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Make sure you visit Molecular Biology Protocols for all your research and molecular biology needs including bioinformatics and protocols.

Discuss and post questions on research on the Molecular Biology Forum. 

Research Areas Links

Apoptosis

Proteomics

Stem Cells

Cell Protocols 

Methods Protocols 

Molecular Biology Supplies Links

Custom Peptides

Custom Antibodies

SiRNA

RNAi 

Molecular Biology Techniques Links

DNA Microarrays

If you are conducting PCRs, there is no better place on the internet for PCR information see PCR Station.

Learn about Gel Electrophoresis and find protocols on gel electrophoresis of DNA, RNA and protein.

Western Blot

 Cell Transfection

Visit HPLC Station for all your HPLC high performance liquid chromatography.  

 Mass Spectrometry

For microscopy visit Microscopy Station.

For bioinformatics information and tools, visit Bioinformatics Info an amazing bioformatics site.

Visit Kill Bed Bugs for killing bed bugs information.

Also see Pest Control for pest control information.

A students guide to observing plants in the microscope.

A students guide to observing plants in the microscope.

Plants in the Microscope

WE will now suppose the young observer to have obtained a microscope, and learned the use of its various parts, and will proceed to work with it. As with one or two exceptions, which are only given for the purpose of further illustrating some curious structure, the whole of the objects figured in this work can be obtained without any difficulty, the best plan will be for the reader to procure the plants, insects, &c. From which the objects are taken, and follow the book with the microscope at hand. It is by far the best mode of obtaining a systematic knowledge of the matter, as the quantity of objects which can be placed under a microscope is so vast, that without some guide the tyro flounders hopelessly in the sea of unknown mysteries, and often becomes so bewildered that he gives up the study in despair of ever gaining any true knowledge of it. I would therefore recommend the reader to work out the subjects which are here mentioned, and then to launch out for himself in the voyage of discoveries. I speak from experience, having myself known the difficulties under which a young and inexperienced observer has to labour in so wide a field, without any guide to help him to set about his work in a systematic manner.

The objects that can be easiest obtained are those of a vegetable nature, as in every town there are squares, an old wall, a greenhouse, a florist's window, or even a green grocer's shop, that will not afford an exhaustless supply of microscopic employment. Even the humble vegetables that make their daily appearance on the dinner-table are highly interesting ; and in a crumb of potato, a morsel of greens, or a fragment of carrot, the enthusiastic observer will find occupation for many hours.

Following the best examples, we will commence at the beginning, and see how the vegetable structure is built up of tiny particles, technically called " cells."

That the various portions of every vegetable should be referred to the simple cell is a matter of some surprise to one who has had no opportunity of examining the vegetable structure, and indeed it does seem more than remarkable that the tough, coarse bark, the hard wood, the soft pith, the green leaves, the delicate flowers, the almost invisible hairs, and the pulpy fruit should all start from the same point, and owe their origin to the simple vegetable cell. This, however, is the case ; and by means of a few objects chosen from different portions of the vegetable kingdom, we shall obtain some definite idea of this curious phenomenon. On plate 1, fig. 1, may be seen three cells of a somewhat globular form, taken from the common strawberry. Any one wishing to examine these cells for himself may readily do so by cutting a very thin slice from the fruit, putting it on a slide, covering it with a piece of thin glass, which may be cheaply bought at the optician's, together with the glass slides on which the objects are laid, and placing it under a power of two hundred diameters. Should the slice be rather too thick, it may be placed in the live-box and well squeezed, when the cells will exhibit their forms very distinctly. In their primary form, the cells seem to be spherical ; but as in many cases they are pressed together, and in others are formed simply by the process of subdivision, the spherical form is not very often seen. The strawberry, being a soft and pulpy fruit, permits the cells to assume a tolerably regular form, and they consequently are more or less globular.

Where the cells are of nearly equal size, and are subjected to equal pressure in every direction, they force each other into twelve-sided figures, having the appearance under the microscope of flat six-sided forms. Fig. 8, taken from the stem of a lily, is a good example of this form of cell, and many others may be found in various familiar objects.

We must here pause for a moment to define a cell before we proceed farther.

The cell is a closed sac or bag formed of a substance called from its function " cellulose," and containing certain fluid contents as long as it retains its life. In the interior of the cell may generally be found a little dark spot, termed the "nucleus," and which may be seen in fig. 1, to which we have already referred. The object of the nucleus is rather a bone of contention among the learned, but the best authorities on this subject consider it to be the vital centre of the cells, to and from which tends the circulation of the contained fluid. In point of fact, the nucleus may be considered as the heart and brain of the cell. On looking a little closer at the nucleus, we shall find it marked with several small light spots, which are termed " nucMoli."

On the same plate (fig. 2) is a pretty group of cells taken from the internal layer of the buttercup leaf, and chosen because they exhibit the series of tiny and brilliant green dots to which the colour of the leaf is due. The technical name for this substance is " chlorophyll," or " leaf-green," and it may always be found thus dotted in the leaves of different plants, the dots being very variable in size, number, and arrangement.

