PLANT CELL AND CONTENTS. 



115 



CHAPTER II. 



THE PLANT CELL IN GENERAL 



The present hypothesis of the structure 

 of all matter is known as the atomic 

 theory. It teaches that all matter, both 

 organic and inorganic, is made up of 

 particles that cannot be divided; these 

 it calls atoms. These atoms exist only 

 in combinations of two, three or more, 

 when they are termed molecules. From 

 these molecules, invisible, are built up 

 the cells, visible, which are the micro- 

 scopical imits of all organisms. 



The Cell is then, from this standpoint 

 the unit of structure of animal and vege- 

 table life; not the smallest unit, w^hich, 

 as we have seen, is the atom, nor the 

 largest, which varies exteusively in both 

 the animal and vegetable w^orlds; but it 

 is the smallest organized unit that has 

 as yet been seen by the human eye aided 

 by the microscope. 



The cell may thus be taken as the unit 

 of plant life; and with its study com- 

 mences that branch of knowledge known 

 as Vegetable Histology. Its exclusive 

 study is termed Vegetable Cytology. 



Vegetable Histology is that portion of 

 knowledge which deals with the cells of 

 plants, either as individuals or in their 

 various combinations known as tissues. 

 It classifies them and arranges them ac- 

 cording to some logical plan of growth 

 or of function, and inquires into their 

 origin, their method of growth and com- 

 bination, and the part they play in the 

 economy of the plant's existence. 



There are reasons to believe that in 

 prc-historic times there was a period 

 when the structure of cells was very 

 simple indeed, and attempts have been 



made to ideally reconstruct those early 

 forms. As time progressed and varying 

 circumstances arose, simplicity of cause 

 and effects gave way to complexity, and 

 the plant world as seen to-day is one 

 vast forest of effects, having their origin 

 in causes remote and present. 



To be rightly understood the cells of 

 animal and plant life must be considered 

 as an elaborate product of millions of 

 years of manufacture. Each part has 

 been, and is being, stuilied with jrreat 

 minuteness, and the results of the study 

 of vegetable Cytology already fill many 

 large volumes. 



For the purposes of the present outline*. 

 the plant cell may be considered as a 

 sac containing a large number of con- 

 tents, wiiich vary widely in physical and 

 chemical properties. 



Cell Wall. The lining membrane is 

 called the Cell Wall. It is not always 

 present, as in many one-celled plants, as 

 yeast, nor is to be found in the youngest 

 growing parts of the plant, as in the 

 apices of stems and roots, nor in the im- 

 mature pollen grains and the just fertil- 

 ized cells of the ovule. 



Cell Contents. While alive and grow- 

 ing the plant cells contain what is called 

 the Plasma, which is a general term in- 

 cluding a number of diverse substances 

 to be studied under the head of cell con- 

 tents. PROTOPLASM has been used 

 extensively in this sense and as a bio- 

 logical conception it is proper so to use 

 it; but protoplasm must be considered 

 as' a combination of substances rather 

 than any one chemical entity. 



CHAPTER III. 



CELL CONTENTS. 



The following classification of cell con- 

 tents has been here adopted: 



1 UNFORMED NITROGENOUS 



CONTENTS. Including the so- 

 called Cytoplasm of the cell body. 



2 FORMED NITROGENOUS CON- 



TENTS. Including the 



(a) Cell Nucleus and its parts. 



(b) Aleurone Grains. 



3 NON-NITROGENOUS CONTENTS. 



Including Starch, Amylodextnn, 

 Fatty oils and fats, Calcmm Salts, 



Sulphur, etc. 

 4. CELL SAP. Containing:^ 



(a) Organic Substances m Solution. 

 As Inulin, Hesperidin, Aspara- 

 gin, Leucin, Tyrosin, other Glu- 

 cosides. Alkaloids, Sugar, Muci- 

 lage, Tannin, Bitter stuffs. 

 Coloring matters. Ethereal Oils, 

 Resins, Gums, Rubbers, Plant 



(b) inorganic substances in solution. 

 Salts of Sodium, Potassium, 

 Lithium, etc. 



