Leaves X V^ ; flowers and capsules natural size.

[572]

UNIV, CALIF, PUBL. BOT, VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN J PLATE 80

'M

N^

A

r

X-'-'/l

PLATE 81

Calycina-virginiea series, an F, ])lant.

Line drawings of morphological details of an F, plant of the calycina-virginiea
series. Note the normal flowers and the slightly auricled leaves. Leaves X %;
flowers and capsule natural size.

[574]

UNIV. CALIF. PUBL. BOT. VOL. 5 [ SETCHELL-GOODSPEED-CLAUSEN ] PLATE 81

PLATE 82

Nicotiana Tabacum var. alba, U. C. B. G. 30/06.

Line drawings of moqihological details of flower and leaf of alba. Note
especially the rugose leaf. Compare this drawing with those of macrophylla
shown in plates 57 and 58, figure 2. Leaves X %; flowers and capsule natural
size.

[576]

UNIV. CALIF. PUBL. BOT. VOL. 5 | SETCHELL-GOODSPEED-CLAUSEN 1 PLATE 82

PLATE 83

Fig. 1. Calycina-virginica series, an Fi plant. A typical Fj plant of the
calycina-virginica series. This plant is at the height of its blooming period. The
garden number was 10FiH,8P54.

Fig. 2. Alha-macroiihyUa series, an Fi plant. Photograph of a typical Fj
plant of the aJba-macrophylJa series. The garden number was 10FiH2,P,-,4. The
plant is at the height of its blooming period.

[578j

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PLATE 84
Alba-macrophylla series, F, leaves.

Fig. 1. Photograph of typical leaves of alba.

Fig. 2. T'hotograph of a typical leaf of 10F,Ho,P,;, Fj of the alhamarcophyUa
series.

Fig. 3. F'hotograph of a typical leaf of IOF1H04P34, Fi of the aJba-macrophyUa
series.

Compare these leaves with those of macrophylla, shown in plate 58, figure 2.
The rugoseness of alha has been carried over, to a somewhat reduced extent, into
the F, hvbrid.

[580]

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PLATE 85

Fig. 1. Alba-macrophylla series, F, plauts. Photograph of two adjacent
plants, llF^Hi^Pj^Paj and llF,H2,P3,Pj3, from the same F, population of the alba-
macrophylla series. An illustration of segregation for height in this population.

Fig. 2. Alba-macrophylla series, an F^ plant. Photograph of a t\^pical Y^
plant, ISF^Ho.P-^P^PjP:^, of a dwarf line of the alba-macrophylla series. The
line here illustrated was derived from the dwarf F^ plant shown in figure 1. This
line has bred true for seven generations.

[582]

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01

INDEX*

(i^HlJiitS

Absciss cells, definition of, 349.

Abscission, 192, 196, 274, 275, 304,
359, 367, 371, 383, 384, 403, 412,
429; relation of nutrition to, 281-
289; effect of non-fertilization,
289, 348; effect of physiological
condition of plant, 294, 348; auto-
matic, 296, 359, 433; axial, 348,
351, 415; floral, 293-298, 366, 408,

413, 417, 444, 448; lateral, 348;
effect of sugar, 381; relation to,
of development of mechanical
tissue in pedicel, 370; spontane-
ous, 390-396, 443; a physiological
problem, 417; relation of fertil-
ization to, 431-433; caused by
p'emature pollination, 433.

Process of, 353-358, 375, 376, 413;
time, 358, 385, 389, 414, 443; in-
fluence on, of age of flower, 396,

414, 416; of humidity, 397; mois-
ture requirement, 448.

Induction of: factors in, 359-360,
362, 416; in Nicotiana, 371-373;
in Lycopersicum, 373-374; in
Datura, 374-375; in pedicel, 399-
404, 414; experimental : by illum-
inating gas, 397-404, 414; by
action of acids on separation
cells, 404-406; by mechanical in-
jury, 406-411, 414. See also Cell
separation; Citrus; Corolla; Fer-
tilization ; Lamella ; Pedicel ; Pol-
lination; Style, etc.

Abscission of Flowers in Nicotiana
and Citrus, Effects of Illuminat-
ing Gas and its Constituents in
Causing, 439.

Abscission of Flowers and Fruits in
Solanaceae with Special Refer-
ence to Nicotiana, 347.

Aesculus, 351.

Age, of leaf, 444; of flower, 229, 396,
414, 417; of plant, 229, 240, 444;
of seed, 451; influence of, in ger-
mination, 453-454, 455.

Alba-macrophyUa series, 461, 504-510;
description of alba, 504, con-
trasted with macrophylla, 505;
generations of, 505, 507; tables
showing segregation in hybrids,
506, 507, 508; discussion of color
and height, 508, 509; results of
investigation, 510.

Allard, H. A., cited, 518-519.

Allelomori.hs, 483, 490, 499, 504, 506,
512, 517.

Ampelopsis, 350, 351.

Anastasia, G. E., cited, 511.

Angustifolia-macrophylla series, 461,
462-494; parents, 463; descrip-
tion of angustifolia, 463-465; de-
scription of macrophyUa, 465-
467; F, generation, 467-469; F„
generation, 469-471, 483-487; F3
and subsequent generations, 472-
481, 483-487; table of F3 families,
473; chart showing relationships
of families, 474; six types of par-
ents selected, and characteriza-
tion of, 474-475; auriculata, 475,
477, 479, 485, 488, 489, 492, 493;
lanceolata, 478, 491; latifolia,
476-478, 488, 491, 492; loriifoUa,
478-479, 491, 492; sessiUfolia,
480-481, 485, 487, 489, 492, 493;
stenophylla, 475-476, 485, 490,
491, 492; summary of color ob-
servations in, 482-483; classifica-
tion with respect to leaf base
modifications, 486; crosses of
derivatives with parents, 487-
490; complexity of germinal dif-
ferences, 490.

Aristolochia Sipho, 353.

Arntzen, V., acknowledgment, 435.

Asparagus, 350.

Atropa, 350.

Auriculata derivatives, 475, 479, 484-
485; X macrophylla, 488; X ses-
siUfolia, 489.

Ayres, A. H., 273.

Begonia, 350, 352.

Beinhart, E. G., cited, 514.

"Boll-shedding" in Egvptian cotton,
287.

Brazilian tobacco, 4; illustrations of,
opp. 32.

Bridges, C. B., cited, 515.

Brunfelsia, 351.

Bud variations in Nicotiana hybrids,
459.

Calycina-virginica series, 494-504;
parents, 494; description of caly-
cina, 494-495; description of vir-
ginica, 495-496, opp. 572; F, gen-
eration, 496-497; Fo generation,
497-499; corolla color, 497-501;
corolla form, 501; F3 and subse-
quent generations, 499-504; com-
plex genotypic differences, 504;
results of investigation, 504.

Capsule in hybrids, 468, 470.

Univ. Calif. Publ. Bot., vol. 5.

[583]

Index

Carbon dioxide, 447, 448, 449. See
also Narcotic vapors.

Carbon monoxide, 449. See also Nar-
cotic vapors.

Cavala tobacco, 5, 233; illustration
of, opp. 34, 463.

Cell separation, with abscission, 354,
413, 416; method of, 376-384;
enzj^me problem of, 383; time of,
in spontaneous abscission, 396;
induction of, 404; figures show-
ing, opp. 422, 424, 428.

Cell turgor, 376, 379-380, 413, 404,
413.

Cestrum fasciculatum, 366, 371, 398,
411.

Chloroform. See Narcotic vapors.

"Chorismus," 3.55.

Cinnamomum, 354.

Citnts, abscission of flowers in, 439,
441, 443; effects of illuminating
gas, 445, 449. See also Abscission.

Citrus limonia, 445.
var. Eureka, 441, 449.
sinensis var. Washington Navel,

441, 445, 446, 449.
var. Valencia, 441, 449.

Clausen, E. E., 301, 435, 457.

Comes, cited, 2, 3, passim, 458, 510,
511.

Complexity of character differences
in Tahacum varieties, 459-460,
4fiS. 470. 491.

Controlled Pollination in Nicotiana,
429.

Corolla, abscission of, 357; in Nicoti-
ana, 383, 413; illustrated, 383;
in Datura, 384, 413.

Corolla color in calycina-virginica
series, 497-501.

Corolla diameters, in N. acuminata,
quantitative expression of imper-
fect dominance in, 117-168;
plates showing fluctuations in,
opp. 164, 166, 168; tables of
measurements of, 224-226 ; method
of measuring, 227. See also Dom-
inance, imperfect.

Crocus, effect of ])oisonous gases on
germination in. 446.

Cross-pollination, 127, 135. 189, 248,
263, 267, 269, 275, 277, 29.3, 295,
387.

Cuba, lenqua fie vuca tobacco, 492.

Cucumis, 351.

Cucurhita, 359.

Culture series in Nicotiana Taharum.
See Alha-macrophylla ; Angustifo-
lia-macrophylla ; Calycina-virgi-
nica.

Cuplme, 350.

Cytology, study of. in relation to
abscission in Nicntiann hybrids,
296, 432; in "separation layer,"

[584]

352; in genera of the Solanaceac,
366; changes in, accompanying
abscission, 376-377; of the pedi-
cel in Nicotiana, 363-365; illus-
trated, 363; in Lycopersicum, 365-
366; illustrated, 365.

Darkness and light, influence of, on
germination, 451.

Datura, 350, 367, 382, 402, 403, 412;
abscission of stvle and corolla,
383-385.
sanguineum, 366, 398, 411.
stramonium, 444.

Davidson, Pirie, 429.

Dominance, Law of, 174.

Dominance, in inheritance of charac-
ters in Nicotiana hybrids. 111,
112, 118, 312, 313, 314, 316, 320,
321.
Imperfect, in corolla diameters,
117, 168; experimental materials,
119; growing conditions, 123; de-
scription of Nicotiana flower, 125;
'technique and method, 126-132;
experimental work, 132, 136;
measurement of diameters, 138;
results, 144, 145; literature, 152;
plates showing, opp. 164, 166,
168.

Don, G., cited,. 2.

Drosophila, 512.

Drought, effect on abscission, 397.

East, E. M., cited, 514.

Environment, influence on Tahacum,
513.

Erodium, genus, 357.

Ether. See Narcotic vapors.

Ethylene, 449. See also Narcotic va-
pors.

Euonymus, 354.

Exfoliation, distinction between, and
abscission, 348.

Ferric chloriile, used in nutrition ex-
periment on Nicotiana, 285.

Fertilization, relation of, to abscis-
sion, .387, 391, 407, 416, 431-433;
selective, 434.

Floral abscission, 294-298, 366, 408,
413, 417, 444. 448; following non-
or unsuccessful pollination, 296;
histological and cytological in-
vestigation of, 296.

Floral characters in F, hvbrids: 457,
passim ; \'o\or, 307-311, 313; leaf,
307-311; flower (habit, size, etc.),
223-227. 307-311, 312; inheritance
of, 169-174, 228. 229, 230, 435;
"unit-character" problem in,
175; influence of age, 229; range
of variability, 229-230; plates
showing, 324-344; apparatus for
measuring size, 435-438. See also
Corolla diameters; Mendelian no-
tation, etc.

Index

Flower form, factor in Mendelian
heredity in Tabacum, 516.

Flower Measurement, Apparatus for,
4.">5; illustrations of, -t.'Uj, 4.17.

Fort Bidwell, California, 120.

Fuchsia, 352, 359.

Gasteria, 350.

Geranium, genus, 357.

Genetic aspects of problem of hered-
ity in Nicotiana hybrids, 301.

Genotypes in Tabacum, 513, 520; ge-
netic behavior of leaf type of,
492-493, 516.

Germination of tobacco seed, 96-100,
. 108, 109, 136, 199, 233, 451; sul-
furic acid method, 199-200, 203-
209, 219, 220; value of separation
of seed, 200; seed used, 201; ger-
minating conditions, 202, 203; re-
lation between age of seed and
its viability, 209-215, 220, 233,
240; hybrid vs. parent seed, 215-
219, 220, 241-247, 248; rate and
amount of germination, 240-247,
248; response to stimulation by
hybrids an<l parental pollen, 276-
281; effect of narcotic vapors on,
446; relation of light and dark-
ness to, 451-455; germinal differ-
ences in culture series of Nicoti-
ana Tabacum hyl)rids, 490.

G-ermination of Tobacco Seed, Notes
on, 199, 233, 451.

Goldschmidt, R., acknowledgment,
435.

Goodspeed, T. H., 87, 169, 189, 199,
223, 233, 249, 273, 293, 301, 429,
435, 439, 451, 457; acknowledg-
ment, 417.

Groth, B. H. A., work of, on Fi hy-
brids, 147.

Harlan, H. V., cited, 512.

Hasselbring, H., cited, 492.

Hayes, H. K., cited, 514.

Heliantliemum, genus, 357.

Heredity, "unit character" concep-
tion, 174-186; physiology of, 177-
181, 197, 301; use of hypothetical
terms in connection with, 181;
conception of reaction system
contrasts in, 361 ; genetic aspects
of problem, 301; residual, in Nic-
otiana Tabacum, 515-516, 520.

Hibiscus rosasinensis, 444.

Histological investigation of abscis-
sion in Nicotiana hybrids, 296.

Histology of the pedicel, 350, 412;
in Nicotiana, 363-365; in Lyco-
persicum, 365-366; in other gen-
era of the Solanaceae, 366.

Hodgson, E. W., 439.

Howard, Gabrielle L. C, cited, 511,
514, 517, 518.

Humidity, influence on abscission
time, 397.

Hydrogen, used in abscission experi-
ments, 447.

Illuminating gas, induction by, of ab-
scission, 397-404, 443; relation
of concentrations of, to leaf-fall,
444. Sec also Narcotic vapors.

Illuminating Gas and its Constitu-
ents, Effects of, in Causing Ab-
scission of Flowers in Nicotiana
and Citrus. 4.S9; composition of,
440; methods of experiment, 440;
results, 441, 442.

Hlumination, effect on abscission, 397.

Impaticns Sultani, .348, 350, 352.

Inheritance in Nicotiana Hybrids,
Studies in, 87, 169, 223.

Inheritance in Nicotiana Tabacum, A
Report on the Crossing of Cer-
tain Varieties, 457; quantitative
characters, 459, 513, 514-516;
bud variations, 459; interspecific
hybrids, 459; Mendelian, 459,
460 (which also see) ; occurrence
of strays, 462; features of, 514;
residual hereditj^, 515-516, 520;
linkage as a factor in, 516-517;
flower form factor in, 516; color,
flower, leaf base, leaf shape, 457,
passim; petiole, 457, passim.

Injury, mechanical, 416. See also Ab-
scission.

loehroma tuberosa 366, 398. 399, 441.

Kendall, J. N., 293, 347, 443.

Lagenaria, 351.

Lamella, middle, dissolution of, 356,
376, 378, 379, 382, 384, 416.

Lanceolata derivatives, 474, 478, 491.

Latifolia derivatives, 474, 476-478;
X anqustifolia, 488; a complex
hybrid, 491.

"Law of Dominance," 174.

"Law of Segregation," 174.

Leaf characters (base, habit, shape)
in hybrids, 307, 311, 467, passim.

Light and darkness, influence of on
germination, 451, 455.

Linkage as a factor in inheritance in
Tabacum, 516-517.

Linum, genus, 357.

Lipman, C. B., acknowledgment to,
289.

Literature cited, 30, 152, 187, 198,
222, 231, 248, 290, 299, 322, 450,
520; summary of literature on ab-
scission, 350-361.

Litmus, reaction of Nicotiana to, 381.

Lloyd, F. E., acknowledgment to, 289.
■ 41 7.

Loriifolia derivatives, 474, 478-479,
491-492, 495.

Lupinus, 446.

[585]

Index

Lycmm, 367.

austruUs, 366, 398, 399, 411.

Lycopersicum, histology of pedicel,
350, 351, 367, 412; development
of separation zone, 367-369; fig-
ure showing, 368; increase in size
and development of mechanical
tissues of pedicel, 369-371; spon-
taneous abscission in, 393, 401,
408, 414; floral abscission in, 408;
figures showing abscission pro-
cess, opp. 428.

Lycopersicum esculeiitum, spontaneous
abscission in, 395.
var. pyriformc, 398, 399, 411.
var. v'ulgarc, 398, 399, 411.

McGee, J. M., 439.

Magnesium, used in nutrition experi-
ment on Nicotiana, 284.

Maryland tobacco, 5, 89; illustrations
of, opp. 36, 461, 463.

Mendelian dominance, 111, 112, 118,
117-168.

Mendelian inheiitance in Nirotiaua
Tahanim, 459, 460, 471, 487, 490,
503, 506, 507-508, 510, 513, 516-
519, 520; methodology of Mendel-
ian analysis in, 513-516; pairs of
factors, 516; consideration of lit-
erature in connection with pres-
ent study, 517-519.

Mendelian notation, 181, 183, 185,

186, 228.

Mexico, white tobacco from. 7.

Mineral acids, action of, on separa-
tion cells of Nicotiana, 404-406.

MirahiJis, 352, 353, 445.
Jalapa, 348, 353.

Moisture, contributing factor in ger-
mination of tobacco seed, 451.

Moisture requirement in process of
abscission, 448.

Muller, H. J., cited, 512.

Narcotic vapors, effect of, on abscis-
sion, 355, 359, 390, 397-404, 416,
445, 447. See also Illuminating
gas.

Nature of the F, Species Hybrids be-
tween Nicotiana sylvestrif! and
Varieties of Nicotiana Tahncnm
with Special Reference to the
Conception of Reaction System
Contrasts in Heredity, 301; ])lates
showing, opp. 324, 326, 328, 330,
332, 334, 336, 338, 340, 342, 344.

"Nic. tahaccum Cuba," 251, 263, 264,
265, 266, 268, 269, 274, 275.

Nicotiana, literature cited, 30, 152,

187, 198, 222, 231, 248, 270, 290,
299, 322, 367, 418, 450.

Nicotiana. Parthenogenesis, Partheno-
carpy, and Phenospermy in, 249.
Nicotiana, Studies in, 1.

Nicotiana acuminata, 23, 262, 350;
plate showing, opp. 158, 168;
description of wild form of,
121; plate showing, opp. 160;
dominance experiments on co-
rolla diameters, 117-168. See
also Dominance, Imperfect.
grandiflora, 119, 120; plate show-
ing, opp. 82.
parvi-Hora, 119, 120.
acutifiora, 22.
aJJiniH, 16, 22, 23, 261, 448.
alata, 17, 22, 262; plate showing,
opp. SO.
var. (jrandiflora, 16, 22, 23.
var. persica, 22.
Bigelovii, 25, 121, 234, 262, 398, 399,
411.

■ Porno,

598.

var. Wallacei, 26, 398.
Forget iana, 23.
glauca, 18, 262, 303, 398, 411.
glutinosa, 18; plate showing, opp.
72.
Langsdorfii, 15-17, 262, 350, 392,
435; plate showing, opp. 64.
var. grandiflora, 16, 23, 393, 406,

407; plate showing, opp. 66.
var. longiflora, 17; plate showing,
oj)p. 68.
longiflora, 21-22; plate showing,
opp. 78.
var. aciitiflora, 21.
multivalvis, 27, 234, 398, 399, 411.
noetiflora, 20; plate showing, opp.
76.
var. albiflora, 20.
Palmeri, 29.

paniculata L., 17, 263; plate show-
ing, op]). 70.
plumhaginifolia, 398.
quadrivalvis, 26, 234, 387, 398, 399,

411.
repanda, 28; plate showing, opp. 84.
rustica, L., 12, 262, 350, 398, 411,
454, 455.
var. asiaiica. 12; ])late showing,

opp. 48.
var. brasilia, 13, 399; plate show-
ing, opp. 50.
var. ]inmili>t, 13; plate showing,

oi)p. 52.
var. jamaicensis, 13, 14; plate

showing, opp. 54.
var. pumila?, 15; plate showing,

opj). 60, 62.
var. scahra, 141 ; plate showing,

opp. 56.
var. iexana, 13, 15, 233; plate
showing, opp. 58.
Sanderac, 398, 399, 411.
suaveolens, 24, 122, 387, 398, 411.

[586]

Index

sylvestris, 29, 189, 261, 262, 277,

296, 302, 303, 350, 387, 388, 389,

411, 448, 459; plate showing, opp.

86.
Tahacum, 3, 261, 296, 302, 350, 352,
353, 454, 455; types of, 4-11,
460-461 ; plate showing hybrid
seedlings of, opp. 168; races in,
458-459, 491; taxonomic i^rob-
lems, 461 ; origin and interrela-
tionships of varieties of, 510-
513; influence of environment,
513; teratological forms in,
513; residual heredity in, 515-
516, 520.

var. alba. See Alia-macrophylla
series.

var. angiistifoUa, 7, 9, 10, 233,
262; description of (height,
habit, leaf, flower, etc.), 463-
465. See also Angustifolia-
macrophylla series.

var. anricnlata, type derivative,
475, 479, 484-485; X macro-
l^hylJa, 488; X sessUifoUa, 489.

var. hrasiUensis ("Brazilian"),
4, 262, 463.

var. caJycina, 6, 262, 461; plate
showing, opp. 38.
"Cavala," 262, 463. See also Ca-
vala tobacco.

var. coJossca, 19.

var. commutata, 16.

var. fruticosa, 6, 7.

var. liavanensis, 4.

var. lancifoJia, 6.

var. macrophyUa, 5, 8, 89, 90, 233,
262, 277, 398, 399, 411, 461-463;
description of, 465-467; con-
trasted with alba, 505. See also
Alba-macropltylla ; Angustifolia
macrophyUa.

var. purpurea. 10-11, 189, 262,
441; plate showing, opp. 46.
"Marvland," 5, 233, 262, 390, 398,
401, 411, 461.

var. sanguiuea, 11.

var. sessilifolia, type derivative,
475, 480, 485; 'x macrophyUa,
487; X aurifulaia, 489.

var. ste7wp]iyUa, tvpe derivative,
474, 47.5-476, 484, 485; X auri-
culata, 489.

var. virginica, 6, 89, 90, 461.
tomentosa, 18, 19, 262, 303; plate

showing, opp. 74.
trigonophylla, 28.

var. ipomopftiflorn, 29.

var. puUa, 29.

var. sordida, 29.
vincaeflora, 24, 122.
viscosa, 23.

Nicotiana hybrids, inheritance in, 87,
117, 169, 223, 457, passim; weight
of seeds, 87-116; technique and
methods of experiment, 126-131;
flowering tendency, 304.
Seed: size, 91; color and weight,
92; germination, 96-101; devel-
opment, 101-103; conclusions re-
garding, 108, 109; abortive
(phenospermic), 265. See also
Germination of tobacco seed;
Mendelian inheritance in Nico-
tiana Tdlxicum.

Nicotiana Hybrids Made with N. syl-
vestris as a Parent, Partial Ster-
ility of, 1S9, 27;i, 293.

Nicotiana Hybrids, Quantitative Stu-
dies of Inheritance in, 87, 169,
223.

Nicotiana Tahacum, Inheritance in.
A Report on the Results of the
Crossing of Certain Varieties,

457.

Niles, California, 121.

Nitrogen (sodium nitrate), used in
nutrition experiments on Nicoti-
ana, 283.

Nutrition, in relation to pollen ger-
mination, 280-281; in relation to
sterility and flower-fall, 281-289;
ferric chloride used in experi-
ments in, 285.

Oxyhathus, 350, 353.

