Pollen-grains: small oval bodies, with projections on them in the equatorial region.

The anther of a bean is so small that sections cannot be made of it without considerable skill: the structure of an anther can however be easily made out by imbedding one from a tiger-lily in paraffin or holding it between two bits of carrot, cutting transverse sections, mounting in water and examining with 1 inch obj.

It contains four chambers, two on each side of the continuation of the filament, and in each chamber lie numerous pollen-grains.

The pistil.

a.

b.

C.

It is found by tearing open the stamen-tube: it is a long green tapering body, somewhat flattened laterally and ending in a point (the style) which bears a tuft of strong hairs.

Slit it open carefully: in it lies a central cavity, containing a number of small oval bodies, the ovules, attached along its ventral side by short pedicles.

It is difficult to get a section of a bean-ovule, but its essential structure may be readily made out by making thin transverse sections of the ovary of a large lily (where the ovules are closely imbedded in a large quantity of parenchyma) and examining with 1 inch obj.

α. The central cellular portion of the ovule (nucleus) made up of a large number of cells. B. Its two coats, an inner (primine) and outer (secundine).

].

The small passage (micropyle) leading through the coats down to the nucleus.

In some specimens, a large cavity (the embryo-sac) will be seen in the nucleus just opposite the micropyle. In the embryo-sac may be seen some small granular cells (the embryo-cell and endosperm cells).

f. The seeds.

Soak some dried beans in water for twenty-four hours; they will slightly swell up and be more readily examined than when dry.

a. Note the black patch on one end of the bean, marking where the stalk (funiculus) which fixed it in the pod was attached to it.

b.

C.

Having wiped all moisture off the bean gently press it while observing that part of the black patch which is next its broader end: close to the patch a minute drop of fluid will be observed to be pressed out through a small opening, the micropyle.

Carefully peel off the outer coat (testa) of the seed the two large fleshy cotyledons will be laid bare.

d. Joining the cotyledons together will be found the rest of the embryo: it consists of a conical part (the radicle) lying outside the cotyledons, with its apex directed towards the point where the micropyle was; and of the rudiments of the stem and leaves (plumule) lying between the cotyledons.

g. The process of fertilization.

This is difficult to follow in the bean; but by using different plants for the observation of its various stages it is fairly easy to observe all its more important steps.

I. A plant well adapted for seeing the penetration of the pollen-tube into the stigma and style is the Evening Primrose (Enothera biennis).

2.

Detach the style from the flower and hold the club-shaped stigma between the finger and thumb of the left hand. Moisten it with a drop of water and then make with a wetted razor several successive cuts through it. This will divide the stigma into several slices. Spread these out on a glass slide with a needle in water and examine the thinnest, after putting on a covering-glass.

The triangular grains of pollen will be seen sending out from one angle a tube into the stigmatic tissue, which is easily seen from its slight difference in colour.

The entrance of the pollen-tube into the micropyle can be readily made out in some species of Veronica. The common V. serpyllifolia - often to be found in shady places on lawns-is well adapted for the purpose. A flower should be taken from which the corolla has just dropped. Dissect out the minute ovary and, using the dissecting microscope, open with a needle one of its two cells in a drop of water; remove the mass of ovules and gently tease them apart. Then put on a covering-glass and examine with a low power till an ovule is found which shews the entry of the pollen-tube. The addition of dilute glycerine will make the ovule more transparent, so

that after some time the embryo-sac can be seen, and the progress of the pollen-tube into the ovule followed.

3. The young fruit of Campanula (especially the common Canterbury Bells of gardens, Campanula media) is convenient for examining the embryo-sac. It is only necessary to cut thin transverse sections of the fruit and examine in water. Some of the ovules cut through will allow the embryo-sac to be seen, and in fortunate sections the embryo-vesicle and the end of the pollen-tube in contact with the embryo-sac.

IX.

THE BELL-ANIMALCULE (Vorticella).

THE great majority of those animal organisms which are more complex than Amaba, begin their existence as simple nucleated cells, having a general similarity to Amaba; and the single nucleated cell which constitutes the whole animal in its primitive condition divides and subdivides until an aggregation of similar cells is formed. And it is by the differentiation and metamorphosis of these primitively similar histological elements that the organs and tissues of the body are built up. But in one group, the Infusoria, the protoplasmic mass which constitutes the germ does not undergo this process of preliminary subdivision, but such structure as the adult animal possesses is the result of the direct metamorphosis of parts of its protoplasmic substance. Hence, morphologically, the bodies of these animals are the equivalents of a single cell; while, physiologically, they may attain a considerable amount of complexity.

The Infusoria abound in fresh and salt waters, and make their appearance in infusions of many animal and vegetable substances, their germs either being contained in the substances infused, or being wafted through the air. Their diffusion is greatly facilitated by the property which many of them possess of being dried, and thus reduced to the condition of an excessively light dust, without the destruc