SUBSTANCES OF PLANTS. 19 



ovary of particular plants, and there the germ or ovules are affected. 

 Both sexes are united in one flower in most plants ; in others they are 

 separated, and the former is therefore called a perfect flower, while 

 the latter is called male and female. These last stand on one stem, 

 or are attached to different plants. Evolution is consequently most 

 perfect and most readily effected in the perfect flowers, as they are 

 called, and likewise when the stem has male and female blossoms. 

 But where the two sexes are entirely separated evolution takes place 

 only where the plants are sufficiently near for the polen of one to be 

 carried by the wind, by insects, or by artificial means to the other. 

 Should this not take place, the germ falls off, or the partial fruit is 

 incapable of germination. Glands within the flowers secrete honey 

 and attract insects which powder parts of their body with polen, and 

 when visiting flowers of another kind, they deposite it. In others, it 

 is said also, where perfect flowers of the two sexes are not near, small 

 flies, being attracted by the honey of one flower, are suddenly enclosed 

 by it and, in their endeavors to escape, necessarily deposite the polen 

 obtained from other flowers. On this system of sexes, Linnaeus founded 

 his arrangement of plants. Further outlines of this will be found in 

 other parts of this treatise, and scientific terms will be defined by the 

 glossary at the end of the volume. We have, however, studiously 

 avoided technical language where it has been possible, wishing to 

 render vegetable physiology as entertaining as it is useful. 



The substances of plants are in general said to consist of wood, gum, 

 fecula or starch, sugar, gluten, albumen, fibrine, gelatin, caoutchouc, 

 or india rubber, wax, fixed and volatile oils, camphor resin, gum-resin, 

 balsam, extract, tannin, indigo, acid, aroma, the bitter, the acid and nar- 

 cotic principles, ligneous-fibre, etc. Many of these, however, are con- 

 vertible into one another by heat, air, moisture, or alkalies, which 

 change more or less the relative proportions of their constituents. 

 Modern chemistry has added others, or arranged the same under new 

 names and forms of combination and much diminished and changed 

 the terms by which vegetable substances have been known. A 

 chemical analysis has proved the substances to be carbon, oxygen, 

 hydrogen, nitrogen, sulphur, silex, oxide of iron, magnesia, carbonate 

 of lime, potash, etc., and the various parts of plants are composed of 

 these in different proportions. The formation of substances composing 

 plants is the result of chemical operations during their growth and the 

 development of fruit. The process of combining the original ele- 

 ments, their absorption by heat and light, their unition in various 

 forms and combinations, and also the resolving of original substances 

 into other forms and compounds, constitute more especially the im- 

 portant and interesting science of organic chemistry. (See another 

 article.) 