Parthenogenesis, Parthenocarpy, and
Phenospermy in Nicotiana, 249-
271, 274-275.

Partial Sterility of Nicotiana Hybrids
Made with A^. sylvestris as a Par-
ent, 189, 273, 293.

Pa via, 351.

Pelargonium, genus, 357.

Pedicel, histology of, 350; technique
of examination, 361; increase in
size and development of mechan-
ical tissues, 369-371; induction
of abscission in, 399-404, 414;
throwing ofl" of, 410'; figures show-
ing, opp. 420, 422, 426, 428.

Persian tobacco, 22.

Peru, 17, 19.

Petum angiu^tifolium, 9.

Petunia, ,367.

hybrida, 366, 398, 399, 411.

Pctunioides, 19-30.

Phenospermy, application of term,
265, 269.

Plienotypo variation, 490, 493.

riios])liorus used in nutrition experi-
ments on Nicotiana, 283.

Physiological "unit characters," 177-
181, 197.

Physiology of Nicotiana hybrids, prob-
lems "of, 275, 297, 313-314.

[587]

Index

Pisum, 176, 446.

Pollen germination, experiments on,
276-281, 288, 289, 304; figures
showing, opp. 292.

Pollination, effect of, on abscission
of corolla, 388, 417; on time be-
tween anthesis and flower-fall,
389; premature, 433; self, efforts
to secure artificially, 433-434.

Pollination, Controlled, in Nicotiana,
429; method and technique of ex-
periments, 430; results of, 431.

Populus, 350, 352.

Potassium, used in nutrition experi-
ments on Nicotiana, 284.

Quantitative characters, inheritance
of, 459, 513, 514-516.

Quantitative Studies of Inheritance
in Xieotiana Hvbrids, b~, 169,
223.

Eaces in Nicotiana Tahacum, 458-459,
491.

Eeaction svstem contrasts in hered-
ity, 301, 313.

Residual heredity in Tahacum, 515-
516, 520.

Bicinus, 351.

Rigor, in relation to poisonous gases,
445.

Bustica, section, 11-12; types of, 12-
19.

Salix, 350, 352.

Salpichrora, 367.

rhomboidea, 366, 398, 399, 411.

Salpiglossus, 367.

sinuata, 366, 398, 399, 411.

Salvia, 350, 352.
splendens, 444.

Scliilolysis, 353.

Seeding character of Nicotiana hy-
brids, 193.

Segregation, in Nicotiana hybrids,
192, 196, 247, 312-313, 459-460,
and passim.

Separation cells, definition of, 349;
in Nicotiana, 352.

Separation layer, definition of, 349;
position of, 350; origin of, 351,
368; cytology of, 352; predeter-
mined location of, 415.

Separation zone, definition of, 349;
development of, 367-369; figure
showing, 368.

SessilifoJia, derivatives, 475, 480, 485;
X mncrophyJla, 487 ; X auricu-
lata, 489.

Setchell, W. A., 1, 457.

Soil conditions, factor in abscission,
416.

Solanaceae, Abscission of Flowers
and Fruits in, 347, 359.

Solanum jasminioides, 366, 398, 411.
marginatum, 366.
nigrum, 352, 366, 398, 399.
tuberosum, 350, 351, 366, 367, 411,

412.
umbeUiferum, 366, 398, 411.
verbascifolium, 366, 371, 398, 399,
411.

Sprengel, cited, 19.

Stenophylla, derivatives, 474, 475-476,
484, 485 ; X auriculata, 490.

Sterility, Partial, of Nicotiana Hy-
brids Made with N. sylvestris as
a Parent, 189, 193, 273.

Style, abscission of, in Datura, and in
Nicotiana, 384-385, 413; effect of
removal of, on abscission, and on
time of flower-fall of corolla,
388-389.

Sugar, influence of amount of, dur-
ing abscission, 381.

Sulfuric acid treatment in germina-
tion of tobacco seed, 199, 200,
203, 209, 219, 220.

Taxonomic problems in Nicotiana Ta-
bacum, 461.

Temj>erature, influence on abscission
time, 397, 409, 414, 416; contrib-
uting factor in germination of
tobacco seed, 451.

Teratological forms in Tabacum, 513.

Thomas, Mrs. R. H., production of
parthenogenetic seed in Nicotiana,
249.

Tobacco smoke. See Narcotic vapors.

Turgor. See Cell turgor.

Turkey, tobacco seeds from, 5.

"Unit character" conception in stu-
dies of heredity, 174-186; bearing
of, on flower size question in
Nicotiana hvbrids, 175; physio-
logical, 177-181, 197.

Vegetative reproduction in Nicotiana,
197.

Verhascum, genus, 357.

Viability of seed, 209-215, 220, 233,
240,' 246, 263, 453, 454.

Vitis, 350.

White, O. E., cited, 521.

White tobacco, 7-8, 233; plate show-
ing, opp. 40, 461.

[588]

EERATA

Page 197, line 30. For materials read laterals.

Page 340, plate 45. Fig. 1 should be fig. 2 ; fig. 2 should be fig. 1.

[5S9J

UNIVERSITY OF CALIFORNIA PUBLICATIONS

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Vol. 5, No. 1, pp. 1-86, pis. 1-28 Issued December 5, 1912

STUDIES IN NICOTIANA, I

B5r
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May, 1909 _ 15

Index, pp. 397-400.

Vol. 4. 1910-1912.

1. Studies In Ornamental Trees and Shrubs, by Harvey Monroe HalL Pp.

1-74; plates 1-11; 15 text-figures. March, 1910 75

2. Qracilariophlla, a New Parasite on Graciluria confervoides, by Harriet

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plate 15. May, 1910 _ _„ 15

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Lyon Gardner. Pp. 121-12te; plates 16-17. August, 1910 15

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 :..„ 05

8. On a Colacodasya from Southern California, by Mabel Effie McFadden.

Pp. 143-150; plate 19. February, 1911 „ „ .05

9. Fructification of Macrocystis, by Edna Juanita Hoflfman. Pp. 151-158;

plate 20. February, 1911 05

10. Erythrophyllum delesserioides J. Ag., by Wilfred Charles Twiss. Pp.

159-176; plates 21-24. March, 1911 15

11. Plantae Mexlcanae Purpusianae, III, by T. S. Brandegee. Pp. 177-194.

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12. New and Noteworthy Californian Plants, I, by Harvey Monroe Hall.

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229-268; plates 25-31. May, 1912 40

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Pp. 269-281. June, 1912 15

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Harper Goodspeed. Pp. 87-168. December, 1912 1.00

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riam, Editors. Price per volume $3.50. Volumes I (pp. 428), II (pp. 450), III (pp.
475), rv (pp. 462), V (pp. 458) and VI completed. Volume VII in progress.

ZOOLOGY. — W. E. Eitter and C. A. Kofoid, Editors. Price per volume $3.50. Volumes I
(pp. 317), II (pp. 382), III (pp. 383), IV (pp. 400), V (pp. 440), VI (pp. 478), VH
(pp. 446), and VIII (pp. 357) completed. Volumes IX and X in progress. Com-
mencing with Volume II, this series contains the Contributions from the Laboratory
of the Marine Biological Association of San Diego.

MEMOIES OF THE XJNIVEESITY OF CALIFOENIA (Quarto).

Vol. 1. 1. Triassic Ichthyosauria, with special reference to the American Forms,
by John 0. Merriam. Pp. 1-196; plates 1-18; 154 text-figures. Sep-
tember, 1908 $3.00

2. The Fauna of Eancho La Brea. Part 1, Occurrence, by John C. Mer-
riam. Pp. 197-213, plates 19-23. November, 1911 30

2. Silva of California, by W. L. Jepson. Pp. 480; plates 85. December,
1910. $9; buckram, $10; carriage extra.

Other series in Classical Philology, Education, Engineering, Entomology, Egjrptian
Archaeology, Graeco-Eoman Archaeology, History, Modem Philology, Philosophy, Semitic
Philology.

UNIVEESITY OF CALIFOENIA CHEONICLE.— An official record of University Ufe,
issued quarterly, edited by a committee of the Faculty. Price $1 per year. Current
volume No. XTV.

ADMINISTEATIVE BULLETINS OF THE UNIVEESITY OF CALIFOENIA.— Edited by
the Eecorder of the Faculties. Includes tho Eeglster, the President's Eeport, the
Secretary's Eeport, and other official announcements.

European agent for the series in American Archaeology and Ethnology, Classical Phil-
ology, Education, Philosophy, and Semitic Philology, Otto Harrassowltz, Leipzig. For th»
series in Botany, Geology, Pathology, Physiology, Zoology, and also American Archaeology
and Ethnology, B. Friedlaender & Sohn. Berlin.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 3, pp. 169-188 Issued January 9, 1913

QUANTITATIVE STUDIES OF
INHERITANCE IN NICOTIANA HYBRIDS. 11,

BY

THOMAS HARPER GOODSPEED

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Kote.—- Tlie University of California Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University will be sent upon request. For sample copies, lists of
publications and other information, address the Manager of the University Press, Berkeley,
California, U. 8. A. All matter sent in exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. 8. A.

OTTO HABBASSOWITZ B. FBIEDLAENDEB & SOHN

LEIPZIG BEBLIN

Agent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnology, Classical Philology, aeology and Ethnology, Botany, Geology,
Education, Modem Philology, Philosophy, Mathematics, Pathology, Physiology, Zool-
Psychology. ogy, and Memoirs.

BOTANY.— W. A. Setchell, Editor. Price per volume, $3.50. Volumes I (pp. 418), n (pp.
360), ni (pp. 400), completed. Volume IV (in progress).

Cited as Univ. Calif. Publ. Bot.

Vol. 1. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Monroe

Hall. Pp. 1-140; plates 1-14. June, 1902 $1.00

2. Two new Ascomycetous Fungi Parasitic on Marine Algae, by Minnie

Eeed. Pp. 141-164; plates 15-16. November, 1902 25

S. Algae of Northwestern America, by William Albert Setchell and Na-

thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 2.26

Vol. 2. 1. A Review of Califomian Polemoniaceae, by Jessie Milliken. Pp. 1-

71; plates 1-11. May, 1904 ..^ .75

2. Contributions to Cytological Technique, by W. J. V. Osterhont. Pp.

73-90; 5 text-figures. June, 1904 .~. .25

3. Limu, by William Albert Setchell. Pp. 91-113. April, 1905 . 25

4. Post-Embryonal Stages of the Laminariaceao, by William Albert

Setchell. Pp. 115-138; plates 13-14. April, 1905 - 25

5. Eegeneration among Kelps, by William Albert SetchelL Pp. 139-168;

plates 15-17. July, 1905 _ SO

6. A New Genus of Ascomycetous Fungi, by Nathaniel Lyon Gardner.

Pp. 169-180; plate 18. July, 1905 . .15

7. Teratology in the Flowers of some Califomian Willows, by William

Wamer Mott. Pp. 181-226; plates 16-20. December, 1905 .50

8. 9, 10, 11. (In one cover.) The Besistance of Certain Marine Algae to

Changes in Osmotic Pressure and Temperature. The Bdle of Os-
motic Pressure in Marine Plants. On the Importance of Physiolog-
ically Balanced Solutions for Plants. The Antitoxic Action of
Potassium on Magnesium. By W. J. V. Ostterhout. Pp. 227-236.
March, 1906 _ _ ^ _ .25

12. Cytological Studies in Cyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-296; plates 21-26. November, 1906 ..._ 1.00

13. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Th^riot. Pp. 297-308; plates 27-28. December, 1906 10

14. Some Unreported Alaskan Sphagna, together with a Suniicary of the

Cryptogamic Work of the University of California Botanical Ex-
pedition to Alaska in 1899, by William Albert SetchelL Pp. 309-
315. September, 1907 _ _ .06

16. On Nutrient and Balanced Solutions, by W. J. V. Osterhont. Pp. 317-

318. October, 1907 „ _ „ .05

16. A Synopsis of the North American Godetias, by Willis Linn Jepson.

Pp. 319-354; plate 29. December, 1907 - _ 40

Index, pp. 355-360.

Vol S. 1007-1909.

1. Compositae of Southem California, by Harvey Monroe Hall. Pp. 1-

302; plates 1-3, with a map. December, 1907 ...^ 8.00

2. The Origin, Stracture, and Function of the Polar Caps in SmUacina

amplexicaulis Nutt., by H. D. Densmore. Pp. S03-330; plates 4-8.
► December, 1908 — _... .86

UNIVEaSITT OF CALIFORNIA PUBLICATIONS— (Continued)

3. 4t. (In one coyer.) The Value of Sodium to Plants by Season of Its
ProtectlTC Action. On the Effects of Certain Poisonous Cases on
Plants. By W. J. V. Osterhout. Pp. 331-340. Juno, 1908 .10

6. Contributions to the Knowledge of the California Species of Crusta-
ceous Corallines. I. by Maurice Barstow Nichols. Pp. 341-348;
plate 9. December, 1908 ..... — „- ._ -. .10

6. Contributions to the Knowledge of the California Species of Crusta-

ceous Corallines, n. by Maurice Barstow Nichols. Pp. 349-370;
plates 10-13. April, 1909 „ 15

7. New Chlorophyceae from California, by Nathaniel Lyon Gardner. Pp.

371-375; plate 14. April, 1909 - _ 10

8. Plantae Mezlcanae Purpusiaoae, by T. S. Brandegee. Pp. 377-396.

May, 1909 ^ .15

Index, pp. 397-400.

Vol. 4. 1910-1912.

1. Studies in Ornamental Trees and Shrubs, by Harvey Monroe Hall. Pp.

1-74; plates 1-11; 15 text-figures. March, 1910 — .75

2. Gracilariophlla, a New Parasite on Gracilaria confervoides, by Harriet

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 _. .10

3. Plantae Mexicanae Purpusianae, II, by T. S. Brandegee. Pp. 85-95.

May, 1910 _ , 10

4. Leuvenia, a New Genus of Flagellates, by N. L. Gardner. Pp. 97-106;

plate 14. May, 1910 lO

5. The Genus Sphaerosoma, by William Albert Setchell. Pp. 107-120;

plate 15. May, 1910 .,.,......„_ . ,.„.„..... 15

6. Variations in Nuclear Extrusion Among the Fucaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; plates 16-17. August, 1910 15

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142;, plate 18. February,
1911 05

8. On a Colacodasya from Southern California, by Mabel Effie McFadden.

Pp. 143-150; plate 19. February, 1911 „ . .05

9. Fructification of Macrocystis, by Edna Juanita Hoffman. Pp. 151-168;

plate 20. February, 1911 _ , — .05

10. Erytlirophyllum delesserioides J. Ag., by Wilfred Charles Twiss. Pp.

159-176; plates 21-24. March, 1911 . — .15

11. Plantae Mexicanae Purpusianae, III, by T. S. Brandegee. Pp. 177-194.

July, 1911 - -.. .15

12. New and Noteworthy Califomian Plants, I, by Harvey Monroe Hall.

Pp. 195-208. March, 1912 ..._ ~ 15

13. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 .- .20

14. Algae Novae et Minus Cognitae, I, by William Albert Setchell. Pp.

229-268; plates 25-31. May, 1912 40

15. Plantae Mexicanae Purpusianae, IV, by tTownshend Stith Erandegee.

Pp. 269-281. June, 1912 , 15

Vol. 5. 1912-.

1. Studies in Nicotiana, I, by V/illiam Albert Setchell. Pp. 1-86. De-

cember, 1912 - 1.25

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

3. Quantitative Studies of Inheritance in Nicotiana Hybrids, II, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 20

UNIVSRSITY OF CALIFORNIA PUBLICATIONS— (Continued)

AMEEICAN ARCHAEOLOGY AND ETHNOLOGY.— A. L. Kroeber, Editor. Price
per volume, $3.50 (Volume I, $4.25). Volumes I-IX completed.
Volumes X and XI in progress.

GEOLOGY. — Bulletin of the Department of Geology. Andrew C. Lawson and John C.
Merriam, Editors. Price per volume, $3.50. Volumes I (pp. 428),
n (pp. 450), in (pp. 475), IV (pp. 462), V (pp. 458), and VI,
completed. Volume vn in progress.

ZOOLOGY. — W. E. Ritter and C. A. Kofoid, Editors, Price per volume, $3.50. Volumes
I ^pp. 317), II (pp. 382), III (pp. 383), IV (pp. 400), V (pp. 440),
VI (pp. 478), vn (pp. 446), and Vni (pp. 357) completed.
Volumes IX, X, and XI in progress. Commencing with Volume n,
this series contains the Contributions from the Laboratory of the
Marine Biological Association of San Diego.

MEMOIRS OF THE UNIVERSITY OF CALIFORNIA (Quarto).

Vol. 1. 1. Triassic Ichthyosauria, with special reference to the Americaai Forms,
by John C. Merriam. Pp. 1-196; plates 1-18; 154 text-figures. Sep-
tember, 1908 _ _ „„ „ $3.00

2. The Fauna of Rancho La Brea. Part 1, Occurrence, by John 0. Mer-
riam. Pp. 197-213, plates 19-23. November, 1911 ... . 30

2. Silva of California, by W. L. Jepson. Pp. 480; plates 85. December,
1910. $9; buckram, $10; carriage extra.

Other series in Classical Philology, Economics, Education, Egyptian Archaeology, Engi-
neering, Entomology, Graeco-Roman Archaeology, History, Mathematics, Psychology, Semitic
Philology, Modern Philology.

UNIVERSITY OF CALIFORNIA CHRONICLE.— An official record of University life,
issued quarterly, edited by a committee of the faculty. Price, $1.00 per
year. Current volume No. XIV.

ADMINISTRATIVE BULLETINS OF THE UNIVERSITY OF CALIFORNIA.— Edited by
the Recorder of the Faculties. Includes the Register, the President's
Report, the Secretary's Report, and other official announcements.

European agent for the series in American Archaeology and Ethnology, Classical Phil-
ology, Education, Philosophy, and Semitic Philology, Otto Harrassowltz, Lelpzlf. For tli«
series in Botany, Geology, Pathology, Physiology, Zoology, and »1bo American Arehaeolog^f
and Ethnology, £. Friedlaender & Sohn. Berlin.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 4, pp. 189-198 Issued March 21, 1913

ON THE PARTIAL STERILITY

OF NICOTIANA HYBRIDS MADE WITH

N. SYLVESTRIS AS A PARENT

BY

THOMAS HARPER GOODSPEED

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Hote. — The University of California Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University will be sent upon request. For sample copies, lists of
publications and other information, address the Manager of the University Press, Berkeley,
California, U. S. A. All matter sent in exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. S. A.

OTTO HAEEASSOWITZ E. FEIEDLAENDEB & SOHN
LEIPZIG BERLIN
Agent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnology, Classical Philology, aeology and Ethnology, Botany, Geology,
Education, Modem Philology, Philosophy, Mathematics, Pathology, Physiology, Zool-
Psychology. ogy, and Memoirs.

BOTANY.— W. A. Setchell, Editor. Price per volxunc, $3.50. Volumes I (pp. 418), n (pp.
860), ni (pp. 400), completed. Volume IV (in progress).

Cited as Univ. Calif. Publ. Bot.

Vol. 1. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Monroe

Hall. Pp. 1-140; plates 1-14. June, 1902 _ $1.00

2. Two new Ascomycetous Fungi Parasitic on Marine Algae, by Minnie

Eeed. Pp. 141-164; plates 15-16. November, 1902 25

3. Algae of Northwestern America, by William Albert Setchell and Na-

thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 2.26

Vol. 2. 1. A Eeview of Califomian Polemoniaceae, by Jessie MUliken. Pp. 1-

71; plates 1-11. May, 1904 - 76

2. Contributions to Oytological Technique, by W. J. V. Osterhout. Pp.

73-90; 5 text-figures. June, 1904 „ .25

3. Limu, by William Albert Setchell. Pp. 91-113. April, 1905 .. J25

4. Post-Embryonal Stages of the Laminariaceae, by William Albert

Setchell. Pp. 115-138; plates 13-14. April, 1905 .26

5. Eegeneration among Kelps, by William Albert Setchell. Pp. 139-168;

plates 15-17. July, 1905 ..._ _ _ .30

6. A New Genus of Ascomycetous Fungi, by Nathaniel Lyon Gardner.

Pp. 169-189; plate 18. July, 1905 „ _ 16

7. Teratology in the Flowers of some Califomian Willows, by William

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 JJO

8. 9, 10, 11. (In one cover.) The Eesistance of Certain Marine Algae to

Changes in Osmotic Pressure and Temperature. The E61e of Os-
motic Pressure in Mailne Plants. On the Importance of Physiolog-
ically Balanced Solutions for Plants. The Antitoxic Action of
Potassium on Magnesium. By W. J. V. Osterhout. Pp. 227-236.
March, 1906 _ _. .25

12. Cytological Studies in Cyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-296; plates 21-26. November, 1906 „ 1.00

13. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Th^riot. Pp. 297-308; plates 27-28. December, 1906 .10

14. Some Unreported Alaskan Sphagna, together with a Sunurary of the

Cryptogamic Work of the University of California Botanical Ex-
pedition to Alaska in 1899, by William Albert Setchell. Pp. 309-
315. September, 1907 _ 05

15. On Nutrient and Balanced Solutions, by W. J. V. Osterhout. Pp. 317-

318. October, 1907 . „. 06

16. A Synopsis of the North American Godetias, by Willis Linn Jepson.

Pp. 319-354; plate 29. December, 1907 _. .40

Index, pp. 355-360.

Vol S. 1907-1909.

1. Compositae of Southern California, by Harvey Monroe Hall. Pp. 1-

302; plates 1-3, with a map. December, 1907 „ 8.00

2. The Origin, Stmcture, and Function of the Polar Caps in Smaadiui

amplexicaulis Nutt., by H. D. Densmore. Pp. 303-330; plates 4-8.
December, 1908 .86

UNIVE3SITY OF CALIFOENIA PUBLICATIONS— (Continued)

S. 4. (In one cover.) The Value of Sodium to Plants by Eeason of Its
Protective Action. On the Effects of Certain Poisonous Gases on
Plants. By W. J. V. Osterhout. Pp. 331-340. June, 1908 10

5. Contributions to the BZnowledge of the California Species of Crusta-

ceous Corallines. I. by Maurice Barstow Nichols. Pp. 341-348;
plate 9. December, 1908 „ 10

6. Contributions to the Knowledge of the California Species of Crusta-

ceous Corallines, n. by Maurice Barstow Nichols. Pp. 349-370;
plates 10-13. April, 1909 „ 15

7. New Chlorophyceae from California, by Nathaniel Lyon Gardner. Pp.

371-375; plate 14. April, 1909 ^ _ .10

8. Plantae Mexicanae Purpusianae, by T. S. Brandegee. Pp. 377-896.

May, 1909 „ ..„ _ 16

Index, pp. 397-400.

Vol. 4. 1910-1912.

