embryology of angiosperms

463 Pages·2012·59.99 MB·English

AN INTRODUCTION
TO THE
EMBRYOLOGY
OF ANGIOSPERMS
BY
P. MAHESHWARl
Professor of Botany, University of Delhi
Delhi, Indiu
FIRST EDITION
McGRAW-HILL BOOK COMPANY, INC.
NEW YORK TORONTO LONDON
1950
BANWAR) LAL JAIN
LATEST* RARE BOOKSELLS^
4 PUBLISHER
MOTI KATRA. AOflA
AN INTRODUCTION TO THE EMBRYOLOGY OP ANGIOSPE^MS
Copyrislit, 3950, by the McGraw-nill Book Company, Inc. Printed in the
United Stales of America. All rights reserved. This hook, or parts thereof,
may not be reproduced in any form without permission of the publishers.
PREFACE
In these days of intense activity, when hundreds of papers are
being published in every field of botany in a steadily increasing
number of periodicals and in a multitude of languages, no apologji^
is needed for an attempt to summarize the existing state of our
knowledge in any l)ranch of the subject and to point out the future
possibilities in it. Since the publication of Coulter and Chamber
lain's "Morphology of Angiosperms" in 1903, no comprehensive
account of this aspect of botany has appeared in the English lan
guage.
The original impetus for writing this work resulted from a course
of lectures which I gave on the subject in 1930 when I was teaching
at the Agra College. Several colleagues and pupils then suggested
that I should produce a book on the embryology of angiosperms.
This suggestion was repeated by Professor G. Tischlcr of the Uni
versity of Kiel, whom I visited in 1936. Teaching and adminis
trative duties and other difficulties made it impossible for me to
carry on this work in India at the speed I should have liked. Soon
after the war was over in 1945, therefore, I took the manuscript to
the United States in order to revise it and put it in shape for publi
cation.
In a strict sense, embryology is confined to a^tudy of the embryo,
but most botanists also include under it the events which lead on
to fertilization. I am in agreement with this wider comprehension
of the subject and have therefore included in this volume not only
an account of the embryo and endosperm, but also an account of
the development of the male and female gametophytes and fertiliza
tion. To emphasize the recent trends of research in the subject,
two chapters of a general nature have been added, one dealing with
embryology in relation to taxonomy, and the other with experi
mental embryology. In the former, an attempt has been made to
indicate the possibilities of the embryological method in the solu
tion of problems of systematic botany. In the latter, emphasis
has been placed on the contacts between embryology, cytology,
genetics, and plant physiology.
•#i PREFACE
In rompiling my materials I must aoknowledge the immense help
whicli I received from the wi-itiiig.s of the late Professor K. Schnarf,
whom I fame to know rather intimat(>ly during my stay in Vienna
in 193(). Without the existence; of his books, entitled "Embryologie
der Angiospermen" (1929), "Vergleit'hende Embryologie der Angio-
spermen" (1931), and "Vergleichende Zytologie des Geschlecht-
sapparates des Kormophyten" (1941), my task would have been
appreciably gi-eatci-. Mention must also be made of the numerous
and v(My valuable publications of Prolessor E. C 11. Soueges (Paris),
J'l'otessor K. V. (). Dahlgren (Uppsala), Dr. J. Alauritzon (Motala),
Dr. F. Fagei-lind (Stockholm), Dr. A. Gustafs.son (Svalof), and
Dr. H. Stcnai- (Sodoi'talje), upon which I drew rather freely. Pro
fessor Dahlgi-en, Dr. Custafsson, and Dr. Stcnar also favored me
with their advice and criticisms wVienever I appUed to tVicm for
help. In addition, a host of teachers and students in the United
States gave me every possible encouragement in the work. To
record my gratitude to all of them hi any complete fashion would
fill se\ei'al pag(>s. I therefore content my.self with naming a few
who took special int(M'est in the project. To Professors R. H.
