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A TEXTBOOK OF THEORETICAL BOTANY 



Cytoplasm is not homogeneous in appearance. There is a hyahne fluid 

 medium, which shows no microscopic structure, called the hyaloplasm, 

 in which are suspended immense numbers of minute granules or droplets 

 consisting of ergastic substances, including oil-drops, protein, volutin and 

 lipin granules, and the larger more definitely visible granules known as 

 mitochondria. None of these is an essential component of the cytoplasm 

 itself, which is the hyaloplasm, and they can be centrifuged out of suspension 

 in the hyaloplasm without injuring it. It is in the hyaloplasm, therefore, that 

 the true living structure of protoplasm must be looked for. 



Cell wall 



Lipoid -protein 

 membrane 



Plasmagel layer 



Plasmasol layer 

 Kinoplasm 



tplast 



Vacuole 



Fig. 3. — Diagram of the structure of the cytoplasmic utricle in a typical 

 cell, very highly magnified. {After Seifriz.) 



The cytoplasm is usually dift'erentiated into zones (Fig. 3). Firstly, 

 there is a very thin external layer of hyaloplasm with relatively few granules, 

 which has sometimes been called the ectoplasm, but is more properly 

 described as the hyaline layer, as the term ectoplasm has been differently 

 employed in Amoeba. In plant cells this hyaline layer is fluid and extremely 

 thin. It is most easily revealed in the form of the very fine extensions which 

 often connect a plasmolyzed protoplast to the pit areas of the cell wall. Thin 

 as it is, it possesses a coherent surface film, probably a monomolecular layer 

 of non-aqueous substance, which is referred to as the protoplasmic 

 membrane, or sometimes the plasmalemma. A similar but tougher 

 membrane forms the boundaries of the vacuoles and is called the tonoplast. 



