Transactions and Proceedings of the New Zealand Institute/Volume 14/Article 43
Art. XLIII.—On the Fresh-water Algæ of New Zealand.
By W. I. Spencer, M.R.C.S. England.
[Read before the Hawke's Bay Philosophical Institute, 11th July, 1881.]
Plate XXIII.
Reference to Sir J. Hooker's "Handbook of the New Zealand Flora," pp. 645–646, will show how little attention has in this country been hitherto bestowed upon one of the most beautiful orders of the vegetable kingdom. And as one reads in paragraph after paragraph, in which the various tribes of the fresh-water Algæ are enumerated, such statements as "Very numerous, not hitherto collected in New Zealand"—"This beautiful fresh-water group has not hitherto been collected in New Zealand"—and again, "The species are very numerous and have never been collected or studied in New Zealand," one cannot help feeling that the reiteration suggests to the naturalists of this colony a powerful incentive to undertake the systematic study of this most remarkable and interesting order of plants.
It is with much diffidence that I lay this paper before you to-night, because I feel that I am treading upon unbroken ground, and that the subject is a vast one, involving for its complete investigation much study and much time, neither of which I have been able to devote to it, and also the consultation and comparison of many books which have not been at my command. Nevertheless, if my imperfect attempt has the result of drawing the attention of some of the many able naturalists in this country to a hitherto neglected section of its natural history, and of enlisting other and more competent workers than myself in its investigation, I shall feel that the object I proposed in drawing up this paper has been fully accomplished.
The fresh-water Algae comprise a large proportion of the Chlorospermeæ or Confervoideæ; the number of green Algae which are inhabitants of sea water being comparatively small. They are to be found on damp ground, under the drippings of water, in ponds, streams, waterfalls, even in hot springs where the water has a nearly boiling temperature. They form a green scum on walls, on the bark of trees, and on stones in damp weather—in fact, given the one condition of fresh water moisture, they are almost ubiquitous. Many are plainly visible to the naked eye, and may be seen floating in water, either as scum, as compact green or purple masses, as skeins of threads attached to stones, sticks, or water plants, or as a simple discoloration mingled with the mud at the bottom;—others again are only discoverable by the microscope, or by the fact that, when they exist in vast numbers, they impart to the water a distinctive colour. But, in whatever situation or habitat these Algæ are found, microscopic analysis reduces them all to the same elements as exist in the higher aerial plants—the vegetable cell—composed of an outer cellulose coat, a primordial utricle, and within this the coloured cell-contents, the endochrome, in which its vital activity is situated.
A comparison of these subaqueous plants with their terrestrial congeners would form a most interesting subject of enquiry, but one of such vast dimensions that I can only venture to touch upon one or two of its most salient points this evening.
Probably the typical form of the vegetable cell is a sphere. In all plants, however, except the very simplest—the unicellular—the spheres by aggregation become changed into various other figures, by mutual compression, and by their growing in the lines of least resistance. Thus we have the free globular cells of the Volvocineæ; the cylindrical ones of the Confervæ, the Zygnemaceæ, etc., corresponding to the elongated cells of vascular and woody tissue;—the quadrangular, polygonal, and irregular cells of Ulvaceæ, Pediastreæ and Desmidiaceæ, which find their analogues in many parts of the epidermis, the expanded portion of leaves, the petals, etc., of the higher plants. Again the markings in dotted, spiral, and glandular vessels, are very similar in appearance, if in nothing else, to the markings in Lyngbyæ, Spirogyræ, Calothrices, etc. It is singular to notice also, how, under some circumstances, the cell appears to endeavour to revert to its typical form, as in pl. XXIII., fig. 10, where the front view of the pediastrum shows a complex geometrical outline, and the side view exhibits four simple circular cells.
Into the question of the modes of combination of these algal cells, and the exquisitely beautiful geometrical figures they often form, or of the siliceous patterns secreted by the Diatoms, it is not my purpose to enter at present, though doubtless they have analogues in the shapes and forms of various flowers, and the arrangements of the elements of many leaf-buds.