1. Studies in Ornamental Trees and Shrubs, by Harvey Monroe HalL Pp.

1-74; plates 1-11; 15 text-figures. March, 1910 _ 75

2. Gracilariophila, a New Parasite on Gracilaria confervoides, by Harriet

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 10

3. Plantae Mexicanae Purpusianae, II, by T. S. Brandegee. Pp. 85-95.

May, 1910 „ .10

4. Leuvenia, a New Genus of Plagellates, by N. L. Gardner. Pp. 97-106;

plate 14. May, 1910 10

5. The Genus Sphaerosoma, by William Albert Setchell. Pp. 107-120;

plate 15. May, 1910 - 15

6. Variations in Nuclear Extrusion Among the Fucaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; plates 16-17. August, 1910 ..........^ .16

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 , .^ .05

8. On a Colacodasya from Southern California, by Mabel Effie McFadden.

Pp. 143-150; plate 19. February, 1911 „ .05

9. Fructification of Macrocystis, by Edna Juanita Hoffman. Pp. 151-158;

plate 20. February, 1911 „ 05

10. Erythrophyllum delesserioides J. Ag., by Wilfred Charles Twiss. Pp.

159-176; plates 21-24. March, 1911 ..... , ...„ .15

11. Plantae Mexicanae Purpusianae, III, by T. S. Brandegee. Pp. 177-194.

July, 1911 _ 15

12. New and Noteworthy Calif omian Plants, I, by Harvey Monroe Hall.

Pp. 195-208. March, 1912 „ 15

13. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 „ 20

14. Algae Novae et Minus Cognitae, I, by William Albert Setchell. Pp.

229-268; plates 25-31. May, 1912 .40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stith Brandegee.

Pp. 269-281. June, 1912 15

Vol. 5. 1912-.

1. Studies in Nicotiana, I, by William Albert Setchell. Pp. 1-86. De-

cember, 1912 1.25

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

3. Quantitative Studies of Inheritance in Nicotiana Hybrids, n, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 20

4. On the Partial Sterility of Nicotiana Hybrids made with N. Sylvestris

as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 : 10

UNIVEESITY OF CALIFOENIA PUBLICATIONS— (Continued)

AMEEICAN ABCHAEOLOGT AKD ETHNOLOGY.— A. L. Kroeber, Editor. Price
per volume, $3.50 (Volume I, ?4.25). Volumes I- IX completed.
Volumes X and XI in progress.

GEOLOGY. — Bulletin of the Department of Geology. Andrew C. Lawson and John 0.
Merriam, Editors. Price per volume, $3.50. Volumes I (pp. 428),
n (pp. 450), in (pp. 475), rV (pp. 462), V (pp. 458), and VI,
completed. Volume VII in progress.

ZOOLOGY. — ^W. E. Bitter and C. A. Kofoid, Editors. Price per volume, $3.50. Volumes
I (pp. 317), n (pp. 382), in (pp. 383), IV (pp. 400), V (pp. 440),
VI (pp. 478), Vn (pp. 446), and Vm (pp. 357) completed.
Volumes IX, X, and XL in progress. Commencing with Volume EC,
this series contains the Contributions from the Laboratory of the
Marine Biological Association of San Diego.

MEMOIES OF THE UNIVEESITY OF CALTFOENIA (Quarto).

VoL 1. 1. Triaasic Ichthyosauria, with special reference to the American Forms,
by John C. Merriam. Pp. 1-196; plates 1-18; 154 text-figures. Sep-
tember, 1908 „. — . Li.^-.: $S.(X)

2. The Fauna of Eancho La Brea. Part 1, Occurrence, by John 0. Mer-
riam. Pp. 197-213, plates 19-23. November, 1911 — .SC

2. Silva of California, by W. L. Jepson. Pp. 480; plates 85. December,
1910. $9; buckram, $10; carriage eztra>

Other series in Classical Philology, Economics, Education, Egyptian Archaeology, Engi-
neering, Entomology, Graeco-Eoman Archaeology, History, Mathematics, Psychology, Semitic
Pliilology, Modem Philology.

UNIVEESITY OF CALIFOENIA CHEONICLE.— An official record of University life,
issued quarterly, edited by a committee of the faculty. Price, $1.00 per
year. Current volume No. XTV.

ADMINISTEATIVE BULLETINS OF THE UNIVEESITY OF CALIFOENIA.— Edited by
the Eecorder of the Faculties. Includes the Eegister, the President's
Eeport, the Secretary's Eeport, and other official announcements.

European agent for the series in American Archaeology and Ethnology, Classical Phil*
ology, Education, Philosophy, and Semitic Philology, Otto Harrassowltx, Leipzig. For tbi
series in Botany, Geology, Pathology, Physiology, Zoology, and also American Archssology
and Ethnology, B. Friedlaender & Sohn. Berlin.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 5, pp. 199-222 Issued May 15, 1913

NOTES ON THE GERMINATION OF
TOBACCO SEED

BY

THOMAS HARPER GOODSPEED

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Note. — The University of California Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University "will be sent upon request. For sample copies, lists of
publications and other information, address the Manager of the University Press, Berkeley,
California, U. S. A. All matter sent in exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. S. A.

OTTO HAEEASOWITZ R. FEIEDLANDEE & SOHN
LEIPZIG BERLIN
Agent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnology, Classical Philology, aeology and Ethnology, Botany, Geology,
Education, Modem Philology, Philosophy, Mathematics. Pathology, Physiology, Zool-
Psychology. ogy, and Memoirs.

BOTANT.— W. A. Setchell, Editor. Price per volume, $3.50. Volumes I (pp. 418), n .(pp
860), in (pp. 400), completed. Volume IV (in progress).

Cited as Univ. Calif. Pnbl. Bot.

VoL 1. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Monroe

Hall. Pp. 1-140; plat«8 1-14. June, 1902 11.00

2. Two new Ascomycetous Fungi Parasitic on Marine Algae, by Minnie

Eeed. Pp. 141-164; plates 15-16. November, 1902 25

S. Algae of Northwestern America, by William Albert Setchell and Na-
thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 2.25

VoL 2. 1. A Review of Califumlan Polemoniaceae, by Jessie Mllliken. Pp. 1*

71; plates 1-11. May, 1904 75

2. Contributions to Cytologlcal Technique, by W. J. V. Osterhout. Pp,

73-90; 5 text-figures. June, 1904 25

3. Limu, by William Albert Setchell. Pp. 91-113. April, 3905 25

4. Post-Embryonal Stages of the Laminariace&o, by William Albert

SetcheU. Pp. 115-138; plates 13-14. April, 1905 25

5. Regeneration among Kelps, by William Albert Setchell. Pp. 139-168;

plates 15-17. July, 1905 .30

6. A New Genus of Ascomycetous Fungi, by Nathaniel Lyon Gardner.

Pp. 169-180; plate 18. July, 1905 15

7. Teratology in the Flowers of some Califomian Willows, by William

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 50

8. 9, 10, 11. (In one cover.) The Resistance of Certain Marine Algae to

Changes in Osmotic Pressure and Temperature. The Rdle of Os-
motic Pressure in Marine Plants. On the Importance of Physiolog-
ically Balanced Solutions for Plants. The Antitoxic Action of
Potassiiim on Magnesium. By W. J. V. Osterhout. Pp. 227-238.
IKIarch, 1906 . _ _ .26

12. Cytologlcal Studies in Cyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-296; plates 21-26. November, 1906 „. 1.00

IS. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Th^riot. Pp. 297-308; plates 27-28. December, 1906 .10

14. Some Unre];>orted Alaskan Sphagna, together with a Sunurary of the

Cryptogamlc Work of the University of California Botanical Ex-
pedition to Alaska in 1899, by William Albert SetchelL Pp. 309-
315. September, 1907 _ .06

15. On Nutrient and Balanced Solutions, by W. J. V. Osterhout. Pp. 317-

318. October, 1907 .._ .06

16. A Synopsis of the North American Godetias, by Willis Linn Jepson.

Pp. 819-354; plate 29. December, 1907 .40

Index, pp. 355-360.

VoL 8. 1907-1909.

1. Compositae of Southern California, by Harvey Monroe Hall. Pp. 1-

302; plates 1-3, with a map. December, 1907 S.OO

S. The Origin, Structure, and Function of the Polar Caps in Smilacina

amplexicaulis Nntt., by H. D. Densmore. Pp. 303-380; plates 4-8.

December, 1908

UNIVERSITY OF OAUFOBNIA PUBUOATIONS— (Oontiiined)

5. A. (In one coyer.) The Value of Sodimn to Plants by Season of Ita

ProtectiTe Action. On tbe Effects of Certain Poisonous Gases on
Plants. By W. J. V. Osterbout. Pp. 331-340, June, 1908 ^0

6. Contributions to the Knowledge of the California Species of Orusta-

ceous Corallines. I. by Maurice Barstow Nichols. Pp. S41-348;
plate 9. December, 1908 _ .10

6. Contributions to the Knowledge of the California Species of Crusta-

ceous Corallines, n. by Maurice Barstovr Nichols. Pp. 349-370;
plates 10-13. April, 1909 _„ M

7. New Chlorophyceae from California, by Nathaniel Lyon Gardner. Pp.

371-375; pUte 14. April, 1009 „ .10

8. Plantae Mexicanae Purposlanae, by T. S. Brandegee. Pp. 377-396.

May, 1909 « — -~. — «16

Index, pp. 397-400.
VoL 4. 1910-1912.

1. Studies in Ornamental Trees and Shrubs, by Harrey Monroe Hall. Pp.

1-74; plates 1-11; 15 text-figures. March, 1910 75

2. GracUarlophila, a New Parasite on Gracilaria confcrvoidei, by Harriet

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 10

8. Plantae Mexicanae Purpusianae, n, by T. 8. Brandegee. Pp. 85-95.

May, 1910 - _ 4.0

4. Leuvenia, a New Genus of Flagellates, by N. L. Gardner. Pp. 97-106;

plat^ 14. May, 1910 .10

5. The Genus Sphaerosoma, by William Albert Setchell. Pp. 107-120;

plate 15. May, 1910 15

6. Variations In Nuclear Extrusion Among the Fucaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; plates 16-17. August, 1910 J15

7. The Nature of the Carpostomes In the Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 „ ~ - .06

8. On a Colacodasya from Southern California, by Mabel Effie McFadden.

Pp. 143-150; plate 19. February, 1911 .05

9. Fructification of Macrocystis, by Edna Juanlta Hoffman. Pp. 151-158;

plate 20. February, 1911 _ — - 06

10. Erythrophyllum delesaerioides J. Ag., by Wilfred Charles Twiss. Pp.

159-176; plates 21-24. March, 1911 . J.6

11. Plantae Mexicanae Purpusianae, HI, by T. S. Brandegee. Pp. 177-194.

July, 1911 _ - — .16

12. New and Noteworthy Califomian Plants, I, by Harvey Monroe HalL

Pp. 195-208. March, 1912 „ - —-. .16

13. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 „ - ~ ^0

14. Algae Novae et Minus Cognitae, I, by WUliam Albert Setchell. Pp.

229-268; plates 25-31. May, 1912 -- 40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stith Brandegee.

Pp. 269-281. June, 1912 ~ 15

16. Comparative Development of the Cystocarps of Antithamnion and

Prionitis, by Lyman Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 20

17. Fungus Galls on Cystoseira and Ealidrys. by Lulu May Estee. Pp. 305-

316; plate 35. March, 1913 - -. .10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374; plates 36-

53. April, 1913 ..™ 75

Vol 5. 1912-.

1. Studies in Nicotiana, I, by William Albert Setchell. Pp. 1-86. De-

cember, 1912 1.25

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

3. Quantitative Studies of Inheritance in Nicotiana Hybrids, n, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 _. .20

4. On the Partial Sterility of Nicotiana Hybrids made with N. Sylvestris

as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 10

5. Notes on the Germination of Tobacco Seed, by Thomas Harper Good-

speed. Pp. 199-222. May, 1913 25

UNIVEESITY OF CALIFORNIA PUBLICATIONS— (Continued)

AMBEICAN AECHAEOLOGY AND ETHNOLOGY.— A. L. Ejoeber, Editor. Price
per volume, $3.50 (Volume I, $4.25). Volumes I-IX completed.
Volumes X and XI in progress.

GEOLOGY. — ^Bulletin of the Department of Geology. Andrew 0. Lawson and Jolm 0.
Merriam, Editors. Price per volume, $3.50. Volumes I (pp. 428),
n (pp. 450), in (pp. 475), IV (pp. 462), V (pp. 458), and VI,
completed. Volume VII in progress.

ZOOLOGY. — ^W. E. Eitter and 0. A. Kofoid, Editors. Price per volume, $3.50. Volumes
I (pp. 317), II (pp. 382), III (pp. 383), IV (pp. 400), V (pp. 440),
VI (pp. 478), Vn (pp. 446), and Vm (pp. 357) completed.
Volumes IX, X, and XI in progress. Commencing with Volume II,
this series contains the Contributions from the Laboratory of the
Marine Biological Association of San Diego.

MEMOIES OF THE UNIVEESITY OF CALIFOENIA (Quarto),

VoL 1. 1. Triaasic Ichthyosaurla, with special reference to the American Forma,
by John C. Merriam. Pp. 1-196; plates 1-18; 154 text-figures. Sep-
tember, 1908 _..„ „ «.... $3.00

2. The Fauna of Rancho La Brea. Part 1, Occurrence, by John 0. Mer-
riam. Pp. 197-213, plates 19-23. November, 1911 _ .30

Vol. 2. Silva of California, by W. L. Jepson. Pp. 480; plates 85. December,

1910. $9; buckram, $10; carriage extra.
Vol. 3. Business Cycles, by Wesley C. Mitchell _ {In press)

Other series in Classical Philology, Economics, Education, Egyptian Archaeology, Engi-
neering, Entomology, Graeco-Koman Archaeology, History, Mathematics, Psychology, Semitic
Philology, Modem Philology.

UNIVERSITY OF CALIFORNIA CHRONICLE,— An official record of University Ufe,
issued quarterly, edited by a committee of the faculty. Price, $1.00 per
year. Current volume No. XIV.

ADMINISTRATIVE BULLETINS OF THE UNIVERSITY OF CALIFORNIA.— Edited by

the Recorder of the Faculties. Includes the Register, the President'!
Report, the Secretary's Report, and other official announcements.

Enropean agent for the series in American Archaeology and Ethnology, Classical PIiil<
ology. Education, Philosophy, and Semitic Philology, Otte Harrassowltz, Leipzig. For tltf
■eries In Botany, Geology, Pathology, Physiology, Zoology, and alio American Arehaeolog;^
and Ethnology, R. Friedlaender & Sohn. Berlin.

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 6, pp. 223-231 Issued April 21, 1915

QUANTITATIVE STUDIES OF INHERITANCE
IN NICOTIANA HYBRIDS. III.

BY

THOMAS HARPER GOODSPEED

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Note. — The University of Oalifomia Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University will be sent upon reciuest. For sample copies, lists of
publications and other information, address the Manager of the University Press, Berkeley,
California, U. S. A. All matter sent in exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. S. A.

OTTO HARPvASOWITZ E. FEIEDLANEEE & SOHN
LEIPZIG BERLIN
Agent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnolog-y, Classical Philology, aeology and Ethnology, Botany, Geography,
Education, Modem Philology, Philosophy, Geology, Mathematics, Pathology, Physi-
Psychology. ology, Zoology, and Memoirs.

BOTANY.— W. A. Setchell, Editor. Price per volume, $3.50. Volumes I (pp. 418), n (pp
860), in (pp. 400), completed. Volume IV (in progress).

Cited as Univ. Calif. Publ. Bot.

Vol. 1. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Monro«

Hall. Pp. 1-140; plates 1-14. Jane, 1902 _ fl.OO

2. Two new Ascomycetous Fungi Parasitic on Marine Algae, by Minnie

Eeed, Pp. 141-164; plates 15-16. November, 1902 25

8. Algae of Northwestern America, by William Albert Setchell and Na-
thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 2.20

Vol. 2. 1. A Eevlew of Califomlan Polemoniaceao, by Jessie Millilfen. Pp. 1-

71; plates 1-11. May, 1904 75

2. Contributions to Cytological Technique, by W. J. V. Ostcrhout. Pp.

73-90; 5 text-figures. June, 1904 25

3. Limu, by William Albert Setchell. Pp. 91-113. April, 1905 25

4. Post-Embryonal Stp.gea of the Laminariaceao, by William Albert

Setchell. Pp. 115-138; plates 13-14. April, 1905 25

5. Eegeneration among Kelps, by William Albert Setchell. Pp. 159-168;

plates 15-17. July, 1905 30

6. A New Genus of Ascomycetous Fungi, by Nathaniel Lyon Gardaer.

Pp. 169-180; plate 18. July, 1905 -.. -.. .15

7. Teratology in the Flowers of some Califomlan Willows, by William

Warner Mott. Pp. 181-226; plates 16-20, December, 1905 50

8. 0, 10, 11. (In one cover.) The Resistance of Certain Marine Algae to

Changes in Osmotic Pressure and Temperature. Tho E61e of Os-
motic Pressure in Marine Plants. On the Importance of Phydolog-
Ically Balanced Solutions for Plants. The Antitoxic Action of
Potassium on Magnesium. By W. J. V. Osterhout. Pp. 227-238.
March, 1906 _ _ — — .26

12. Cytological Studies in Cyanophyccae, by Nathaniel Lyon Gardner.

Pp. 237-296; plates 21-26. November, 1906 „ _ „. 1.00

18. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Th^riot. Pp. 297-308; plates 27-28. December, 1906 _ .10

14. Some Unreported Alaskan Sphagna, together with a Sumirary of the

Cryptogamic Work of the University of California Botanical Ex-
pedition to Alaska in 1899, by WilUam AJ.bert SetchelL Pp. S09-
815. September, 1907 — .06

15. On Nutrient and Balanced Solutions, by W. J. V. Osterhout. Pp. 817-

318. October, 1907 „ _ ^ .06

16. A Synopsis of the North American Ctodetlas, by Willlfl Linn Jepson.

Pp. 319-854; plate 29. December, 1907 .40

Index, pp. S55-360.

Vol 8. 1907-1909.

1. Composltao of Southern California, by Harvey Monroe HalL Pp. 1-

802; plates 1-3, with a map. December, 1907 S.OO

8. The Origin, Stracture, and Function of the Polar Caps in SmQadTui

amplexic/iuUs Nutt., by H. D. Densmoro. Pp. 303-330; plates 4-8.

December, 1908 35

8. 4. (In one cover.) The Value of Sodium to Plants by Season of Ita

Protective Action. On the Effects of Certain Poisonous Gases on

Plants. By W. J. V. Osterhout. Pp. 831-340. June, 1908 -10

UNIVE3SITY OF OAUFOENIA PUBLICATIONS— (Oontlnned)

6. Contributions to the BJQO-wledge of tha California Species of Orusta-

ceous Corallines. I. by M&urlce Barstow Nichols. Pp. S41-S48;

Plata 9. December, 1908 .10

5. Contributions to tha Kno-wledge of the California Species of Crusta-
ceoua Corallines. U. by Maurice Barstow Nichols. Pp. 349-370;
plates 10-13. April, 1909 _ 16

7. New Chlorophyceae from California, by Nathaniel Lyon Oardner. Pp.

371-375; plate 14, April, 1BG9 _ „...„ .10

8. Plantae Mexlcanae Purpnsiaaae, by T. S. Brandegee. Pp. 377-396.

May, 1909 15

Index, pp. 897-400.

Vol 4. 1910-1912.

1. Studies In Ornamental Trees and Shrubs, by Harvey Monroe Hall. Pp.

l-7i; plates 1-11; 15 text-figiires. March, 1910 75

2. Oracilariophila, a New Parasite on Gracilaria conferv aides, by Harriot

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 10

3. Plantae Mexicanae Purpuaianae, II, by T. S. Brand&geo. Pp. 85-95.

May, 1910 _ _ _ , „ .10

4. Leuvenia, a New Genus of Flagellates, by N.,L. Gardner. Pp. 97-106;

plate 14. May, 1910 „...„ .10

5. The Genus Sphaerosoma, by William Albert Setchell. Pp. 107-120;

plate 15. May, 1910 15

6. Variations in Nuclear Extrusion Among the Fncaceae, by Nathaniel

Lyon Gardner. Pp. 121-1S6; platen 16-17. August, 1910 15

7. The Nature of the Carpostomes in tha Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 _ .05

8. On a Colacodasya from Southern California, by Mabel Effie McFadden.

Pp. 143-150; plate 19. February, 1911 _ „ _ .05

9. Fructification of Macrocystis, by Edna Juanita Hoffman. Pp. 151-158;

plate 20. February, 1911 _ .05

10. ErythrophyUum dclesserioides J. Ag., by Wilfred Charles Twiss. Pp.

159-176; plates 21-24. March, 1911 _ .16

11. Plantae Mexicana« Purpusianae, m, by T. S. Brandegee. Pp. 177-194.

July, 1911 _ 15

12. New and Noteworthy Califomian I*lants, I, by Harvey Monroe Hall.

Pp. 195-208. March, 1912 _ .15

13. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 „ _ 20

14. Algae Novae et Minus Cognitae, I, by William Albert Setchell. Pp.

229-268; plates 25-31. May, 1912 40

15. Plantae Mesicanae Purptisianae, IV, by Townshend Stith Brandegee.

Pp. 269-281. June, 1912 15

16. Comparative Development of the Cystocarps of Antithamnion and

Prionitis, by Lyman Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 .20

17. Fungus Galls on Cy/^toseira and Halidrys. by Lulu May Bstee. Pp. 305-

316; plate 35. March, 1913 .10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374; plates 36-

53. April, 1913 ,^ - 75

19. Plantae Mexicanae Purpusianae, V, by fowushend Stith Brandegee.

Pp. 375-388. June, 1913 15

Index, pp. 389-397.

Vol. 6. 1912-.

1. Studies in Nicotiana, I, by William Albert Setchell. Pp. 1-86. De-

cember, 1912 1.25

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

3. Quantitative Studies of Inheritance in Nicotiana Hybrids, n, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 _. .20

4. On the Partial Sterility of Nicotiana Hybrids made with N. Sylvestris

as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 „ 10

5. Notes on the Germination of Tobacco Seed, by Thomas Harper Good-

speed. Pp. 199-222. May, 1913 25

6. Quantitative Stutlies of Inheritance in Nicotiana Hybrids, III, by

Thomas Harper Goodspeed. Pp. 223-231. April, 1915 10

XJNIVEESITY OF OALIFOENIA PUBLICATIONS— (Continued)

Vol. 6. 1914-

1. Parasitic Florideae, I, by William Albert Setchell. Pp. 1-34, plates

1-6. April, 1914 „ 35

2. Thytomorula regularis, a Ssrinmetrical Protophsrte Related to Coelas-

trum, by Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914. .05

3. Variation in Oenothera ovata, by Katherine Layne Brandegee. Pp. 41-

50, plates 8-9. June, 1914 10

4. Plantae Mexicanae Purpusianae, VI, by Townsbend Stith Brandegee.

Pp. 51-77. July, 1914 ,25

5. The Scinaw Assemblage, by William Albert Setchell. Pp. 79-152,

plates 10-16. October, 1914 75

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 7, pp. 233-248 Issued June 25, 1915

NOTES ON THE GERMINATION OF TOBACCO

SEED, II

BY

THOMAS HARPER GOODSPEED

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Note. — The University of California Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University will be sent upon request. For sample copies, lists of
publications and other information, address the Manager of the University Press, Berkeley,
California, U. S. A. All matter sent in exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. S. A.

OTTO HAEEASOWITZ E. FEIEDLANDER & SOHN
LEIPZIG BEELIN
Agent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnology, Classical Philology, aeology and Ethnology, Botany, Geography,
Education, Modern Philology, Philosophy, Geology, Mathematics, Pathology, Physi-
Psychology. ology. Zoology, and Memoirs.

BOTANY.— W. A. Setchell, Editor. Price per volume, $3.50. Volumes I (pp. 418), n (pp>
360), III (pp. 400), IV (pp. 379), completed. Vols. V and VI in progress.

