CHAPTER VII.—MICROSCOPIC TECHNIQUE AND REAGENTS.
CHAPTER VII.—MICROSCOPIC TECHNIQUE AND REAGENTS.
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BOTANY
CHAPTER I PRINCIPAL GROUPS OF PLAN’TS’~ :
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INTRODUCTORY
THERE are four main lines of botanical work now recognized, —namely, Morphology, Histology, Physiology, and Ecology. MorpPHo_ocy treats of the form and structure of plants and the subject is sometimes divided into (1) external morphology or organography and (2) internal morphology or anatomy (histol- ogy). The former deals with external characters of plant parts and the latter with their minute inner structure. PHysioLoGy may be defined as the study which considers life processes and the condi- tions which influence these. Ecotocy is the study of the adapta- tion of plants and their parts to external conditions. It is impor- tant to bear in mind, however, that these several departments are more or less interdependent, and that one of them cannot be intelligently studied without a consideration of the problems of the others. For instance, as Goebel states, we cannot under- stand the relation of the external forms of organs without refer- ence to their functions. In other words, form and function have a direct relation; one influences the other. So, too, in the study of ecology we study the influence of external conditions on plants and these, as indicated above, have a direct influence on physiological processes, and thus the study of ecology merges into the study of physiology on the one hand and into morphology on the other.
While this book will deal chiefly with the structure of plants and their parts, still it will be necessary occasionally to refer to some of the characters of plants which properly belong to other departments of botanical study.
Basis of Plant Structure.—In order to understand the sig- nificance and relation of the various parts of plants it is necessary
I
2 A TEXT-BOOK OF BOTANY.
' to know something of their functions and habits of life as well
as of their internal structure. It is desirable at this point to give a brief consideration to the cell, as it is the unit of plant structure. If we make a section of a plant and examine it by means of the microscope, the cut surface presents the appearance of a network, indicating that the tissue is made up of small compart-
.i ments ar.chambers. One of these compartments together with
[i e
"its coritént’ “cbifstitutes the structure known as the CELL (see : Frontispiece): oa
The cell-gontents vary greatly in appearance and composi- tion, but in all active or living cells there is always present the substance known as PROTOPLASM. The protoplasm is the basis of all plant structures whether they belong to the lowest or high- est forms; for by its aid or from it all parts of the plant are developed. Even the cell-wall is a product of protoplasmic activity. The protoplasmic content of the cell consists of several intimately
‘related but more or less distinct portions,—namely, a somewhat
thin, semi-liquid, granular portion known as the CYTOPLASM ; a more or less spherical body embedded in the cytoplasm called the NUCLEUS; and frequently, but not always, certain small
‘bodies which are more or less variable in shape called PLASTIDs,
these being also embedded in the cytoplasm (see Frontispiece). The cytoplasm and nucleus are sometimes considered together as a unit, which is known as the proTopLast. A fuller discussion of the differentiated portions of the protoplasm will be found in