The colour of the endochrome of the fresh water Algæ varies nearly as much as it does in flowering plants. In most it is green; in some, as the Oscillatorieæ, it varies from light green through various shades of blue and purple to black; in the Protococci again, we meet with different and often brilliant tints of red, and lastly in some Desmids and the majority of Diatoms with a reddish or yellowish brown hue, although the endochrome of many Diatoms is, in early life, of a brilliant green colour. Taking the fresh-water Algæ altogether, and comparing them with the leaves and flowers of the aerial plants, there appears to be a strong resemblance between the colours exhibited by these two extremes of the vegetable kingdom. The various shades of green, from dark olive to emerald, of red, and of blue, from purple to sky blue, which we find in the Algæ, are very much the prevailing tints of the leaves and flowers of aerial plants. And again the reddish and yellowish brown hues of some Batrachospermeæ, Lyngbyæ, Desmids and Diatoms, correspond closely with the shades assumed by the leaves of trees, shrubs, and herbs, after they have lost their summer verdure, and to which is due the picturesqueness of their autumnal foliage. Many Confervoids, which when young have green endrochrome, assume in more adult age a yellowish or brownish hue, and the analogy between this change and that which occurs in the leaves of the oak, the ash, the elm, and other trees, is at least both striking and suggestive.
Many Algæ exhibit colours which cannot be referred to autumnal influences, or to the effects of age. The prevailing tints among some of the Volvocineæ and Oscillatorieæ have strong points of resemblance with those of the flowers of phanerogamous plants. In the latter the diversities of colour appear to be connected in some way (of which various explanations have been advanced) with the multiplication of the plant, and so we find that the flowers are the parts which are most liable to variations of colouration. On the other hand, in these simple organisms there is no division into stem, leaves, and flowers, almost every portion is concerned in the process of reproduction—each filament or frond represents a perfect herb, shrub, or tree, and every sporiferous cell is the analogue of a flower. In the phænogamic class the floral colours are useful as attractions to insects of various kinds, which, visiting them for food, carry away the pollen to other flowers, and so conduce to their fertilization. Although, so far as I am aware, no observations have been made on the subject, is it not something more than possible that the multitudes of Infusoria, Rotatoria, Paramecia, etc., which we continually meet with seeking their food amongst the Algæ, may assist in the same way as insects in conveying antheridial spores from one plant to another; and that the varying colours of the filaments may be attractive to them as those of flowers are to insects; and that thus may be reproduced in the subaqueous world some of those phenomena with which we are familiar in the aerial? Should future observation verify this conjecture we shall see amongst the Algæ the exact analogue of the entomophilous fertilization of flowers, and also be able to understand why the various and beautiful tints they exhibit are, to a certain though much less extent, reproduced in the filaments and fronds of the fresh-water Algæ.
In submerged vegetation anemophilous fertilization is of course out of the question, yet even here a substitute appears to have been afforded by the provision of cilia to the androspores and zoospores, to enable them to perform the requisite movements through the water which is their home, and to guide themselves, the former to their relative gymnospores, the latter to appropriate places whereon to rest and recommence the process of germination and growth.
In the methods of fructification, moreover, the resemblances between flowering plants and Algæ are probably as close as in any other particular. Setting aside the Volvocineæ, Palmellaceæ, and some others in which the process of multiplication is merely a process of cell division, either intrinsic or extrinsic, we find in the Confervæ, Siphonaceæ, Oscillatorieæ, etc., that the single cell has the power of producing reproductive spores, thus (keeping in mind that an algal cell is the equivalent of a phænogamic flower) affording an analogy with the class of so-called hermaphrodite flowers. A strictly monœcious form of fertilization is met with in the Œdogoniaceæ, where the contents of certain inflated cells are vivified by the contents of contiguous antheridial cells which, by rupture of the cell division, gain access to the inflated cells. A distinct advance upon this method is found in many Œdogonia and Chætophoræ. Here the distinction between antheridial and sporidial cells is evident—they often occur upon different filaments, though sometimes upon distant portions of the same, and are easily recognized by their shape and appearance. The contents of the antheridial cell (androspore) when mature escape through rupture of the cell wall, and, being furnished with cilia, lead an active locomotor life until, coming in contact with the gonidial cell (oospore), the locomotion comes to an end and the contents of the two combined form a zoospore which eventually becomes a young plant.
