Special Botany

PART II SPECIAL BOTANY SECTION I CRYPTOGAMS I SPECIAL BOTANY Special Botany is concerned with the special morphology and physiology of plants. While it is the province of general botany to investigate the structure and vital processes of the whole vegetable kingdom, it is the task of special botany to interpret the structure and vital processes of its separate divisions. The aim of general morphology is to determine the phylogenetic dei^ivation of the external and internal segmentation of plants, and to refer their numerous structural peculiarities to the primitive forms from which they have arisen. The purpose of special morphology, on the other hand, is to trace the development which has been reached in the different divisions of the plant kingdom, to understand the form of individual plants, and to trace the connection between one form and another. Thus the methods of special morphology are also phylogenetic, and furnish the basis for a NATURAL system of classification of vegetable organisms, based upon their actual relationships. Such a system must necessarily be very imperfect, as it is not possible to determine, directly, the phylogenetic connection of different plants, but only to infer their relationships indirectly from morpho- logical comparisons. Such a natural system, founded on the actual relationshijD existing between different jDlants, stands in direct opposition to the artificial system, to which has never been attributed more than a practical value in grouping the plants in such a manner that they could easily be determined and classified. Of all the earlier artificial systems, the sexual system proposed by Linnaeus in the year 17.35 is the only one which need be considered. LiNNiEUS, in establishing his classification, ntilised characteristics which referred exclusively to the sexual oi'gans, and on this basis distinguished twenty-four classes of plants. In the last or twenty-fourth class he included all such plants as were devoid of any visible sexual organs, and termed them collectively Cryptogams. Of the Cryptogams there were at that time but comjjaratively few forms known, and the complicated methods of reproduction of this now large class were absolutely unknown. In contrast to the Cryptogams, the other twenty-three classes were distinguished as Phanerogams or plants whose flowers with their sexual organs could be easily seen. Linn^us divided the Phanerogams, according to the distribution of the sexes in their flowers, into such as possessed hermaphrodite flowers (Classes .329 :^30 BOTANY i-aht ii I. -XX.), and those in which the flowers were unisexual (XXI. -XXIII.). Plants with hermaphrodite flowers lie again divided into three groups : those with free stamens (II.-XV.), which he further distinguished according to the number, mode of insertion, and relative length of the stamens ; those with stamens united with each other (XVI. -XIX. ) ; and those in which the stamens were united with the pistil (XX.). Each of the twenty-four classes was similarly subdivided into orders. While some of the classes and orders thus constituted represent naturally related groups, although by the method of their arrangement in the artificial system they are isolated and widely removed from their proper position, they include, for the most part, plants which phylogenetically are very far apart. LiNN^us himself (1738) felt the necessity of establishing natural families in which the jjlants should be arranged according to their " relationships." So long, however, as the belief in the immutability of species prevailed, the adoption of a system of classification ex- pressive of relationship and family could have no more than a hypo- thetical meaning, and merely indicated a supposed agreement between A plants having similar external forms. true basis for a natural system of classification of organisms was first aflbrded by the theory of evolution. The system adopted as the basis of the following description and systematic arrangement of plants is the natural system of Alexander Braun, as modified and further perfected by Eichler, Engler, Wettstein, and others. According to this system, we have to distinguish between Cryptogams as the lower division, and Phanerogams