Plant Cells and Living Matter

A small portion of a delicate blade of grass, cut off with a pair of scissors, transferred to a slide together with a drop of dilute glycerine (two parts of pure glycerine and one part of distilled water), was examined with a power of 1200 diam. I had at my disposal for these examinations two excellent immersion lenses, made respectively by Tolles, of Boston, and Vérick, of Paris. In some parts, in trichomes, stomata, air-vessels &c., nothing more could be seen with such amplification than with comparatively low powers of the microscope ; the epidermal fields as well as the surrounding frames of cellulose appeared structureless, or at most only very indistinctly granular. The main mass of tissue enclosed by the epidermal system, the parenchyma, presented blunt polygons separated from each other by a shining narrow rim of cellulose, and containing numbers of chlorophyll-granules. Some contained only very few and very small such granules, surrounded by an extremely delicate uncoloured reticulum, of which the filaments were of about the same breadth as the points of their intersection. In some polygonal fields there were a number of coarse chlorophyll-granules interspersed in a network, the threads of which had points of intersection that were thickened so as to constitute distinct though not green minute granules, while in other fields there were so many coarse and smaller green granules that they nearly completely filled up the polygon. Under all circumstances, however, the granules, closely focussed, appeared stellate, and were interconnected by means of delicate filaments running in large numbers from each granule to all its neighbours. If of small size a chlorophyll-granule appeared homogeneous, of a comparatively higher lustre, and of less intense green colour; larger granules exhibited an indistinct reticular structure in their interior; the largest showed-the reticular structure very plainly, and not infrequently in the centre a small shining body was observed sending radiating spokes toward the periphery, inosculating with a thin wall that enclosed the granule in toto. Toward the apex of the blade the granules became fewer in number and smaller in size; at the apex there were no chlorophyll granules.

In fig. 1 are represented chlorophyll-granules (CHL.) interspersed in the reticulum (R), surrounded by the cellulose frame (c).

These observations show that the vegetable living matter enclosed by the wall of cellulose is arranged in the form of a network, and that a similar reticular arrangement exists in the chlorophyll-granules. It is well known that chlorophyllgranules are themselves minute masses of the living matter of plants, coloured green by a colouring matter, to which the name chlorophyll is given. Living matter has been called by Hugo von Mohl “protoplasm,” by Lionel Beale “bioplasm,” and by me, because etymologically more correct, “bioplasson.” I am no stickler for new names, but in scientific discussions we should use, if possible, correct names; and of the four synonymous designations, viz. living matter, protoplasm, bioplasm, and bioplasson, I therefore confine myself generally to the first and last, although the term protoplasm is best known and by others most used..

In the year 1873, in a communication to the Vienna Academy of Sciences, entitled “Phases of Living Matter,” Carl Heitzmann first described, in Amæba, the youthful condition of masses of living matter as being constituted by homogeneous granules, and advanced stages as being characterised by vacuolation followed by reticulation. These statements were confirmed as regards vegetable organisms in a paper on “The Structure and Growth of some Forms of Mildew,” in the ‘New York Medical Journal’November, 1878, by William Hassloch, who says that the first visible form elements of the plant are homogeneous granules, and the first appearing buds compact projections, either globular or elongated, the first differentiation consisting in the occurrence of a central vacuole, while after a certain development has been attained the plant protoplasm appears in the form of a network.

