Botany : specially written to meet the requirements of teachers' D, matriculation, public service entrance, intermediate and pharmacy A examinations

compounds of plants. Place a drop of strong nitric acid on the white of a hard boiled egg. The yellow colour which appears shows the presence of a protein, in this case albumen. Now wash flour in a piece of fine muslin, till nothing but an elastic substance remains. This is gluten, another protein, which responds to the same test.

The protoplasm or living substance of both plants and animals is in the nature of a protein. Protoplasm is found only in living things, and there is no life without it. Indeed it is the life substance.

SEEDS. Have ready a number of seeds of different plants, some quite dry and others that have been soaked in water for twenty-four hours. Seeds of the broad bean, scarlet runner, pumpkin, sunflower, castor oil, onion, maize and barley will be suitable for the purpose.

Examine a dry bean seed (Figs. 11-12). Observe that it is kidney-shaped and that it is covered with a brown coat, the testa. Note the black scar, the hilum, which shows where the seed was attached to the wall of the pod by a little stalk or funicle. Now take a seed that has been soaked, and, after drying, squeeze it between the finger and thumb. A drop of water will appear near one end of the hilum. This indicates the position of the micropyle, a small opening, through which, before it could develop into a seed, the ovule received a tube bearing fertilizing materal from the pollen grain, and through which passes the bulk of the water absorbed by the seed.

Now remove the brown coat or testa which protects the more delicate parts within. Carefully separate the two fleshy cotyledons which contain the store of food that is to support the infant plant. Test the bean cotyledons for starch and protein. Both are present,

the protein being legumin, a substance of similar composition to the protein which forms the curd of milk. The legumin is so plentiful that a drop of nitric acid placed on the inner side of the cotyledon produces an intense yellow. Now examine the young plant that lies curved between the cotyledons. Observe that it is attached to both cotyledons at about its middle point. The portion above the point of attachment is the plumule or young stem, and, by examining this with a lens, the undeveloped leaves may be seen.

Immediately below the cotyledons is the hypocotyl, which in the broad bean never appreciably develops; but which, in the scarlet runner, pumpkin, and many other plants lengthens to such an extent as to lift the cotyledons well above the ground. In such cases the hypocotyl develops to form the lower part of the stem. Continuous with the hypocotyl, but showing no definite point of junction therewith, is the radicle, or young root. This points towards the micropyle, through which, under suitable conditions it will, later on, emerge.

The cotyledons, plumule, hypocotyl, and radicle collectively form the embryo bean plant.

The so-called sunflower seed (Figs. 16-18) is really a fruit, in which the seed is still covered by the original seed case which has been formed from the ovary wall. Take one of the soaked specimens and observe that the seed case may be split along the edge. If this is done carefully it will be seen that the enclosed seed is attached to the pointed end by a very short stalk. On removing the thin seed-coat, separate the two cotyledons and observe the small plumule and radicle situated at the extremity of the pointed end. The iodine test shows that starch is absent from the cotyledons, but the nitric acid and tissue paper tests show that proteins and oil are abundant. C

The castor-oil seed (Figs. 13-15) differs considerably from both bean and sunflower. At the pointed end is a spongy mass the caruncle, which rapidly absorbs water. If the seed be placed in hot water a bubble of air will come out of the micropyle, indicating that it is in the region of the caruncle. The advantage of this is obvious. On removing the skin it would appear as if there were not two cotyledons as in the bean and sunflower. As a matter of fact, in the castor oil bean the cotyledons are two flat bodies lying inside the oily mass that forms the bulk of the seed. This oily mass is called endosperm, and, like the cotyledons, serves to support the young plant. Seeds with endosperm are called albuminous while those without are termed exalbuminous.

In most dicotyledons, i.e., plants that have two seed-leaves, the seeds are exalbuminous, while in all monocotyledons, i.e., plants that have only one seedleaf, they are albuminous. Now, with a sharp knife slice the castor seed longitudinally through its flatter sides into two fairly equal parts. As shown in Fig. 14, the cut edges of the two flat cotyledons will be seen with the radicle extending downwards from the point of junction below, and the tiny plumule pointing upwards just above it. Now slice another seed through its rounded sides as shown in Fig. 15. The desired result may not be attained till after several attempts, but finally, even without a lens, it should be possible to see the veining of the exposed surface of the cotyledon. The radicle appears below, and, with great care and patience, it will be possible so to split a seed as to see the plumule as well.

The reserve food in the endosperm consists of oil and protein and does not respond to the test for starch. The cotyledons show abundant protein as well as oil.

It may be mentioned in passing that the scarlet outgrowth forming the cup of the titoki seed is similar

SEEDS

- Insert Diagram of seeds cross-sections -

to the caruncle of the castor bean, but, being much larger, is called an aril.

The Maize grain (Figs. 19-21) is a fruit and not a seed; but it differs from the fruit of the sunflower. Whereas, in the latter, the seed case is merely a loose covering which can be removed, in the former, this case has coalesced with the coat of the seed, and formed a single envelope which is firmly united with the food materials within. If on the growing corn-cob the development of the maize grain is carefully watched from day to day, it will be noted that there is no shedding of a seed case, and that therefore the ovary wall must fuse with the seed-coat and form part of the grain itself. Externally the grain is a blunt wedgeshaped body flattened on one side and having a rough apex which shows its point of attachment to the cob, and in which is the opening that corresponds with the micropyle of a dicotyledon. This may be located by placing the grain in hot water, when a bubble of air comes out as in the case of the castor bean. On the flat side, is a more or less triangular depression bisected vertically by a narrow ridge which indicates the position of the radicle and plumule. Now take a well-soaked grain, and, with a pin, prick away, from the side remote from the depression, the endosperm, which above and on the outside consists of amber-coloured matter, and further in of white easily powdered substance. In this way a tough elastic shield-shaped body will be exposed. This is the cotyledon, attached to the front of which may be seen the plumule and radicle forming a straight line on the flat side. Now split another grain through the flatened sides as shown in Fig. 21. In this, with the assistance of a lens, the structure of the young shoot may be seen. The iodine test shows that the endosperm is chiefly starch. When a drop of nitric acid is applied to the cut surface of the grain, the cotyledon becomes yellow, showing the