as the higher division of the plant kingdom. SECTION I CRYPTOGAMS The Ciyptogams include an extraordinary variety of the most different plant forms, ranging from unicellular organisms to plants exhibiting segmentation into stem, leaf, and root. The Cryptogams, however, are collectively distinguished from Phanerogams by the mode of their dissemination by spores, in contrast to that of the Phanerogams, which is effected by seeds ; sjjores are formed also by Phanerogams, but they are not the immediate cause of the origin and development of new individuals. Seeds are multicelluhir bodies, within which is included the multicellular rudiment or embryo of a plant ; while spores, which, in the case of the Cryptogams, become separated from the mother plant, and give rise to a new and independent organism, are unicellular structures. Cryptogams could SECT. I CRYPTOGAMS 331 therefore be termed SPORE plants, and Phanerogams seed plants or Spermaphy tes ; although previous usage and custom would recommend -- adherence to the older terms. The Cryptogams are divided into the following main groups : I. The Thallophyta, embracing a great variety of plants whose vegetative portion may consist of one or many cells in the form of a more or less branched thallus. Reproduction is both sexual and asexual, but there is usually no definite succession of the two modes of reproduction. II. The Archegoniatae exhibit a regular alternation of two generations in their life -history. The asexual generation forms spores, and is called the Sporophyte. From the spore the sexual generation or Gametophyte develops ; this bears sexual organs of characteristic construction, tlie male and the female organs archegonia. the latter, after fertilisation, the organs being called antheridia, From the egg-cell contained in sporophyte again arises. The Archegoniatae are divided into 1. The Bryophyta, which include forms with a leaf-like thallus, as well as cormophytic forms, with evident segmentation into stems and leaves. The Bryophytes possess no true roots, and their conducting bundles, when present, are of the simplest structure. The sporophyte is a stalked or unstalked capsule, which lives semi- parasitically on the sexual plant. 2. The Pteridophyta have small thalloid gametophytes ; the sporophytes exhibit a segmentation into stems, leaves, and roots, and also possess true vascular bundles ; they thus resemble the Phanero- gams in structure. The Thallophytes and Bryophytes are also characterised as Cellular Plants, in contrast to the Pteridophytes or Vascular Cryptogams, which, together with the Phanerogams, are collectively designated Vascular Plants. Bryophyta and Pteridophyta must be regarded as having had a common origin from the higher Algae, the development of the two groups having been on different lines. I. THALLOPHYTA It was formerly customary to divide the Thallophyta into Algae, Fungi, and Lichens. The Algae are Thallophytes which possess chromatophores with pigments, particularly chlorophyll ; they are, therefore, capable of assimilating and providing independently for their own nutrition. The Fungi, on the other hand, are colourless and have a saprophytic or parasitic mode of life. Such a method of classification, however, although possessing a physiological value, has no phylogenetic significance, as it does not express the natural relationships between the various groups. In the Lichens (Lichenes), whi.;h were formerly regarded as simple organisms, the thallus afi"ords an instance of a symbiosis of Algae 332 BOTANY part ii and Fungi. From a strictly systematic standpoint, the Fungi and Algae composing the Lichens should be classified separately, each in their own class ; but the Lichens, among themselves, exhibit such a similarity in structure and mode of life, that a better conception of their characteristic peculiarities is obtained by their treatment as a distinct class in connection with the Fungi. The phylogenetic connections of the fourteen classes into which -- the Thallophyta are divided are expressed, so far as is possible, in the following scheme : Bacteria, Bacteria. Cyanojihyceae, Blue-green Algae. �Myxomyeetes, Slime-Fungi. CO O) �Periclineae, Dinoflagellates. jum Conjugatae, Conjugates 'a; IHatomeae, Diatoms ^ Hctcrocontae. Chlorophyceae, Green Algae mm^mPihochpliyceae, Red Algae. t^^^^^mEumycetes, Fungi. ^^^^I'hycomycetes, Algal Fungi. 