The microscope : being a popular description of the most instructive and beautiful subjects for exhibition

Front matter

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Preface

iv

That these works are not read attentively or well understood by many young persons, who now purchase Microscopes and collect objects, seems probable from the remarks which are made and the questions that are asked when looking at preparations from the Vegetable and the Animal Kingdom. We not unfrequently hear the section of an Echinus spine pronounced 1 4 very pretty, exactly like a crochet pattern” — the Echinus itself being an unknown thing. Spicules of Holothuria or Gorgonia are brilliant little clubs and crosses ; but what a Holothuria is they cannot imagine. The foot of a Dytiscus, with its cluster of suckers, is like the eye of a peacock’s feather ; cells of spiral fibre nothing more than coils of variegated wire ; and the head of Ehingia, with its wonderful eyes, is looked at as a beautiful piece of network. It is the design of this Catalogue to give simply that elementary knowledge of vegetable and animal physiology, which will enable the young student to understand the Slides in the Object-box, and excite the desire to learn more from better books.

It is also hoped that many will be led to purchase the preparations of Whole-mounted Insects , and by the careful study of them take the first steps into the wide and pleasant field of Natural History. As the ear is educated by the study of music, so the eye is educated by a habit of observation. An artist’s eye catches the faintest tint of colour, observes the minutest curve in an outline ; a physician’s eye scans quickly, and reads deeply the confused or obscure diagnosis of disease, unperceived by others, and every line in the patient’s face or movement of the body is to him an index of the inner life ; the naturalist’s eye, quickened in all its powers by observation, sees the folding of a leaf, the spot upon the wall, the tract of an insect on his path, where the untrained eye sees

PREFACE.

VU nothing. The Microscope gives this training, if it is rightly used, that is, with intelligent enquiry, with careful reading on the various subjects, as they are suggested by mounted objects,* and observation of the living creatures in this beautiful world around ns.

None but those who have enjoyed it can tell how refreshing and uplifting to the spirit is an hour at the Microscope — an hour of thoughtful reverent study of the wisdom, power and love of God in creation. Science, when it is merely u la grande curiosite,” or when pursued for selfish pleasure and ambition, is not the end for which the Microscope was given to us. There must be a link with the unseen and the eternal, a light from the true wisdom, if our ways are to be ways of pleasantness, and our paths to end in peace.

Woodeaton Rectory,

* “ Kirby & Spence’s Entomology.”

“ Insecta Britannica.”

“Westwood’s Introduction to Entomology.” " Balfour’s Botany.”

“ Lindley’s Vegetable Kingdom.”

“ Unger’s Letters.”

“ Johnson on Zoophytes.”

“ Harvey on Seaweeds.”

Table Of Contents

PAGE

ON THE USE OF THE MICROSCOPE.

Directions for Mounting Objects 4

„ „ Mounting in Balsam 5

PAET I.

OBJECTS FROM THE VEGETABLE KINGDOM.

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— Indian Corn — Cuticle of Saccalobium, of Elaeagnus, of Tillandsia, of Onosma, of Opuntia 7

Raphides. — Cuticle of Hyacinth — Raphides from Rhubarb — Anagallis — Spiral fibre — Spiral Cells of Oncidium — Spiral Vessels of Collomia — Spiral Cells of Balsam — Spiral Cells of Sphagnum — Scalariform Vessels 16

Pollen. — Pollen of Mallow, of Hollyhock, of Passion-flower, of (Enothera — A Few Words more on the Pollen— Pollen- tubes — Stamens 20

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

Eccremocarpus or Calampelis 24

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 26

Moss. — Slides of Dicranum, Funaria, &c., &c. — Spore-cases of Fern — Elaters of Equisetum — Elaters of Jungermannia — Jungermannia Bidentata 29

