CONTENTS OF THE CELLS. 



9 



55 CLASSIFICATION OF PRODUCTS. The peculiar 

 secretions of plants are of two kinds those which are 

 composed of the elements of pure cellulose, or of carbon, 

 hydrogen and oxygen, as Sugar, Starch, Acids and Oils, 

 and those in which nitrogen is combined with the other 

 three elements, as Gluten, Albumen, and the Alkaloids. 

 The first are called TERNARY PRODUCTS, because they 

 have but three elements, and the second QUATERNARY 

 PRODUCTS, because they have four. 



TERNARY PRODUCTS. 



56. STARCH. This is not only one of the most im- 

 portant, but also one of the most interesting and remark- 

 able of vegetable secretions. It is a highly organized 

 substance, as may be seen by referring to fig. 1 , Plate II. 

 which shows two well-defined starch-cells. At 6 are two 

 distinct grains separated from the celL Each of these 

 grains consists of numerous layers deposited round a 

 nucleus; but as the layers are of unequal thickness, 

 the nucleus is not in the middle. Starch is found in 

 every plant and every part of the plant ; but it abounds 

 in tubers, roots, seeds, and in the pith of the Sago Palms. 

 It is an important principle of nutriment, useful in the 

 Arts, and under the microscope exhibits the most inter- 

 esting and elegant forms. A good test of the presence of 

 starch is that it turns deep blue or violet, when moistened 

 with a solution of iodine. 



57. DEXTRINE. This is a form of starch soluble in 

 cold water. It has not only the same elements as pure 

 cellulose, but they are combined in precisely the same 

 proportions. In the course of growth, when there is an 

 excess in the supply of dextrine, it is solidified, and in 

 the form of starch is accumulated for future support. 

 When its active presence is again called for, it is recon 

 verted into dextrine, and being thus rendered soluble in 

 cold water, it enters readily into the vital operations. 



58. SUGAR. This product, in the living plant, gener- 

 ally exists in solution, though it sometimes occurs in the 

 nectaries in the form of crystals. It is abundant in all 

 the growing parts, in pulpy fruits, sweet roots, and in 

 the sap of the Rock-Maple and Sugar-Cane. Sugar 

 starch and dextrine are nearly identical; an'i in the 

 vital action of plants they are repeatedly converted anc 

 reconverted into each other. 



59. MUCILAGE or VEGETABLE JELLY has very 

 nearly the same composition as starch. When dry it is 



Peculiar secretion. Those which are composed of the elements of cellulose 

 What called? Why? Those In which nitrogen Is combined. What called 

 Why? Starch, In what plants fonnd ? What parts? Uses. Tet of starch 

 Dextrine, difference between it and starch. What changes occur ? Sugar, I 

 what slats? What plants? What parts ftrand? What substances nearlj 



2 



ough and horny, but it swells and becomes gelatinous by 

 ,he application of moisture. It is not only contained in 

 ,he cells, but, in some instances, it forms a large portion 

 of the cell wall, as in some of the Sea-weeds. In that 

 species which is known as Carragheen Moss, the cell 

 wall and, in fact, the entire substance of the plant is 

 composed of mucilage, and to this it is indebted for its 

 culinary celebrity, being much used in the preparation of 

 )lancmangc. Mucilage is soluble in cold water, and is 

 bund in the tubers of the Orchis, the bark of Slippery 

 Elm, the leaves of the Sassafras tree, the seed of Flax, 

 and in the bark, roots and seeds of many other plants, 

 [t also appears as an excretion in Gum Tragacanth. 



60. ESSENTIAL OILS. These are generally volatile 

 and aromatic, and thus they give to plants their peculiar 

 odors. They are well known in their concentrated forms, 

 which, in the hands of the druggist, are converted into 

 essences, to be used in Medicine and Perfumery, as the 

 Oil of Peppermint and the Oil of Orange -flowers. 

 What is commonly known as the Spirits of Turpentine is 

 an essential oil obtained by distillation from Turpentine 



a resinous substance that exudes from Pines and other 

 Cone-bearing trees. 



61. All these substances undergo various changes on 

 exposure to the air, by which they are converted into 

 Resins, Gums, Wax and Balsams. Having no properties 

 which can either nourish the plant or be instrumental in 

 its growth, they may safely be considered as excretions. 

 The Leaf is the only excreting organ of vegetables, and 

 through this only liquids or gases can be exhaled. Sub- 

 stances, therefore, which are inclined to pass into the 

 solid state must generally be retained in the system, but 

 sometimes they exude directly from the surface in the 

 form of Gums, Resins, and like substances; but they 

 chiefly pass into the superannuated tissues, seeming 

 especially inclined to occupy the intercellular spaces. 

 The essential oils abound in flowers and leaves of herbs 

 and shrubs, and the bark and fruits of aromatic trees. 



62. CAOUTCHOUC. This substance belongs to the 

 same class as the next above, and like them may be 

 termed an excretion, as it seems to have no part or office 

 in the vegetable life and growth. It occurs in the 

 form of minute globules, which are suspended in the 

 milky juice of many plants in precisely the same manner 

 as the globules of butter in animal milk. When the 

 liquid is left undisturbed, the globules, being lighter, 



Identical? Mucilage, what resemble ? In what plants? What parts? Es- 

 sential Oils, their character. Instances. What do they often become on ex- 

 posure to the air? What may such substances be considered? In what 

 plants do essential oils abound ? In what parta ? Caoutchouc, In what plant* 

 fonnd? 



