Objects for the microscope; a popular description of the most instructive and beautiful subjects for exhibition or examination

Front matter

field

wweth institute.

Ci-ub library.

Chapter I

Shapes of Cells — Cell-contents — Oil Cells — Hairs of Plants — Cuticle and Stomata — Cuticle of Yucca, of Aloe, of Deutzia Scabra, of Amaryllis, of Ind'an Corn, of Saccalobium, ofElseagnus, of Tillandsia, of Onosma, of Opuntia ... .. 9

Rawhides. — Cuticle of Hyacinth — Raphides from Rhubarb — Anagallis — Spiral fibre — Spiral Cells of raOucidium — Spiral Vessels of Collomia — Spiral Cells of Balsam —Spiral Cells of Sphagnum - Scalar iform Vessels 19

Pollen — Pollen of Mallow, of Hollyhock, of Passion-flower, of (Enothera — A few words more on the Pollen — Pollen-tubes —Stamens ... ... ... ... ... ... ... 23

Seeds. — Poppy — Sweet-William — Silene, or Stellaria — Orchis —

Eccreraocarpus or Calampelis ... ... ... ... ... 28

Chapter II. Sections Of Wood

Ruscus — Whanghae Cane— Asparagus — Section of Hazel, of Pine, of Yew — Cedar of Lebanon — Vegetable Ivory — Fossil Coniferous Wood — Pine Wood — Section of Cocoa-nut, of Cob-nut, of Snake-wood ... ... — ... ... ... ... 29

Moss. — Slides of Dicranum, Funaria, Etc., Etc. — Spore-cases of Fern — Slaters of Equisetum — Elaters of Jungermannia — Jungermannia Bidentata . ... ... ... ... ... ... 32

Fungi. — Slide of Puccinia, or Phragmidium — Blight of Wheat

(Smut)— Uredo Foetida, or Bunt — Uredo, or iEcidium ... 39 iv

CONTENTS.

Chapter III. Infusorial Earths

PAGE

Diatoms of Guano — Naviculae— Navicula Hippocampa -Pleuro sigma — Meloseira — Meloseira Borreri — Achnanthes Longipes,

— Synedra Ulna — Bacillariae — Goraphonema — Licmophora — Rhabdonema — Grammatophora Marina — Biddulphia — Amphitetras — Isthmia Obliqua — Arachnoidiscus — Heliopelta — Actinocyclus — Asteromphalus Astetolampra — Coscinodiscus 42

Desmidiacece. — Volvox Globator — Closterium — Confervae — Zyg-

PAET II.

OBJECTS FROM THE ANIMAL KINGDOM.

Chapter I. Objects From The Arachnida

Spider’s Foot — Spider’s Legs — Spider’s Spinnarets — Spider’s

Eyes — Spider’s Jaws — Spider’s Palpi — Epidermis of Spider 57

Chapter II. Insect Parts

Tongues of Insects — Tongue or Proboscis of Hive Bee— Tongue of Wasp — Butterfly’s Tongue or Proboscis — Proboscis or Tongue of Blow-flv — Proboscis of Tabanus, of Gnat, of Empis-fly, of Dioctria — Head of Conops, of Rhingia, or Syrphus, of Drone-fly, or Heliophilus, of Eristalis, of Tipula, of Limnobia, of Hemerobious, of Panorpa— Tongue of Cricket — Gizzard of Cricket — Mouth of Soldier-beetle, Calathus Castelloides, of Brachinus, of Onthophagus, of Anchomenus, of Crioceris, of Ladybird, of Stenopterus Rufus .. ... ... 64

Antennae. — Antennae of Cockchafer, of Nitidularia. of Hydrophilus, of Elater, of Syrphus, of Blow-fly, of Bee, of Ichneumon, of Argynnis — Palpi of Argynnis — Antennae of Dragon-fly, of Silkworm-moth ... 79

Spirccdes and Tracheae. — Spiracles of Dytiscus — Traheae of Dytiscus- -Spiracles of Cockchafer, of Fly, of Tipula, of Water Larvae — Aerating Leaflet of Libellula — Abdomen of Ephemera, or Spiracles ... ... ... ... ... ... 83

CONTENTS.