Many botanists have observed and described reticulated living matter, not only when in its naked condition, as plasmodium, as it is called, but also when enclosed in a cellulose wall. Allow me to cite a few examples: Sachs has figured “a cell of Zygnema cruciatum, with two stellate chlorophyllbodies which are suspended in the interior of the cell; they are united by a colourless bridge of protoplasm in which lies a nucleus; the rays which form the union with the parietal sac are already nearly colourless in the middle. In each of the two chlorophyll-bodies lies a large grain of starch (amplification 550),” also “forms of the protoplasm contained in cells of Indian corn (Zea mais); A, cells from the first leaf-sheath of a germinating plant, showing the frothy condition of the protoplasm, i.e. the many vacuoles separated by thin plates; B, cells from the first internode of the germinating plant; the protoplasm is broken up into many rounded masses in each of which there is a vacuole (b); these are the so-called ‘sap vesicles.’” Sachs has also figured”parenchyma cells from the central cortical layer of the root of Fritillaria imperialis, longitudinal sections, A, very young cells, lying close above the apex of the root, still without cell sap or vacuoles. B, cells of the same description about 2 millimètres above the apex of the root; by the entrance of cell sap the vacuoles s, s, s, have been formed, c, cells of the same description about 7 to 8 millimètres above the apex of the root,” in one of which the reticulum is very plainly seen. Bessey says “in the stamenhairs of Tradescantia Virginica the protoplasm forms a rather thick layer over the inner surface of the cell wall, and in some part of this layer the nucleus lies embedded. From the nucleus, and from various parts of the protoplasmic layer, there pass to the opposite side of the cell thicker or thinner bands and strings, and gives a figure of the same after Hofmeister. Prantl has figured Meristem cells of the stem of Vicia faba in which filaments of living matter emanating from the nucleus go to the peripheric layer of living matter, and also hairs from the epidermis of ovary of Cucurbita, in some of the compartments of which the reticulum is very distinctly shown with quite low power (× 100).

Heitzmann, the discoverer of the reticulum of living matter and of its continuity throughout the entire animal organism, states in his magnificent work just published, entitled ‘Microscopical Morphology of the Animal Body in Health and Disease’ p. 57, “My own limited researches enable me to assert that the granules of living matter in vegetable protoplasm are, as a rule, united in the shape of a reticulum, in the same manner as in animal protoplasm. Besides, the researches of W. Hassloch elucidate the identity of both animal and vegetable living matter in a satisfactory manner. I may add that all cells of the vegetable organisms are uninterruptedly connected by means of delicate offshoots piercing the walls of the cellulose. The granules of amylum are transformed living vegetable matter. The plant in toto is an individual and not composed of individual cells.” But demonstration of this statement is wanting. Low powers of the microscope, and even high powers, show that a less or more thick cloak of cellulose surrounds each plant “cell,” and separates it from its neighbours. The observations of the chlorophyll-granules and of the interior of the polygonal cellulose frames of blades of grass herein detailed, while they fully bear out the assertions of Heitzmann and Hassloch as to the reticular structure, and perhaps even as to the growth phases, at least so far as dimension is concerned, of masses of living matter of plants, do not advance our knowledge much further. All my endeavours definitely to determine whether the plant “cells” are interconnected or not were unsuccessful with the means I employed in both transparent specimens and in sections. The inspection, under all sorts of circumstances, of the wall of cellulose, although it frequently gave me the impression that it was faintly granulated, and although delicate filaments emanating from the most peripheral chlorophyll-granules were often seen tending towards the wall, did not enable me to arrive at a conclusion concerning its intimate structure.

Francis Darwin has discovered protoplasmic filaments protruding from the cellulose investment of the glandular hairs on the leaves of Dipsacus sylvestris (‘Quarterly Journal of Microscopical Science‚ 1877, p. 245). Previously, Hoffman (“Ueber contractile Gefilde bei Blatterschwämmen,” ‘Botan. Zeitung‚1853,p. 857, and 1859, p. 214) had described contractile filaments projecting from cell walls in Amanita (Agaricus) muscaria, and although De Bary has expressed the opinion that these are not protoplasmic, Darwin believes them to be so (‘Quart. Journ. Mic. Sc. ‚ Jan., 1878, p. 74). Later, W. J. Beal (‘American Naturalist,’ October, 1878, p. 643) described threads, but does not say that they are protoplasmic, projecting from the end of hairs of several plants. Darwin has observed filaments of living matter, emanating from the interior of plant cells, pierce the cellulose frame. They protruded from terminal cells only, and of course showed no interconnection between neighbouring cells. Such interconnection I can now demonstrate.

