Cryptogamic Botany
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McGRAW-HILL PUBLIOA:r'IONS IN THE BOTANIOAL SOIENOES EDMUND W. SINNOTT, CONSULTING EDlTOR CRYPTOGAMIC BOTANY VOLUME II BRYOPHYTES AND PTERIDOPHYTES This book is produced in jul! compliance with the government's regulations jor con serving paper and other essential materials. SELECTED TITLES FROM McGRAW-HILL PUBLICATIONS IN THE BOTANICAL SCIENCES.. EDMUND W. SINNOTT, Consulting Editor Babcock and Clausen-Genetics Lutman-Microbiology Belling-The Use of the Microscope Maximov-Plant Physiology Boysen Jensen-Growth Hormones Miller-Plant Physiology in Plants Pool-Flowers and Flowering Plants Braun-Blanquet and Fuller and Con Sass-Elements of Botanical Micro- ard-Plant Sociology technique Curtis-The Translocation of Solutes Seifriz~ Protoplasm in Plants Sharp-Introduction to Cytology Eames-Morphology of Vascular Plants Sharp-Fundamentals of Cytology Eames and MacDaniels-Plant Sinnott-Botany Anatomy Sinnott and Dunn-Genetics Fitzpatrick-The Lower Fungi Smith-Cryptogamic Botany Gltumann and Dodge-Com}Jarative Vol. I, Algae and Fungi Morphology of Fungi Vol. II, Bryophytes and Haupt-An Introduction to Botany Pteridophytes Haupt-Laboratory Manual of Ele- Fresh-water Algae of the U. S. mentary Botany Swingle-Systematic Botany Hill'-Economic Botany Weaver-Root Development of Field Hill, OV6rhoZts, and*Popp-Botany Crops Weaver and Bruner-Root Develop Johansen-Plant Microtechnique ment of Vegetable Crops Loomis and Shull-Methods in Plant Physiology Weaver and Clements-Plant Ecology Experiments in Plant Physiology W odehouse-Pollen Grains There are also the related series of McGraw-Hill Publications in the Zoologi cal Sciences, of which A. Franklin Shull is Consulting Edit_.9r, and in the Agricultural Sciences, of which Leon J. Cole is Consulting Editor. CRYPTOGAMIC BOTANY VOLUME II BRYOPHYTES AND PTERIDOPHYTES BY GILBERT M. SMITH Stanford University FIRST EDITION THIRD IMPRESSION McGRAW-HILL BOOK COMPANY, INC. NEW YOp..K AND LONDON 1938 1;)6~6,., COPYRIGHT, 1938, BY THE MCGRA W-HILL BOOK COMPANY, INC. PRINTED IN THE UNITED STATES OF AMERICA All rights reserved. This book, or parts thereof, may not be reproduced in any form without permission of the publishers. THE MAPLE PRESS CO~PANY, YORK, PA. PREFACE In preparing the illustrations for this volume, most of the hab~t sketches of Bryophyta were drawn by Mrs. Carl F. Janish, and those of . the Pteridophyta were drawn by Maximo V. Rodrigo. I am deeply indebted to Professor D. H. Campbell for placing at my disposal his extensive collections of preparations and preserved material of bryophytes and pteridophytes. These unique collections, many of them made in inaccessible. tropical countries, have made possible a much fuller series 0," o'ii.gi~~l illustrations of bryophytes and pterido phytes. Professor G. S. Bryan has furnished preparations of Andraea. Many of the illustrations are based upon preparations made especially by Dr. D. A. Johansen. My thanks are again due him for helpful aid in 'securing illustrative material at the proper stage of development and for his technical skill in preparing it for microscopical study. GILBERT M. SMITH. STANFORD UNIVERSITX, March, 1938.. CONTENTS PAQE PREFACE .••••••• V CHAPTER I BRYOPHYTA-INTRODUCTION. ... 1 CHAPTER II HEPATICAE ...... 9 CHAPTER III ANTHOCEROTAE . 76 CHAPTER IV MUSCI . 84 CHAPTER V P~ERIDOPHYTA-INTRODUCTION . 114 CHAPTER VI PSILOPHYTINAE . · 141 OHAPTER VII LYCOPODINAE ..... · 162 CHAPTER VIII EQUISETINAE ..... · 221 CHAPTER IX FILICINAE. .' 248 INDEX .. · 367 vii CRYPTOGAMIC BOTANY VOL. II BRYOPHYTES AND PTERIDOPHYTES CHAPTER I BRYOPHYTA-INTRODUCTION The Bryophyta have a sharply defined alternation of generations in which the diploid asexual generation, although lllorphologically distinct from the haploid sexual generation, is always attached to it and wholly or partially dependent uporl it for nutrition. This condition is in contrast with that in Pterijiophyta and more advanced plants, where the asexual generation, the sporophyte, is always an independent plant at maturity. The sporophytes of plants higher than Bryophyta are ·internallY differ entiated into xylem and phloem; whereas Bryophyta lack these tissues. The sexual generation of Bryophyta, the gametophyte, .is always an independent plant at maturity and one that is nutritionally self-sustaining because of the presence of chloroplasts within its body. In many cases the plant body is a thallus, that is, without differentiation into root, stem, and leaf. In those cases where it is externally differentiated into stem and leaf, there are never any roots; only one-celled absorptive organs (rhizoids). All Bryophyta are oogamous, and the gametes are produced within multicellular sex organs in which there is an outer sterile layer of jacket cells. In this respect they are immediately distinguishable from algae since sex organs of the latter, when multicellular, always have all cells gamete-producing. Life Cycle of Bryophyta. The life cycle of a bryophyte consists of a regular alternation of an asexually reproducing generation with a sexually reproducing one. This was first clearly demonstrated by Hofmeister in 1851,1 but the periodic doubling and halving in the number of chromo somes associated with the alternation was not clearly recognized until 1894. 