V

PAGE

Spiracles of Larva of Bot-fly... .. .. ... ... ... 86

Wings of Insects. — Wing of Scatophaga, of House-fly, of Blue-bottle-fly, of Syrphus, of Midge, of Gnat, of Beetle, of Cricket 86

Scales of Insects . — Scales of Morpho Menelaus, of Polyommatus Argus, of Hipparcliia Janira, of Pontia Brasscia, of Silkworm-moth, of Clothes- moth, of Podura, of Lepisma Saccharina ... 91

Elytra of Diamond Beetle ... . .. ... ... .. ... 94

Feet of Insects. —Foot of Syrphus — Leg of Dytiscus, or Dyticus — Foot of Wasp, of Ophion, Leg of Bee, of Gyrinus, of Brachinus, of Anchomenus, of Calathus Castelloides — Sting of Wasp and Bee, of Gnat, of Tabanus .. ... . .. 94

Egg of Bot-fly, or (Estrus . 98

Chapter III. Insects Mounted Whole

The Telephorus, or Soldier-beetle — Helphorus Granularis -

Catheretes Urticse — Coccinella, or Lady-bird 100

Hemiptera. — Yelia Rivulorum — Notonecta, or the Water Boatman — Reduvius, or Bed-bug— -Cimex, or Field-bug — Aphis — Aphrophora, or Cuckoo-spit — Thrips ... 106

Hymenoptera. — Tenthredo, or Saw-fly — Cypheus Pygmseus — Ihcneumon-fiy — Microgaster Glomeratus— Aphidius l Avenge — Ephedrus Plagiator— Ceraphron Carpenterii — Chelymorpha Phyllophora, or the Turtle-shaped Leaf-bearer 110

Chapter IV. Diptera

Culex Pipiens ... ... 120

Scatophaga — The family of the Brachycera— the Scatophaga — Lonchoptera — Bibeo — Dolichopus — The Opomyza — Chlorops — Phoro — Leptis — Asilus — Empis Empis Stercorea — Hilara— Syrphus Pyrastri— Borborus Equinus — - Sepedon— Sepsis ... ... ]25

The Halteres . Poisers , of Diptera. — Halteres of Blow-fly— Halteres of Tabanus ... ... ... ... ... 140

VI

CONTENTS.

Chapter V. Parasites

PAGE

The Flea. — The Pygidium of a Flea .. ... ... .. ... 144

The Acari , or Tics, Mites.— Acarus Domesticus, or Common Cheese-mites — Acarus Passularum — Acarus Passerinus — Ixodes, or Dog-tick — Melophagus — Stenopteryx — Ornithomyia — Nycteribia — Chlifer — Acarus Gamasus — Trombidium Phalangii —Trombidium Autumnale— Water-mites — Entozoa 147

Chapter VII. Palates

Palate of Helix Pomatia —Helix Aspersa — Limax — Helix Hortensis — Helix Nemoralis — Helix Rufescens — Helix Vigata — Zonites, or Helix Nitida — Palate of Whelk, of Purpurea, of Nasa, of Trochus Ziziphinus, of Trochus Crassus, of Trochus Umbilicatus, of Periwinkle, of Haliotis, or Aumer, of Pleurobranch, of Aplysia, of Doris, of Limpet, of Chiton, of Yellow Nerite, of Neritina Fluviatilis, of Lymneus Stagnalis, of Planorbis Cornea, of Paludina, of Cyclastoma ... 158

Chapter VIII. Slides Of Zoophytes

Anthoza. — Sertularia Pumila — Sertularia Polyzonias — Sertularia Operculata — Sertularia Rosacea — Laomedea Geniculata — Laomedea Dichotoma — Plumularia Cristata — Plumularia Falcata ... ... ... ... ... .. ... .. 167

Polyzoa. — Gemicellaria — Gemmellaria Loriculata — Gemecelaria, or Notomia Bursana — Cellularia Avicularia — Flustra Truncata — Pustulipora Fpssil — Flustra Chartaceae — Cellularia Reptans — Cellularia Ciliata — Crisea Eburnea — Crisea Cornuta — Serialaria Lendigera — Fresh- water Zoophytes ... ... 171

CONTENTS.