1 ^Phaeopliyeeae, Brown Algae. mmm^ma Characeae, Stone-worts. The Bacteria and Cyanophyceae are amoug the most simply organised Tliallophyta ; they are closely connected and are often grouped together as the Schizophyta. They occupy an isolated position in contrast to the remaining simi)le Thallophytes, which with greater or less probability may be derived from the Flagellatae. The Flagellatae used to be (and frequently still are) placed with the lowest animals. As a matter of fact they combine plant and animal characteristics, and may also be regarded as the starting-point of the lower animals. The Myxomycetes may also have sprung from them as a group of colourless saprophytes. The Peridineae are a further-developed branch of the Flagellatae. The simplest forms among the Heterocontae, the Green Algae, and the Phaeophyceae connect directly with the Flagellata ; on the other hand a direct connection of the latter with the Conjugatae and Diatomeae (which together form the Zygophyceae), while probable, is not shown in existing forms. The Phycomycetes have branched off from the main series of the Chlorophyceae. The origin of the Red Algae and the Eumycetes, which appear to have sprung from a common stock, is still in doubt. The Cliaraceae occupy a qiiite isolated and very advanced position, and have been usually regarded as the most highly developed of the Green Algae ; they rather appear to be connected in important characters with the Brown Algae. The Thallophytes are commonly multiplied and distributed by asexually produced spores, the mode of development of which differs in the several groups. In many cases the spores arise by a pi'ocess of cell division within certain cells, which are knowni as sporangia ; SECT. 1 CRYPTOGAMS 333 in other cases they aiise by modification and separation of cells of the thallus or by a process of cell-budding. When the spores possess cilia and are able to move actively in the water, they are known as swarm-spores (zoospores) ; when they do not bear cilia they ai-e termed aplanospores. In the latter case the spores if distributed, by water may be naked, or they may be provided with a cell-wall and suited for distribution in the air. Sexual reproduction is also of wide-spread occurrence. It consists, in the simplest cases, in the production of a single cell, the ZYGOSPORE or zygote, by the union or conjugation of two similarly formed sexual cells or gametes (isogamy). The organs in which the gametes are formed are termed gametangia ; planogametes are provided with cilia while a})lanogametes are non-ciliated. In many of the more highly developed forms, however, the gametes are differentiated as small, usually ciliated, male cells or SPERMATOZOIDS, and as larger non-ciliated female cells, the egg-cells or oospheres. The spermatozoids are formed in ANTHERIDIA, the oos2:)heres in OOGONIA. As a result of the fusion of an egg-cell and a spermatozoid, an oospore is produced (oogajiy). It must be assumed that the sexual cells have been derived in the phylogeny of i)lants from asexual spores, and that asexual multiplication has taken origin from simple cell division. The gametangia, oogonia, antheridia, and sporangia of the Thallophyta are homologous structures. The sexual reproduction has originated independently in several distinct groups. While the reproduction of some^Thallophyta is exclusively asexual, and of otliers exclusively sexual, in many others both forms of reproduction occur. In the latter case this may occur on the one plant, or separate successive generations may be distinguishable. Generally speaking, there is, however, no regular succession of asexual and sexual generations in Thalloi)hytes, the mode of reproduction being to a great extent under the influence of external conditions (^). Only in some Brown Sea-weeds, in the Red Sea-weeds, and some Fungi is there an alternation of a sexual generation (gametophyte) with an asexual (sporophyte), such as is found in all Bryophytes and Pteridophytes. In the union of tlie two sexual cells the fusion nucleus obtains the double uumlier of chromosomes it becomes diploid while the sexual cells always have ; HAPLOID nuclei. A reduction division of the diploid nucleus to the hajiloid must thus occur in the course of the ontogenetic development. In most cases this happens on the germination of the zygospore or oospore. In some Brown Algae with an alternation of generations and similarly in all archegoniate plants a dijiloid sporophyte is first developed from the germinating oospore and the reduction division takes place in the asexual sporangia which the sporophyte bears. From the haploid spores of these sporangia, haploid garaetophytes in turn develop. 