35 

 Flowering Plants. 



The inetJwds of formiui^ Seeds. In the slu l}- of the flower its function ■ • 

 of forming seeds, from the very start, should be made the most promi- 

 nent fact about it, much more so than the mere names of the parts, or 

 the forms of the flowers, and classification of the plants. 



The preceding lessons on plants in which their methods of reproduc- 

 tion was observed will have aroused an interest in the question of how 

 flowering plants reproduce themselves. The observation of the simple 

 spores of mushrooms, moulds, etc., growing into the same forms; the 

 spores of the fern growing into the little prothallium, which produces 

 the large fern; the pine pollen carried by the wind to the cones, where it 

 causes the ovule to grow into a complex seed, all prepare the pupil to 

 take an interest in how the conspicuous flowers manage to form the seeds 

 all ready to grow into the form of the parent plants. 



Begin with the fact that flowers produce pollen and ovules, and that 

 the pollen must reach the ovules before the ovules will grow into seeds. 

 This will bring the pupils to see first the pollen bearing part, the sta- 

 mens, and the ovule bearing part, the pistil. 



For the first lesson, have a number of different kinds of flowers. Se- 

 lect one in which the parts are large and easily seen; for example, the 

 California Poppy. Cut the flower in two by a cut perpendicularly 

 through the center. (Or, separate the parts in any other way that suits 

 your own views of clearness.) The cut will expose the numerous ovules 

 in their case. Have their position clearly seen, then the case (ovary), 

 its attachment, its upward extension into styles and stigmas. The whole 

 is the pistil. Next find the pollen in the stamens. The parts and posi- 

 tion of the stamen. With a hand lens it may be seen that the stigmas 

 are covered over with pollen grains. 



Explain that a pollen grain grows by a long filament (something as a 

 mould spore grows) which reaches down through the stigma and style 

 until it reaches the ovules. After it reaches the ovule, the ovule grows 

 into a seed, and at the same time the ovary (and sometimes the other 

 parts around it in many kinds of plants) grows into pods and fruits of 

 countless forms. 



A beautiful experiment showing the growth of pollen grains is easily 

 managed with the use of a compound microscope as follows: Make a 

 solution of sugar about lo per cent, (one part of sugar to nine or ten 

 of water) place a little of the sugar solution in a watch crystal, 

 sprinkle in this considerable pollen of sweet peas. In a few minutes 

 the pollen grains begin to grow. Examine by taking up a drop of the 

 solution with the pollen grains in it and placing it on a glass slip, cover 

 with a cover-glass. The pollen grains will grow while you are watching 

 them. (The grains may be sown in a drop of the sugar solution and 

 placed in a moist cell as shown in the demonstration.) Most pollen 

 grains grow when treated in this way, but not all so quickly. 