The Zygnemaceæ are veritable diœcious plants, and propagate by a process of conjugation—the cells of two contiguous filaments throw out a connecting tube through which the contents of one (the antheridial) cell pass into the other (the gonidial), and thus fertilize them, the result being a zoospore. In this process the fertilization of the ovule by the pollen tube in Phanerogams is closely imitated. But further, that abnormal self-fertilization that takes place in certain flowers under unusual conditions, and which is termed cleistogamy, would appear to occur at times in certain Spirogyræ, the filaments of which have the power of producing zoospores—the so-called pseudogonia—in certain cells without conjugation; in fact these cells are, like the cleistogamous flowers, not only hermaphrodite, but contain within themselves the power of self-fecundation.
In the following list of fresh-water Algæ which have come under my observation during the last eighteen months I have included only such as I feel pretty certain I have verified. Many others are not enumerated, because I am at present doubtful of their classification; but with further search and observation I have no doubt the list may be extended indefinitely.
Batrachospermeæ.
1. Batrachospermum moniliforme. Not uncommon.
2. {{{1}}}„ pulcherrimum, H., xiv., 1. From river Esk.
3. {{{1}}}„ vagum, H., lxiii., 2. From a creek on the Ruataniwha Plains. An unusual specimen of this plant was given me by Mr. Hamilton, from the Horokiwi river. Its peculiarity consists in the development of a vast number of hair-like appendages, on some parts of the filament, of considerable length, and forming in some places a densely intricate matwork round the filament which not only obscures it but also the whorls that emanate from it.
Chætophoracæ.
1. Draparnaldia tenuis, H., xi.
2. Chætophora endiæfolia, H. ix.
{{{1}}}„ elegans, H., ix.
{{{1}}}„ sp. n.
Fig. 1.
In the species marked n. above, the filament tapers from base to apex. It is irregularly branched, with few ramuli. Gelatinous investment not apparent. Cells of the ramuli (varying from four to eight) filled with endochrome. Terminal cell broad at the base, narrowing to a not very acute point, exceeding the ordinary cells three or four times in length, hyaline. Cells of the filament and branches as long, or twice as long, as broad. Antheridial cells half to a quarter as long as broad, compressed. Stipitate, capsular fructification was observed attached to both sporiferous and antheridial filaments. Zoospore, the only one seen, commencing to germinate, quadrangular in outline, contains two large sporules, surmounted by four cilia, one at each angle; motile.
Confervaceæ.
1. Conferva bombycina, M.D., p. 158.
{{{1}}}„ floccosa, M.D., pl. V.
2. Cladophora crispata, H., lv.
{{{1}}}„ glomerata, H., lvi.
{{{1}}}„ lyallli, Hooker, Fl. N.Z.
{{{1}}}„ sp. n. (1).
{{{1}}}„ sp. n. (2).
3. Ulothrix mucosa, M.D., pl. V.
Cladophora lyallii is described by Hooker—"Handbook N. Z. Flora," p. 717, and "Fl. N.Z. Ant. Voyage," vol. ii. p. 262. He mentions it as having been found in Stewart Island.
Cladophora crispata occurs in Kerguelen's Land. Hooker "Ant, Voyage."
Cladophora, sp. n. (1), I found in gently flowing water, attached by a short stem to a piece of iron pipe. It is nearly spherical in shape, about 112″ in diameter, tufted, green. Filaments bright green, alternately branched, articulations 1½ to 2 times longer than broad, slightly constricted at the nodes. Branches of two kinds—chætophorous, of which the articulations are 2–3 times longer than broad, filled with endochrome, ending in elongated bristly processes; and sporiferous with articulations constricted at the nodes, cells from ½ to 1½ times as long as broad, terminal cells sometimes clubbed. Capsular fructification on some of the rami either terminal or shortly stipitate. Fig. 2.
