VEGETABLE GARDENING, OR OLERICULTURE 1 1 



and the green color are important factors connected with the func- 

 tion of the leaf. The broad surface gives an extensive area over 

 which the green tissue is spread, and provides for a large number 

 of small openings, particularly on the underside of the leaves, 

 through which air is taken in and through which moisture is 

 thrown off. These small openings, which are provided with more 

 or less active motor cells along their edges, are called stomates, or 

 stomata. It is through these openings that the excess of moisture 

 pumped up by the root with the dilute mineral food is thrown out 

 of the plant system. If it were not for these, the plant would be- 

 come overstocked with moisture, affected with oedema, and sickly 

 in appearance. It is by this rapid movement of water from the 

 roots through the leaves to the air by means of the stomata that 

 the tissue of the plant is kept in a tense condition. As soon as 

 there is insufficient moisture at the root of the plant to provide 

 for this rapid movement the plant wilts or flags, and as soon as 

 moisture is again supplied the tense or turgid condition of the 

 tissue is restored. These stomata are, therefore, very important 

 organs, intimately associated with the process of plant nutrition. 

 They are also important in connection with plant diseases, as will 

 be noted later. 



The green color of the leaves, above referred to, is caused by 

 small (microscopic) bodies contained in the cells which build up 

 the outer layers of the leaf (all plant tissue is made up of small 

 independent parts called cells, which might be likened to the in- 

 dividual bricks used to build the walls of a building). These little 

 green bodies, which are called chloroplasts by botanists, are pres- 

 ent in sufficient numbers when the plant is in a healthy condition 

 to give it its characteristic green color. Their function is, perhaps, 

 the most important of any connected with plant growth, for under 

 the influence of sunlight they are able to take the crude materials 

 gathered by the root and supplied by the air, and from them to 

 develop the materials necessary to build the various plant tissues. 

 Some of these products will be recognized under the names 

 " starch," "sugar," and "oil." The starches are changed into 

 sugars and are used by the plant in building up certain portions of 

 its structure. The oils are frequently stored up either for use by 

 the young plant in the seed or in various parts of the plant tissue, 