Vlll

Contents

r.\OE

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

(Smut) — Uredo Foetida, or Bunt — Uredo, or iEcidium SG

Chapter III. Infusorial Earths

Diatoms of Guano — Naviculse — Navicula Hippocampa — Pleurosigma — Meloseira — Meloseira Borreri — Achnanthes Longipes— Synedra Ulna — Bacillarise — Gomphonema — Licmophora — Rhabdonema — Grammatophora Marina — Biddulphia — Am* phite tras — Is thmia Obliqua — Arachnoidiscus — Heliopelta — . Actinocyclus — Asteromphalus Asterolampra — Coscinodiscus 39

Desmidiacece • — Volvox Globator — Closterium — Confervse — Zyg-

nema — Achyla Prolifera 4 G

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 53

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-fly — Proboscis of Tabanus, of Gnat, of Empis-fly, of Dioctria — Head of Conops, of Rhingia, or Syrphus, of Drone-fly, or Helophilus, of Eristalis, of Tipula, of Limnobia, of Hemerobius, 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 GO

Antennae. — Antennae of Cockchafer, of Nitidularia, of Hydrophilus, of Elater, of Syrphus or of Blow-fly, ‘of Bee, of Ichneumon, of Argynnis — Palpi of Argynnis— Antennae of Dragon-fly, of Silkworm- moth 75

CONTENTS.

IX

PAGK

Spiracles and Tracheae . — Spiracles of Dytiscus — Tracheae of Dytiscus — Spiracles of Cockchafer, of Fly, of Tipula, of Water Larvae — Aerating Leaflet of Libeflula — Abdomen of Ephemera, or Spiracles * 79

Circulation of Blood 81

Spiracles of Larvae of Bat-fly 81

Wings of Insects . — Wing of Scatophaga, of House-fly, of Blue-bottle-fly, of Syrphus, of Midge, of Gnat, of Coleoptera, of Cricket . 83

Scales of Insects. — Scales of Morpho Menelaus, of Polyommatus Argus, of Hipparchia Janira, of Pontia Brassica, of Silkwormmoth, of Clothes-moth, of Podura, of Lepisma Saccharina ... 88

Elytra of Diamond Beetle 91

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 91

Egg of Bot-fly, or (Estrus 95

Chapter III. Insects Mounted Whole

The Telephorus, or Soldier-beetle — Melophorus Granularis —

Catheretes Urticse — Coccinella, or Lady-bird ... 97

Hemiptera. — Velia Rivulorum — Notonecta, or the Water Boatman — Reduvius or Bed-bug — Cimex, or Field-bug — Aphis —

A phrophora, or Cuckoo-spit — Thrips 106

Hymenoptera. — Tenthredo, or Saw-fly — Cypheus Pygmaeus — Tchneum on-fly — Microgaster Glomeratus — Aphidius Avense — Ephedrus Plagiator — Ceraphron C’arpenterii — Chelymorpha Phyllophora, or the Turtle-shaped Leaf-bearer Ill

Chapter IV. Diptera

Ptychoptera 121

Scatophaga. — The Family of the Brachycera — The Scatophaga — Lonchoptera — Bibeo — Dolichopus — The Opomyza — Chlorops — Phora — Leptis — Asilus — Empis — Empis Stercorea— Hilara — Syrphus Pyrastri — Borborus Equinus — Sepedon — Sepsis... 122

X

CONTENTS.

PAGE

The Halteres, Poisers, of Dipter a. — Halteres of Blow-fly — Halteres

ofTabanus 138

Chapter V. Parasites

The Flea. — The Pygidium of a Flea 141

Pediculus, or Louse 143

The Acari, or Ticks, Mites. — Acarus Domesticus, or Common Chese-mites — Acarus Passularum — Acarus Passerinus — Ixodes, or Dog-tick — Melophagus — Stenopteryx — Ornithomyia — Nycteribia — Chelifer — Acarus Gamasus — Trombidium Phalangii — Trombidium Autumnale — Water-mites— Entozoa 104

Chapter VI. Palates

Palate of Helix Pomatia — Helix Aspersa — Limax — Helix Hortensis —Helix Nemoralis — Helix Rufescens — Helix Virgata —