Cited as Univ. CaUf. Publ. Bot.

VoL 1. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Monroe

HaU. Pp. 1-140; plates 1-14. June, 1902 fl.OO

2. Two new Ascomycetous Pungi Parasitic on Marine Alga«, by Minnie

Eeed. Pp. 141-164; plates 15-16.' November, 1902 .25

S. Algae of Northwestern America, by William Albert Setchell and Na-
thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 — 2.25

VoL 2. 1. A Eevlew of Califomlan Polemoniaceae, by Jessie Milliien. Pp. 1-

71; plates 1-11. May, 1904 « 75

2. Contributions to Cytological Technique, by W. J. V. Ostorhout. Pp.

73-90; 5 text-figures. June, 1904 25

3. Limu, by WiUiam Albert SetcheU. Pp. 91-113. April, 1905 26

4. Post-Embryonal Stages of the Laminariaccao, by William Albert

Setchell. Pp. 115-138; plates 13-14. April, 1905 .25

5. Eegeneration among Kelps, by William Albert Setchell. Pp. 139-168;

plates 15-17. July, 1905 — SO

6. A New Gtenus of Ascomycetous Fungi, by Nathaniel Lyon Gardner.

Pp. 169-180; plate 18. July, 1905 15

7. Teratology in the Flowers of some Calif ornian Willows, by William

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 „ 50

8. 9, 10, 11. (In one cover.) The Eeslstance of Certain Marine Algae to

Changes in Osmotic Pressure and Temperature. The EOle of Os-
motic Pressure in Marine Plants. On the Importance of Physiolog-
ically Balanced Solutions for Plants. The Antitoxic Action of
Potassium on Magnesium. By W. J. V. Osterhout. Pp. 227-238.
March, 1906 „ _ - _ — .25

12. Cytological Studies In Cyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-296; plates 21-26. November, 1906 _ _. 1.00

13. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Thfirlot Pp. 297-308; plates 27-28. December, 1906 .10

14. Some Unreported Alaskan Sphagna, together with a Suuiirjiry of the

Cryptogamic Work of the University of California Botanical Ex-
pedition to Alaska in 1899, by William Albert SetchelL Pp. 809-
815. September, 1907 _ — .08

15. On Nutrient and Balanced Solutions, by W. J. V. Osterhout. Pp. 817-

318. October, 1907 _ M

16. A Synopsis of the North American Godetlas, by Willis Linn Jepson.

Pp. 319-364; plate 29. December, 1907 ~ .40

Index, pp. 355-360.

Vol 8. 1907-1909.

L Composltae of Southern California, by Harvey Monroe HalL Pp. 1-

302; plates 1-3, with a map. December, 1907 8.00

8. The Origin, Structure, and Function of the Polar Caps In SmQacina

amplexicaulis Nutt., by H. D. Densmore. Pp. 303-830; plates 4-8.

December, 1908 _ 35

3. 4. (In one cover.) The Value of Sodium to Plants by Season of Its

Protective Action. On the Effects of Certain Poisonous Gases oa

Plants. By W. J. V. Osterhout. Pp. 831-S40. June, 1908 M

UNIVBBSITY or OAUPORNIA PUBIIOATIONS— (Oontlliued)

6. Contnbnticns to the Knowledge of the California Species of Crnstfr-
ceous Corallines. I. by Maurice Barstow Nichols. Pp. S41-S48;
plate 9. December, 1908 _ JLO

6. Contributions to the Knowledge of the California Species of Cmsta-

ceous Corallines, n. by Maurice Barstow Nichols. Pp. 349-S70;
plates 10-13. April, 1909 _ _ .16

7. New Chlorophyceae from California, by Nathaniel Lyon Gardner. Pp.

371-375; plate 14. April, 1909 _ „ .10

8. Plantae Mexicanae Purpusianae, by T. S. Brandegee. Pp. 377-396.

May, 1909 _ _ 15

Index, pp. 397-400.

Vol 4. 1910-1912.

1. Studies in Ornamental Trees and Shrubs, by Harvey Monroe Hall. Pp.

1-74; plates 1-11; 15 text-figures. March, 1910 75

2. Oracilariophila, a New Parasite on Gracilaria confervoides, by Harriet

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 10

3. Plantae Mexicanas Purpusianae, II, by T. S. Brandegee. Pp. 85-95.

May, 1910 - - - .10

4. Leuvenia, a New Genus of Flagellates, by N. L. Gardner. Pp. 97-106;

plate 14. May, 1910 _ _ .10

5. The Genus Sphaerosoma, by William Albert Setcheli. Pp. 107-120;

plate 15. May, 1910 ..., 15

6. Variations In Nuclear Extrusion Among the Fucaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; plates 16-17. August, 1910 .16

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 .05

8. On a Colacodasya from Southern California, by Mabel Effie McFadden.

Pp. 143-150; plate 19. February, 1911 — .05

9. Fructification of Macrocystis, by Edna Juanita Hoffman. Pp. 151-158;

plate 20. February, 1911 - — .06

10. Erythrophyllum delesserioides J. Ag., by Wilfred Charles TwlfiS. Pp.

159-176; plates 21-24. March, 1911 _ » .16

11. Plantae Mexicanae Purpusianae, HI, by T. S. Brandegee. Pp. 177-194.

July, 1911 ...- - - 16

12. New and Noteworthy Califomian Plants, I, by Harvey Monroe Hall.

Pp. 195-208. March, 1912 ..._ - 15

13. Die Hydrophyllaceen der Sierra Nevada, by Augu.st Brand. Pp. 209-

227. March, 1912 ^ - --.-. — -- -20

14. Algae Novae et Minus Cognitae, I, by William Albert Setcheli. Pp.

229-268; plates 25-31. May, 1912 ..„ - 40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stith Brandegee.

Pp. 269-281. June, 1912 15

16. Comparative Development of the Cystocarps of Antithamnion and

PrioniUs, by Lsnnan Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 20

17. Fungus Galls on Cystoseira and Ealidrys. by Lulu May Estee. Pp. 305-

316; plate 35. March, 1913 10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374; plates 36-

53. April, 1913 --- ■ 75

19. Plantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee.

Pp. 375-388. June, 1913 - 15

Index, pp. 389-397.

Vol 5. 1912-.

1. Studies in Nicotiana, I, by William Albert Setcheli. Pp. 1-86. De-

cember, 1912 — - — 1'25

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 - 1.00

8. Quantitative Studies of Inheritance in Nicotiana Hybrids, n, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 20

4. On the Partial Sterility of Nicotiana Hybrids made with N. Sylvestris

as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 — -10

5. Notes on the Germination of Tobacco Seed, by Thomas Harper Good-

speed. Pp. 199-222. May, 1913 25

6. Quantitative Studies of Inheritance in Nicotiana Hybrids, HI, by

Thomas Harper Goodspeed. Pp. 223-231. April, 1915 10

7. Notes on the Germination of Tobacco Seed, II, by Thomas Harper

Goodspeed. Pp. 233-248. June, 1915 15

UNIVEESITY OF CAUFOKNIA PUBLICATIONS— (Ooutinued)

Vol. 6. 1914-

1. Parasitic Florideae, I, by William Albert Setchell. Pp. 1-34, plates

16. Aprn, 1914 .35

2. Fhytomorula regularis, a Symmetrical Protophyte Eelated to Coelas-

trum, by Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914. .05

3. Variation in Oenothera ovata, by Katberine Layne Brandegee. Pp. 41-

50, plates 8-9. June, 1914 .10

4. Plantae Mexicanae Purpusianae, VI, by Townsbend Stith Brandegee.

Pp. 51-77. July, 1914 . — .25

5. The Scinaia Assemblage, by William Albert Setchell. Pp. 79-152,

plates 10-16. October, 1914 „ .75

6. Notes on Pacific Coast Algae. I. Fylaiella Postelsiae, n. sp., a New

Type in the Genus Fylaiella, by Carl Skottsberg. Pp. 153-164, plates
17-19. May, 1915 15

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 8, pp. 249-272, plate 35 Issued July 21, 1915

PARTHENOGENESIS, PARTHENOCARPY AND
PHENOSPERMY IN NICOTIANA

BY

THOMAS HARPER GOODSPEED

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Note. — The University of California Publications are offered in exchange for the puhll-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University will be sent upon request. For sample copies, lists of
publications and other information, address the Manager of the University Press, Berkeley,
California, U. S. A. All matter sent in exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. S. A.

OTTO HARRASOWITZ E. FEIEDLANDER & SOHN
LEIPZIG BERLIN
Agent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnology, Classical Philology, aeology and Ethnology, Botany, Geography,
Education, Modem Philology, Philosophy, Geology, Mathematics, Pathology, Physi-
Fsychology. cdogy, Zoology, and Memoirs.

BOTANY.— W. A. Setchell, Editor. Price per volume, ?3^0. Volumes I (pp. 418), n (ppt

360), III (pp. 400), IV (pp. 379), completed. Vols. V and VI in progress.

Cited as Univ. Calif. Publ. Bot.

VoL 1. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Monroe

HaU. Pp. 1-140; plates 1-14. June, 1902 :.-.u-.^— $1.00

2. Two new Ascomycetous Fungi Parasitic on Marine Algae, by Minnie

Eeed. Pp. 141-164; plates 15-16. November, 1902 „ .25

3. Algae of Northwestern America, by William Albert Setchell and Na-

thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 2.26

VoL 2. 1. A Review of Callfomlan Polemoniaceae, by Jessie Milliken. Pp. 1-

71; plates 1-11. May, 1904 .76

2. Contributions to Cytologlcal Technique, by W. J. V. Osterhout. Pp.

73-90; 5 text-figures. June, 1904 26

8. Llmu, by William Albert Setchell. Pp. 91-113. AprU, 1905 - .25

4. Post-Embryonal Stages of the Laminariaceao, by William Albert

Setchell. Pp. 115-138; plates 13-14. April, 1905 25

6. Regeneration among Kelps, by William Albert Setchell. Pp. 139-168;

plates 15-17. July, 1905 ^ .80

6. A New Genus of Ascomycetous Fungi, by Nathaniel Lyon Gardner.

Pp. 169-180; plate 18. July, 1905 _. .15

7. Teratology in the Flowers of some Callfomlan Willows, by William

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 50

8. 9, 10, 11. (In one cover.) The Resistance of Certain Marine Algae to

Changes In Osmotic Pressure and Temperature. The Rfile of Os-
motic Pressure in Marine Plants. On the Importance of Physiolog-
ically Balanced Solutions for Plants. The Antitoxic Action of
Potassium on Magnesium. By W. J. V. Osterhout. Pp. 227-236.
March, 1906 ...„ _ .25

12. Cytologlcal Studies in Oyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-296; plates 21-26. November, 1906 LOO

18. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Thfiriot. Pp. 297-308; plates 27-28. December, 1906 M

14. Some Unreported Alaskan Sphagna, together with a Summary of the
Cryptogamic Work of the University of California Botanical Ex-
pedition to Alaska In 1899, by William Albert SetchelL Pp. 309-
315. September, 1907 .06

16. On Nutrient and Balanced Solutions, by W. J. V. Osterhout. Pp. 317-

318. October, 1907 .06

16. A Synopsis of the North American Godetlas, by Willis T.tnn Jepson.

Pp. 319-854; plate 29. December, 1907 .40

Index, pp. 355-360.

VOL 8. 1907-1009.

1. Composltae of Southern California, by Harvey Monroe Hall. Pp. 1-

302; plates 1-3, with a map. December, 1907 J.00

5. The Origin, Structure, and Function of the Polar Caps In SmQaoina

amplexicaulia Nutt., by H. D. Densmore. Pp. 303-330; plates 4-8.

December, 1908 35

8. 4. (In one cover.) .The Value of Sodium to Plants by Reason of Its
Protective Action. On the Effects of Certain Poisonous Oases on
Plants. By W. J. V. Osterhout. Pp. 331-340. June, 1908 JO

UNIVBaSITY OP OAUFOBNIA PUBLIOATIONS— {Oontlnuod)

6. Contributions to the Knowledge of the California Species of Crnstar
ceous Corallines. I. by Maurice Barstow Nichola. Pp. 841-348;
plate 9. December, 1908 .10

6. Oontribntlons to the Knowledge of the California Species of Crusts

ceoua Corallines, n. by Maurice Barstow Nichols. Pp. S49-S70;
plates 10-13. April, 1909 _ „„ jfi

7. New Chlorophyceae from California, by Nathaniel Lyon Gardner. Pp.

871-375; plate 14. April, 1909 . _ _ _ .10

8. Plantae Mexicanae Purpusianae, I, by T. S. Brandegee. Pp. 377-396.

May, 1909 15

Index, pp. S97-400.
Vol 4. 1910-1912.

1. Studies in Ornamental Trees and Shrubs, by Harvey Monroe HalL Pp.

1-74; plates 1-11; 15 text-figures. March, 1910 .75

2. Gracilariophila, a New Parasite on Gracilaria confervoides, by Harriet

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 10

8. Plantae Mexicanae Purpusianae, II, by T. S. Brandegee. Pp. 85-95.

May, 1910 „ _ .10

4. Leuvenia, a New Genus of Flagellates, by N. L. Gardner. Pp. 97-106;

plate 14. May, 1910 „ .10

5. The Genus Sphaerosoma, by William Albert Setchell. Pp. 107-120;

plate 15. May, 1910 16

6. Variations in Nuclear Extrusion Among the Fucaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; plates 16-17. August, 1910 _ „ .15

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 :. .05

8. On a Colacodasya from Southern Oalifcmla, by Mabel Eflle McFadden.

Pp. 143-150; plate 19. February, 1911 .05

9. Fructification of Macrocystis, by Edna Juanita Hoffman. Pp. 151-158;

plate 20. February, 1911 _ „ 05

10. Erythrophyllum delesserioides J. Ag., by Wilfred Charles Twiss. Pp.

159-176; plates 21-24. March, 1911 „ J.5

11. Plantae Mexicanae Purpusianae, m, by T. S. Brandegee. Pp. 177-194.

July, 1911 „ .15

12. New and Noteworthy Califomian Plants, I, by Harvey Monroe HaU.

Pp. 195-208. March, 1912 „ _ „ J.5

IS. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 „ .20

14. Algae Novae et Minus Cognitae, I, by William Albert Setchell. Pp.

229-268; plates 25-31. May, 1912 „ .40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stith Brandegee.

Pp. 269-281. June, 1912 15

16. Comparative Development of the Cystocarps of Antithamnion and

Prionitis, by Lyman Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 .20

17. Fungus Galls on Cystoseira and Ealidrys. by Lulu May Estee. Pp. 305-

316; plate 35. March, 1913 - .10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374; plates 36-

53. April, 1913 - .75

19. Plantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee.

Pp. 375-388. June, 1913 .16

Index, pp. 389-397.
Vol. 6. 1912-.

1. Studies in Nicotiana, I, by William Albert Setchell. Pp. 1-86. De-

cember, 1912 1.26

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, I, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 - 1.00

3. Quantitative Studies of Inheritance In Nicotiana Hybrids, n, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 _. .20

4. On the Partial Sterility of Nicotiana Hybrids made with N. Syivestris

as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 „ „ - .10

5. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Good-

speed. Pp. 199-222. May, 1913 _ 26

6. Quantitative Studies of Inheritance in Nicotiana Hybrids,^ m, by

Thomas Harper Goodspeed. Pp. 223-231. April, 1915 10

7. Notes on the Germination of Tobacco Seed, II, by Thomas Harper

Goodspeed. Pp. 233-248. June, 1915 15

8. Parthenogenesis, Parthenocarpy and Phenospermy in Nicotiana, by

Thomas Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 25

UNIVEESITT or CALIF OENIA PUBLICATIONS— (Continued)

Vol. 6. 1914-

1. Parasitic Florideae, I, by William Albert Setcbell. Pp. 1-34, plates

16. April, 1914 „ JSS

2. Phytomorula regularis, a Symmetrical Protopliyte Belated to Coelaa-

trum, by Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914. .05

3. Variation in Oenothera ovata, by Katherine Layne Brandegee. Pp. 41-

50, plates 8-9. June, 1914 „„ J.0

4. Plantae Mexicanae Furpusianae, VI, by Townshend Stith Brandegee.

Pp. 51-77. July, 1914 „ .25

5. The Scinaia Assemblage, by William Albert Setchell. Pp. 79-152,

plates 10-16. October, 1914 „ .75

6. Notes on Pacific Coast Algae. I. Pylaiella Fostelsiae, n, sp., a New

Type in the Genus Pylaiella, by Carl Skottsberg. Pp. 153-164, plates
17-19. May, 1915 15

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

VoL 5, No. 9, pp. 273-292, plate 36 October 4, 1916

ON THE PARTIAL STERILITY 0¥ NICOTIAN A

HYBRIDS MADE WITH N. SYLVESTRIS

AS A PARENT. II

BY

T. H. GOODSPEED and A. H. AYRES

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

M'ote. — The University of California Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University will be seat upon request. For sample copies, lists of
pabllcations and other information, address the Manager of the University Press, Berkeley,
Oallfomla, U. S. A. All matter sent in. exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. S. A.

OTTO HAEEASOWITZ E. FEIEDLANDER & SOHN
LEIPZIG BERLIN
Agent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnology, Classical Philology, aeology and Ethnology, Botany, Geography,
Education, Modem Philology, Philosophy, Geology, Mathematics, Pathology, Physi-
Piiychology. ology, Zoology, and Memoirs.

BOTANY.— W. A. Setchell, Editor. Price per volume, $3.50. Volumes I (pp. 418), n (pp,
360), III (pp. 400), IV (pp. 379), completed. Vols. V and VI in progresa

Cited as Univ. Calif. Publ. Bot.

Vol 1. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Monroe

HalL Pp. 1-140; plates 1-14. June, 1902 11.00

2. Two new Ascomycctous Fungi Parasitic on Marine Algae, by Minnie

Eeed. Pp. 141-164; plates 15-16. November, 1902 .._ ™ .25

8. Algae of Northwestern America, by V/illiam Albert Setchell and Na-
thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 2J2§

VoL 2. 1. A Bevlew of Callfomian Polemonlaccae, by Jessie MlUiken. Pp. 1-

71; plates 1-11. May, 1904 „ „ „ ,75

2. Contributions to Cytological Technique, by W. J. V. Osterhout. Pp.

73-90; 5 text-figures. June, 1904 .25

3. Llmu, by WllUam Albert SetcheU. Pp. 91-113. April, 1905 „ J25

4. Post-Embryonal Stages of the Laminarlaceao, by William Albert

SetcheU. Pp. 115-138; plates 13-14. April, 1905 „.. .25

5. Eegeneratlon among Kelps, by William Albert Setchell. Pp. 139-168;

plates 15-17. July, 1905 _ - 30

6. A New Genus of Aecomycetous Fungi, by Nathaniel Lyon Gardner.

Pp. 169-180; plate 18. July, 1905 „ „.. .15

7. Teratology in the Flowers of some Callfomian Willows, by William

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 .60

8. 9, 10, 11. (In one cover.) The Resistance of Certain Marine Algae to

Changes in Osmotic Pressure and Temperature. The Edle of Os-
motic Pressure in Marine Plants. On the Importance of Physiolog-
ically Balanced Solutions for Plants. The Antitoxic Action of
Potassium on Magnesium. By W. J. V. Osterhout. Pp. 227-238.
March, 1906 .8S

12. Oytologlcal Studies in Cyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-296; plates 21-26. November, 1906 LOO

18. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Th6rlot. Pp. 297-308; plates 27-28. December, 1906 JIO

14. Some Unreported Alaskan Sphagna, together with a Summary of tb«
Cryptogamlc Work of the University of California Botanical Ex-
pedition to Alaska in 1899, by William Albert SetchelL Pp. 809-
315. September, 1907 M

16. On Nutrient and Balanced Solutions, by W. J. V. Osterhont. Pp. 817-

318. October, 1907 .06

16. A Synopsis of the North American GodettSLO, by Willis Linn Jepson.

Pp. 319-354; plate 29. December, 1907 .40

Index, pp. 355-360.

Vol 8. 1907-1909.

L Composltae of Southern California, by Harvey Monroe HalL Pp. 1-

302; plates 1-8, with a map. December, 1907 8.00

8. The Origin, Structure, and Function of the Polar Caps in SmQaeina

amplexicaHlis Nutt., by H. D. Densmore. Pp. 303-830; jdAtes 4-8.

December, 1908 — 86

B. 4. (In one cover.) The Value of Sodium to Plants by Eeason of Its

Protective Action. On the Effects of Certain Poisonous Gases on

Plants. By W. J. V. Osterhout. Pp. 831-340. June, 1908 S9

6. Contributions to the E^nowledge of the California Species of Cmstar-
c ceous Corallines. I. by Maurice Barstow Nichols. Pp. 841-348;

plate 9. December, 1908 JO

UNIVERSITY OF OALIFOBNIA PT7BLIOATION8— (OontlnMd)

6. Ck>ntrlbntioQs to the Knowledge of the California Species of Orasti^

ceoMs Corallinos. n. by Maurice Bantow Nlcholfl. Pp. 349-S70;
plates 10-13. April, 1909 JB

7. New CUorophyceae from Calif omia, by Nathaniel Lyon Oardner. Pp.

371-875; plate U. April, 1B09 _ .10

8. Plantae Mexicanae Purpusianae, I, by T. S. Brandegee. Pp. 377-396.

May, 1909 , _ .15

Index, pp. 307-400.
Vol «. 1910-1912.

1. Stndles In Ornamental Trees and Shmbs, by Harrey Monroe HalL Pp.

1-74; plates 1-11; 15 text-figiires. March, 1910 75

2. Qracllariophlla, a New Parasite on Gracxlaria confervoides, by Harriet

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 10

8. Plantae Mezicanae Pnrpnslanae, n, by T. S. Brandegee. Pp. 86-95.

May, 1910 „ ._ J.0

4. Leuvenia, a New Genns of Flagellates, by N. L. Gardner. Pp. 97-106;

plate 14. May, 1910 JO

5. The Genus Sphaerosoma, by William Albert Setchell. Pp. 107-120;

plate 15. May, 1910 15

6. Variations in Nuclear Extrusion Among tlie Fucaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; plates 16-17. August, 1910 J.8

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 „ JOS

8. On a Colacodasya from Southern California, by Mabel Effis McFadden.

Pp. 143-150; plate 19. February, 1911 _ .08

9. Fructification of Macrocystis, by Edna Jnanlta Hoffman. Pp. 151-158;

plate 20. February, 1911 _ .05

10. Erjfthrophyllum delesserioides J. Ag., by Wilfred Charles Twlss. Pp.

159-176; plates 21-24. March, 1911 JO

11. Plantae Mexicanae Purpusianae, m, by T. S. Brandegee. Pp. 177-194.

12. New and Noteworthy Califomian Plants, I, by Harvey Monroe HalL

Pp. 195-208. March, 1912 J5

IS. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 _ .20

14. Algae Novae et Minus Cognltae, I, by William Albert Setchell. Pp.

229-268; plates 25-31. May, 1912 — .40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stlth Brandegee.

Pp. 269-281. June, 1912 - .18

16. Comparative Development of the Cystocarps of Antithamnion and

Prionitis, by Lsrman Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 „ „ ™ .20

17. Fimgus Galls on Cystoseira and Edlidrys. by Lulu May Estee. Pp. 305-

316; plate 35. March, 1913 10

18. New Fucaceae, by Nathaniel Lyoa Gardner. Pp. 317-374; plates 36-

53. April, 1913 - - 75

19. Plantae Mexicanae Purpusianae, V, by Townshend Stlth Brandegee.

Pp. 375-388. June, 1913 - .15

Index, pp. 389-397.
Vol, B. 1912-.