334 BOTANY paut ii Class I Bacteria (-) Bacteria are unicellular or filamentous organisms of very simple construction. Chlorophyll is wanting in them, and their mode of A life is consequently a parasitic or saprophytic one. large number of species exist distributed over the whole earth, in water, in the soil, in the atmosphere, or in the bodies of dead or living plants and animals. They are often termed Fission-Fungi, or Schizomycetes, since the multijDlication of the unicellular forms takes place by a division into two and the separation of the segments. This mode of multiplication is also found in other unicellular plants. The cells of the Bacteria are surrounded by a thin membrane, and contain a protoplasmic body, which is usually coloin^less, and can be made to contract away from the membrane by plasmolysis. The protoplasm may contain one or more vacuoles. One or several granular structures are also present in the protoplast; these so-called chromatin bodies may be deeply coloured by stains, and have been regarded as nuclei by various authors. Since, as yet, undoubted karyo- kinetic division has not been observed in these bodies, the presence of nuclei in the bacterial cell cannot be regarded as certainly established. For the most part the Bacteria are extraordinarily minute organisms, and probably include the smallest known living beings. The spherical cells of the smallest forms are only 0"0008 mm. in diameter ; the rod-shaped cells 0'0015-0"004 mm. long, while species is about O'OOl mm. of the tubercle bacillus are the transverse diameter of only most The simplest form of Fission-Fungi is represented by minute spherical cells, COCCI. Forms consisting of rod-shaped cells are designated BACTERIUM or BACILLUS. Rod-shaped forms with a slight spiral curvature are called vibrio, and those more strongly curved SPIRILLUJNI. Straight filamentous forms are termed leptothrix, spirally wound filaments, spirochaete. In the highest stage of their development the Fission-Fungi consist of cell filaments exhibiting false branching. The unicellular cocci, rod - shaped forms, and vibrios may also remain united in chains after the cell-division. Frequently the cell-membranes undergo a mucilaginous swelling, the cells or cell-rows being embedded in the gelatinous mass. This stage of development is termed zoogloea. Many Bacteria are motile. Their independent movements are due to the vibration and contraction of fine protoplasmic cilia. These flagella, according to A. Fischer, are either distributed over the whole surface of the cells (peritrichous) (e.g. Bacillus suhtilis, Fig. 244-, a, d ; Bacillus ttjphi, Fig. 242, c; Bacillns fetani, Fig. 247, e), or they spring 1 SECT. I CRYPTOGAMS 335 from a single point either as a single flagellum (monotrichous) or A as a group (lophotrichous). single, polar fiagellum occurs in Vibrio cholerae (Fig. 242, a) ; a polar terminal tuft of flagella in Spirillum undula (Fig. 242, b, d) ; a lateral tuft in the swarm-spores of Cladothrix (Fig. 243). The ciliary tufts may become so closely intertwined as to present the appearance of a single thick flagellum. The cilia are never drawn within the body of the cell, but undergo dissolution before the formation of spores takes place, or under unfavourable conditions (Fig. 242, e). Multiplication of the individual is accomplished vegetatively by the active division or fission of the cells ; the preservation and dis- -- FiG. 242. Types of arrangement of flagella. a, Vibrio cholerae ; h, d, Spirillum undula ; d, development of a new bunch of cilia in divi- sion ; c, Bacillus typhi ; e, Bacillus subtilis. (After A. Fischer, x 