My first successful observations were made in specimens of the flowers of flowering flax (Norimbergia gracilis), and of the leaf and stem of the common india-rubber plant (Ficus elastica), and were obtained as follows. The analogy between epidermal layers, as well as other parts of a plant, and animal epithelia, led me to the inference that reagents successfully applied for elucidating the structure of animal epithelia might serve for the same purpose in plants. Now, each epithelial body is a nucleated, reticulated bioplasson mass, enclosed by a continuous layer of bioplasson and separated from all its neighbours by a cloak of cement-substance. The cement-substance answers to the cellulose wall of plant cells, and as a memento of Schleiden and his cell doctrine, I would advocate not only the retention of the term cellulose, but its extension to animal tissues, i.e. to take the place of the term cementsubstance. It is known to histologists that the cement-substance is traversed by numerous conical filaments which by their discoverer, Max Schultze, were termed “thorns or prickles·”It is also known that upon applying a 2 per cent, solution of silver nitrate to fresh epithelia, the cement-substance assumes a dark brown hue, and appears perforated by numerous light transverse lines; while if, on the contrary, a one half per cent, solution of gold chloride be applied to epithelium, the bioplasson reticulum in its interior assumes a dark violet tint, the cement substance remains unstained, and in it Max Schultze’s thorns, also coloured deep violet, appear very plainly. Thus it has been proved that the wall of cementsubstance does not completely isolate the single epithelia, but is pierced by bridges of living matter which interconnect all epithelia into one continuous bioplasson mass.

I placed pieces of the flower of “Norimbergia” into a 2 per cent, solution of silver nitrate for about half an hour, then washed the specimens with distilled water and exposed them to daylight. I found that nitrate of silver does not invariably affect the cellulose alone, but sometimes stains also the “cell”-contents; a corresponding general tinction occasionally happens in the case of animal epithelia. Frequently, while the cellulose wall on the inner surface of the flower was comparatively little coloured by the silver salt and dark granular precipitates filled the spaces between the radiating cellulose offshoots, the polygonal frames on the outer surface of the flower were beautifully stained dark brown by the silver salt; and examined with Tolle’s immersion lens, showed numerous interruptions in their continuity, as represented in fig. 2, exactly like the light-coloured transverse markings seen in cement-substance of animal epithelia under similar circumstances. Usually the hairs were stained deeply brown; in many compartments one or several light fields were seen, of irregular shapes, freely branching ; the periphery of such a light-coloured field often looked serrated, and a reticulum proceeding from it pervaded the whole compartment. This appearance is shown in fig. 3. In a number of instances I observed that the septum separating two neighbouring compartments was marked by light-coloured lines, as represented in the compartment was to the apex of the hair; at the end, the whole hair, as a rule, appeared uniformly dark brown, or contained in its interior an extremely delicate, light-coloured reticulum only.

After a one half per cent, solution of gold chloride had been brought to bear upon pieces of the flower for about forty minutes, the wall of cellulose became more distinct although not coloured by the gold salt. In the interior of the polygonal fields, on the inner surface, a scalloped body had made its appearance; it was slightly retracted from the cellulose frame and offshoots, bordered by a continuous delicate layer, and filled with a very distinct reticulum in connection with a central coarsely granular and also reticulated nucleus. The bordering layer and the reticulum around the nucleus, as well as the nuclear wall and the intranuclear granules and reticulum, were of a dark violet colour, just as in animal epithelia exhibited a distinctly reticular structure. The hairs showed dark violet granules and clusters of granules in the interior of the compartments; these granules had radiating offshoots which formed a network, with frequently distinctly granular thickened points of intersection, as represented in fig. 5. There could be no doubt that this was the positive image of the structure that was demonstrated by the silver staining in a negative manner as depicted in fig. 3. In some, especially in small hairs, the dark violet reticulum in the compartment was very dense. Frequently, delicate violet filaments pierced the transverse septa of neighbouring compartments and interconnected the reticula and bioplasson formations in their interiors, as seen in fig. 5.