VU

Chapter IX. Sea-weeds — Marine Alg.e

PAGE

Marine Algae— Callithamnion — Ceramium — Ptilota Plumosa — Plocamium Vulgare, Coccineum — Polysiphonia — Spheiococcus — Griffithsia — Gracillaria — Laurentia — Odonthalia— Bonnemaisonnia — Delesseria — Rhodomela — Spyridia Filame n tosa — Chaetospora Wiggii — Haly menia — Da sy a — Dasy a Arbuscula — Dasya Occellata — Dasya Venusta — Goadby’s Solution for Marine Algae ... ... ... ... ••• 181

Chapter XIV. Spicules Of Holothurle

Spicules of Synapta — Spicules of Chirodota — Calcareous Spicules of Doris— Calcareous Skeleton of Doris — Spicules of Gorgonia — Spicules of Alcynonium Digitatum— Section of Echinus Spine ... 208 viii

CONTENTS,

OBJECTS FOR POLARISCOPE.

PAGE

Polarized Light — Selenite — Rhinoceros Horn — Whalebone — Elytra of Dytiscus — Cuticle of Deutzia Leaf — Section of Quartz — List of Objects ... ... ... ... .. .. 212

Chapter XV. Anatomical Injected Preparations

Liver : Human, Rabbit, Pig, Monkey — Villi, Small Intestines of Man, of Monkey, of Pig. of Tog, of Cat, of Rabbit — Duodenum of Mouse — Lung : Human, Monkey, Bear, Puppy, Pig,

Cat, Sheep, Fowl, Goose, Turtle, Rattlesnake, Frog, Tortoise,

— Gill of Eel — Fin of Turtle — Stomach of Mouse— Skin — Palm of Hand — Foot of Cat- Skin of Toad — Ciliary Processes—Eye of Ox — Ear of Mouse— Toe of White Mouse — Kidney — Tongue: Human, Dog, Cat, Mouse — Brain: Human,

Chapter XVI. Slides Of Crystallization

Selenite — Acetate of Copper -Sulphate of Copper — Alum — Oxalurate of Ammonia — Murexide, or Purpurute of Ammonia — Hydrochlorate, or Muriate of Ammonia— Oxalate of Ammonia— Salt of Brucia — Iodo-disulphate of Quinine — Borax, or Bi-borate of Soda — Boracic Acid — Sulphate of Magnesia — Ammonio-Phosphates of Magnesia — Uric Acid, or Lithic Acid — Nitrate of Potash, or Nitre — Saltpetre — Salicine — Nitrate of Silver 224

ON THE USE OF THE MICROSCOPE.

Although a minute description of the construction of the microscope would be out of place in this small work, and involve more of the science of optics than could be understood without diagrams and much knowledge of the laws of light, yet it will be useful to give a few hints on the practical management of a newly-purchased instrument.

Assuming the student to be desirous of obtaining an efficient instrument at a moderate cost, he cannot do better than procure what is ordinarily* termed a student’s microscope, which may be obtained from £3 3s. to £5 5s.

It had long been a desiderata with microscopists to obtain the advantage of binocular vision with stereoscopic effect. Mr. F.

H. Wenham was the successful adapter of the stereoscopic principle to the microscope, which the following extract from ‘ Recreative Science,’ will clearly explain : —

The result is obtained by the introduction of a small, but very accurately formed, double reflecting prism, immediately above the object glass, so as to intercept half the rays of light which pass through it. Fig. 1 will explain the principle : — a is the body of an ordinary microscope ; at b a

Objects for the Microscope.

square hole is cut, through which the prism c is made to slide so far that its edge will just reach the central line of the objective, and should be made to draw back so as to clear the aperture altogether, when the tube a acts as a single microscope. When the prism is thrust in, it collects a portion of the rays, and reflects them to the opposite side of the tube, where an opening is made large enough to allow them to pass through, into the supplementary body, e, which in size corresponds to the main tube ; the remainder of the rays pass uninterruptedly up

Fig. 2 is an enlarged outline of the prism. Let e e be a ray of light having passed through the object glass, and entering the prism at right angles at the point f ; passing on, it is intercepted by the surface A b, which being inclined within the angle of total reflection, the ray is towards h, from which point it is again reflected in the direction required. If the prism be correctly made, and of the smallest size possible for admitting the pencil, the difference between the direct and reflected image is scarcely observable; a faulty prism can therefore be easily detected.