2250.) -- Fig. 243. Cladothrix dichotoma Formation of swarm cells from the cells of the filament. (After A. Fischer,- x 1000.) tribution of the species by the asexual formation of resting spores. These arise as endospores (Figs. 244, e, 246, e, f) in the middle or at one end of a cell by the inner portion of the protoplasm separating itself from the peripheral, and surrounding itself with a thick membrane. The membrane of the mother cell becomes swollen and disintegrated when the spore is ripe. Spores are not found in all species. Bacillus suUilis, the Hay bacillus (Fig. 244), which ai)pears as a rule in the decoction obtained by boiling hay in water, will afford an example of the life- history of a Bacterium. The spores of this species, Avhich withstand the effect of the boiling water, produce on germination rod-shaped swarming cells with cilia on all sides ; these divide and may remain connected in short chains. At the surface of the fluid these swarming cells change into non-motile cells without cilia, which divide up, giving rise to long intertwined chains of cells. These are associated together in the pellicle covering the surface (zoogloea stage). Spore formation occurs when the nutritive substances in the fluid are exhausted. Although the cycle of forms passed through in the life-history of a Bacterium is a very simple one, the individual species, which can often be barely distinguished by morphological characters, show great variety in their metabolic processes and in their mode of life. The majority of Bacteria require oxygen for 336 BOTANY PAKT II their respiration, and are therefore aerobic ; many can, however, develop without tliis gas, while some species, e.g. the butyric acid bacterium and the tetanus bacillus, are strictly an- aerobic and only succeed in the absence of oxj'geu. Some bacteria produce by their respiration con- siderable heat ; this is the explana- tion of the spontaneous heating of damp hay, dung, tobacco, and cotton- wool. In such substrata Bacillus calfactor develops ; it is adapted to live at high temperatures (above 40�) and is still motile at over 70� C. ==/iV-;i/V:5^ ;^-�.;j�.,. ,^ . '\ ,^- � . ,�/:;' '<iS;jf. ,, ,' ��^i;- '��..-.:";';. ^.,%.t- ::-,;.''" �' ' - -- Fif;. 244. Bacillus subtilis. a, d, Motile cells and chain of cells ; b, non-motile cells and chains of cells ; 0, spores from the zoogloea, e. (From A. Fischer, Varies, iiber Baeterieii. a-d, x 1500; c, X 250.) (cf. p. 248). Saprophytic and parasitic species are distinguished, though a sharp separation is often impossible. In cultures the parasitic forms can be made to lead a saprophytic life on suitable substrata. To the saprophytic Bacteria belong in the first place the forms ^y^[^.^ inhabit water. The widely distributed Cladotlirix dichotoma is morphologically the highest among these. It is found in stagnant water, and consists of falsely branching delicate filaments attached to Algae, stones, and woodwork, and forming a slimy coating over them ; the filaments are composed of rod-shaped cells. Reproduction is effected by ciliated swarm-cells, which originate by division from cells of the filament and are set free by the swelling of the sheath (Fig. 243). The swarm-cells come to rest after a time and grow into new filaments. Another very common form is Crenothrix KiUiniana, which consists of un- brauched filaments attached to the sub- stratum, but easily broken. It often forms masses in the cavities of water-pipes, blocking them up and rendering the water undrinkable. The reproduction of Crcnotlirix is effected by small, round, nonmotile cells, whicli arise by subdivision of the cells of a filament enclosed by its sheath. The numerous kinds of Sulphur Bacteria, of whicli Berjijiatoa alba is the most Fn;. �lAb.