THE PLANT CELL. 



INTRODUCTION. 



In order to study the life-phenomena of any organism, and to 

 arrive at a definite explanation of them, it is often found necessary 

 to enquire into its minute structure ; and, in the case of the 

 plant, the study of the cell, including its form, growth, component 

 parts, and the varied conditions under which it can exist, is an 

 essential part of the science of Botany, as a branch of Biology. 

 The facts and features brought to light by the microscope, coupled 

 with those pertaining to Chemistry and Physics, have long afforded 

 proofs of statements and observations which were formerly only 

 regarded in the light of speculation. 



In the following pages the object will be to give a con- 

 cise and correct idea of the principal structural elements of 

 plant-tissues ; stress has been laid upon practical microscopical 

 observations and reactions with various reagents, for these, 

 although generally simple to perform, sometimes afford a very 

 clear demonstration of important life-factors. A brief account 

 has also been given of the most important chemical and physical 

 phenomena occurring in a cell. 



Cells; Types met with in the Plant. — From a purely biological 

 standpoint a cell or protoplast is defined as "a mass of protoplasm, 

 sometimes with and sometimes without a definite limiting mem- 

 brane, having situated in its substance (except in a few cases) a 

 nucleus and often accessory portions, such as plastids, chloroplasts, 

 vacuoles, and food-granules of various kinds." The cases between 

 which this definition distinguishes are : — 



i. The Amoeboid Cell (plasmodia). — Here the protoplasm is not, 

 during at least the greater part of its existence, limited by any 



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