The adjustment for difference of distance between the eyes is effected by means of the draw tubes ; if they are at the utmost limit of proximity when close in, by drawing them out they can be made to suit every position of eyesight. This is very conveniently done by means of a rack and pinion movement, as shown in Fig. 3.

The opaque principle of illumination should be used in all cases where possible, as this gives to objects a more natural appearance. The effect upon looking through a binocular microscope for the first time is very striking; many peculiarities are instantly presented to the eye, which, the principal body.

Fig. 2.

Objects for the Microscope.

with a single body, would be observed with difficulty. The instrument figured is one of those exhibited by Messrs. Crouch at the Manchester Exhibition of Science and Art.

The advantage of the binocular is chiefly in the rest it gives the eyes, which have no unequal and unnatural strain.

The field of vision is extended, and objects are seen in relief, round, life-like, and distinct. The joints of insects are seen in a wonderful manner, the ball and socket joints and hinge joints, if well prepared, are now perfectly realised ; the hairs of plants and animals are seen in their true position ; suckers, especially those on the foot of Dvticus, present themselves in the erect attitude of life, and Diatoms

Objects for the Microscope .

mounted dry on a black disc exhibit their form and markings as if the more elaborate parabolic reflector was beneath. To testthis, obtain a slide of Heliopelta, or of Isthmia enervis, or of Arachnoidiscus, which will show the advantage of the binocular with a very moderate power.

Fossil foraminated Shells (Barbadoes).

Spicules of Gorgonia.

Section of Rush.

Capsules of Moss.

Any of these will answer the same purpose.

Whilst adding a few thoughts to this introductory chapter, let me answer one or two questions not unfrequently put to me.

How much does this microscope magnify ?

That is, a small binocular with simple eye-piece, and three object glasses of two-inch, one-inch, and half-inch focus. The scale of magnifying power varies with different makers ; but if I give my own microscope as an example, it will help to make others understood.

The two-inch object glass, which has an angular aperture of 15°, will magnify twenty-five diameters, or 400 times superficial measurement.

The one-inch object glass has usually about 33° angular aperture, magnifies fifty to sixty diameters, or 960 times superficial measurement.

The half-inch object glass has an angular aperture of 60° or 65°, and consequently magnifies 120 diameters, or 1,920 times superficial measurement.

Again I am asked, What is the angle of aperture ?

This cannot here be explained beyond the brief statement, that it is the angle made by two lines from' opposite sides of the aperture of the object glass with the point of the focus of the lens. A diagram is necessary to make this quite clear.

The two-inch object glass requires a certain distance, as at a, to bring the object under examination into distinctness or focus.

The inch, half-inch, quarter-inch glasses, require nearer and nearer approach to the object for the same purpose.

Objects for the Microscope.

The angles so made by the dotted lines are measured by a graduated semicircle of 180°, under peculiar management of light well known by opticians, but beyond our present enquiry ; and denote the number of extreme lateral rays which the object glass admits.

The larger the angle the greater is the number of rays admitted, and the more brilliantly the object is illuminated the greater, consequently, is the defining power. Experiment has shown that obliquity of light is needful for the perception of the most delicate markings, and that an outline visible with an object glass of small angular aperture admitting but few oblique rays, as in Fig. 1, would be tilled up with lines of beauty, and striae of inconceivable delicacy under an object glass of large aperture, as Fig. 3, which gives it an oblique illumination.

The markings on butterfly scales and the valves of Diatomacee will illustrate this.

Again, it is asked, What is that particular fault which object glasses by inferior makers are liable to, called spherical aberration ? It is when objects at the circumference of the field are not in focus at the same time as those in the centre, or when part of a single object fades a wav towards the circumference.