But the most complete proof of the existence of living matter within the cellulose walls of plant “cells “I obtained in sections of the stems of leaves of the common india-rubber plant (Ficus elastic a), a silver-stained specimen of which is represented in fig. 6. The latex oozing out of the stem proved to be composed of a viscid, as if mucous, colourless liquid, in which were suspended innumerable isolated granules of a high lustre, somewhat similar to that of fat; gold chloride staining made the smallest granules appear dark violet, while the larger were only indistinctly coloured, retaining their high lustre. Transverse sections of the stem, examined in dilute glycerine, showed chlorophyll-granules and the reticular structure. The parenchyma of some specimens, especially those treated with strong alcohol, plainly exhibited the layer of living matter in the interior of the “cell,” which Von Mohl called “Primordial utricle,’ and sacs, more correctly “protoplasmic sac;’ and in many cases the bioplasson mass showed the reticular structure. Treatment of gold chloride not only rendered the network of many bioplasson bodies distinctly visible, but in some cases offshoots emanating from such bodies were seen to penetrate more or less far into the cellulose investment; what has been sometimes described by authors, especially in growing tissues, as “intercellular spores “and “middle lamellae,” in the cellulose were revealed to be in a number of instances accumulations and filaments of living matter wedged in between the “plant cells,” very much like the wedges of bioplasson and the medullary elements which I have found to grow between animal epithelia in cases of new growths (“Microscopical Study of Papilloma of the Larynx,” ‘Archives of Laryngology,’ March, 1880). Treatment with the solution of silver nitrate revealed in the darkened substance of the cellulose light spaces occupying the position of such wedges. These light spaces sent off comparatively broad offshoots parallel to the inner surfaces of the cellulose frame, and innumerable delicate light offshoots from both the central space and the broad offshoots traversed the brown cellulose in uninterrupted connection with the delicate light reticulum seen here and there within the so-called “plant cell.” The appearance of the silver-stained cellulose frame in a portion of such a specimen is accurately reproduced in fig. 6, and the results obtained in-these specimens I have verified by very numerous other examinations.

My researches demonstrate, and so far as I know, demonstrate for the first time, that the frame of cellulose, analogously to the cement substance of animal epithelia and the basis substance of other animal tissues, is pierced by either single filaments of living matter or a reticulum with more or less large accumulations .of living matter, interconnecting all neighbouring tissue elements, and that the plant, therefore, like the animal, is one continuous mass of living matter, with interspaces which contain some non-living material.

The structure of plant tissue may be illustrated by the structure of hyaline cartilage of animals. For many years it was believed that cartilage consists of a homogeneous nonliving basis substance in which are embedded, at various distances apart, isolated living cartilage corpuscles—cartilage-“cells” as they were called. The more or less convincing observations made by Heitzmann, and after him by Hertwig, Thin, Prudden, Spina, and Flesch, have shown this to be a mistake; and the results which I obtained in the histological examination of the cartilages of the larynx (published in the ‘Archives of Laryngology,’October, 1881, and January, 1882), have proved beyond question that hyaline cartilage is a filigree of living matter, in the meshes of which lumps of basis substance are embedded. According to the former view cartilage could be compared to a pudding, in the dough of which a certain number of.raisins are embedded ; in truth, it is like a framework composed of larger and smaller raisins and bands and strings of raisin substance, in the meshes or interspaces of which blocks of dough are embedded.

Just so in the tissue of plants, the so-called plant “cells” are connected one with the other, and blocks of cellulose fill up the interstices in the network of living matter.

Not to trespass too much upon the patience of the reader, I must leave undetailed here the far-reaching consequences of the “bioplasson doctrine”for the better understanding of the relations and phenomena of plant life.