Search -
An Outline of the First Principles of Botany
An Outline of the First Principles of Botany Author:John Lindley Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: bud is excited, the tissue developes in three directions, the one upwards, the other downwards, and the third horizontal. 60. That part which developes downwa... more »rds is called the descending axis or root; that upwards, the ascending axis or stem; and the part from which these two axes start is called the collet or neck. 61. This elongation in opposite directions takes place simultaneously ; hence it follows that all plants must necessarily have an ascending and descending axis, or a stem and root. 62. The only apparent exceptions to this are vesicular Algae. III. ROOT. 63. The root is formed by the descending and dividing fibres of the stem. 64. Anatomically it differs from the stem in the absence of spiral vessels (23), of pith (15), and of buds, and in the want of stomata (44). chapter{Section 465. The functions of the root are to fix plants in the earth, and to absorb nutriment from it. 66. This absorption takes place almost exclusively by the extremities, which consist of a lax coating of cellular tissue lying upon a concentric layer of woody fibre, in the midst of which is placed a bundle of ducts. IV. STEM. 67. The stem is produced by the successive developement of leaf-buds (142), which elongate in opposite directions. 68. If an annular incision be made below a branch of an Exogenous plant (80), the upper lip of the wound heals rapidly, the lower lip not: the part above the incision increases sensibly in diameter, the part below does not. 69. If a ligature be made round the bark, below a branch, the part above the ligature swells, that below it does not swell. 70. Therefore the matter which causes the increase of Exogenous plants in diameter descends. 71. If a growing branch is cut through below a leaf-bud, that branch never increases i...« less