— Zonites, or Helix Nitida — Palate of Whelk, of Purpurea, of Nasa, of Trochus Ziziphinus, of Trochus Crassus, of Trochus Umbilicatus, of Periwinkle, of Haliotes, or Aumer of Pleurobranch, of Aplysia, of Doris, of Limpet, of Chiton, of Yellow Nerite, of Neritina Fluviatilis, of Lymneus Stagjnalis, of Planorbis Cornea, of Paludina, of Cyclastoma 149

Chapter VII. Slides Of Zoophytes

Sertularia Pumila' — Sertularia Polyzonias— Sertularia Operculata — Sertularia Rosacea — Laomedea Geniculata — Laomedea Dichotoma — Plumularia Cristata — Plumularia Falcata 158

Polyzoa. — Gemicellaria — Gemmellaria Loriculata — Gemecelaria, or Notomia Bursaria — Cellularia Avicularia — Flustra Truncata Pustulipora Fossil— Flustra Chartacese — Cellularia Reptans — Cellularia Ciliata — Crisea Eburnea — Crisea Cornuta — Serialaria Tendigera 163

Chapter VIII. Sea-weeds— Marine Alga2

Marine Algae — Callithamnion — Ceramium — Ptilota Plumosa — Plocamium Yulgare, or Coccineum — Polysiphonia— Spherococcus — Griffithsia — Gracillaria — Lauren tia — Odonthalia — Bonnemaisonnia — Delesseria — Rhodomela — Spyridia Filamentosa — Chaetospori Wiggii — Halymenia — Dasya — Dasya Arbuscula — Dasya Occellata — Dasya Venusta — Goadby’s Solution for Marine Algae 168

CONTENTS.

XI

PAGE

Chapter XIV. Slides Of Crystallization

Selenite — Acetate of Copper — Sulphate of Copper— Alum — Oxalurate of Ammonia — Purpurate or Murexide of Ammonia — Hydrochlorate or Muriate of Ammonia — Oxalate of Ammonia— Salt of Brucia — Iododi-sulphate of Quinine — Borax, or Borate of Soda — Boracic Acid — Sulphate of Magnesia — Ammonio-Phosphate of Magnesia — Uric Acid, or Lithic Acid — Nitrate of Potash, or Nitre, Saltpetre — Salicine — Nitrate of Silver 202

A DESCRIPTIVE CATALOGUE

OF THE

MOST INSTRUCTIVE AND BEAUTIFUL OBJECTS

FOR

THE MICROSCOPE.

“ The microscope is an optical instrument by means of which we are enabled to see objects or parts of objects too minute to be seen with the naked eye ; the name being taken from two Greek words, fwcpdv (mikron), a little thing , and aKoirtco (skopeo), I look at.1’ — Lardner.

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 one of those called 4 * The Society of Arts Microscopes.” They are made by Mr. Baker, 244, High Holbom,* and only cost £3 3s., complete in a neat mahogany cabinet. They are excellent working instruments, and for their utility and cheapness combined were

* Mr. Baker, who has devoted a great deal of attention to the improvement of philosophical instruments for educational purposes, also supplies a portable microscope for only 9s., which is very useful for botanical investigations. He makes several other patterns, varying in price up to £2 2s., which will exhibit Infusoria and other interesting objects.

ON THE USE OF awarded a prize medal by the Society from which they derive their name.

The microscope itself is illustrated in the accompanying engraving : it moves on the joints at a, so that the observer can incline it at any angle, to enable him to look through it with convenience. In a small brass box will be found the object glasses, attached to an adapter, which is to be screwed into the lower part of the body of the instrument at b. The object glasses are three in number, and when altogether their focus will be about a quarter of an inch ; that is to say, they will require to be about that distance from the object on the stage f. When the instrument is in use, by unscrewing the lower one e, the focus will be about half an inch, and by removing the next one d, the focus will be about one inch. The magnifying powers will be as under : —

The one combination only, 0, 1-in. focus, magnifies 6,400 times. The two ditto, C and D, $-in. ditto, ditto 16,900 „

The three ditto C,D, and E, J -in. ditto, ditto 122,500 „

THE MICROSCOPE.