In the centre of the same plate (fig. 12) is a group of cells from the pith of the elder-tree. This specimen is notable for the number of little " pits " which may be seen scattered across the walls of the cells, and which resemble holes when placed under the microscope. In order to test the truth of this appearance, the specimen was coloured blue by the action of iodine, when it was found that the blue tint spread over the pits together with the cell-walls, showing that the membrane is continuous over the pits.

Fig. 7 exhibits another form of cell, taken from the Sparganium, or bur-reed. These cells are tolerably equal in size, and have assumed a squared shape. They are obtained from the lower part of the leaf. The reader who has any knowledge of entomology will not fail to observe the similarity in form between the six-sided and square cells of plants and the hexagonal and squared facets of the compound eyes belonging to insects and crustaceans. In a future page these will be separately described.

Sometimes the cells take most singular and unexpected shapes, several examples of which will be briefly noticed.

In certain loosely made tissues, such as are found in the rushes and similar plants, the walls of the cells grow very irregularly, so that they push out a number of arms which meet each other in every direction, and assume the peculiar form which is termed "stellate," or star-shaped tissue. Fig. 3 shows a specimen of stellate tissue taken from the seed-coat of the privet, and rather deeply coloured, exhibiting strongly the beautiful manner in which the various arms of the stars meet each other. A smaller group of stellated cells may be seen in fig. 4, taken from the stem of a large Rush, and exemplifying the peculiarities of the structure.

The reader will at once see that this mode of formation leaves a vast number of interstices, and gives great strength with little expenditure of material. In waterplants, such as the reeds, this property is extremely valuable, as they must be greatly lighter than the water in which they live, and at the same time must be endued with considerable strength, in order to resist its pressure.

A less marked example of stellate tissue is given in fig. 11, where the cells are extremely irregular in their form, and do not coalesce throughout. This specimen is taken from the pithy part of a Bulrush. There are very many other plants from which the stellate cells may be obtained, among which the Orange affords very good examples in the so-called "white" that lies under the yellow rind, a section of which may be made with a very sharp knife, and laid under the field of the microscope.

Looking towards the bottom of the plate, and referring to fig. 27, the reader will observe a series of nine elongated cells, placed end to end, and dotted profusely with chlorophyll. These are obtained from the stalk of the .common chickweed. Another example of the elongated cell is seen in fig. 14, which is a magnified representation of the rootlets of wheat. Here the cells will be seen in their elongated state, set end to end, and each containing its nucleus. On the left hand of the rootlet (fig. 13) is a group of cells taken from the lowest part of the stem of a wheat plant which had been watered with a solution of carmine, and had taken up a considerable amount of the colouring substance. Many experiments on this subject were made by the Kev. Lord

S. G. Osborne, and may be seen at full length in the pages of the Microscopical Journal, the subject being too large to receive proper treatment in the very limited space which can here be given to it.

One very remarkable point is, that the carmine was always found to be taken most plentifully into the nucleoli, and to give them a very deep colouring. These specimens exhibited the phenomenon which has already been casually mentioned, that the rotation of the granules in the interior of the cell takes place to and from the nuclei.

Fig. 9 on the same plate exhibits two notable peculiarities the irregularity of the cells, and the copiously pitted deposit with which they are covered. The irregularity of the cells is mostly produced by the way in which the multiplication takes place, namely, by division of the original cell into two or more portions, so that each portion takes the shape which is assumed when a component part of the parent cell. In this case the cells are necessarily very irregular, and when they are compressed from all sides, they form solid figures of many sides, which, when cut through, present a flat surface marked with a variety of irregular outlines. This specimen is taken from the rind of a Gourd.

The "pitted" structure which is so well shown in this figure is caused by a layer of matter which is deposited in the cell and thickens its walls, and which is perforated with a number of very minute holes called "pits." This substance is called "secondary deposit." That these pits do not extend through the real cell wall has already been shown in fig. 12, p. 29.

This secondary deposit I pray the reader's pardon for using such language, but there is no alternative is exhibited in more modes than one. In some cases it is deposited in rings round the cell, and is clearly placed there for the purpose of strengthening the general structure. Such an example may be found in the Mistletoe, tig. 5, where the secondary deposit has formed itself into clear and bold rings, that evidently give considerable strength to the delicate walls which they support. Fig. 10 gives another good instance of a similar structure ; differing from the preceding specimen in being much longer and containing a greater number of rings. This object is taken from an anther of the Narcissus. Among the many plants from which similar objects may be obtained, the Yew is, perhaps, one of the most prolific, as ringed wood-cells are abundant in its formation, and probably aid greatly in giving to the wood the strength and elasticity which have long made it so valuable in the manufacture of bows.