2 This alternation of generations is obligatory in the sense that a zygote resulting from gametic ~nion always grows into a sporophyte and 1 Hofmeister, 1851. 2 Strasburger, 1894. 1 2 BRYOPHYTES AND PTERIDOPHYTES.. that spores prod.uced by a sporophyte always germinate to form a gameto phyte. It is not obligatory in the. sense that gametophyte and sporophyte must always alternate with each other, because vegetative propagation of the gametophyte may result in a life cycle in which there is a succession of gametophytic individuals before there is the formation of a sporophyte. It should also be noted that vegetative budding does not always result in a generation similar to the parent one. Thus, vegetative budding of· gametophytic tissue may ;result in the formation of a sporophyte. This production of a sporophyte from a gametophyte and without any union of gametes is apogamy. Conversely, a sporophyte may bud off a mass of cells which develops into a gametophyte. Production of a gametophyte from a sporophyte without the formation of spores is apospory. Apogamy. and apospory are of rare occurrence in Bryophyta as compared with Pteridophyta.1 Most of the recorded cases among bryophytes are among the Musci where a wounding of sporophytes2 induces an aposporous production of gametophytes. The Anthocerotae are also known to be aposporous.3 Origin of the Bryophyta. The Bryophyta ~re undoubtedly a series of great antiquity, but the paleontological evidence in support of this contention is very meager. This is not surprising when one takes into consideration the delicate tissues of the bryophytes and the consequently poor chance of their becoming fossilized. However, anacrogynous Jungermanniales are known to have been present in the middle Car boniferous. 4 The presence of Musci in the upper Carboniferous is not established with as great certainty,5 but there seem to be good reasons for believing that moss-like plants existed at that time. Fragments of typic?-l Sphagnum leaves have been found in the Cretaceous.6 Although it is generally agreed that the Bryophyta have arisen from the green algae, the manner in which they have arisen is a matter of speculation since there is a wide gap between the Chlorophyceae and the simplest known bryophyte. It is generally agreed that the progenitors of the Bryophyta belonged to the ulotrichaceous series of the Chloro phyceae. Typical Ulotrichales are filamentous and have a plant body primarily fitted for an aquatic existence. The Bryophyta are largely' terrestrial, and those of tliem that are aquatic in habit, as Riella, are land plants in which the aquatic habit is secondarily acquired. The transfer of algae from an aquatic to a terrestrial environment is thought to have lead to a development of a more massive plant body in which the reduced surface, in proportion to the volume, tended to prevent undue drying of the thallus. The primitive Bryophyta, similar to many present- 1 See p. 132 for a fuller account of these phenomena. 2 Marchal and Marchal, 1911. 3 Bornhagen, 1926; Rink, 1935. 4 Walton, 1925. 6 Walton: 1928. 6 Arnold, 1932. BRYOPHYTA-INTRODUCTION 3 day species, probably grew where there was an abundance of moisture in the soil. Thus there was but little evolution of water-absorbing tissues, except for the elongation of certain of the cells on the under surface into rhizoids. The abundance of moisture also resulted in a retention of the method of gametic union typical of algae, that is, by one or both of a pair of uniting gametes moving freely in all directions by swimming through water. The persistence of this primitive method of gametic union among all pteridophytes and in certain of the lower gymnosperms is one of the striking features in the evolution of plants. Origin of the Sex Organs. Although it is relatively easy to visualize the manner in which the plant body of an alga may be evolved into a plant body such as is found in bryophytes, it is much more difficult to' . ~ FIG. I.-Diagrams Bhowing the hypothetical origin of sex organs of Bryophyta. (Based upon Davia, 1903.) envisage how the sex organs typical of Bryophyta have evolved from those of algae. The advantage of the sterile jacket layer present in sex organs of Bryophyta is obvious-it protects the delicate gametes from undue drying as they develop. The need of this protection is shown by the widespread occurrence among Bryophyta of additional features protecting the sex organs against loss of water. These inClude: embed ding of the organs within the thallus; the development of accessory envelopes; and the surrounding of the organs by leaves. The most attactive hypothesis e:x;plaining'the origin of the sex organs characteristic of bryophytes holds that archegonia and antheridia are fundamentally alike and that they arose by sterilization of the outermost cells of a multicellular gametangium, similar in general appearance ,to the gametangium of Ectocarpus.