Cladophora, sp. n. (2). Filaments have a distinct gelatinous investment. Cells three times longer than broad. Here and there, mostly at attachment of rami, occur large hexagonal cells, very like the inflated cells of Œdogonium, containing a circular spore. Terminal cells elongated, tapering to a rounded point. Antheridial cells broader than long, spores subglobose, compressed. Free zoospores I have seen only once, and failed to discover cilia. Fig. 3.
Zygnemaceæ.
1. Spirogyra communis, H., xviii.
{{{1}}}„ quinina, H., xxviii.
{{{1}}}„ nitida, H., xxii.
{{{1}}}„ interrupta, H., xxi.
{{{1}}}„ rostrata, H., xxiii.
{{{1}}}„ quadrata, H., xxxvii.
{{{1}}}„ pellucida, H., xxv.
{{{1}}}„ sp. (?)
2. Zygnema cruciata, H., xxxviii.
This family is tolerably abundant in the locality. I have, I think, been able to discriminate all the species that have come under my observation, with one exception. In this specimen the band of endochrome commences at one end of the cell, and after making a spiral and a half reaches the further extremity of the cell, where it bends upon itself, and after another spiral and a half reaches the end from which it started; here it bends a second time, and finally terminates at the opposite end of the cell, forming altogether a series of figure-of-8 knots. Fig. 4.
In this family the normal mode of reproduction is by the conjugation of cells of distinct filiaments; it is distinctly diœcious. In certain cases, however, and they are not uncommon, the endochrome of a filament appears to have the power of self-fertilization, and spores are formed in the cells either with or without communication with contiguous cells. In this process we have a close analogy with the peculiar phenomenon of self-fertilization seen in some normally wind- or insect-fertilized flowers at certain seasons. In fact, we find cleistogamous flowers in our subaqueous plants as well as in their aerial congeners.
Œdogoniaceæ.
Œdogonium ciliatum (?), H., lii.
{{{1}}}„ compressum, H., liii.
Oscillatoriaceæ.
1. Bacterium, M. Dic., p. 3.
2. Vibrio rugula (?), M. Dic., p. 3.
3. Spirillum volutans, M. Dic., p. 3.
4. Spirulina jenneri, M. Dic., p. 3.
5. Oscillatoria autumnalis, H., lxxii.
{{{1}}}„ decorticans, H., lxxi.
{{{1}}}„ nigra, H., lxxi.
{{{1}}}„ tenuis, H., lxxii.
{{{1}}}„ limosa, H., lxxi.
{{{1}}}„ contexta (?), H., lxxi.
{{{1}}}„ sp. n. (?)
6. Microleus gracilis, H., lxx.
7. Lyngbya muralis, H., lix.
8. Calothrix.
9. Polypothrix (?).
Oscillatoria.—I have no doubt that with further research this list may be indefinitely extended. The characters of some of the species are not very distinctly marked; and I imagine their nomenclature is not yet settled. Certainly the description and figure of O. autumnalis as given by Hassall are very different from those in the Micrographic Dictionary. The peculiar characteristic of this genus, from which its name is derived, is the singular movements of the filaments. What the cause of these movements is has been the subject of some speculation, but has not been determined. No special organs of motion have been discovered. Whether they are vital or merely mechanical phenomena, is at present impossible to decide. I have seen them in plants which had been immersed many days in Hantzsch's fluid still continuing, feebly but quite perceptibly. The movements are of two kinds—oscillatory and progressive. In the first, the filament, being apparently fixed at one end, sways backwards and forwards upon a centre like the pendulum of a clock, and it may either remain in a state of rigidity, or may curve with a flexibility resembling that of the long thin branch of a tree when agitated by the wind. The other movement is one of direct progression. A filament will, after a period of quiescence, begin to move forward, end on as it were, and having advanced a certain distance will, without any discoverable cause, suddenly reverse the direction and retrograde. It is a very interesting sight sometimes to watch these minute organisms in their advance across the field of the microscope, I have seen in O. tenuis the two or three end cells waving backwards and forwards slowly and deliberately as though the filament were feeling its way across the field of view. On meeting an obstacle, such as another Alga, the filament would halt as though it were investigating the nature of the obstruction—if the Alga happened to lie at an acute angle the Oscillatoria would accommodate itself and move along the side in contact with it; if, however, it lay at a right angle, it would, after a short examination, pass either over or under it, and continue its onward march, or occasionally begin to move backwards, and so retrace its steps. In one specimen the terminal cell was surmounted by a short bristle, which was used apparently as a feeler. The singular deliberative motions I have attempted to describe, I have never seen except when the filament was moving forward; they do not seem to occur when it is performing a movement of retrogression.