Another fault is chromatic aberration, when coloured fringes surround the object under examination, whereas an achromatic lens shows a clear colourless field and a purely bright object.

Objects for the Microscope.

Defining power, not the magnifying power, is the thing to care for ; we want to see the real structure of an object, not an exaggerated representation ; and those are the best glasses which transmit clear light, give a perfectly flat field, and by which we see sharp distinct lines in the object we are investigating.

I will but add a few practical hints on the management of the microscope : —

Do not imagine that an expensive apparatus is necessary. The greatest discoveries have been made with the simplest instruments.

Have good object glasses, and do not waste money on an elaborate stage.

Use low powers in preference to high ones, unless absolutely necessary ; and, remember, we do not want objects magnified so much as we want them defined. A clearlydefining low power is the best working glass.

A few simple tools will be sufficient for all purposes of dissection and examination, viz. —

Slides of glass.

Circles and squares of thin glass.

A pair of forceps.

A lancet.

A few needles, fixed in handles. Split one end of a match, and tie the needle in with some waxed silk.

Two or three camel-hair pencils.

Six watch glasses.

These are all that are absolutely necessary for daily study.

FOR MOUNTING OBJECTS.

This need not be a difficult or expensive process ; but to succeed with insect preparations time and experience are essential. The easiest beginning is with vegetable specimens— cuticles, pollen, &c. — and with palates which are mounted in fluid.

You must have a turn-table, price 6s. to 8s., and make a cell on each glass slide you mean to use, with gold size or Brunswick black. It is better to see this done than to

Objects for the Microscope.

read the best description of “how to do it.” A small bottle of gold size or Brunswick black costs 6d.

Make a solution of salt and water ; be careful that it is very clean, and better use distilled or filtered water — five grains of salt to one ounce of water. This is the best preservative for palates.

Pure glycerine— a small bottle, Is. This is excellent for leaves of moss and cuticles ; but they also mount very well and more easily in Mr. Topping’s liquid : one part of acetate of alumina to four parts of distilled water.

Let your cells be quite dry ; it is better to make a dozen or more at once and keep them by you. When required, fix the slide upon the turn-table, put a drop of the liquid in the cell with a camel-hair pencil, then lay the object in it. Have a thin glass cover ready, and let it gently fall over the cell. Remove the superfluous moisture with a little sponge or blotting paper ; and then, with a steady hand, take a brushful of Brunswick black, make the revolving table run round quickly, and, touching the edge of the cell, a circle of the varnish will safely fix it. Let the varnish be thin, and the circle also ; for it dries better, and there is less danger of its running into the cell-contents. The next day go over it again, making the circle thicker and wider.

FOR MOUNTING IN BALSAM.

Have a bottle of clear, pure Canada balsam — it costs Is.

A little spirit of turpentine, 3d.

Spirits of wine, one ounce, Is.

A brass table, or tripod.

A spirit lamp.

Solution of caustic potash.

The use of balsam in preparing insect parts is not only to preserve, but to show the structure of the object. When properly applied, it enters into the minutest parts, displacing the air, and rendering the external tegument — hairs, spines, or suckers — perfectly transparent.

For instance, many young students, anxious to see the leg of a fly, or of a beetle, clip it off, and put it under the

Objects for the ./I ficroscope.

microscope. They are somewhat disappointed at seeing indistinctly a row of black joints, and nothing more.

Let that leg be first soaked for a few days in a little potash and water, to soften it and dissolve the internal substance ; then washed in clean water and dried ; then soaked for a few minutes in turpentine, and finally mounted in balsam ; every joint will be clear, every hair visible, the pulvillus transparent, and the structure admirably displayed.

The same results are obtained with the eyes, tongues, and wings of all insects.

The actual mounting is a matter of experience : to keep out air-bubbles is the great and only difficulty.

Place a slide on the brass table, over the spirit lamp, and when heated moderately put a drop of balsam in the centre of it ; let this also become warm, but not very hot, and then lay the prepared object in it. As bubbles arise, skim them off with a needle, and take care that the balsam does not boil, or your specimen is lost ; — it will be full of obstinate air-bubbles, irrevocably fixed in the tissue. When it looks clear, examine under the microscope, and if all right replace it on the table, and having previously warmed a thin glass cover, let it drop gently over the object.

