74. Q. What other families of plants are examples of Acrogens? A. Ferns and Mosses. 75. Q. What are Endogens? A. Plants whose vessels and woody fibers first grow within the stem. The seed has but a single lobe, or cotyledon. 76. Q. What families of plants are found in the type of Endogens? A. Grasses, Rushes, Lilies, and Palms, with similar families. 77. Q. In the growing plant what part grows from the axis upward, and what part from the axis downward? A. The stem grows from the axis upward, and the root downward. 78. Q. What is the root formed by the downward elongation of the axis called? A. It is called the primary root. 79. Q. What is the stem of a plant? A. That part which bears the leaves, flowers, and fruit. 80. Q. What is the length of life of the stem and roots? A. It may be only a single year, or annual; two years, or biennial; or a number of years, or perennial. 81. Q. What are thorns? A. Undeveloped branches, and many plants which are thorny when wild are not so under cultivation. 82. Q. Of what are leaves constituted? A. Cells, with cavities, fibro-vascular bundles and epidermis. 83. Q. How do the veins in the leaves of Endogens differ from those in the leaves of Exogens? A. They are generally parallel or straight in Endogens, and do not form a network as in Exogens. 84. Q. What are five of the names given to leaves according to their shapes? A. Lanceolate, or narrow and tapering; oblong, or narrow and not tapering; cordate, or heart-shaped; sagittate, or arrow-shaped; and ovate, or egg-shaped. 85. Q. What is the function or use of leaves? A. To expose the juices of the plant to light and air, and thus aid in forming the woody matter of the stem and the various secretions. 86. Q. What constitute a plant’s organs of nutrition? A. The root, stem and leaves. 87. Q. What is the flower of a plant? A. It is the organ, or assemblage of organs, for the production of the seed. 88. Q. What are the four whorls in which the parts of a flower are usually arranged called? A. The outer whorl is the calyx, the next the corolla, the third the stamens, and the innermost the pistil. 89. Q. To what is the term fruit applied in botanical language? A. To the mature, perfect pistil, whether dry or succulent. 90. Q. What nutritious grains are classed among the family of Endogens called grasses? A. Wheat, barley, oats, rice and Indian corn. 91. Q. What other families are noted members of the type of Endogens? A. Palms and bananas. 92. Q. What are some of the other families of the type of Endogens? A. The orchid, the lily and the bulrushes. 93. Q. What are Exogens? A. Plants whose woody fibres grow in outer layers. The seed has two lobes, or cotyledons. 94. Q. How many different species are included in this type? A. About seventy thousand. 95. Q. What are Incomplete Exogens? A. Those whose flowers have no corolla. They are of two kinds.