Oscillatoria, sp. n.? The usual method of reproduction in this genus is stated to be by the breaking up of the filaments, each articulation of which then takes upon itself the functions of a gonidium. I believe, however, they do sometimes emit spores, though I have not had an opportunity of watching them after their detachment from the parent filament. And in one instance—a specimen occurring as a purple stratum on a damp stone, which I have not been able to specify—there appears to be a series of special sporiferous cells, amongst, but quite distinct from, the ordinary articulation. (Fig. 5.)
Lyngbya, common.
Polypothrix distorta (?). I do not feel sure of this species, as I have seen only a single specimen.
Nostochaæ.
Nostoc commune, M. Dic., 4. {{{1}}}„ verrucosum, H., lxxvi.
Ulvaceæ.
Enteromorpha intestinalis, H., lxxvii; M. Dic., 5.
Ulva bullosa, H., lxxviii.
{{{1}}}„ crispa, H., lxxviii.
Tetraspora (lubrica?), H., lxxviii.
Palmellaceæ.
Microhaloa rupestris, M. Dic., 3.
Botrydina vulgaris, H., lxxxi.
Coccochloris vulgaris, M. Dic., 3.
{{{1}}}„ protuberans, H., lxxvi.
Pleurococcus.
Hydrocytrum acuminatum, M. Dic., 45.
Desmidiaceæ (including Pediastreæ).
1. Hyalotheca dissiliens, R., i; H., lxxxiii.
{{{1}}}„ dubia, R., xxxv.
2. Aptogonum undulatum.
3. Sphærozosma vertebratum, R., vi.
{{{1}}}„ pulchrum, R., xxxv.
4. Micrasterias pinnatifida, R., x.
{{{1}}}„ ampullacea, Maskell, "Trans. N.Z.I.," vol. xiii.
{{{1}}}„ var. α, β.
5. Cosmarium cucumis, H., lxxxvi.
{{{1}}}„ undulatum, R., xv.
{{{1}}}„ tetraophthalmium, E., xvii.
{{{1}}}„ botrytis, R., xvi.
{{{1}}}„ margaritiferum, R., xvi.
{{{1}}}„ sp. n.
6. Staurastrum muticum, E., xxi.
{{{1}}}„ orbiculare, R., xxi.
{{{1}}}„ gracile, R., xxii.
{{{1}}}„ tetracerum, R., xxiii.
{{{1}}}„ paradoxum, R., xxiii.
{{{1}}}„ sp. n.
7. Closterium lunula, R., xxvii.
{{{1}}}„ acerosum, R., xxvii.
{{{1}}}„ lanceolatum, R., xxviii.
{{{1}}}„ moniliferum, R., xxviii.
{{{1}}}„ jenneri, R., xxviii.
{{{1}}}„ leibleinii, R., xxviii.
{{{1}}}„ dianæ (venus), R., xxviii.
{{{1}}}„ attenuatum, R., xxix.
{{{1}}}„ striolatum, R., xxix.
{{{1}}}„ lineatum, R., xxx.
{{{1}}}„ cornu, R., xxx.