Before taking leave of the cells and their remarkable forms, we will just notice one example which has been drawn in fig. 6. This is a congeries of cells, containing their nuclei, starting originally end to end, but swelling
and dividing at the top. This is a very young group of cells from the inner part of a Lilac bud, and is here introduced for the purpose of showing the great similarity of all vegetable cells in their earliest stages of existence. No one who did not know the history of chat little group could imagine what would be its perfected condition, for it might either spread itself into a leaf, or extend itself into a flower, or end its days as a hair, for all the indications that it affords of its future.

Having now examined the principal forms of cells, we arrive at the " ducts," a term which is applied to those long and delicate tubes which are formed of a number of cells set end to end, their walls of separation being absorbed. At first the young microscopist is apt to puzzle himself between ducts and vessels, but may easily set himself right by remembering that ducts are squared at their ends, and vessels or wood-cells are pointed.

In fig. 19 the reader will find a curious example of the "dotted duct," so called from the multitude of little markings that cover its walls, and which are arranged in a spiral order. Like the pits and rings already mentioned, the dots are composed of secondary deposit in the interior of the tube, and vary very greatly in number, function, and dimensions. This example is taken from the wood of the willow, and is remarkable for the extreme closeness with which the dots are packed together.

Immediately on the right hand of the preceding figure may be seen another example of a dotted duct (fig. 20), taken from a Wheat stem. In this instance the cells are not nearly so long, but are wider than in the preceding example, and are marked in much the same way with a spiral series of dots. About the middle of the topmost cell is shown the short branch by which it communicates with the neighbouring duct.

Fig. 23 exhibits a duct taken from the common Carrot, in which the secondary deposit is placed in such a manner as to resemble a net of irregular meshes wrapped tightly round the duct. For this reason it is termed a " netted, duct." A very curious instance of these structures is given in fig. 26, at the bottom of the plate, where are represented two small ducts from the wood of the Elm. One of them that on the left hand is wholly marked with spiral deposit, the spires being complete j while in the other instance the spiral is comparatively imperfect, and the cell walls are marked with pits. If the reader would like to examine these structures more attentively, he will find plenty of them in many familiar garden vegetables, such as the common Eadish, which is very prolific in these interesting portions of vegetable nature.

There is another remarkable form in which this secondary deposit is sometimes arranged, that is well
worthy our notice. An example of this structure is given in fig. 18, taken from the stalk of the common Fern or Brake. It is also found in very great perfection in the Vine. On inspecting the illustration, the reader will observe that the deposit is arranged in successive bars or steps, like those of a winding staircase. In allusion to the ladder-like appearance of this formation, it is called " scalariform," or ladderlike form.

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Information on Warm Stage Microscopes.

Information on Warm Stage Microscopes.

Warm stage

A warm stage is an apparatus for applying warmth to a specimen under continuous observation. A simple form consists of an oblong copper plate 3×1 inches, from one side of which projects a long narrow strip and which has an aperture 1/2 inch diameter in the centre of the 3 X 1-inch portion. It is placed on the stage of the microscope and held like an ordinary 3×1 glass slip in such a position that the long strip projects in front of the microscope. A spirit lamp is placed under the far end of the projecting strip and adjusted so that its flame impinges on the strip, or is slightly to one side, until the portion of the copper plate which is near the 1/2-inch aperture is at blood heat. The correct temperature is readily ascertained if a small piece of a mixture of cacao butter and wax is placed on the copper near the aperture. The mixture is made in such proportions that it melts at blood heat, and when the piece melts on the copper the correct temperature has been reached.

The drop of fluid to be examined is placed on a large cover glass and a smaller cover glass is placed over it, and the two laid upon the copper plate. To prevent evaporation the upper cover glass should be smeared round its edge with olive oil or vaseline.

Tips on Microscope Usage. Here are some tips if you are using a microscope: Microscope Don'ts.

Tips on Microscope Usage. Here are some tips if you are using a microscope: Microscope Don'ts.

Microscope Don't

Tips on Microscope Usage

Here are some tips if you are using a microscope.

• Don't allow dust and dirt to settle on the microscope.
• Don't carry the microscope by the arm.
• Don't use alcohol on the microscope.
• Don't expect too great a range in the fine adjustment.
• Don't take the fine adjustment apart.
• Don t bring the objective into contact with the cover glass.
• Don't fail to focus up before turning the nosepiece unless you know the objectives are parfocal.
• Don't forget that high powers have short working distances.
• Don't focus down with the eye at the eyepiece.
• Don't fail te secure good, even illumination.
• Don't drop the objectives and oculars.
• Don't try to take an objective apart.
• Don't try to work with dirty lenses.
• Don't try to clean them with a dirty cloth.
• Don't fail to clean oil from an immersion lens immediately after using.
• Don't try to work with an immersion lens when there are air bubbles in the oil.
• Don't use high powers when low ones will do.
• Don't use higher oculars than necessary.
• Don't expect a lens to work at its r/est unless used on a cover thickness, and with a tube length, for which it is corrected.
• Don't shut one eye.
• Don't get discouraged if desired results do not come immediately.