Wetmoi-e and 1. \V. Bailey I am heavily indebted for the free use of
their facilities and their assistance in otlier ways during my several
months' stay at IIai-\-ard. Professor A. F. Blakeslee and Alary E.
Sanders, Smith College, Northampton; Professor E. W. Simiott,
Yale University; Professors A. J. Ivuues and L. W. Sharp, Cornell
University; Drs. D. C. Cooper, R. A. Brink, and C. L. Huskins,
University of Wisconsin; Dr. Th. Just, University of Notre Dame,
now at the Field Museum of Natm'al History, Chicago; Professor
J. T. Buchholz, Uni\-ersity of Illinois; Professor A. S. Foster, Pro
fessor (1. L. Stebbins, Mrs. M. S. Cave, Drs. L. Constance, Katherine
ICsau, and C. M. Rick, all of the Univ(n-sity of California; Pro
fessor (i. M. Snhth, Stanfoi'd University; Dr. D. .1. Johansen, Po
mona, and Professoi- A. W. Ilaupt, Univ^ersity of California at
Los Angeles, gave me the benc^tit of their suggestions and criti
cisms. Last but not least, my colleagues and pupils. Dr. B. M.
Johri, Reayat- Kahn, S. Narayanaswami, and J. S. Agrawal gave
m(> their- fullest cooperation in the preparation of the bibliography
and re\'ision of the proofs.
Onl\- a few of the illustrations ar(> original, most of them having
been boi'rowed from th(> woi'ks of other' authors. Considerable
car-e has been exercised, however, in their selection'not oidy that the
PREFACE vii
text may be made as clear as posRil)le but also that tlie student may
acquire some familiai'ity with the names and conti-ibutions of the
better known embryologists, both past and present. While most
of the copying and redrawing was done b\- me personally, I am
glad to acknowledge the very able assistance I i-eceived from a few
friends. Figures 36, 68, 92, and 214 were drawn by Airs. J. A.
Adams of Poughkeepsie, N. Y., daughter of my former teacher,
the late Dr. Winfield Dudgeon of Allahabacl; Miss C. Pratt,
Harvard University, drew Figures 24, 41, 50, (io, 74, 89, 104, 118,
121, and 167; Dr. B. G. L. Swamy, liangalore, drew Figures 19,
145, 149, 150, 153, and 163; Mrs. M. S. Cave, University of Cali-
foi-nia, drew Figure 14; Miss C. (!. Nast, Wayne University, drew
Figure 111; and my former reseai-ch assistant, Ashraful Haque,
University of Dacca, drew Figui-es 21, 43, 47, 54, 60, 61, 82, 85,
91, 147, 148, 152, 154, 157, 158, 159, 161, 162, 164, 165, 170, 172,
173, 175, 191, and 216. To all these I wish to tender my most
grateful thanks for the willingness with which they cooperated
with me.
A wor'd about the citation of literature. No attempt has lieen
made to give a complete list of all that has been published on
angiosperm embryology, as this would make the volume too cum
bersome, but it is hoped that the I'eferences which have been cited
will facilitate the task of the student who wishes to acquire fuller
information.
In a work of this natiu-e it is unavoidable that there should be
some errors of judgment and also oversights and omissions. I
should appreciate the suggestions and criticasms of those who use
the book.
P. MAHESHWARI
TjNiVKRsrrY OF DHLHI, INDIA
July, 1950

CONTENTS
PRKFACK V
1. HISTORICAL SKIVTCII I
Discoveiy of PoUon Tube—Schleideii's Theory ol' Oiigin of JMnbryo—
Discovery of True Relation between Pollen Tube and lunbrvo—Diseovei'V
of Sexual Fusion in Lower Plants—Discovery of Nature and l)evelo|3n:eut
of Male and Female Ganieto))Iiytes—lunbryo—Discovery of Syufiiamy—
Chalazofiamy—Double Fei'tilizatioii—Parthenogenesis—Twentieth Cen
tury—References.
(jT^. THK MH'ROSPOUANGIUM 28
Wall Payers—Sporogenous Tissue—Oytoniixis—Cytokinesis—i\Iicrosi)oro
Tetrad— References.