1. Studies in Nicotiana, I, by William Albert Setchell. Pp. 1-86. De-

cember, 1912 — - 1.1KJ

2. Quantitative Studies of Inheritance In Nicotiana Hybrids, I, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

3. Quantitative Studies of Inheritance In Nicotiana Hybrids, n, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 _. .20

4. On the Partial Sterility of Nicotiana Hybrids made with N. Sylvestris

as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 „ - - .10

5. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Good-

speed. Pp. 199-222. May, 1913 „ - .25

6. Quantitative Studies of Inheritance in Nicotiana Hybrids, m, by

Thomas Harper Goodspeed. Pp. 223-231. April, 1915 _ — .10

7. Notes on the Germination of Tobacco Seed, 11, by Thomas Harper

Goodspeed. Pp. 233-248. June, 1915 15

8. Parthenogenesis, Parthenocarpy and Phenospermy in Nicotiana, by

Thomas Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 25

9. On the Partial Sterility of Nicotiana Hybrids made with N. STjlvestris

as a Parent. 11, by T. H. Goodspeed and A. H. Ayres. Pp. 273-292,
plate 36. October, 1916 .20

UNrVEESITY OP CALIFOENIA PUBUOATIONS— (Oontlnned)

Vol. 6. 1914-

1. Parasitic Plorideae, I, by William Albert Sstchell. Pp. 1-34, plates

16. April, 1914 .35

2. Fhytomorula regularis, a Syuuaetrical Protophyte Related to Codas-

trum, by Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914. .05

3. Variation in Oenothera ovata, by Katlierlne Layne Brandegee. Pp. 41-

50, plates 8-9. June, 1914 ...._ .10

4. Plantae Mexicanae Purpusianae, VI, by TownsSiend Stitb Brandegee.

Pp. 51-77. July, 1914 - ..™_.„ . — .25

5. The Scinaia Assemblage, by William Albert Setchell. Pp. 79-152,

plates 10-16. October, 1914 — .75

6. Notes on Pacific Coast Algae. I. Pylaiella Postelsiae, n. sp., a New

Type in the Genus Pylaiella, by Carl Skottsberg. Pp. 153-164, plates
17-19. May, 1915 -15

7. New and Noteworthy Calif omian Plants, n, by Harvey Monroe Hall.

Pp. 165-176, plate 20. October, 1915 ~ .15

8. Plantae Mexicanae Purpusianae VII, by Townshend Stith Brandegee.

Pp. 177-197. October, 1915 .25

9. Floral Relations Among the Galapagos Islands, by A. L. Kroeber.

Pp. 199-220. March, 1916 20

10. The Comparative Histology of Certain Califomian Boletaceae, by

Harry S. Yates. Pp. 221-274, plates 21-25. February, 1916 „ 50

11. A Revision of the Tuberales of California, by Helen Margaret Gilkey.

Pp. 275-356, plates 26-30. March, 1916 80

12. Species Novae vel Minus Cognitae, by T. S. Brandegee. Pp. 357-361.

May, 1916 05

Vol. 7. 1916-

1. Notes on the Califomian Species of Trillium L, I. A Report of the

General Results of Field and Garden Studies, 1911-1916, by Thomas
Harper Goodspeed and Robert Percy Brandt. Pp. 1-24, plates 1-4.
October, 1916 25

2. Notes on the Califomian Species of Trillium L. II. The Nature and

Occurrence of Undeveloped Flowers, by Thomas Harper Goodspeed

and Robert Percy Brandt. Pp. 25-38, plates 5-6. October, 1916 ... .15

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 10, pp. 293-299 November 7, 1916

ON THE PARTIAL STERILITY OF NICOTIANA

HYBRIDS MADE WITH N. SYLVESTRIS

AS A PARENT. Ill

AN ACCOUNT OF THE MODE OF FLORAL ABSCISSION
IN THE Fi SPECIES HYBRIDS

BY

T. H. GOODSPEED and J. N. KENDALL

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Kote. — Tlie University of California Publications are offered in excliange for the pnbU-
cationB of learned societies and institutions, universitiea and libraries. Complete lists of
all the publications of the University will be sent upon request For sample copies, lists of
publications and other information, address the Msuiager of the University Press, Berkeley,
Oallfomla, U. S. A. Ail matter sent in exchange should be addressed to The Bxchango
Department, University Library, Berkeley, California, U. S. A.

OTTO HAEEASOWITZ E. FEIEDLANDEE & SOHN

LEIPZIG BEELIN

A?ent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnology, Classical Philology, aeology and Ethnology, Botany, Geography,
Education, Modem Philology, Philosophy, Geology, Mathematics, Pathology, Phyai-
Psychology. ology. Zoology, and Memoirs.

BOTANY,— W. A. Setchell, Editor. Price per volume, fS.50. Volmnes I (pp. 418), n (ppi
360), m (pp. 400), IV (pp. 379), completed. Vols. V and VI in progress.

Cited as Univ. Calif. Publ. Bot.

VoL I. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Uonxoe

HalL Pp. 1-140; plates 1-14. June, 1902 11.00

2. Two new Ascomycetous Fnngl Parasitic on Marine Algae, by ISiimie

Eeed, Pp. 141-164; plates 15-16. November, 1902 ..„ :8a

8. Algae of Northwestern America, by William Albert Betchell and Na-
thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 — 2.2B

Vol. 2. 1. A Bevlew of Califumlan Polemonlaceae, by Jessie MUliken. Pp. 1-

71; plates 1-11. May, 1904 .75

2. Contributions to Cytological Technique, by W. J. V. Osterhout. Pp.

73-90; 5 text-figures. June, 1904 .26

3. Limu, by William Albert Setchell. Pp. 91-113. April, 1905 .25

4. Post-Embryonal Stages of the Lamlnaxiaceao, by WiUlam Albert

Setchell. Pp. 115-138; plates 13-14. AprU, 1905 26

6. Eegeneration among Kelps, by William Albert SetchelL Pp. 1SS>-168;

plates 15-17. July, 1905 _ ~ .30

6. A New Genus of Ascomycetouij Fungi, by Nathaniel Lyon Gardner.

Pp. 169-180; plate 18. July, 1905 „ „ _ -. .15

7. Teratology in the Flowers of some Califomiau Willows, by William

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 .60

8. 9, 10, 11. (In one cover.) The Eeaistance of Certain Marine Algae to

Changes in Osmotic Pressure and Temperature. The E61e of 0>
moUc Pressure in Marine Plants. On the Importance of Physiolog-
ically Balanced SolutioM for Plants. The Antitoxic Action of
Potassium on Magnesium. Ey W. J. V. Osterhont. Pp. 227-236.

March, 1906 .26

12. Oytological Studies In Cyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-296; plates 21-26. November, 1906 _ 1.00

15. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Th6rlot. Pp. 297-308; plates 27-28. December, 1906 JO

14. Some Unreported Alaskan Sphagna, together with a Sununary of the
Cryptogamic Work of the University of California Botanical Ex-
pedition to Alaska In 1899, by William Albert Setchell. Pp. SOS-
SIS. September, 1907 .08

16. On Nutrient and Balanced Solutions, Ly W. J. V. Osterhont. Pp. 317-

318. October, 1907 J»

16. A Synopsis of the North American GodeUas, by Willis Linn Jepson.

Pp. 319-354; plate 29. December, 1907 .40

Index, pp. 355-360.

ToL 3. 1907-1909.

1. Compositae of Southern California, by Harvey Monroe Hall. Pp. 1-

802; plates 1-3, with a map. December, 1907 8.00

2. The Origin, Structure, and Function of the Polar Caps in SmUacina

amplejricaulis Nutt, by H. D. Densmoro. Pp. SOS-SSO: plates 4-8.

December. 1908 _ — — .35

8. 4. (In one cover.) The Value of Sodium to Plants by Season of Its
Protective Action. On the Effects of Certain Poisonous Gases on
Plants. Ey W. J. V. Osterhont. Pp. S31-S40. June, 1908 JU

5. Contributions to the Knowledge of the California Species of Orusta-

eeous OoraUines. I. by Maurice Barstow Nichols. Pp. S41-S48;
plate 9. December, 1908 M

UKIVB2SITY OF OAUTOENIA PUBLIOATIONS— (Continued)

6. Oontrlbutlona to the Knowledge of the California Speclea of Oruatar

ceous Corallines, n, by Maurice Barato\r Nlchola. Pp. 34»^70;
plates 10-lS. April, 1909 . j[6

7. New Ohlorophyceae from California, by Nathaniel Lyon Oardner. Pp.

371-375; plate 14. April, 1909 _„ „ .10

8. Plantae Mexicanae Purpusianae, I, by T. S. Brandegee. Pp. 377-396.

May, 1909 _ _ _ _ .15

Index, pp. 397-400.
Vol 4. 1910-1912.

1. Studies in Ornamental Trees and Shrubs, by Harrey Monroe HalL Pp.

1-74; plates 1-11; 15 text-figiures. March, 1910 „ .75

2. Oracllarloplllls^ a New Parasite on GraaUirM confer voides, by Harriet

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 10

8. Plantae Mexicanae Purpusianae, II, by T. S. Brandegee. Pp. 85-95.

May, 1910 „ .10

4. Leuvenia, a New Oenus of Flagellates, by N. L. Gardner. Pp. 97-106;

plate 14. May, 1910 „ . „ JO

5. The Genus Sphaerosoma, by William Albert Setchell. Pp. 107-120;

plate 15. May, 1910 „ j,6

6. Variations in Nccloar Bxtnisicn Among tbe Facaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; pla'ies 16-17. August, 1910 J.5

7. The Nature of the Carpostomes In the Cyrtocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 .05

8. On a Colacodasya from Southern California, by Mabel Effle McFadden.

Pp. 143-150; plate 19. February, 1911 _ .06

9. Fniptlflcatlon of Macrocystls, by Bdna Juanita Hoffman. Pp. 151-158;

plate 20. February, 1911 _ _ _ „ „_ .05

10. Erythrophyllum delesserioide» J. Ag., by Wilfred Charles Twlss. Pp.

159-176; plates 21-24. March, 1911 . . ^5

11. Plantae Mexicanae Purpusianae, m, by T. S. Brandegee. Pp. 177-194.

July, 1911 _ _ „ _ .15

12. New and Noteworthy Califomlan Plants, I, by Harvey Monroe HalL

Pp. 195-208. March, 1912 _.. J.5

IS. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 _ .20

14. Algae Novae et Minus Cognitae, I, by William Albert Setchell. Pp.

229-268; plates 25-31. May, 1912 .„ ,. .- \.....~ .40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Sttth Brandegee.

Pp. 269-281. June, 1912 „ .15

16. Comparative Development of the Cystocarps of Antithamnion and

Prionitis, by Lyman Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 _ „ .20

17. Fungus Galls on Cystoseira and Halidrys. by Lulu May Estee. Pp. 305-

316; plate 35. March, 1913 „ .10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374; plates 36-

53. April, 1913 , .75

19. Plantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee.

Pp. 375-388. June, 1913 - » .15

Index, pp. 389-397.
Vol S. 1912-.

1. Studies in Nieotiana, I, by William Albert Setchell. Pp. 1-86. De-

cember, 1912 _ _.— „ 1J25

2. Quantitative Studies of Inheritance In Nieotiana Hybrids, I, by Thomaa

Harper Goodspeed. Pp. 87-168. December, 1912 _ — 1.00

3. Quantitative Studies of Inheritance in Nieotiana Hybrids, n, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 _ .20

4. On the Partial Sterility of Nieotiana Hybrids made with N. Bylvestria

as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 „ - _ - ao

5. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Good-

speed. Pp. 199-222. May, 1913 28

6. Quantitative Studies of Inheritance In Nieotiana Hybrids, m, by

Thomas Harper Goodspeed. Pp. 223-231. April, 1915 _ .10

7. Notes on the Germination of Tobacco Seed, II, by Thomas Harper

Goodspeed. Pp. 233-248. June, 1915 15

8. Parthenogenesis, Parthenocarpy and Phenospermy in Nieotiana, by

Thomas Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 25

UNIVBESITY or CALIFOENIA PUBLICATIONS— (Continued)

9. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris
as a Parent, n, by T. H. Goodspeed and A. H. Ayres. Pp. 273-292,
plate 36. October, 1916 20

10. On the Partial Sterility of Nicotmna Hybrids made with N. sylvestris
as a Parent. III. An Account of the Mode of Floral Abscission in
the F, Species Hybrids, by T. H. Goodspeed and J. N. Kendall.
Pp. 293-299. November, 1916 05

Vol 6. 1914-

1. Parasitic Florideae, I, by William Albert Setchell. Pp. 1-34, platei

1-6. April, 1914 _ J3B

2. Phytomorula regularis, a Symmetrical Protophyte Belated to Coel<u-

trum, by Charles Atwood Eofold. Pp. 35-40, plate 7. April, 1914. .05

3. Variation In Oenothera ovata, by Eatherlne Layne Brandegee. Pp. 41>

50, plates 8-9. June, 1914 J.0

4. Plantae Mexicanae Purpusianae, VI, by Townshend Stitb Brandegee.

Pp. 51-77. July, 1914 ^...^.i;^.. ■■ .26

5. The Scinaia Assemblage, by William Albert SetchelL Pp. 79-152,

plates 10-16. October, 1914 .78

6. Notes on Pacific Coast Algae. I. Pylaiella Postelsiae, n.8p., a New

Tjrpe in the Genus Pylaiella, by Carl Skottsberg. Pp. 153-164, plates
17-19. May, 1915 „_ .15

7. New and Noteworthy Califomian Plants, n, by Harvey Monroe HalL

Pp. 165-176, plate 20. October, 1915 .15

8. Plantae Mexicanae Purpusianae VII, by Townshend Stith Brandegeo.

Pp. 177-197. October, 1915 .25

9. Floral Belatlons Among the Galapagos Islands, by A. L. Eroeber.

Pp. 199-220. March, 1916 _ .20

10. The Comparative Histology of Certain Califomian Boletaceae, by

Harry S. Yates. Pp. 221-274, plates 21-25. February, 1916 > .50

11. A Revision of the Tuberales of California, by Helen Margaret Gllkey.

Pp. 275-356, plates 26-30. March, 1916 _ .80

12. Species Novae vel Minus Cognltae, by T. S. Brandegee. Pp. 357-361.

May, 1916 05

Vol. 7. 1916-

1. Notes on the Califomian Species of Trillium L. I. A Eeport of the

General Results of Field and Garden Studies, 1911-1916, by Thomas
Harper Goodspeed and Robert Percy Brandt. Pp. 1-24, plates 1-4.
October, 1916 25

2. Notes on the Califomian Species of Trillium L. IL The Nature and

Occurrence of Undeveloped Flowers, by Thomas Harper Goodspeed

and Robert Percy Brandt. Pp. 25-38, plates 5-6. October, 1916 ... .15

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 11, pp. 301-346, plates 37-48 January 17, 1917

THE NATURE OF THE Fi SPECIES HYBRIDS

BETWEEN NICOTIANA SYLVESTRIS AND

VARIETIES OF NICOTIANA TABACUM

WITH SPECIAL REFERENCE TO THE CONCEPTION
OF REACTION SYSTEM CONTRASTS IN HEREDITY

BY

T. H. GOODSPEED and R. E. CLAUSEN

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Note. — The University of California Publications are offered in exchange for the pnbU-
catlons of learned societies and institutions, universities and libraries. Complete lists of
ail the publications of the University will be sent upon request. For sample copies, lists of
public ations and other information, address the Manager of the University Press, Berkeley,
California, U. 8. A. All matter sent In exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. S. A.

OTTO HARRASOWITZ E. FEIEDLANDEE & SOHN
LEIPZIG BERLIN
Agent for the series in American Arch- Agent for the series in American Arch-
aeology and Ethnology, Classical Philology, aeology and Ethnology, Botany, Geography,
Eaucation, Modern Philology, Philosophy, Geology, Mathematics, Pathology, Phyai-
Fsychology. &logy. Zoology, and Memoirs.

BOTAir?.— W. A. Setchell, Editor. Price per volume, 93.60. Volumes I (pp. 418), H (pp
360), III (pp. 400), IV (pp. 379), completed. Vols. V and VI in progress.

Cited as Univ. Calif. PabL Bot.

VoL 1. 1. A Botanical Survey of San Jacinto Mountain, by Harvey Monroe

Hall. Pp. 1-140; plates 1-14. June, 1902 ..„ fl.OC

2. Two new Ascomycetoun Fungi Parasitic on Marine Al^ae, by Minnie

Eoed. Pp. 141-164; plates 15-16. November, 1902 „ - _ J23

3. Algae of Northwestern America, by William Albert Setchell and Na-

thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 2.25

Vol. 2. 1. A Eevlew of Califomian Polemoniaceae, by Jessie Millllcen. Pp. 1-

71; plates 1-11. May, 1904 .„ „ _ ~ .TO

2. Contributions to Cjrtological Technique, by W. J. V. Osterhout. Pp.

73-90; 5 text-figures. Juue, 1904 .25

3. Llmu, by William Albert Setchell. Pp. 91-113. April, 1905 __ .25

4. Post-Embryonal Stages ol' the LaminarlaceaL\ by William Albert

Setchell. Pp. 115-138; plates 13-14. April, 1905 .„ 35

5. Eegeneration among Kelps, by William Albert Setchell. Pp. 139-168;

plates 15-17. July, 1905 . -. .30

6. A New Genus of Ascomycetous Fungi, by Nathaniel Lyon Gardner.

Pp. 169-180; plate 18. July, 1905 _ 15

7. Teratology in the Flowers of some Califomian Willows, by William

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 _ ,60

8. 9, 10, 11. (In one cover.) The Eesistance of Certain Marine Algae to

Changes in Osmotic Pressure and Tempera tur a. The Edle of Os-
motic Pressure in Marine Plants. On the Importance of Physiolog-
ically Baiaaced Solutions for Plants. The Antitoxic Action of
PotA-ssium on Magnesium. By W. J. V. Osterhout. Pp. 227-238.
March, 1906 . _ «.. . — ....,.., .25

12. Cytologlcal Studie.s In Cyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-296: plates 21-26. November, 1906 _ LOO

IS. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Th6riot. Pp. 297-308; plates 27-28. December, 1906 . JO

14. Some Unreported Alaskan Sphagna, togsther with a Smr.a:ary of the

Cryptogaraic Work of the University of California Botanical Ex-
pedition to Alaska In 1899, by William Albert SetcbelL Pp. 809-
315. September, 1907 _ UJS

15. On Nutrient and Balanced Solutions, by W. J. V. Osterhout. Pp. 817-

318. October, 1907 _ .06

16. A Synopsis of the North American Godetlaa, by Willis Linn Jepson.

Pp. 319-354; plate 29. December, 1907 ., .40

Index, pp. 365-360.

▼oL 8. 1907-1909.

1. Cornpositae of Southern California, by Harvey Monroe HalL Pp. 1-

302; plates 1-3, with a map. December, 1907 . _ 3.00

2. The Origin, Structure, and Function of the Polar Caps in SmUa^ina

anple.x^rnulit: Nutt,, by H. D. Densmore. Pp. S03-3S0; plates 4-8.

December, 1908 „ .„.. _ _ .SB

8. 4. (In one cover.) The Value of Sodium to Plants by Eeason of Its

Protective Action. On the Effects of Certain Poisonous Oases on

Plants. By W. J. V. Osterhout. Pp. 331-340. June, 1908 J.0

5. Contributions to the Knowledge of the California Species of Orn«t»-

ceoHS Corallines. I. by Manrice Barstow Nichols. Pp. S41-S48;

plate 9. December, 1908 .10

FNIVEaSITY OF OAI^ITOENIA PXJBLIOATIONS— (Contlnuad)

6. Contributions to the Knowledpo of the California Species of CruBta-

ceous CoraUlnes. n. by Maurice Barstow Nichols. Pp. S49-S70;
plates 10-13. April, 1909 _ Jfl

7. New Chlorophyceae from California, by Nathaniel Lyon Qardner. Pp.

371-375: plate 14. April. 1309 „ „ .10

8. Piantae Mexicanae Purpusianae, I, by T. S. Brandegee. Pp. 377-396.

May, 1909 „ „ _ 16

Index, pp. 397-400.
VoL 4. 1910-lfn2.

1. Stnrlies In Ornamental Trees and Shrnb*. by Harrey Monroe HalL Pp.

1-74,- plates 1-11; 15 text- figures. March, 1910 .75

2. Gracilririophlla, a New Parairite on Grardana ronfcrvoides, by Harriet

L. Vi^ilson. Pp. 75-84; plates 12-13. May. 1910 _ .10

3. Piantae Mexicanae Purpusiaaae, II, by T, S. Brandegee. Pp. 85-95.

May. 1910 . _ _ JO

4. Leuvenia, a New Genus of Flagellates, by N. I*. Gardner. Pp. 97-106;

plate 14. May. 1910 J.0

5. The Genus Sphaerosoma, by WUliain Albert Setchell. Pp. 107-120;

plate 15. May, 1910 „. .15

6. Variations in Nccloar Extrusion Among the Fncaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; places 16-17. Augnst, 1910 _ JJ

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtio gigarii-

no'>des, by Ada Sara McFadden. Pp. 137-142; plate 18. February,

1911 „ - „. sa

8. On a Colacodasya from Southern Galifornla, by Mabel Bflae McFadden.

Pp. 143-150; plate 19. Febniary. 1911 _ .05

9. Fructification of Macrocystis, by Edna Juanlta Hoffman. Pp. 151-158;

plate 20. February, 1811 _ _ .08

10. Erythrnphyllum delesKcrwides J. Ag.. by Wilfred Charles TwIes, Pp.

159-176; plates 21-24. March, 1911 _ ._. J.5

11. Piantae Mexicanae Purpusianae, III, by T. S. Brandegee. Pp. 177-194.

July, 1911 _ _ .15

12. New and Noteworthy CalifomlaB Plants, I, by Harvey Monro© HalL

Pp. 195-208. March. 1912 .._ _ — -..- J.5

IS. Die Hydrophyllaceen der Sierra Nevada, by Augnst Brand. Pp. 209-

227. March, 1912 - — .20

14. Algae Novae et Minus Cognitae, L by William Albert SetchclL Pp.

229-268; plates 25-31. May, 1912 - - .40

15. Piantae Mexicanae PturpTistanae, fv, by Townshend Stith Brandegee.

Pp. 269-281. June, 1912 18

16. Comparative Development of the Cystocarps of Antiihamnion and

Frionitis, by Lyman Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 - -aO

17. Fungiis Galls on Cyntoseira and Halidrys. by Liilu May Estee. Pp. 305-

316; plate 35. March, 1913 ...„ , „ 10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374; plates 36-

53. April, 1913 „ 75

19. Piantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee.

Pp. 375-388. June, 1913 . .IS

Index, pp. 389-397.
Vol 5. 19 12-.