Haying inclined the microscope at such an angle that you can look through it conveniently, screw on the adapter, and remove the two object glasses d and e ; next turn the mirror g about, so as to reflect the light up into the body of the instrument, and illuminate the field of view equally ; then place an object on the stage f, and by turning the milled heads h raise or depress the microscope, until the distance between the lower lens and the object on the stage is about one inch. Now look through the instrument, and turn the milled heads h backwards and forwards until the most distinct view of the object is obtained : by adding the other lenses d and e, the magnifying power is increased and the focus shortened, as already explained. The slow motion i is used for the accurate adjustment of the focus, when the high powers are employed ; it offers the advantage of much greater delicacy and exactness than is attainable by the use of the milled heads h.

Mr. Baker also supplies with these instruments a pair of forceps for dissecting, and another pair to attach to the stage for holding any minute substance for examination, the uses of which are too obvious to require any explanation.

The cabinet also contains a capillary cage, or live-box; a very useful piece of apparatus for examining aquatic objects, such as Infusoria, &c. To use it, the cover being removed, a drop of water containing the object is placed on the glass plate ; the cover is then slid on and pressed down until the fluid is spread out, between the two glasses, conveniently for observation.

In order to properly observe opaque objects, it will also be necessary to be furnished with a condenser, which is either fitted to the stage or as a separate stand, with the arm holding the lens adjustable to any position that is required: but it can only be used by the direct rays of the sun, lamp, or candle ; the ordinary daylight being too much diffused for that purpose.

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.

b 2

ON THE USE OF

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 clearly - defining 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 read the best description of “ how to do it.” A small bottle of gold size or Brunswick black costs 9 d.

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 MICROSCOPE.

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. Eemove 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 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

ON THE USE OF THE MICROSCOPE.

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 he satisfied with bad mounting, half-prepared objects, and untidy slides.

PART I.

OBJECTS FROM THE VEGETABLE KINGDOM.

“ 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.

a 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 micrqscope 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 unprofitable 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.

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

THE VEGETABLE KINGDOM.

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 u 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 crenolated cells, which, as a tesselated pavement, protect the more delicate machinery within.

We find, with 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 observation, 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

Unger’s Letters.

SHAPES OF CELLS.

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 a stem ; some have variegated Vails produced by its secondary deposits, like fibre coiled around, and these fibro-cells are abundant in some plants. We have them from the Oncidium and Opuntia. Some cells of spiral fibre act as trachea or 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 u Histology,” u Carpenter on the Microscope,” u Mohl on the Vegetable Cell,” u Schlacht on the Microscope,” “ Unger’s Letters,” &c., &c., &c. Then shall we use 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 enquiring 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, examine for yourself thus : — Take a 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

THE VEGETABLE KINGDOM.

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, Sweet-william, &c., &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 u 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 polariseope objects, because the examination of a starch granule with polarized light shews 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 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 ; ” “ Hafmeister’s Die Enstehung des Embryo.” These nuclei are to be observed in pollen -grains, in the hairs of Tradescantiae, or Spiderwort, especially in the pollen of the fir-tree tribe.

HAIRS OF PLANTS'.

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 Eue, or Hop, or Mulberry.

Sometimes these oil cells are internal, as in the rind of an orange, where they are very large and most easily observed; also, in the leaves of Myrtle and Magnolia, of Hypericum, St. John’s wort, so common in woods and hedges, those little dark dots are the oil cells, and transparent, if you hold the leaf up against the light, and examine it with a pocket lens.

HAIRS OF PLANTS.

The hairs of plants will furnish you with abundant material for study and delight throughout the summer long, and the variety in their form will astonish you. Look, also, at the beautiful bead-like hairs of the Spiderwort — a rich purple chain of cells fringing each stamen. White, transparent, glittering rows of cells from the flocculent mass of hairs we see on the leaves and stem of the common Groundsel. The common garden Yerbena has the mouth of its corolla closed by a dense row of beaded hairs protecting its pistil. I cannot describe more, but look at these. Some are simple ; some are branched, or star-like, or tufted, and contain simply water : —