^3. THIO ArKGASPORANGIUM 54
Integuments—Alicropyle—Nticeilus—Integumentary Tapetum—Hypo-
stase—I'^jjistase—Vascular Sup])ly of Ovule—AicliesijOiium .Megasjjoro-
genesis—Functioning .Megaspore—Failure of Wall Formation dui'ing
Mciosis—References.
\ 4. THK FKMALK OAMETOPHYTIO 84
Moriosporic embryo sacs—Polygonum Type—Ocnothei'a Tyi)e—Bisporic
e»ihrijo sacs—Allium Typo—Tetrasporic embryo sacs—Peperomia Tyi)0—
PenaeaTy])e—DrusaTypo— FritillariaTyi^e—PlumbagellaTy])e—Adoxa
Tyjje—Plumbago Type—Aberrant and unclassijicrl types—Limnanthcs
dovglasii—Balsamiia vulgaris—Chrysanthemum cinerariaeJoHum—Or-
ganizniion of mature embryo sac—]''gg Ai)paratus—Antijiodal Cells—
I'olar Nuclei—Fnrbryo Sacs with Disturbed Polarity—Food Reserves in
the Fmbryo Sac—Embryo Sac Ilaustoria—References.
Jtb. THK .MALK (IAMHTOPHVI'I-; 154
Microspore—Formation of Vegetative and Cenerative Cells—J)ivision of
Genorativo Cell—Male "Cells" or "Xuclei"--Vegetative Nucleus—De
velopment of Pollen in ("j'peraceac—Embryo-sac-liiie Pollen Orains—
References.
(if). FKRTILIZATION" 181
Coruiination of Pollen—Course of Pollen Tube—lintry of Pollen Tube
intc L'^mbryo Sac—Rate of Growth of Pollen Tube—(Jametic Fusion—
M'i!fi;de Fusions and Polyspei'my—Single Fertilization- Persistence and
P<,>s.-i')iri Ihuistorial Function of Pollen Tube- X-bodies—References.
<^'i. T>i>. KxDospioRM 221
'iyi)es of lOndosperm Formation—Free Nuclear Fndos|)erni—Cellular
iMiiiosperni—Helobial i'hidosperm—Relationships lictween Different
Ty;:'s oT Endosperm—Histology of Endosperm—Xenia—Mosaic, Endo-
spe'iii -Piefcrences.
k
« CONTENTS
8. THU EMBRYO , ,. 268
Dicotyledons—Cruoifer Type—Asterad Type—Solanad Type—Cheno-
podiad Type—Caiyophyllad Type—Monocotyledons—Modifications of
suspensor—Unclassified and abnormal embryos—Unorganized and reduced
einbryos—References.
9. Ai'OMixis , , 313
Nonrecurrent apomixis—Recnrrent apomixis—Generative Apospory—So
matic Apospory—Unclassified Cases—Organization of Aposporic Embryo
Sacs—f3evoloiiment of ]<]mbryo in Aposporic Embryo Sacs—Adventive
eml>ryony—References.
10. POT.YEMBKYONY 343
Cleavage Polyembryony—Origin of Emliryos from Cells of Embryo Sac
Other than Egg—Embryos Arising fi-om Colls Outside Embryo Sac—•
Embryos Oj-iginating fi'om Other l^mbryo Sacs in Ovule—A Few Special
Cases—Twins and Triplets—Conclusion- References.
11. EMUKYOLOGY IN RELATION TO TAXONOMY , 357
Empetraceae—Lennoaccae—Cactaceae—(iarryaceac—Onagraceae—Calli-
trichaceae—Ijiliaceao-allioideae—Liliaceae-aspliodeloideae—Liliaceae-lili-
oid(;ae—References.
12. ExpuKiMENTAL EMBKYOLOGY 375
Control of Fei'tilization—Embrj'o Culture—Induced Parthenogenesis—
Production of Adventive Embryos—Induced Parthenocarpy—Conclu
sion—References.