1. Studies In Nicotiana, I, by WUlIam Albert Setchell. Pp. 1-86. De-

cember. 1912 ~- l-SS

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, I, by Thomaa

Harper Goodspeed. Pp. 87-168. December, 1912 _ 1.00

3. Quantitative Studies of Inheritance in Nicotiana Hybrids, II, by

Thomas Harper Goodspeed. Pp. 169 188. January, 1913 _. .20

4. On the Partial Sterility of Nicotiima Hybrids made with N. Sylvestris

as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 - - .10

5. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Good-

speed. Pp. 199-222, May, 1913 .25

6. Quantitative Studies of Inheritance in Nicotiana Hybrids, m, by

Thomas Harper Goodspeed. Pp. 223-231. April, 1915 _ .10

7. Notes on the Germination of Tobacco Seed, II, by Thoraaa Harper

Goodspeed. Pp. 233-248. June, 1915 .- ~ .15

8. Parthenogenesis, Parthenocarpy and Phenospermy in Nicotiana, by

Thomas Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 J^

UNIVERSITY OF CALIFOENIA PUBLICATIONS— (Oontinaed)

9. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestria
as a Parent, n, by T. H. Goodspeed and A. H. Ayres. Pp. 273-292,
plate 36. October, 1916 „ :20

10. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris

as a Parent. III. An Account of the Mode of Floral Abscission in
the F, Species Hybrids, by T. H. Goodspeed and J. N. Kendall.
Pp. 293-299. November, 1916 .05

11. The Nature of the Fj Species Hybrids between Nicotiana sylvestris

and Varieties of Nicotiana tabacum, with Special Reference to the
Conception of Reaction System Contrasts in Heredity, by T. H.
Goodspesd and E. E, Clausen. Pp. 301-346, plates 37-48. Janu-
ary, 1917 45

Vol 6. 1914-

1. Parasitic Florideae, I, by William Albert ^etchell. Pp. 1-34, plates

1 -6. April, 1914 „ ~..;.'-^^----- - ...._ aSS

2. Phytomorula regularis, a Symmetrical Protophyte Related to Coelas-

trum, by Charles Atwood Kcfoid. Pp. 35-40, plate 7. April, 1914. .05

3. Variation in Oenothera ovata, by Katherlne Layne Brandegee. Pp. 41-

50, plates 8-9. June, 1914 J.0

4. Plantae Mexicanae Purpusianae, VI, by Townshend Stith Brandegee.

Pp. 51-77. July, 1914 „ .25

5. The Scinain Assemblage, by William Albert Setchell. Pp. 79-152;

plates 10-16. October, 1914 _ „ _ .75

6. Notes on Pacific Coast Algae. I. Pylaiella Postelsiae, n. sp., a New

Type In the Genus Pylaiella, by Carl Skottaberg. Pp. 153-164, plates
17-19. May, 1915 „ .15

7. New and Noteworthy Califomian Plants, n, by Harvey Monroe HalL

Pp. 165-176, plate 20. October, 1915 ^ .15

8. Plantae Mexicanae Purpusianae VII, by Townshend Stith Brandegee.

Pp. 177-197. October, 1915 25

9. Floral Relations Among the Galapagos Islands, by A. L. Kroeber.

Pp. 199-220. March, 1916 „ .20

10. The Comparative Histology of Certain Califomian Boletaceae, by

Harry S. Yates. Pp. 221-274, plates 21-25. February, 1916 50

11. A Revision of the Tuberales of California, by Helen Margaret Gilkey.

Pp. 275-356, plates 26-30. March, 1916 > .80

12. Species Novae vel Minus Cognitae, by T. S. Brandegee. Pp. 357-361.

May, 1916 „ _ .05

Vol. 7. 1916-

1. Notes on the CaUfomlan Species of Trillium L. I. A Report of the

General Results of Field and Garden Studies, 1911-1916, by Thomas
Harper Goodspeed and Robert Percy Brandt. Pp. 1-24, plates 1-4.
October, 1916 25

2. Notes on the Califomian Species of Trillium L. II. The Nature and

Occurrence of Undeveloped Flowers, by Thomas Harper Goodspeed

and Robert Percy Brandt. Pp. 25-38, plates 5-6. October, 1916 ... .16

3. Notes on the Califomian Species of Trillium L. III. Seasonal Changes

in Trillium Species with Special Reference to the Reproductive Tis-
sues, by Robert Percy Brandt. Pp. 39-68, plates 7-10. December,
1916 30

4. Notes on the Califomian Species of Trillium L. IV. Teratological

Variations of Trillium sessile var. gigantexim H. & A., by Thomas
Harper Goodspeed. Pp. 69-100, plates 11-17. January, 1917 30

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 12, pp. 347-428, 10 text figs., plates 49-53 March 6, 1918

ABSCISSION OF FLOWERS AND FRUITS IN

THE SOLANACEAE, WITH SPECIAL

REFERENCE TO NICOTIANA

BY

JOHN N. KENDALL

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Koto. — The University of California Publications are offered in exchange for the pnbU-
eations of learned societies and institutions, universities and libraries. Complete llsti of
all the publications of the University will be beat upon request. For sample copie:^, lists of
ptxbUcationfl and other information, address the Manager of the University Press, Berkeley,
California, U. 8. A. All matter sent in exchange should be addressed to The Exchange
Department, University Library, Berkeley, California, U. S. A.

BOTAliT.— W. A. Setchell, Editor. Price per volume, ^.60. Volnmea I (pp. 418), n (pp
360), III (pp. 400), IV (pp. 379), completed. Vols. V, VI and VII in
progress.

Cited as Univ. Calif. PnbL Bot.

Vol 1. 1. A Botuiical Sorvey of San Jacinto Mountain, by Harvey Monro*

HalL Pp. 1-140; plates 1-14. June, 1902 11.00

8. Two new Ascomycetou* Fungi Parasitic on Marine Alfcae, by Mliuile

Eeed. Pp. 141-164; plates 15-16. November, 1902 3S

S. Algae of Northwestern America, by William Albert Setchell and N*-

thaniel Lyon Gardner. Pp. 165-418; plates 17-27. March, 1903 — a.2S

VoL 2. 1. A Eeview of Callfomlan Polemoniaceae, by Jessie Mllllken. Pp. 1-

71; plates 1-11. May, 1904 _ .75

2. ContrlbuUona to Cytological Technique, by W. J. V. Osterhout. Pp.

73-90; 5 text-figures. June, 1904 .25

8. Limu, by WiUiam Albert SetcheU. Pp. 91-113. April, 1905 .25

4. Post-Embryonal Stages of the Laminarlaceae, by William Albert

Setchell. Pp. 115-138; plates 13-14. April, 1905 .26

5. Regeneration among Kelps, by William Albert SetcheU. Pp. 139-168;

plates 15-17. July, 1905 — — — .30

6. A New G^enua of Axcomycetous Fungi, by Nathaniel Lyon Qardner.

Pp. 169-180; plate 18. July, 1905 _ __ - — 4.6

7. Teratology in the Flowers of some Callfomlan Willows, by William

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 _ JW

8. 9, 10. 11. (In one cover.) The Eesiatance of Certain Marine Algae to

Changes in Osmotic Pressure and Temperature. The E61e of OiS-
motic Pressure in Marine Plants. On the Importance of Phyrioiog-
Ically Balanced Solutions for Plants. The Antitoxic Action of
Potassium on Magnesium. By W. J. V. Osterhout. Pp. 227-236.
March, 1906 . — .28

12. Cytological Studies in Cyanophyceae, by Nathaniel Lyoa Gardner.

Pp. 237-296; plates 21-26. November, 1906 — LOO

18. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Th6riot. Pp. 297-308; plates 27-28. December, 1906 .10

14. Some ^Unreported Alaskan Sphagna, togsther with a Sun.iEary of the
Cryptogamlc Work of the University of California Botanical Ex-
pedition to AJaska in 1899, by WiUiam Albert SetcnelL Pp. 30»-
315. September, 1907 .06

IB. On Nutrient and Balanced Solutions, by W. J. V. Osterhout. Pp. 317-

318. October, 1907 .06

16. A Synopsis of the North American Codettas, by Willis Linn Jepson.

Pp. 319-354; plate 29. December, 1907 ^ M

Index, pp. 365-360.

Voi, 8. 1907-1909.

L Compositae of Southern California, by Harvey Monroe Hall. Pp. 1-

S02; plates 1-S, with a map. December, 1907 8.00

e. The Origin, Structure, and Function of the Polar Caps in SmUacina

amplexiravlis Nutt., by H. D. Denamore. Pp. 303-330; plates 4-8.

December, 1908 ~ _ - — -SO

8. 4. (In one cover.) The Value of Sodium to Plants by Reason of Its

Protective Action. On the Effects of Certain Poisonous Oases on

Plants. By W. J. V. Osterhout. Pp. 331-340. June, 1908 .10

5. Oontrlbr.tions to the B^owledge of the California Species of Cmata-

ceoms Corallines. I. by Maurice Barstow Nichols. Pp. 841-348;

plato 9. Decemb«, 1908 . — '. .M

UmVEOSITT OF OAUFOBNIA PUBLIOATION8 — (Continued)

6. Ck)ntrll>Titlonfl to the Knowledge of the Oalifomla Species of Onurt»>

ceous Corallinos. n. by Maurice B&rstow Nichola. Pp. 349-370;
plates 10-13. April, 1909 „ M

7. New Chlorophyceae from California, by Nathaniel Lyon Oardner. Pp.

871-375; plate 14. April, 1909 ..„ _ J.0

8. Plantae Mexicanae Farpusianae, I, by T. S. Brandegee. Pp. 377-396.

May, 1909 ._ „ „ .15

Index, pp. 397-400.
▼oL 4. 1910-1912.

1. StndJes in Ornamental Trees and Shrnhs, by Harrey Monroe HalL Pp.

1-74; plates 1-11; 15 text-flgiues. March, ISIO _ .78

2. GracilariopMla, a New Paraait* on GrarxUirui confervoides, by Harriet

L. Wilson. Pp. 75-&4; plates 12-13. May, 1910 „„ J.0

8. Plantae Mexicanae Pnrpuflianae, II, by T. 8. Brandegee. Pp. 85-95.

May, 1910 _ _ J,0

4. Lenvenla, a New Genus of Flagellates, by N. L. Gardner. Pp. 97-106;

plate 14. May, 1910 .,„„.._ „.. ;_„.. .^ .10

6. The Genus Sphaerosoma, by William Albert SetchelL Pp. 107-120;

plate 15. May, 1910 „ JL5

6. Variations in Nuclear Eztinsion Among the Fncaceae, by Nathaniel

Lyon Oardner. Pp. 121-136; pla^ies 16-17. August, 1910 . JLB

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtia gigarti-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 „ .03

8. On a Colacodasya from Southern Calif omla, by Mabel Effie McFadden.

Pp. 143-150; plate 19. February, 1911 _ .OS

9. Fructification of Macrocystls, by Edna Jnanita Hoffman. Pp. 151-158;

plate 20. February, 1911 „ .08

10. Eryihrophyllum delesserioides J. Ag., by Wilfred Charles Twlss. Pp.

159-176; plates 21-24. March, 1911 .„^ ^„„ J.5

11. Plantae Mexicanae Purpusianae, III, by T. S. Brandegee. Pp. 177-194.

July, 1911 _ „ ._..... J5

12. New and Noteworthy Calif omian Plants, I, by Harvey Monroe HaU.

Pp. 195-208. March, 1912 _ J.0

13. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 „ _ „ JBO

14. Algae Novae et Minus Cognitae, I, by William Albert SetchelL Pp.

229-268; plates 25-31. May, 1912 ..:..:.....„... __ .40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stith Brandegee.

Pp. 269-281. June, 1912 , .15

16. Comparative Development of the Cystocarps of Antithnmnion and

Prionitis, by Lyman Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 ..„................„.:..... ..^ ™...^ .20

17. Fungiis Galls on Cysioseira and Ealidrys. by Lulu May Estee. Pp. S05-

316; plate 35. March, 1913 „ _ .10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374; plates 36-

53. April, 1913 ; , „ .76

19. Plantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee.

Pp. 375-388. June. 1913 _ JJ

Index, pp. 389-397.
Vol B. 1912-.

1. Studies in Nicotiana, I, by William Albert Setchell. Pp. 1-88. De-

cember, 1912 _ 1.23

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, I, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 _ 1.00

8. Quantitative Studies of Inheritance in Nicotiana Hybrids, n, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 _ .20

4. On the Partial Sterility of Nicotiana Hybrids made with N. Sylvestris
as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 _ .10

6. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Good-
speed. Pp. 199-222. May, 1913 _ JZ6

6. Quantitative Studies of Inheritance in Nicotiana Hybrids^ m, by

Thomas Harper Goodspeed. Pp. 223-231. April, 1915 .10

7. Notes on the Germination of Tobacco Seed, n, by Thomas Harper

Goodspeed. Pp. 233-248. June, 1915 15

8. Parthenogenesis, Parthenocarpy and Phenospermy In Nicotiana, by

Thomas Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 _ .25

UNTTEESITY OF OALIFOEinA PUBLICATIONS— (Oontlnned)

9. On the Partial Sterility of Nicotiana Hybrids made ■with N. sylvestria
as a Parent. II, by T. H. Goodspeed and A. H. Ayres. Pp. 273-292,
plate 36. October, 1916 ,20

10. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris

as a Parent, m. An Account of the Mode of Floral Abscission In
the F, Species Hybrids, by T. H. Goodspeed and J. N. KendalL
Pp. 293-299. November, 1916 .05

11. The Nature of the F, Species Hybrids between Nicotiana sylvestris

and Varieties oi Nicotiana tabaciim, with Special Reference to the
Conception of Reaction System Contrasts in Heredity, by T. H.
Goodspeed and R. E. Clausen. Pp. 301-346, plates 37-48. Janu-
ary, 1917 -.._ AS

12. Abscission of Flowers and Fruits in the Solanaceae, with Special

Reference to Nicotiana, by John N. Kendall, Pp. 347-428, 10 text
figures, plates 49-53. March, 1918 85

V6L 6. 1914-

1. Parasitic Florideae, I, by William Albert SetchelL Pp. 1-34, platet

1-6. April, 1914 JS

2. Phytomomla regularis, a Symmetrical Protophyte Related to Coelat-

tram, by Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914. .05

8. Variation In Oenothera ovata, by Eatherine Layne Brandegee. Pp. 41-

50, plates 8-9. June, 1914 _ JO

4. Plantae Mezlcanae Porpusianae, VI, by Townshend Stith Brandegee.

Pp. 51-77. July, 1914 .Sf

6. The Scinaia Assemblage, by William Albert Setchell. Pp. 79-152,

platfcs 10-16. October, 1914 „ .78

6. Notes on Pacific Coast Algae. I. PylaieUa Postelsiae, n. sp., a New

Type In the Genus Pylaiella, by Carl Skottsberg. Pp. 153-164, plates
17-19. May, 1915 . . .15

7. New and Noteworthy Califomian Plants, n, by Harvey Monroe HalL

Pp. 165-176, plate 20. October, 1915 .16

8. Plantae Mezlcanae Purpusianae VII, by Townshend Stith Brandegee.

Pp. 177-197. October, 1915 .25

9. Floral Relations Among the Galapagos Islands, by A. L. Kroeber.

Pp. 199 220. March, 1916 _ „ _ J20

10. The Comparative Histology of Certain Califomian Boletaceae, by

Harry S. Yates. Pp. 221-274, plates 21-25. February, 1916 „_ .60

11. A Revision of the Tuberales of California, by Helen Margaret GUkey.

Pp. 275-356, plates 26-30. March, 1916 _ .80

12. Species Novae vel Minus Cognltae, by T. S. Brandegee. Pp. 357-361.

May, 1916 „ _ .05

13. Plantae Mexicanae Purpusianae, vni, by Townshend Stith Brandegee.

Pp. 363-375. March, 1917 - .16

14. New Pacific Coast Marine Algae, I, by Nathaniel Lyon Gardner, Pp.

377-416, plates 31-35. June, 1917 40

15. An Account of the Mode of Foliar Abscission in Citrus, by Robert W.

Hodgson. Pp. 417-428, 3 text figures. February, 1918 10

Vol 7. 1916-

1. Notes on the Califomian Species of TriUium L. I. A Report of the

General Results of Field and Garden Studies, 1911-1916, by Thomas
Harper Goodspeed and Robert Percy Brandt. Pp. 1-24, plates 1-4,
October, 1916 „ „ „ „ — SS

2. Notes on the Califomian Species of Trillium L. II. The Nature and

Occurrence of Undeveloped Flowers, by Thomas Harper Goodspeed

and Robert Percy Brandt. Pp. 25-38, plates 5-6. October, 1916 _ OB

3. Notes on the Califomian Species of TriUium L. HI. Seasonal Changes

in Trillium Species with Special Reference to the Reproductive Tis-
sues, by Robert Percy Brandt. Pp. 39-68, plates 7-10. December,
1916 „„ - ^

4. Notes on the Califomian Species of Trillium L. IV. Teratologlcal

Variations of Trillium sessile var. giganteum H. & A., by Thomas
Harper Goodspeed. Pp. 69-100, plates 11-17. January, 1917 JO

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 13, pp. 429-434 August 10, 1918

CONTROLLED POLLINATION IN NICOTIANA

BY
THOMAS HARPER GOODSPEED AND PIRIE DAVIDSON

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Kote. — Tlie Unlyeraity of Oalifomla Publications are offered in exchange for the pnbU-
eatlons of learned societies and iBstitutions, universities and libraries. Complete lists of
aU the publications of the University will be sent upon request. For sample copies, lists of
publications and other information, address the Manager of the University Press, Berkeley,
Oalifomla, U. S. A. All matter sent in exchange should be addressed to The Exchange
Department, University Library, Berkeley, Caiifomia, U. S. A.

BOTANY. — W. A. Setchell, Editor. Price per volume, $3.50; beginning with vol. 5, $5.00.
Volumes I (pp. 418), II (pp. 360), III (pp. 400), IV (pp. 379), completed.
Vols, V, VI and VII in progress.

Cited as Univ. Calif. PnbL Bot.

Vol 1. 1. ▲ Botaziical Survey of San Jacinto Mountain, by Harvey Mooxoa

HalL Pp. 1-140; plates 1-14. June, 1902 -_ 11.00

a. Two new Ascomycetous Fungi Parasitic on Marine Al^aa, by Minnie

Reed. Pp. 141-164; plates 15-16. November, 1902 .25

8. Algae of Northwestern America, by William Albert Setchell and Ka-

thaniel Lyon Qardner. Pp. 165-418; plates 17-27. March, 1903 — 2.2S

VoL 8. LA Beview of Califomlan Polemoniaceae, by Jessie MllUfcen. Pp. 1-

71; plates 1-11. May, 1904 _ — ; .76

2. Contributions to Cytological Technique, by W. J. V. Osterhout. Pp.

73-90; 5 text-figures. June, 1904 Jffi

8. Llmu, by William Albert SetcheU. Pp. 91-113. April, 1905 _ M

4. Post-Embryonal Stages of the Laminarlaceao, by William Albert

Setchell. Pp. 115-138; plates 13-14. April, 1905 J»

6. Eegeneration among Kelps, by William Albert SetchelL Pp. 13^168;

plates 15-17. July, 1905 .„ — JO

'6. A New Genus of Ascomycetous Fungi, by Nathaniel Lyon Qardner.

Pp. 169-180; plate 18. July, 1905 — - — .16

7. Teratology in the Flowers of some Califomian Willows, by WilUam

Warner Mott. Pp. 181-226; plates 16-20. December, 1905 .„ _ JiO

8. 8, 10, 11. (In one cover.) The Beslstance of Certain Marine Algae to

CJhanges in Osmotic Pressure and Temperatoz). The BCle of Os-
motic Pressure in Marine Plants. On the Importance of Physiolog-
ically Balanced Solutions for Plants. Tho Antitoxic Action of
Potassium on Magnesium. By W. J. V. Osterhout. Pp. 227-238.
March, 1906 — .86

a. Oytological Studies In Cyanophyceae, by Nathaniel Lyon Gardner.

Pp. 237-286; plates 21-26. November, 1906 LOO

18. On a Small Collection of Mosses from Alaska, by J. Cardot and T.

Thfiriot Pp. 297-308; plates 27-28. December, 1906 JO

14. Some Unreported Alaskan Sphagna, together with a Smrirjiry of tho
Cryptogamlc Work of the University of California Botanical Ex-
pedition to Alaska In 1899, by William Albert SetchelL Pp. 809-
816. September, 1907 .05

16. On Nutrient and Balanced Solutiona, by W. J. V. Osterhout. Pp. 317-

S18. October, 1907 M

16. A Synopsis of the North American Oodetias, by Willis Linn Jepson.

Pp. 319-364; plate 29. December, 1907 .40

Index, pp. 365-360.

yoL 8. 1907-1909.

L Compositae of Southern California, by Harvey Monroe Hall. Pp. 1-

802; plates 1-3, with a map. December, 1907 8.00

5. The Origin, Structure, and Function of the Polar Caps in 8mil<fcina

omplexicaulis Nutt., by H. D. Densmore. Pp. 803-330; plates 4-8.

December, 1908 .35

8. 4. (In one cover.) The Vala* of Sodinm to Plants by Season of Its
Protectire Action. On the Effects of Certain Poisonous Ceases on
Plants. By W. J. V. Osterhout. Pp. 831-340. June, 1908 M

6. Contributions to the Knowledge of the Oalifomla Species of Orosta-

ceoma Corallines. L by Maurice Barstow Nichols. Pp. S41-84B;

plate 9. December. 1908 — •!•

6. Contributions to the Knowledge of the California Species of Crusta-
ceons Corallines, n. by Maurice Barstow Nichols. Pp. 849-870;
plate« 10-13. April, 1809 M

UNIVKaSITY OP OAUrOSNIA PUBUOATIONS— (Continued)

•/. New Clilorophyceae from Oallfomla, by Nathaniel Lyon Gardner. Pp.

S71-375; plate 14. April, 1909 -.^ JO

8. Plantae Mexicanae Farpusianae, I, by T. S. Brandegee. Pp. 377-898.

May, 1909 .15

Index, pp. 897-400.
TOL A. ieiO-1912.

1. Studies in Ornamental Trees and Shrubs, by Harrey Monroe TT»M. Pp.

1-74; plates 1-11; 15 text-figures. March, ISiO _ .75

2. OracilariopMla, a New Parasite on Gractlaria confer voidet, by Harriet

L. Wilson. Pp. 75-84; plates 12-13. May, 1910 „„ _ J.0

8. Plantae Mexicanae Purpusianae, II, by T. S. Brandegee. Pp. 85-95.

May, 1910 .... ..„ . .„ JlQ

i. Lenvenia> a New Genus of Flagellates, by N. L. Gardner. Pp. 97-100;

plate 14. May, 1910 _ ..._ J.0

8. The Genus Sphaerosoma, by William Albert SetchelL Pp. 107-120;

plate 15. May, 1910 _ „ .......„._„. J.6

6. Variations in Nuclear Extrusion Among the Fucaceae, by Nathaniel

Lyon Gardner. Pp. 121-136; plates 16-17. August, 1910 JLO

7. The Nature of the Carpostomea In the Cystocarp of Ahnfeldtio gigarii-

noides, by Ada Sara McFadden. Pp. 137-142; plate 18. February,
1911 - „ — „.„ .05

8. On a Oolacodasya from Southern California, by Mabel Effle McFadden.

Pp. 143-150; plate 19. February, 1911 ..._ _.... .06

9. Fructification of Macrocystis, by Edna Jnanita Hoffman. Pp. 151-158;

plate 20. February, 1911 _ .06

10. Erythrophyllum dclesaerioides 3. Ag., by Wilfred Charles Twlss. Pp.

159-176; plates 21-24. March, 1911 ^, J.5

11. Plantae Mexicanae Purpusianae, m, by T. S. Brandegee. Pp. 177-19i.

July, 1911 „ „ „- _ -...„ _ — __ as

12. New and Noteworthy Calif omian Plants, I, by Harvey Monroe Hall.

Pp. 195-208. March, 1912 „ „ _ — JLO

IS. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-

227. March, 1912 -— , — — ..- ..-.-- J20

14. Algae Novae et Minus Cognitae, I, by William Albert SetchelL Pp.

229-268; plates 25-31. May, 1912 - —, .40

15. Plantae Mexicanae Purpuaianaei IV, by Townshehd Stith Brandegee.

Pp. 269-281. June, 1912 _ .IS

18. Comparative Development of the Cystocarps of Antithamnion and
Prionitis, by Lyman Luther Daines. Pp. 283-302; plates 32-34.
March, 1913 _. .— : .20

17. Fungus Galls on Cystoseira and Halidrys. by Lulu May Estee. Pp. SOS-

SIS; plate 35. March, 1913 , _ — .10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374; plates 36-

53. April, 1913 .. _ - - -^ .75

19. Plantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee.

Pp. 375-388. June, 1913 „___ _....^.... — . — ^__._;.:, -_ .14

Index, pp. 889-397.
VoL B. 1912-.