{{{1}}}„ acutum (tenerrimum), R., xxx.
8. Pediastrum tetras, R., xxxi.
{{{1}}}„ heptactis, R., xxxi.
{{{1}}}„ pertusum, R., xxxi.
{{{1}}}„ napoleonis, R., xxxi.
{{{1}}}„ boryanum, R., xxxi.
{{{1}}}„ ellipticum, R., xxxi.
{{{1}}}„ sp. n.
9. Scenedesmus quadricauda, R., xxxi.
{{{1}}}„ obliquus, R., xxxi.
{{{1}}}„ obtusus, R., xxxi.
I have included the Pediastreæ in this family for the sake of convenience, although the definition of the Desmids as given by both Hassall and Ralfs would exclude them, and Carpenter arranges them as a separate family. (When this paper was read I had not seen Mr. Maskell's article on the Desmidiaceæ of Canterbury.[1] Since then I have considerably modified my remarks on this family, in order to avoid useless repetition and to bring it as far as possible into accordance with Mr. Maskell's paper).
Micrasterias ampullacea, var. (α) from Ruataniwha.
{{{1}}}„{{{1}}}„ var. (β) Ruataniwha. This plant resembles var. β, in general outline, but differs in the smoothness of the edges of the fronds, in the flatness of the tips of the segments of the lobes, and in the absence of punctæ inside the margins of the frond. The flask-like shape of the segments is very marked. I have placed it under the head of M. ampullacea, var. β, for the present, but I am not sure that it will remain there permanently. Fig. 6.
Cosmarium cucumis? I have marked this with a note of interrogation, because I have seen only one specimen. It corresponds, however, so entirely with Ralfs' description in the smoothness of the frond, the deep constriction, and the equality of length and breadth, and the rotundity of the ends of the segments, that I have little doubt as to its identity.
Cosmarium tetraophthalmium is common.
{{{1}}}„ margaritiferum abundant.
{{{1}}}„ sp. n. Frond quadrate, slightly longer than broad, not deeply constricted. Segments conical truncated, united at the truncations, edges smooth. End view circular. This plant is remarkable for its peculiar hour-glass shape. I have found no description of anything like it in such books as have been accessible to me. If it prove a new species I should propose the name of C. clepshydra. Fig 7.
Staurastrum, sp. ? Edges of frond smooth, segments united below, divaricating. Upper and outer borders concave, uniting at an acute angle, inner slightly convex, lower rounded. On the upper concave border are three hyaline processes with smooth sides and flattened ends. At junction of outer and lower borders is one process similar to the upper ones but curved slightly outwards. This little plant is unlike anything in Ralfs—it might be an unusual form of S. lave, but in the latter the processes are forked, in the former not. Fig. 8.
Closterium. In this genus I have not found any specimen that could not be referred to Ralfs.
Pediastrum tetras, and P. heptactis are both common.
{{{1}}}„ pertusum. Intestines of the frond hyaline; some of the inner cells are gone, therefore the foraminal appearance is uncertain. The rectangularity of the outer row of cells and the shape of the notch point to pertusum. On the other hand, the number of rows, and the number of circumferential cells, might lead one to infer a new species. On careful comparison, however, I am inclined to consider it as an unusually large specimen of P. pertusum. Number of rows, five; number of cells in inner circle, five. The two next rows are broken down. The fourth circle contains apparently eighteen, and the outer one—the fifth—twenty-one cells. Fig. 9.
Pediastrum, sp. n. Frond square, divided into four equal lobes by a crucial hyaline division. Lobes divided into segments by a deep narrow notch, which extends from the four corners towards the centre of the frond, the segments again partially subdivided by a broad shallow notch. Side view, four cells placed end to end, the central ones about twice the size of the terminal. Although at first sight so very unlike, there is a remarkable similarity between this plant and P. tetras; in fact, the only point of difference consists in the secondary segmentation of the lobes. Fig. 10.