13. THKORE ricAL CONCLUSIONS • 411
Male Ganietophyte—Female Gametophyte—Fei'tilization—Endosperm—
Embryo—References.
NAME INDEX 433
SUBJECT AND PLANT INDEX 441
CHAPTER 1
HISTORICAL SKETCH
In tracing the history of a branch of natural science it is customary
to go back to the days of Aristotle. The greater part of his technical
writings is unfortunately lost to us, but it seems fairly certain that
he did not recognize the presence of sex in plants. He believed
instead that the male and female principles were so blended that
they generated of their own accord and the offspring arose from the
superfluous food in the plant.
Aristotle bequeathed all his earthly possessions to his favorite
pupil Theophrastus. In his "Enquiry into Plants," written in the
third century B.C., the latter referred to the pollination of the date
palm, presumably on the basis of the account of Herodotus, who
had traveled in the East in the fifth century B.C. The Arabs and
Assyrians, Herodotus found, used to have a special ceremony at a
certain time of the year, in which a man climbed up a male tree,
brought down the inflorescence, and handed it over to the high
priest, who touched the female inflorescences with it, in order to
ensure a good supply of dates.
Approximately three hundred years after Theophrastus, PUny
wrote an encyclopedia of natural history in which he mentioned the
male palm with its erect leaves as having somewhat of a military
bearing, while the females with their softer foliage and feminine ways
bent toward it, to save themselves as it were from the curse of
virginity or widowhood. However, Pliny did not make any ob
servations of his own. His writings and ideas were based on other
people's reports and on the literature on the subject that existed in
those days.
After this the problem of sexuality in plants seems to have been
laid aside and forgotten for hundreds of years. Indeed, many scien
tists of the fifteenth and sixteenth centuries totally denied the
occurrence of sex in plants and regardetl even the mention of it as
inappropriate and obscene. Some thought the stamens to be ex
cretory organs and the pollen to be a waste product.
1
2 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS
It was only with the invention of the microscope that actual
observation of the sexual cells took the place of conjectures.
Leeuwenhoek (1677)' discovered the sperms of some animals but
mistook them at first for "Wild animalcules" arising in the seminal
fluid by some sort of putrefaction.
In his "Anatomy of Plants," Grew (1682) made the first explicit
mention of the stamens as the male organs of the flower.
He thought that the pollen grains, by merely falling upon the stigma,
transmitted to the ovary a "vivifick effluvium" which prepared it
for the production of the fruit.
Rudolph Jakob Camerarius (1694), Director of the Botanical
Garden at Tubingen, approached the matter more scientifically. He
observed that in a female mulberry tree, which was growing without
any male plants in the vicinity, the fruits contained only abortive
seeds. Inspired by this discovery he next took some female plants
of Mercurialis annua and kept them in pots completely isolated from
the influence of male plants. Here too, he found tliat, although the
plants grew well, not one of the fi'uits contained a fertile seed. This
encouraged him to make further obser\-ations, which he summarized
in a famous treatise called "De sexu plantarum." He carefully de
scribed the flower, anthers, pollen, and ovules. On removing the
male flowers (glohuli) of Ricinus before the anthers had shed and
preventing the growth of the younger ones, he never obtained any
perfect seed but only empty fruits which withered and fell to the
ground. A similar lack of seed formation was noted in Zea mays
when the stigmas had been removed from the young ear. In con
clusion he said: "In the plant kingdom, the production of seed,
which is the most perfect gift of nature and the general means of
maintenance of the species, does not take place unless the anthers
have previously prepared the young plant contained in the ovary."
To the anthers, in his opinion, was to be attributed, therefore, the
role of the male sexual organs just as the ovary with its style was
considered the female sexual organ.
We thus see that although Camerarius was not clear about the
exact manner in which the pollen functioned, he nevertheless made
a notable contribution to our knowledge by showing that some kind
' Dates in parentheses refer to works listed in the bibliography at the end of
each chapter.