1. Studies in Nicotiana, I, by William Albert Setchell. Pp. 1-86. De-

cember, 1912 - 1.28

2. Quantitative Studies of Inheritance In Nicotiana Hybrids, I, by Thomaa

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

8. Quantitative Studies of Inheritance in Nicotiana Hybrids, H, by

Thomas Harper Goodspeed. Pp. 169-188. January, 1913 ..„ JW

4. On the Partial Sterility of Nicotiana Hybrids made with N. Sylveatria
as a Parent, by Thomas Harper Goodspeed. Pp. 189-198. March,

1913 - - — .10

6. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Good-
speed. Pp. 199-222. May, 1913 — - - .28

6. Quantitative Studies of Inheritance in Nicotiana HybrldS; m, by

Thomas Harper Goodspeed. Pp. 223-231. April, 1915 .10

7. Notes on the Germination of Tobacco Seed, n, by Thomas Harper

Goodspeed. Pp. 233-248. June, 1915 - 15

8. Parthenogenesis, Parthenocarpy and Phenospermy in Nicotiana, by

Thomas Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 _ .25

9. On the Partial Sterility of Nicotiana Hybrids made with N. sylventris

as a Parent, n, by T. H. Goodspeed and A. H. Ayres. Pp. 273-292,
plate 36. October, 1916 .20

irtnVEESrry of OAilFOENiA FUBLICATIONS— (Continued)

10. On tlie Partial Sterility of Nicotiana Hybrids made with N. sylvestris

as a Parent. HI. An Account of the Mode of Floral Abscission In
the Fi Species Hybrids, by T. H. Goodspeed and J. N. Kendall
Pp. 293-299. November, 1916 06

11. The Nature of the Fi Species Hybrids between Nicotiana sylvestris

and Varieties of Nicotiana tahacum, with Special Reference to tbo
Conception of Reaction System Contrasts in Heredity, by T. H.
Goodspeed and R. E. Clausen. Pp. 301-346, plates 37-48. Janu-
ary, 1917 --. - - ~~ ~. M

12. Abscission of Flowers and Fruits in the Solanaceae, with Special

Reference to Nicotiana, by John N. Kendall. Pp. 347-428, 10 text
figures, plates 49-53. March, 1918 „. 85

13. Controlled Pollination in Nicotiana, by Thomas Harper Goodspeed and

Pirie Davidson. Pp. 429-434. August, 1918 10

VoL 6. 1914-

1. Parasitic Florideae, I, by WUliam Albert Sotchell. Pp. 1-S4, plates

1-6. April, 1914 . — ~. — . — — M

2. Phytomorula regularis, a Symmetrical Protophjrte Related to Coelat-

trum, by Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914. .06

3. Variation in Oenothera ovata, by Katherine Layne Brandegee. Pp. Al-

so, plates 8-9. June, 1914 .„ _ :..... _ 4.0

4. Plantae MexLcanae Purpusianae, VI, by Townshend Stlth Brandegee.

Pp. 51-77. July, 1914 Jt5

6. The Scinaia Assemblage, by William Albert SetchelL Pp. 79-152,

plates 10-16. October, 1914 .78

6. Notes on Pacific Coast Algae. L Pylaiella Postelsiae, n. 8p., a New

Type in the Genua Pylaiella, by Carl Skottsberg. Pp. 153-164, plates
17-19. May, 1915 — .15

7. New and Noteworthy Calif omian Plants, II, by Harvey Monroe HalL

Pp. 165-176, plate 20. October, 1915 — .16

8. Plantae Mexicanae Purpusianae VII, by Townshend Stlth Brandegee.

Pp. 177-197. October, 1915 - .28

9. Floral Relations Among the Galapagos Islands, by A. L. Kroeber.

Pp. 199-220. March, 1916 „ - JIO

10. The Comparative Histology of Certain Califomlan Boletaceae, by

Harry S. Yates. Pp. 221-274, plates 21-25. February, 1916 _ .60

11. A Revision of the Tuberales of California, by Helen Margaret QUkey.

Pp. 275-356, plates 26-30. March, 1916 80

12. Species Novae vel Minus Cognltae, by T. S. Brandegee. Pp. 357-361.

May, 1916 _ „ .05

13. Plantae Mexicanae Purpusianae, vni, by Townshend Stith Brandegee.

Pp. 363-375. March, 1917 - 16

14. New Pacific Coast Marine Algae, I, by Nathaniel Lyon Gardner, Pp.

377-416, plates 31-35. June, 1917 40

15. An Account of the Mode of Foliar Abscission In Citrus, by Robert W.

Hodgson. Pp. 417-428, 3 text figures. February, 1918 10

16. New Pacific Coast Marine Algae 11, by Nathaniel Lyon Gardner. Pp.

429-454, plates 36-37. July, 1918 - 25

Vol. 7. 1916-

1. Notes on the CaUfomlan Species of Trillium L. I. A Report of the

General EesiUts of Field and Garden Studies, 1911-1916, by Thomas
Harper Goodspeed and Robert Percy Brandt. Pp. 1-24, plates 1-4.
October, 1916 — JB5

2. Notes on the Callfomian Species of Trillium L. II. The Nature and

Occurrence of Undeveloped Flowers, by Thomas Harper Goodspeed

and Robert Percy Brandt. Pp. 25-38, plates 5-6. October, 1916 _ 06

5. Notes on the Callfomian Species of Trillium L. III. Seasonal Changes

In Trillium Species with Special Reference to the Reproductive Tis-
sues, by Robert Percy Brandt. Pp. 39-68, plates 7-10. December,

1916 _ „ - .SO

4. Notes on the Callfomian Species of Trillium L. IV. Teratologlcal
Variations of Trillium sessile var. giganteum H. & A., by Thomas
Harper Goodspeed. Pp. 69-100, plates 11-17. January, 1917 J80

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 14, pp. 435-437, plate 54, 1 figure in text September 25, 1918

AN APPARATUS FOR FLOWER MEASUREMENT

BY

T. H. GOODSPEED AND R. E. CLAUSEN

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFORNIA PUBLICATIONS

Note. — The University of California Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University will be sent upon request. For sample copies, lists
of publications and other information, address the MANAGER OF THE UNIVERSITY
PRESS, BERKELEY, CALIFORNIA, U. S. A. AU matter sent in exchange should be
addressed to THE EXCHANGE DEPARTMENT, UNIVERSITY LIBRARY, BERKELEY,
CALIFORNIA, U. S. A.

WILLIAM WESLEY & SONS, LONDON
Agent for the series in American Archaeology and Ethnology, Botany, Geology,

Physiology, and Zoology.

BOTANY. — W. A. Setchell, Editor. Price per volume, $3.50; beginning with vol. 5, $5.00.
Volumes I (pp. 418), II (pp. 360), III (pp. 400), IV (pp. 379), completed. Volumes
V, VI and VII in progress.

Cited as Univ. Calif. Publ. Bot.

Volume 1, 1902-1903, 418 pages, with 27 plates $3.50

Volume 2, 1904-1907, 360 pages, with 29 plates 3.50

Volume 3, 1907-1909, 400 pages, with 14 plates 3.50

Vol. 4. 1910-1912.

1. Studies in Ornamental Trees and Shrabs, by Harvey Monroe Hall. Pp. 1-74,

plates 1-11, 15 text fig-ures. March, 1910 75

2. Gracilariophila, a New Parasite on GracUaria confervoides, by Harriet L.

Wilson. Pp. 75-84, plates 12-13. May, 1910 10

3. Plantae Mexicanae Purpusianae, II, by T, S. Brandegee. Pp. 85-95, May,

1910 --..^....„:.....^ 10

4. Leuvenia, a New Genus of Flagellates, by N. L. Gardner. Pp. 97-106, plate

14. May, 1910 „ 10

5. The Genus SpJiaerosoma, b William Albert Setchell. Pp. 107-120, plate

15. May, 1910 ._ .15

6. Variations in Nuclear Extrusion Among the Fucaceae, by Nathaniel Lyon

Gardner. Pp. 121-136, plates 16-17. August, 1910 .15

7. The Nature of the Carpostomes in the Cystocarp of Ahnfeldtia gigartinoides,

by Ada Sara McFadden. Pp. 137-142; plate 18. February, 1911 .05

8. On a Colacodasya from Southern California, by Mabel Effie McFadden.

Pp. 143-150, plate 19. February, 1911 .05

9. Fructification of Maerocystis, by Edna Juanita Hoffman, Pp, 151-158, plate

20. February 1911 ::... 05

10. Erythrophyllum delesserioides J. Ag., by Wilfred Charles Twiss. Pp. 159-

176, plates 21-24. March, 1911 .15

11. Plantae Mexicanae Purpusianae, m, by T. S. Brandegee. Pp. 177-194.

July, 1911 15

12. New and Noteworthy California Plants, I, by Harvey Monroe Hall. Pp,

195-208. March, 1912 15

13. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-227.

March, 1912 .20

14. Algae Novae et Minus Cognita*, I, by William Albert Setchell. Pp. 229-268,

plates 25-31. May, 1912 .' , 40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stith Brandegee. Pp.

269-281. Jime, 1912 „ 15

16. Comparative Development of the Cystocarps of Antithamnion and Prionitis,

by Lyman Luther Daines. Pp. 283-302, plates 32-34. March, 1913 20

17. Fungus Galls on Cystoseira and Halidrys, by Lulu May Estee. Pp. 305-316,

plate 35. March, 1913 .". ..i.^:.:.-.... .10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374, plates 36-53,

April, 1913 75

19. Plantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee. Pp.

375-388. June, 1913 15

Index, pp. 389-397.

UNIVERSITY OF CALIFORNIA PUBLICATIONS— (Continued)

Vol. 5. 1912-.

1. Studies in Niootiana, I, by William Albert Setcliell. Pp. 1-86. December,

1912 : 1.25

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, I, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

3. Qua.ntitative Studies of Inheritance in Nicotiana Hybrids, II, by Thomas

Harper Goodspeed, Pp. 169-188, January, 1913 20

4. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, by Thomas Harper Goodspeed, Pp, 189-198, March, 1913 10

5. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Goodspeed.

Pp. 199-222. May, 1913 25

6. Quantitative Studies of Inheritance in Nicotiana Hybrids, IH by Thomas

Harper Goodspeed. Pp. 223-231. April, 1915 10

7. Notes on the Germination of Tobacco Seed, II, by Thomas Harper Good-

speed. Pp, 233-248, June, 1915 15

8. Parthenogenesis, Parthenocarpy and Phenospermy in Nicotiana, by Thomas

Harper Goodspeed. Pp, 249-272, plate 35. Jidy, 1915 .25

9. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, II, by T, H. Goodspeed and A, H, Asrres. Pp. 273-292, plate 36.
October, 1916 20

10. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, III, An Account of the Mode of Floral Abscission in the T^ Species
Hybrids, by T. H, Goodspeed and J. N. Kendall. Pp. 293-299. November,
1916 05

11. The Nature of the F, Species Hybrids between Nicotiana sylvestris and

Varieties of Nicotiana Tabacum, with Special Reference to the Conception
of Reaction System Contrasts in Heredity, by T. H. Goodspeed and R. E.
Clausen. Pp. 301-346, plates»37-48, January, 1917 45

12. Abscission of Flowers and Fruits in the Solanaceae, with Special Reference

to Nicotiana, by John N, Kendall. Pp. 347-428, 10 text figures, plates 49-

53. March, 1918 85

13. Controlled Pollination in Nicotiana, by Thomas Harper Goodspeed and Pirie

Davidson. Pp. 429-434. August, 1918 10

14. An Apparatus for Flower Measurement, by T. H. Goodspeed and R. E.

Clausen, Pp. 435-437, plate 54, 1 figure in text. September 25, 1918 .05

Vol. 6. 1914-.

1. Parasitic Florideae, by William Albert Setchell. Pp. 1-34^ plates 1-6.

April, 1914 , 35

2. Fhytomorula reriularis, a Symmetrical Protophsrte Related to Coelastnim, by

Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914 .05

3. Variation in Oenothera ovata, by Katherine Layne Brandegee. Pp. 41-50,

plates 8-9, June, 1914 10

4. Plantae Mexlcanae Purpusianae, VI, by Townshend Stith Brandegee. Pp.

51-77, July, 1914 25

5. The Scinaia Assemblage, by William Albert Setchell, Pp. 79-152, plates

10-12. October, 1914 75

6. Notes on Pacific Coast Algae, I, Pylaiella Postelsiae, n. sp., a New Type in

the Genus Pylaiella, by Carl Skottsberg. Pp. 153-164, plates 17-19. May,
1915 15

7. New and Noteworthy Califomian Plants, II, by Harvey Monroe Hall. Pp.

165-176, plate 20. October, 1915 15

8. Plantae Mexicanae Purpusianae, VII, by Townshend Stith Brandegee. Pp.

177-197. October, 1915 25

9. Floral Relations Among the Galapagos Islands, by A. L. Kroeber. Pp.

199-220. March, 1916 20

10. The Comparative Histology of Certain Califomian Boletaceae, by Harry S.

Yates. Pp. 221-274, plates 21-25. February, 1916 50

11, A Revision of the Tuberales of California, by Helen Margaret Gilkey. Pp.

275-356, plates 26-30. March, 1916 80

UNIVERSITY OF CALIFORNIA PUBLICATIONS— (Continued)

12. Species Novae vel Minus Cognitae, by T. S. Brandegee. Pp. 357-361. May,
^ 1916 .05

. 13. Plantae Mexicanae Purpusianae, Vin, by Townshend Stith Brandegee. Pp.

363-375. March, 1917 15

14. New Pacific Coast Marine Algae, I, by Nathaniel Lyon Gardner, Pp. 377-

416, plates 31-35. June, 1917 40

15. An Account of the Mode of Foliar Abscission in Citrus, by Robert W.

Hodgson. Pp. 417-428, 3 text figures. February, 1918 .10

16. New Pacific Coast Marine Algae, II, by Nathaniel Lyon Gardner. Pp. 429-

454, plates 36-37. July, 1918 .^ 25

Vol. 7. 1916-.

1. Notes on the Califomian Species of Trillmm L. I, A Report of the General

Results of Field and Garden Studies, 1911-1916, by Thomas Harper Good-
speed and Robert Percy Brandt. Pp. 1-24, plates 1-4. October, 1916 25

2. Notes on the CaUfornian Species of Trillmm L. II, The Nature and Occur-

rence of Undeveloped Flowers, by Thomas Harper Goodspeed and Robert
Percy Brandt. Pp. 25-38, plates 5-6. October, 1916 .15

3. Notes on the Califomian Species of TrilUum L. in. Seasonal Changes in

Trillium Species with Special Reference to the Reproductive Tissues, by
Robert Percy Brandt. Pp. 39-68, plates 7-10, December, 1916 30

4. Notes on the Calif ornian Species of TriJlium L. IV, Teratological Varia-

tions of Trillium sessile var. giganteum H. & A., by Thomas Harper Good-
speed. Pp. 69-100, plates 11-17. January, 1917 30

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 15, pp. 439-450 December 28, 1918

NOTE ON THE EFFECTS OF ILLUMINATING
GAS AND ITS CONSTITUENTS IN CAUS-
ING ABSCISSION OF FLOWERS IN
NICOTIANA AND CITRUS

BY

T. H. GOODSPEED, J. M. McGEE and R. W. HODGSON

UNIVERSITY OP CALIFORNIA PRESS
BERKELEY

UNIVEESITY OF CALIFOKNIA PUBLICATIONS

Note. — The University of California Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
aJl the publications of the University will be sent upon request. For sample copies, lists
of publications and other information, address the MANAGEE OF THE UNIVEESITY
PEESS, BEEKELEY, CALIF OENIA, U. S. A. All matter sent in exchange should be
addressed to THE EXCHANGE DEPARTMENT, UNIVEESITY LIBEAEY, BEEKELEY,
OALIFOENIA, U. S. A.

WILLIAM WESLEY & SONS, LONDON
Agent for the series in American Archaeology and Ethnology, Botany, Geology,

Physiology, and Zoology.

BOTANY.— W. A. Setchell, Editor. Price per volume, $3.50; beginning with vol. 5, $5.00.
» Volumes I (pp. 418), II (pp. 360), IH (pp. 400), IV (pp. 379), completed. Volumes
V, VI and VII in progress.

Cited as Univ. Calif. Publ. Bot.

Volume 1, 1902-1903, 418 pages, with 27 plates „ $3.50

Volume 2, 1904-1907, 360 pages, with 29 plates _ 3.50

Volume 3, 1907-1909, 400 pages, with 14 plates _ 3.50

Vol. 4. 1910-1912.

1. Studies in Ornamental Trees and Shrubs, by Harvey Monroe HsJl. Pp. 1-74,

plates 1-11, 15 text figures. March, 1910 75

2. Gracilariophila, a New Parasite on GracUaria confervoides, by Harriet L.

Wilson. Pp. 75-84, plates 12-13. May, 1910 _ 10

3. Plantae Mexicanae Purpusianae, II, by T. S. Brandegee. Pp. 85-95. May,

1910 10

4. Leuvenia, a New Genus of Flagellates, by N. L. Gardner. Pp. 97-106, plate

14. May, 1910 10

5. The Genus Sphaerosoma,. "b William Albert SetchelL Pp. 107-120, plate

15. '\ May, 1910 :....„ .„ J - _ 15

6. Variations in Nuclear Extrusion Among the Fucaceae, by Nathaniel Lyon

Gardner. Pp. 121-136, plates 16-17. August, 1910 , 15

7. The Nature of the Carpostomes in the Cystocarp of Almfeldtia gigartinoides,

by Ada Sara McFadden. Pp. 137-142, plate 18. February, 1911 05

8. On a Celacodasya from Southern California, by Mabel Ef&e McFadden.

Pp. 143-150, plate 19. February, 1911 „ : „ 05

9. Fructification of Macrocystis, by Edna Juanita Hoffman. Pp. 151-158, plate

20. February 1911 05

10. Erytlirophylhm delesserioides J. Ag., by Wilfred Charles TwLss. Pp. 159-

176, plates 21-24. March, 1911 .„ ^^...^.L 15

11. Plantae Mexicanae Purpusianae, in, by T. S. Brandegee. Pp. 177-194.

July, 1911 15

12. New and Noteworthy California Plants, I, by Harvey Monroe Hall. Pp.

195-208. March, 1912 15

13. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-227.

March, 1912 20

14. Algae Novae et Minus Cognltae, I, by William Albert SetcheU. Pp. 229-268,

plates 25-31. May, 1912 40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stith Brandegee. Pp.

269-28i. June, 1912 15

16. Comparative Development of the Cystocarps of Antithamnion and Prionitis,

by Lyman Luther Daines. Pp. 283-302, plates 32-34. March, 1913 20

17. Fungus Galls on Cystoseira and Halidrys, by Lulu May Estee. Pp. 305-316,

plate 35. March, 1913 10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374, plates 36-53.

April, 1913 „ 75

19. Plantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee. Pp.

375-388. June, 1913 ~ 15

Index, pp. 389-397.

UNIVBESITY OF CALIFORNIA PUBLIC ATIOKS—(Oontmued)

Vol. 5. 1912-.

1. Studies in Nicotiana, I, by William Albert Setchell. Pp. 1-86. December,

1912 - 1.25

2. Quantitative Studies of Inheritance in Nicotiana Hybrids, I, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

3. Quantitative Studies of Inheritance in Nicotiana Hybrids, II, by Thomas

Harper Goodspeed. Pp. 169-188, January, 1913 20

4. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, by Thomas Harper Goodspeed. Pp. 189-198. March, 1913 10

5. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Goodspeed.

Pp. 199-222. May, 1913 _ 25

6. Quantitative Studies of Inheritance in Nicotiana Hybrids, III, by Thomas

Harper Goodspeed. Pp. 223-231. April, 1915 10

7. Notes on the Germination of Tobacco Seed, II, by Thomas Harper Good-

speed. Pp. 233-248. June, 1915 , „. .15

8. Parthenogenesis, Parthenocarpy and Phenospermy in Nicotians, by Thomas

Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 .„.....„ .25

9. On the Partial Sterility of Nicotiana Hybrids made with N, sylvestris as a

Parent, II, by T. H. Goodspeed and A. H. Asrres. Pp. 273-292, plate 36.
October, 1916 „ 20

10. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, III, An Account of the Mode of Floral Abscission in the F^ Species
Hybrids, by T. H. Goodspeed and J. N. Kendall. Pp. 293-299. November,
1916 ...„ 05

11. The Nature of the Fi Species Hybrids between Nicotiana sylvestris and

Varieties of Nicotiana Tabacttm, with Special Reference to the Conception
of Reaction System Contrasts in Heredity, by T. H. Goodspeed and R. E.
Clausen. Pp. 301-346, plates 37-48. January, 1917 45

12. Abscission of Flowers and Fruits in the Solanaceae, with Special Reference

to Nicotiana, by John N. Kendall. Pp. 347-428, 10 text figures, plates 49-

53. March, 1918 85

13. Controlled PoUination in Nicotiana, by Thomas Harper Goodspeed and Plrie

Davidson. Pp. 429-434. August, 1918 _ 10

14. An Apparatus for Flower Measurement, by T. H. Goodspeed and R. B.

Clausen. Pp. 435-437, plate 54, 1 figure in text. September 25, 1918 .05

15. Note on the Efifects of Illuminating Gas and its Constituents in Causing

Abscission of Flowers in Nicotiana and Citrus, by T. H. Goodspeed, J. M.
McGee and R. W. Hodgson. Pp. 439-450. December, 1918 15

Vol. 6. 1914-.