Dry it on the mantelpiece, or a stone slab, and then clean the slide by scraping off the balsam and washing it with a little turpentine ; or soda and water will clean it nicely ; only if it is left in the solution it will unsettle the balsam.

Try experiments for yourself, and do not be discouraged by a great many failures ; neither be satisfied with bad mounting, half-prepared objects, and untidy slides.

PAET I.

OBJECTS FROM THE VEGETABLE KINGDOM.

ie Search out the wisdom of Nature, — there is depth in all her doings.

She hath on a mighty scale a general use for all things ;

Yet hath she specially for each its microscopic purpose.

There is use in the prisoned air that swelleth the pods of the laburnum, Design in the venomed thorns that sentinel the leaves of a nettle,

A final cause for the aromatic gum that congealeth the moss around a rose,

A reason for each blade of grass that raiseth its small spine.”

Proverbial Philosophy.

" On every herb on which you tread Are written words which, rightly read,

Will lead you from earth’s fragrant sod

To hope and holiness and God.” Anon.

Chapter I

In every collection of objects for the microscope we find many preparations from the vegetable world — slides of cuticles, fibro-cells, pollen-grains, raphides, &c. &c. ; and few lose more in being hastily looked at, as merely pretty objects, without that knowledge of flower-life which alone can enable us rightly to appreciate them.

If we are wholly ignorant of the structure of plants, their uses, their variety, and the secret mechanism by which their life is renewed day by day, we are apt to look at these slides for mere amusement, for the lust of the eye, pleased as a child or as a savage with, strange forms or brilliant colours. Therefore, before we take them up, it will not be UiiDrofitable to learn if we do not know, and refresh our memory if we have once known, something of the mysteries of creation in vegetable life.

Objects for the Microscope .

Thousands of years have passed away since angel voices sang the praises of God when He had finished the fair work of creation, and — looking upon the lowliest herb of the field as upon the birds of the air, the living creatures of the deep, wide sea, the beasts of the earth, and man, the lord of all — “ behold it was very good.” Thousands of years have passed away : man has changed, it may be that the lower creatures have partaken of his fall ; but of the beautiful flowers and the stately trees we have no reason to believe that there is aught in them that offends their Maker; we fearlessly search into the recesses of their being, and behold they are wondrously beautiful and still “ very good.”

A flower-plant has been likened by Unger,* a German botanist, to “ a most skilfully-planned chemical laboratory, a most ingenious mechanism for the display of physical forces, and one of the simplest, and consequently one of the most sublime, structures ever designed or executed.”

He also likens the growth of a plant to the building of a glorious edifice ; he compares the cells of vegetable life, in their varied forms and sizes, to the stones of a building forming a kind of masonry. In some parts of a plant the cells are long, and form pipes or cylinders, or they are condensed and thickened into fibre. In the cuticle of leaf and flower we have flattened, oblong, or crenellated cells, which, as a tesselated pavement, protect the more delicate machinery within.

We find, by the help of a microscope, not only this, but also the store chambers of cell-contents where the materials for the plant edifice are collected and preserved.

Again, in the building of a plant there are air-passages resembling regularly-shaped rooms, or romantic caves, or microscopic grottos, terminating in what are called stomata; which stomata have folding doors or valves to open or shut at pleasure, so that the air circulates freely through the plant organism. These are mostly on the under side of a leaf, so the under cuticle is the one we mount for observa-

* ‘Unger’s Letters.*

Objects for the Microscope.

tion, and we shall notice these stomata more particularly when the slides are described.

