124 PART II. — VEGETABLE HISTOLOGY. 



PART II. 

 VEGETABLE HISTOLOGY. 



CHAPTER I. 



Introduction. — The Cell in General. — The Cell-Wall. — 

 The Protoplasm and other Cell-Contents. 



Vegetable Histology has already been defined as that 

 branch of botany which treats of the microscopic structure of 

 plants. To pursue it successfully the student should be provided 

 with a good compound microscope, having a range of magnify- 

 ing powers of from twenty-five to about seven hundred diameters, 

 and he should make use of it to verify, by actual observation, 

 the descriptions given in the text. To aid him in this, and 

 especially to assist the student who wishes to pursue the subject 

 without the aid of a teacher, "Practical Exercises" have been 

 prepared and appended to each chapter ; and there is given, in 

 the Appendix to this Part, a description of the more important 

 apparatus, micro-reagents, staining fluids, etc., used in vegetable 

 histology. 



The Cell in General. A cell has been defined as a nucleated 

 mass of protoplasm. It may or may not possess a cell-wall of 

 different composition. In the majority of vegetable cells such 

 a wall is present, while most animal cells are destitute of it ; but 

 in all essential respects animal and vegetable cells resemble each 

 other. Cells constitute the structural units of the organism. All 

 plant bodies are composed of cells or of these together with the 

 products of cell activity. Within the compass of the cell occur 

 all those essential phenomena which are called vital ; the life of 

 the plant resides in its cells ; the sum of the activities it exhibits 

 is the sum of the activities of its component cells. 



Vegetable cells, on the average, are not more than the one 

 five-hundredth or the one six-hundredth of an inch in diameter, 