--Stre'ptocuixusviestnterioides. A, Isolated cells without f^elatinous sheiith ; B, C, formation of cliaiii of cells with jjelatinons sheath ; D, portion of mature zooi,'loea ; E, formation of isolated cells in the lilaments of the zoogloea. (After Van TiEOHEM, X 520.) widely distributed, are found in sulpliurous springs and at the bottom of pools where sulpliuretted hydrogen is being formed by decomposition of organic SECT. I CRYPTOGAMS 337 material. These Bacteria oxidise sulphuretted hj-drogen into sulphur, and store the latter substance in the form of rounded granules within their cells, ultimately oxidising it to sulphuric acid. Leptothrix ochracea, the so-called Iron-Bacterium, oxidises oxide of iron to the liydrated oxide of iron which it accumulates in the sheaths of its filaments. It occurs in ditches and swampy places in meadows. The zymogenous or fermentation Bacteria and the saprogenous or decomposi- tion Bacteria are other saprophytic forms. The former oxidise or ferment carbohydrates. The latter decompose nitrogenous animal or vegetable substances (albumen, meat, etc.) with the liberation of ill-smelling gases. Thus Streptococcus {Leucoihostoc) mesaitcrioidcs (Fig. 245) causes fermentation of beet-sugar. It forms large mucilaginous masses like frog-spawn, the bead-like rows of cells being surrounded by a gelatinous investment. The acetic acid bacteria (Fig. 246 a, b, c) oxidise alcohol to acetic acid. The transformation of c^ -- Fro. 241.;. Bacteria of fermi'iitation. �-<-, Vinegar bacteria ; a, Bacillus aceti ; b, Bac. Pcistev. nanus : '-, Bac. Kiitzingianus; il, Bac. acicli Zadfci, lactic acid bacillus; e, Clostridium hutyricnin, butyric acid bacillus ; /, Plcctridium paluclosum, fermentation bacterium from marsh water. (From A. Fischer, Varies, iiber Bacterien, x 1000.) sugar into lactic acid is brought about by the rod -like cells oi Bacillus ccculi lactici (Fig. 246, cl). ClosLrklmm bulyricum (Fig. 246, c) forms butyric acid from various carbohydrates in the absence of oxygen, while certain marsh Bacteria (Fig. 246, /) in the absence of oxygen form marsh-gas and hydrogen from cellulose. Bacillus vulgaris is the most common cause of decomposition of meat, albumen, etc. The Purple Bacteria, M'hich develop in water with decomposing organic matter in the absence of oxygen and the presence of light, contain, according to Molisch (�'), a green and a red pigment (bacterio-chlorin and bacterio-purpurin). Other bacteria secrete pigments in their cells or around them. The latter is the case with Bacillus iwodiijiosus, the ellipsoid peritrichous rod-shaped cells of which form fuchsin-red colonies on milk or bread, and so- have given rise to tlie miracle of the bleeding Host. The photogenic bacteria pi'oduce within their cells a substance which becomes phosphorescent on oxidation. The most widely sj^read of these phosphorescent bacteria is Bacterium phos2}horeum, which occurs on meat. The parasitic bacteria inhabit joth animals and plants. The best known forms which cause diseases of plants (bacterioses) are Pscudomonas Ryacinthi, giving rise Z 338 BOTANY PART II to a rot of Hyacinths ; Bacillus 2)liytophthorus, which attacks the potato ; and Bacillus Oleac, which gives rise to the Canker of the Olive Tree ("). The numerous pathogenic Bacteria are the most important causes of infectious o c '^o o 00 o c. a. <^ CtCD ^^/^ V.]f '-4 -- Fig. 247. Pathogenic Bacteria, n, Pus cocci ; h, erysipelas cocci ; f, gonorrhoea cocci ; d, splenic fever bacilli ; e, tetanus bacilli ; /, diphtheria bacilli ; g, tubei'cle bacilli ; h, typhoid bacilli ; i, colon bacilli ; k, cholera bacilli. (From A. Fischer, VorJcs. iibei- Bacterien, x about 1500.) diseases. Their injurious influence on the tissues and blood of men and animals is brought about by the excretion of poisonous substances, to which the name toxins has been giveu. The following forms may be mentioned. Stuijhylococcus ^ /( ky > ---, r-N 'V a h c Fio. 248.-- Stained preparations from Ziegler'.s Text-hook of Pathology, a, Gonoeocci in the gonorrhoeal discharge, mucus and pus corpuscles with cocci (methylene blue and eosin), x 700 ; b, tubercle bacilli in sputum of ]ihthisis (fuchsiii and methylene blue), x 400; c, splenic fever bacilli in the pustule of the disease (methylene blue and vesuvin), x 3o0. (From A. Fischer, Vorles. iiber Bacterien.) 2)yocjenes (Fig. 247, a), the cocci of which form irregular or racemose masses, is the most common cause of suppuration, while Streptococcus pyogenes (Fig. 247, I), with cocci united in chains, occurs in erysipelas and other suppurative lesions. Micrococcus {Diplococcus) gonorrhoeae (Figs. 247, c, 248, a) has somewhat flattened cocci arranged in pairs, and causes