Scenedesmus quadricauda. I have placed before you a figure of this Desmid, because it shows the unusual phenomenon of a broad well-defined coating of hyaline matter external to the cells, and further that the bristles are appendages of the investing coat and not of the cells themselves. Fig. 11.
Diatomaceæ.
Meridion constrictum, H., xcvi.; M. Dic., 12.
Diatoma elongatum, H., xciv.
{{{1}}}„ vulgare, H., xciv.; M. Dic., 12.
{{{1}}}„ grande, M. Dic.
Melosira.
Campylodiscus costatus, M. Dic., 12.
Surirella bifrons, M. Dic., 13.
Synedra splendens, H., xcvii.
Cocconeis placentula.
Navicula.
Gyrosigma macrum, M. Dic., 11.
{{{1}}}„ attenuatum, M. Dic., 11.
Pinnularia oblonga, M. Dic., 11.
Stauroneis phœnicenteron, M. Dic, 11.
Encyonema.
The usual modes of multiplication of the Diatomaceæ are stated to be either division or conjugation. Facke however suspected, though he did not actually observe, a formation of spores or gonidia such as are found in many of the filamentous Confervoids. This method of reproduction I beheve I have seen in Synedra ulna. In the autumn of last year I found, amongst a growth of Spirogyræ and Oscillatoriæ, a number of unusually large specimens of Synedra, some of such magnitude as to be visible to the naked eye. They were active, and evidently in a state of vigorous growth.
In fig. 12 I have endeavoured to depict the various stages of sporidial growth: a shows a full-grown Synedra with the endochrome diffused throughout the frond; at b the endochrome is beginning to gather itself into a distinct mass; at c it has divided, and a portion is attached to each of the frustules, and a division into definite masses is commencing; at d this division is complete, the masses forming lenticular bodies; at e they have moved into pairs, so that their convex surfaces are in contact; in the next stage (f) each pair has united and formed an elliptical spore; at g the frustule has been ruptured, and the spores are escaping. The escaped spores were evidently held together by a hyaline substance, and exhibited the peculiar motion termed swarming; h, i, j, show different stages of growth of the young Synedræ, until, at k, a perfect siliceous deposit has been formed, and the young Diatom is ready to recommence the whole process so soon as its endochrome is sufficiently mature.
Volvocineæ.
1. Protococcus viridis, M. Dic., 3.
{{{1}}}„ vulgare.
2. Hæmatococcus sanguineus.
{{{1}}}„ binalis.
{{{1}}}„ murorum, H., lxxxi.
3. Volvox globator, M. Dic., 3.
4. Pandorina murorum, M. Dic, 45.
Hæmatococcus.—I have had a colony of this protophyte in my possession for two years. I first discovered it in a jar which happened to be standing in the rain and was half filled with water. By keeping water continually in the jar the supply of Hamatococcus has never failed. Mr. Hamilton, of Petane, also brought me a sample in the wool of a sheep.[2]
EXPLANATION OF PLATE XXIII.
| Fig. | 1. | Chætophora, showing stipitate fructification; (a) filament, (b) antheridial filament, (c) zoospore. |
| {{{1}}}„ | 2. | Cladophora (a) ordinary cells. (b) sporiferous cells. |
| {{{1}}}„ | 3. | {{{1}}}„ (a) portion of filament. (b) antheridial filament. (c) zoospores. |
| {{{1}}}„ | 4. | Spirogyra. |
| {{{1}}}„ | 5. | Oscillatoria with sporidial cells. |
| {{{1}}}„ | 6. | Micrasterias ampullacea, var. β. |
| {{{1}}}„ | 7. | Cosmarium, sp.? |
| {{{1}}}„ | 8. | Staurastrum, sp.? |
| {{{1}}}„ | 9. | Pediastrum pertusum. |
| {{{1}}}„ | 10. | {{{1}}}„ sp.? (a) front. (b) end. |
| {{{1}}}„ | 11. | Scenedesmus quadricauda. |
| {{{1}}}„ | 12. | Synedra ulna—to illustrate sporidial multiplication. |