1. Parasitic Florideae, by William Albert Setchell. Pp. 1-34, plates 1-6.

April, 1914 „ 35

2. Phytomorula regularis, a Symmetrical Protophyte Related to Coelastrum, by

Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914 05

3. Variation in Oenothera ovata, by Katherine Lajme Brandegee. Pp. 41-50,

plates 8-9. June, 1914 10

4. Plantae Mexicanae Purpusianae, VI, by Townshend Stith Brandegee. Pp.

51-77. July, 1914 25

5. The Scinaia Assemblage, by William Albert Setchell. Pp. 79-152, plates

10-12. October, 1914 .75

6. Notes on Pacific Coast Algae, I, PyJaiella Postelsiae, n. sp., a New Type in

the Genus Pylaiella, by Carl Skottsberg. Pp. 153-164, plates 17-19. May,
1915 ...,.._^. 15

7. New and Noteworthy Callfomian Plants, II, by Harvey Monroe Hall. Pp.

165-176, plate 20. October, 1915 15

8. Plantae Mexicanae Purpusianae, VII, by Townshend Stith Brandegee. Pp.

177-197. October, 1915 _ 25

9. Floral Relations Among the Galapagos Islands, by A. L. Kroeber, Pp.

199-220. March, 1916 20

UNTVEESITT OF CALIFORNIA PUBLICATIONS— (Continued)

10. The Comparative Histology of Certain Callfomian Boletaceae, by Harry S.

Tates. Pp. 221-274, plates 21-25. February, 1916 50

11. A Revision of the Tuberales of California, by Helen Margaret Gilkey. Pp.

275-356, plates 26-30. March, 1916 80

12. Species Novae vel Minns Cognitae, by T. S. Brandegee. Pp. 357-361. May,

1916 _ ~ - .05

13. Plantae Mexicanae Purpusianae, Vm, by Townshend Stith Brandegee. Pp.

363-375. March, 1917 - .15

14. New Pacific Coast Marine Algae, I, by Nathaniel Lyon Gardner. Pp. 377-

416, plates 31-35. June, 1917 - - .40

15. An Account of the Mode of Foliar Abscission in Citrus, by Robert W.

Hodgson. Pp. 417-428, 3 text figures. February, 1918 10

16. New Pacific Coast Marine Algae, II, by Nathaniel Lyon Gardner. Pp. 429-

454, plates 36-37. July, 1918 - 25

17. New Pacific Coast Marine Algae, HI, by Nathaniel Lyon Gardner. Pp. 455-

486, plates 38-41. December, 1918 - 35

Vol. 7. 1916-.

1. Notes on the Califomian Species of TriUium L. I, A Report of the General

Results of Field and Garden Studies, 1911-1916, by Thomas Harper Good-
speed and Robert Percy Brandt. Pp. 1-24, plates 1-4. October, 1916 25

2. Notes on the Califomian Species of Trillium L. II, The Nature and Occur-

rence of Undeveloped Flowers, by Thomas Harper Goodspeed and Robert
Percy Brandt. Pp. 25-38, plates 5-6. October, 1916 15

3. Notes on the Califomian Species of Trilli/um L. in, Seasonal Changes in

TriUium Species with Special Reference to the Reproductive Tissues, by
Robert Percy Brandt. Pp. 39-68, plates 7-10. December, 1916 80

4. Notes on the Califomian Species of Trillium L. IV, Teratological Varia-

tions of Trillium sessile var. giganteum H. & A., by Thomas Harper Good-
speed. Pp. 69-100, plates 11-17. January, 1917 ~ .80

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 16, pp. 451-455 April 3, 1919

NOTES ON THE GERMINATION OF
TOBACCO SEED III

NOTE ON THE RELATION OF LIGHT AND
DARKNESS TO GERMINATION

BY
T. HARPER GOODSPEED

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

UNIVERSITY OF CALIFOENIA PUBLICATIONS

Note. — Tlie University of California Publications are offered in exchange for the publi-
cations of learned societies and institutions, universities and libraries. Complete lists of
all the publications of the University will be sent upon request. For sample copies, lists
of publications and other information, address the MANAGER OF THE UNIVERSITY
PRESS, BERKELEY, CALIFORNIA, U. S. A. All matter sent in exchange should be
addressed to THE EXCHANGE DEPARTMENT, UNIVERSITY LIBRARY, BERKELEY,
CALIFORNIA, U. S. A.

WILLIAM WESLEY & SONS, LONDON
Agent for the series in American Archaeology and Ethnology, Botany, Geology,

Physiology, and Zoology.

BOTAITY.— W. A. Setchell, Editor. Price pier volume, $3.50; beginning with vol. 5, $5.00.
Volumes I (pp. 418), II (pp. 360), III (pp. 400), IV (pp. 379), completed. Volumes
V, VI and VII in progress.

Cited as Univ. Calif, Publ. Bot.

Volume 1, 1902-1903, 418 pages, with 27 plates $3.50

Volume 2, 1904-1907, 360 pages, with 29 plates 3.50

Volume 3, 1907-1909, 400 pages, with 14 plates _ 3.50

Vol. 4. 1910-1912.

1. Studies in Ornamental Trees and Shrubs, by Harvey Monroe Hall. Pp. 1-74,

plates 1-11, 15 text figures, March, 1910 75

2. Gracilariophila, a New Parasite on Gracilaria confervoides, by Harriet L.

Wilson. Pp. 75-84, plates 12-13. May, 1910 10

3. Plantae Mexicanae Purpusianae, II, by T. S. Brandegee. Pp. 85-95. May,

1910 10

4. Leuvenia, a New Genus of Flagellates, by N. L. Gardner. Pp. 97-106, plate

14. May, 1910 _ 10

5. The Genus Sphaerosoma, b William Albert Setchell. Pp. 107-120, plate

15. May, 1910 „ _ 15

6. Variations in Nuclear Extrusion Among the Fucaceae, by Nathaniel Lyon

Gardner. Pp. 121-136, plates 16-17. August, 1910 ,... .15

7. The Nature of the Carpostomes in the Cystocarp of AhtifekUia gigartinoides,

by Ada Sara McFadden. Pp. 137-142, plate 18. February, 1911 05

8. On a Celacodasya from Southern California, by Mabel Effle McFadden.

Pp. 143-150, plate 19. February, 1911 .05

9. Fructification of Macroeystis, by Edna Juanita Hoffman. Pp. 151-158, plate

20. February 1911 „ „ - -.:. — ...;....... 05

10. ErytlirophylluTv, delesserioides J. Ag., by Wilfred Charles Twiss. Pp. 159-

176, plates 21-24. March, 1911 ? 15

11. Plantae Mexicanae Purpusianae, in, by T. S. Brandegee. Pp. 177-194.

July, 1911 ~ — 15

12. New and Noteworthy California Plants, I, by Harvey Monroe Hall. Pp.

195-208. March, 1912 15

IS. Die Hydrophyllaceen der Sierra Nevada, by August Brand. Pp. 209-227.

March, 1912 20

14. Algae Novae et Minus Cognitae, I, by William Albert Setchell. Pp. 229-268,

plates 25-31. May, 1912 40

15. Plantae Mexicanae Purpusianae, IV, by Townshend Stith Brandegee. Pp.

269-281. June, 1912 „ 15

16. Comparative Development of the Cystocarps of Antithamnion and Prionitis,

by Lyman Luther Daines. Pp. 283-302, plates 32-34. March, 1913 .20

17. Fungus Galls on Cystoseira and Ealidrys, by Lulu May Estee. Pp. 305-316,

plate 35. March, 1913 10

18. New Fucaceae, by Nathaniel Lyon Gardner. Pp. 317-374, plates 36-53.

April, 1913 „ 75

19. Plantae Mexicanae Purpusianae, V, by Townshend Stith Brandegee. Pp.

375-388. June, 1913 - 16

Index, pp. 389-397.

UNIVERSITY OF CALIFORNIA PUBLICATIONS— (Continued)

Vol. 5. 1912-.

1. Studies in NiooUana, I, by William Albert Setcbell. Pp. 1-86. December,

1912 ~ 1.25

2. Quantitative Studies of Inheritance in Nicotianu Hybrids, I, by Thomas

Harper Goodspeed. Pp. 87-168. December, 1912 1.00

3. Quantitative Studies of Inheritance in Nicotiana Hybrids, II, by Thomas

Harper Goodspeed. Pp. 169-188. January, 1913 20

4. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, by Thomas Harper Goodspeed. Pp. 189-198. March, 1913 10

5. Notes on the Germination of Tobacco Seed, I, by Thomas Harper Goodspeed. '

Pp. 199-222. May, 1913 25

6. Quantitative Studies of Inheritance in Nicotiana Hybrids, III, by Thomas

Harper Goodspeed. Pp. 223-231. April, 1915 10

7. Notes on the Germination of Tobacco Seed, II, by Thomas Harper Good-

speed. Pp. 233-248. June, 1915 15

8. Parthenogenesis, Pa'tthenocarpy and Phenospermy in Nicotiana, by Thomas

Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 25

9. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, II, by T, H. Goodspeed and A. H. Ayres. Pp. 273-292, plate 36.
October, 1916 20

10. On the Partial Sterility of Ni<-otian<i Hybrids made with N. sylvestris as a

Parent, III, An Account of the Mode of Floral Abscission in the Fi Species
Hybrids, by T. H. Goodspeed and J. N. Kendall. Pp. 293-299. November,
1916 :.. „ „ .....,- .05

11. The Nature of the Fj Species Hybrids between Nicotiana sylvestris and

Varieties of Nicotiana Tabacum, with Special Reference to the Conception
of Reaction System Contrasts in Heredity, by T. H. Goodspeed and R. E.
Clausen. Pp. 301-346, plates 37-48. January, 1917 46

12. Abscission of Flowers and Fruits in the Solanaceae, with Special Reference

to Nicotiana. by John N. Kendall. Pp. 347-428, 10 text figures, plates 49-

53. March, 1918 85

IS. Controlled Pollination in Nicotiana, by Thomas Harper Goodspeed and Pirie

Davidson. Pp. 429-434. August, 1918 10

14. An Apparatus for Flower Measurement, by T. H. Goodspeed and R. E.

Clausen. Pp. 435-437, plate 54, 1 figure in test. September 25, 1918 .05

15. Note on the Effects of Illuminating Gas and its Constituents in Causing

Abscission of Flowers in Nicotiana and Citrus, by T. H. Goodspeed, J. M.
McGee and R. W. Hodgson. Pp. 439-450. December, 1918 15

16. Notes on the Germination of Tobacco Seed, III. Note on the Relation of

Light and Darkness to Germination, by T. Harper Goodspeed. Pp. 451-

455. April, 1919 05

Vol. 6. 1914-.

1. Parasitic Florideae, by William Albert Setchell. Pp. 1-34, plates 1-6.

April, 1914 .35

2. Fhytomonda regularis, a Symmetrical Protophyte Related to Coelastrum, by

Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914 .05

3. Variation in Oenothera ovata, by Katherine Layne Brandegee. Pp. 41-50,

plates 8-9. June, 1914 10

4. Plantae Mexicanae Purpuslanae, VI, by Townshend Stith Brandegee. Pp.

51-77. July, 1914 25

5. The Scinaia Assemblage, by William Albert Setchell. Pp. 79-152, plates

10-12. October, 1914 .75

6. Notes on Pacific Coast Algae, I, Pylaiella Postelsiae, n. sp., a New Type In

the Genus Fvlaiella, by Carl Skottsberg. Pp. 153-164, plates 17-19. May,
1915 ...... :„^...i i...:t..i...::....... .15

7. New and Noteworthy Callfomian Plants, II, by Harvey Monroe Hall. Pp.

165-176, plate 20. October, 1915 15

8. Plantae MerJcanae Purpuslanae, VII, by Townshend Stith Brandegee. Pp.

177-197. October, 1915 ., 25

UNIVERSITY OF CALIFORNIA PUBLICATIONS— (Continued)

9. Floral Relations Among the Galapagos Islands, by A. L. Kroeber. Pp.

199-220. March, 1916 .-- 20

10. The Comparative Histology of Certain Califomian Boletaceae, by Haxry S.

Yates. Pp. 221-274, plates 21-25. February, 1916 50

11. A Revision of the Tuberales of California, by Helen Margaret Gilkey. Pp.

275-356, plates 26-30. March, 1916 80

12. Species Nova« vel Minus Cognitae, by T. S. Brandegee. Pp. 357-361. May,

1916 „ ~ - - ~ -05

15. Plantae Mexicanae Purpusianae, VIII, by Townshend Stith Brandegee. Pp.

363-375. March, 1917 ■ -— .15

14. New Pacific Coast Marine Algae, I, by Nathaniel Lyon Gardner. Pp. 377-

416, plates 31-35, June, 1917 40

19. An Account of the Mode of Foliar Abscission in Citrus, by Robert W.

Hodgson. Pp. 417-428, 3 text figures. February, 1918 — .10

16. New Pacific Coast Marine Algae, II, by Nathaniel Lyon Gardner. Pp. 429-

454, plates 36-37. July, 1918 25

17. New Pacific Coast Marine Algae, m, by Nathaniel Lyon Gardner. Pp. 455-

486, plates 38-41. December, 1918 35

18. New Pacific Coast Marine Algae IV, by Nathaniel Lyon Gardner. Pp. 487-

496, plate 42. January, 1919 15

Vol. 7. 1916-.

1. Notes on the Califomian Species of TrilVmm L. I, A Report of the General

ResiQts of Field and Garden Studies, 1911-1916, by Thomas Harper Good-
speed and Robert Percy Brandt. Pp. 1-24, plates 1-4. October, 1916 25

2. Notes on the Califomian Species of Trillium L. II, The Nature and Occur-

rence of Undeveloped Flowers, by Thomas Harper Goodspeed and Robert
Percy Brandt, Pp. 25-38, plates 5-6. October, 1916 i,t«,~......,-...^.,^.i~^~,.~- .15

3. Notes on the Califomian Species of TrilUum L. in, Seasonal Changes in

Trillium Species with Special Reference to the Reproductive Tissues, by
Robert Percy Brandt, Pp. 39-68, plates 7-10. December, 1916 30

4. Notes on the Califomian Species of Trillium L, IV, Teratological Varia-

tions of Trillium sessile var. giganteum H. & A., by Thomas Harper Good-
speed. Pp. 69-100, plates 11-17. January, 1917 SO

UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

BOTANY

Vol. 5, No. 17, pp. 457-582, 2 figures in text, plates 55-85 April 14, 1922

INHERITANCE IN NICOTIANA TABACUM

I

A REPORT ON THE RESULTS OF CROSSING
CERTAIN VARIETIES

BY

WILLIAM ALBERT SETCHELL

THOMAS HARPER GOODSPEED
AND

ROY ELWOOD CLAUSEN

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY, CALIFORNIA

UNIVEESITY OF CALIFORNIA PUBLICATIONS

Note. — The University of California Publications are offered in exchange for the puhli
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WILLIAM WESLEY & SONS, LONDON
Agent for the series in American Archaeology and Ethnology, Botany, Geology,

Physiology, and Zoology.

BOTANY.— W. A. Setchell, Editor. Price per volume, 53.50 (vol. 5, $6.00) ; beginning "with
volume 6, $5.00. Volumes I, n, HI, IV, and IX completed. Volumes VIE, vni, and
X in progress.

Cited as Univ. Calif. Publ. Bot.
Vol 5. 1912-1922.

1. Studies in Nicotiana. I, by William Albert Setchell. Pp. 1-86. December,

1912 $1.25

2. Quantitative Studies of Inheritance in Nicotiana Hybrids. I, by Thomas

Harper Goodspeed, Pp. 87-168, plates 1-28. December, 1912 1.00

3. Quantitative Studies of Inheritance in Nicotiana Hybrids. II, by Thomas

Harper Goodspeed. Pp. 169-188, plates 29-34. January, 1913 20

4. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, by Thomas Harper Goodspeed. Pp. 189-198. March, 1913 10

5. Notes on the Germination of Tobacco Seed. I, by Thomas Harper Good-

speed. Pp. 199-222. May, 1913 25

6. Quantitative Studies of Inheritance in Nicotiana Hybrids, in, by Thomas

Harper Goodspeed. Pp. 223-231. Apnl, 1915 _ „ 10

7. Notes on the Germination of Tobacco Seed. II, by Thomas Harper Good-

speed. Pp. 233-248. June, 1915 .15

8. Parthenogenesis, Parthenocarpy and Phenospenny in Nicotiana, by Thomas

Harper Goodspeed. Pp. 249-272, plate 35. July, 1915 _ — .. .25

9. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent. II, by T. H. Goodspeed and A, H. Ayres. Pp. 273-292, plate 36.
October, 1916 20

10. On the Partial Sterility of Nicotiana Hybrids made with N. sylvestris as a

Parent, in. An Account of the Mode of Floral Abscission in the Fj Species
Hybrids, by T. H. Goodspeed and J. N. Kendall. Pp. 293-299. November,
1916 - - .06

11. The Nature of the F, Species Hybrids between Nicotiana sylvestris and

Varieties of Nicotiana Tabacum, with Special Reference to the Conception
of Reaction System Contrasts in Heredity, by T. H. Goodspeed and K. E.
Clausen. Pp. 301-346, plates 37-48. January, 1917 45

12. Abscission of Flowers and Fruits in the Solanaceae, with Special Reference

to Nicotiana, by John N. Kendall. Pp. 347-428, 10 text figures, plates 49-

53, March, 1918 86

13. Controlled Pollination in Nicotiana, by Thomas Harper Goodspeed and Pirie

Davidson. Pp. 429-434. August, 1918 .10

14. An Apparatus for Flower Measurement, by T. H. Goodspeed and R. E.

Clausen. Pp. 435-437, plate 54, 1 figure in text. September, 1918 OB

15. Note on the Effects of Illuminating Gas and Its Constituents in Causing

Abscission of Flowers in Nicotiana and Citrus, by T. H. Goodspeed, J. M.
McGee and R. W. Hodgson. Pp. 439-450. December, 1918 „ 10

16. Notes on the Germination of Tobacco Seed. Ill, Note on the Relation of

Light and Darkness to Germination, by T. Harper Goodspeed. Pp. 451-

455. April, 1919 05

17. Inheritance in Nicotiana Tabacum. I, A Report on the Results of Crossing

Certain Varieties, by William Albert Setchell, Thomas Harper Goodspeed,
and Roy Elwood Clausen. Pp. 457-582, 2 figures in text, plates 55-85.

April, 1922 1.76

Index in press.

UNIVERSITY OF CALIFOBNIA PUBLICATIONS— (Continued)

Vol 6. 1914-1919.

1. Parasitic Florideae, by William Albert Setchell. Pp. 1-34, plates 1-6.

April, 1914 _ „ „ .35

2. Phytomorula regularis,- a Symmetrical Protophyte Related to Coelastrum, by

Charles Atwood Kofoid. Pp. 35-40, plate 7. April, 1914 05

3. Variation in Oenothera ovata, by Katherine Layne Brandegee. Pp. 41-50,

plates 8-9. June, 1914 10

4. Plantae Mexicanae Purpuslanae. VI, by Townshend Stitb Brandegee. Pp.

51-77. July, 1914 „ .25

5. The Scinaia Assemblage, by William Albert Setchell. Pp. 79-152, plates

10-16. October, 1914 .75

6. Notes on Pacific Coast Algae. I, Pylaiella Fostelsiae, n. sp., a New Type in

the Genus PyJaiella, by Carl Skottsberg. Pp. 153-164, plates 17-19. May,

1915 15

7. New and Noteworthy Callfornian Plants. II, by Harvey Monroe Hall. Pp.

165-176, plate 20. October, 1915 .._ 15

8. Plantae Mexicanae Purpusianae. VII, by Townshend Stith Brandegee. Pp.

177-197. October, 1915 _... _— _ 25

9. Floral Relations among the Galapagos Islands, by A. L. Bjroeber. Pp.

199-220. March, 1916 20

10. The Comparative Histology of Certain Califomian Boletaceae, by Harry S.

Yates. Pp. 221-274, plates 21-25. February, 1916 50

11. A Revision of the Tuberales of California, by Helen Margaret GUkey. Pp.

275-356, plates 26-30. March, 1916 .80

12. Species Novae vel Minus Cognitae, by T. S. Brandegee. Pp. 357-361. May,

1916 , :..... „ _ 05

13. Plantae Mexicanae Purpuslanae. vm, by Townshend Stith Brandegee.

Pp. 263-375. March, 1917 _ 15

14. New Pacific Coast Marine Algae. I, by Nathaniel Lyon Gardner. Pp. 377-

416, plates 31-35. June, 1917 40

15. An Account of the Mode of Foliar Abscission in Citrus, by Robert W.

Hodgson. Pp. 417-428, 3 text figures. February, 1918 10

16. New Pacific Coast Marine Algae, n, by Nathaniel Lyon Gardner. Pp. 429-

454, plates 36-37. July, 1918 -.. 25

17. New Pacific Coast Marine Algae, m, by Nathaniel Lyon Gardner. Pp.

455-486, plates 38-41. December, 1918 — .35

18. New Pacific Coast Marine Algae. IV, by Nathaniel Lyon Gardner. Pp.

487-496, plate 42. January, 1919 15

19. Plantae Mexicanae Purpusianae. IX, by Townshend Stith Brandegee. Pp.

497-504. November, 1919 05

Index in preparation.

Vol. 7. 1916-.

1. Notes on the Califomian Species of Trillmm L. I, A Report of the General

Results of Field and Garden Studies, 1911-1916, by Thomas Harper Good-
speed and Robert Percy Brandt. Pp. 1-24, plates 1-4. October, 1916 25

2. Notes on the Califomian Species of TriUium L. II, The Nature and Occur-

rence of Undeveloped Flowers, by Thomas Harper Goodspeed and Robert
Percy Brandt. Pp. 25-38, plates 5-6. October, 1916 „ 15

8. Notes on the Califomian Species of Trillium L. Ill, Seasonal Changes in
Trillium Species with Special Reference to the Reproductive Tissues, by
Robert Percy Brandt. Pp. 39-68, plates 7-10. December, 1916 30

4. Notes on the Califomian Species of Trillium L. IV, Teratologlcal Varia-
tions of TriUium sessile var. giganteum H. & A., by Thomas Harper Good-
speed. Pp. 69-100, plates 11-17. January, 1917 _... .30

I7NIVEESITY OF CALIFORNIA PUBLICATIONS— (Continued)

5. A Preliminary List of the Uredinales of California, by Walter 0. Blasdale.

Pp. 101-157. August, 1919 _ 30

6, 7, 8. A Rubber Plant Survey of Western North America, L Chrysothamnus
nauseosiis and Its Varieties, by Harvey Monroe HalL II. Chrysll, a New
Rubber from Chrysothamnus nauseosus, by Harvey Monroe HaU and
Thomas Harper Goodspeed. III. The Occurrence of Rubber In Certain
West American Shrubs, by Harvey Monroe Hall and Thomas Harper
Goodspeed. Pp. 159-278, plates 18-20, 8 figures in text. November, 1919. 1J25

9. Phycological Contributions. I, by William Albert Setchell and Nathaniel

Lyon Gardner. Pp. 279-324, plates 21-31. April, 1920 „ _ ^

10. Plantae Mexicanae Purpusianae. X, by Townshend Stith Brandegee. Pp.

325-331. December, 1920 . „ _ „« JIO

Vol 8. 1919-.

1. The Marine Algae of the Pacific Coast of North America. Part L

Myxophyceae, by William Albert Setchell and Nathaniel Lyon Gardner.

Pp. 1-138, plates 1-8. November, 1919 _ ZIM

2. The Marine Algae of the Pacific Ccast of North America. Part EL

Chlorophyceae, by William Albert Setchell and Nathaniel Lyon Gardner.

Pp. 139-374, plates 9-33. July, 1920 _ 2.76

VoL 9. A Report upon the Boreal Flora of the Sierra Nevada of California, by Frank

Jason Smiley. Pp. 1-423, plates 1-7. October, 1921 _ 5.00

Vol 10. 1922-.

1. The Genus Fueus on the Pacific Coast of North America, by Nathaniel Lyon

Gardner (In press)

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