Manual of experimental botany by Payne Frank Owen

Author:Payne, Frank Owen
Language: eng
Format: epub
Tags: Botany
Publisher: New York , Cincinnati [etc.] American book company
Published: 1912-03-25T05:00:00+00:00

Method. — Examine the leaves selected, givii^ special attention to the under surface where the veins are more prominent. The network is easily discovered in most leaves, but in cases of some leaves it will be necessary to hold them between the eye and the light. Fleshy leaves often' do not show their net veining because there is so much pulp in them. Tear a leaf as in the preceding Experiment and note how insularly it tears. Why? Study the general plan of the veins and discover if possible the general scheme of veining.

Conoluiion. — How many types of net _*

veined leaves can you find? veining.

Note. — The veining of leaves usually indicates the kind of plant, whether monocotyl or dicotyl.

Parallel veining is never found in dicotyl plants, and net veimng very rarely in monocotyl plants.

Such monocotyls aa arrowhead {sagittaria), elephant's-ear (fioiadium), and a few others seem to have net venation, but a close examination will show that the veins run generally parallel with each other and only the large ribs form a sort of network.

Leaf Impressions

For greater ease in studying leaves, the use of leaf impressions is very helpful. They may be made in the following manner: —

Apply a preparation of vaseline and lampblack to the under surface of the leaf, using a dabber made of tightly rolled cotton batting covered with chamois skin.

The leaf should be touched lightly all over its under surface, and great care should be used not to have much of the preparation on the dabber.

EIP. BOT. —10

The leaf, coated with the preparation, is laid upon the paper upon which the impression is to be made and placed between two folds of cardboard. Run this through a clothes wringer, and the impression will be complete.

A little practice will enable one to produce beautiful impressions which surpass half-tones in delicacy and accuracy.

Note. — How to make the impression ink. Mix thoroughly together a tablespoonful of vaseline with a teaspoonful of lampblack. Melt the mixture and stir it until it is uniformly black.

How to use it. Place a small portion of the preparation on the middle of a plate of glass. What can be taken on the point of a knife blade is plenty.

Spread this ink evenly over\he glass by dabbing it with the dabber mentioned in the preceding exercise, and use the plate as long as any ink remains upon its surface.

In this way there will be no unevenness in the blackness of the impressions.

If carefully made, the finest details of veining, outline, and surface features will be distinctly shown.

Skeleton Leaves

The framework of many leaves may be studied from their skeletons. Skeleton leaves are very beautiful, are easily made, and are useful for study. As permanent mounts under glass they are an attractive addition to the school museum.

Skeleton leaves are made as follows: —

(a) Select leaves having a more or less firm framework, such as oak, elm, apple, holly, and beech. The Judas tree (cercis) is the easiest leaf to skeletonize.

(6) Place the leaves in a saucepan with enough water to cover them and add a heaping tablespoonful of cleaning powder.

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