The origin of every plant is a single cell. The perfection of a plant, from the tiniest moss to the loftiest oak, is in a countless multitude of simple cells containing various substances needful for its growth, and of an infinite variety of shape and substance : for some cells are very thick ; some are dotted, to allow of the circulation of air in the deep recesses of the stem ; some have variegated walls produced by its secondary deposits, like fibre coiled around, and these Jibro-cells are abundant in some plants. We have them from the Oncidium and Opuntia. Some cells of spiral fibre act as trachea for breathing organs, or give lightness and elasticity to a stem. They are abundant in strawberry leaves, vine leaves, rhubarb stems, spinach, and there are beautiful examples in the slide of spiral cells from the balsam. Much more can be learnt from the examination of the fresh plant, because of the difficulty of preserving cells and their contents. Is it not wonderful to think of a little plant having its store chambers secreting starch, sugar, gum, oils, raphides, colouring matter— aye, and beautiful crystals floating in the cell-fluid, or suspended, as are the cystolithes, in the cell-chambers of the nettle tribe ?

The very knowledge that such things are, and that they may be seen in an infinite variety, will lead us first to look at these slides understandingly, then to seek further by examination of living plants. This will induce us to study such books as Quekett’s ‘ Histiology,’ ‘ Carpenter on the Microscope,’ ‘Mohl on the Vegetable Cell,’ ‘ Schacht on the Microscope,’ ‘Unger’s Letters,’ &c. &c. Then we shall see our microscope worthily, and our cabinet of objects will cease to be a mere toy.

SHAPES OF CELLS.

As the object of this little book is to excite and not to satisfy the desire of an inquiring mind, let me here suggest that it is well to prove all things ; and before you quite believe that every flower and plant is made up of single cells of varied form, examm^ for yourself thus : — Take a

Objects for the Microscope.

flower, a few bits of stalk, a lily leaf, or small piece of rhubarb stalk, another of cucumber, a thin slice of raw potato, a wallflower, or a primrose — any flower : macerate it in water for a day or two, until it begins to decompose, and the smallest portion placed under the microscope with a drop of water will show you the now separating cells of various shape : those in stalks oblong or cylindrical ; those in the surface of petals and leaves square, or round, or hexagonal, or irregular, with zigzag boundaries, or papilliform, as in the Geranium, Sweetwilliam, &c. ; those of the parenchyma or pulp of the leaf generally oval. In looking at these, you will certainly find a variety of contents which are seldom preserved for any length of time, and which you must therefore observe in the fresh and living plant.

CELL-CONTENTS.

In the slice of potato you will find every cell crowded with starch-granules, that is, if it is a good potato ; for starch is to the potato what fat is to an animal, and if it is in “ good condition ” the cells should be full of it. The test of this is a drop of tincture of iodine, which turns the starch-granules to a beautiful blue or violet colour ; and a diseased potato with empty cells will therefore be detected by a drop of that same iodine.

In the stem of a lily you will find starch-grains, mixed with green granules of chlorophylle, a kind of vegetable wax, which gives the green colour to leaves.

All our farinaceous plants contain abundance of starch, especially wheat, barley, oats, maize, rice, arrow-root ; and the granules differ from each other in size and form so decidedly, that they cannot well be mistaken by a careful observer. They are prepared for the microscope, and sold as polariscope objects, because the examination of a starch granule with polarized light shows it with a beautiful black cross, revolving with the polarizer ; or, if over a selenite stage, a brilliant play of colours is obtained.

Besides starch-grains and chlorophylle, you will find something else in the cells of that lily stem, which I select as an easy one to obtain in any garden. In some cells, not

Objects for the Microscope.

in all, you will probably observe a larger granule, with a lesser one within, or perhaps several lesser ones ; the large granule is the nucleus, the minute inner ones the nucleoli ; they are the supposed origin of new cells, and much that is exceedingly interesting has been written in the works before referred to : ‘Mohl on the Vegetable Cell ; ’ ‘ Hofmeister’s Die Enstehung des Embryo.’ These nuclei are to be observed in pollen-grains, in the hairs of Tradescantise, or Spiderwort, especially in the pollen of the fir-tree tribe.

OIL CELLS.

Cells containing oil are beautiful objects when found as on rose-trees, on the stem of Saxifrage, Geraniums, Collomia, Drasena, raised upon delicate stalks, often brightly coloured, or glittering diamond-like in the sunshine.* Sometimes the oil cells are sessile, in golden spots upon the back of a black-currant leaf ; or white and silvery in the recesses of a Sage leaf, a leaf of Rue, or Hop, or Mulberry.