CHAPTER VII 



ERGASTIC SUBSTANCES 



In Chapter II emphasis was laid on the conception of the protoplast as 

 a living system of active components which by themselves would be non- 

 living. It is nevertheless convenient to deal separately with materials 

 which, for the time at least, are relatively inactive. These, for the most 

 part, are accumulations of the products of protoplasmic activity and 

 represent by-products, supporting structures, and reserves which are 

 later to be used in metabolism. They are thought of as non-living sub- 

 stances, but to whatever extent they affect the vital activities of proto- 

 plasm they must logically be regarded as a part of the living system. 



The relatively inactive or "lifeless" substances in or on protoplasm 

 were called metaplasm by Hanstein (1868). This term has been com- 

 monly employed in this sense, but unfortunately it has been widely used 

 in another meaning (see p. 45). We have, therefore, adopted Meyer's 

 (1896) expression, ergastic substances. "■ 



Vacuoles. — Although the semipermeable membranes bounding vacu- 

 oles are definitely a part of the protoplasmic system (p. 42), it is con- 

 venient to treat vacuoles in this chapter because of the ergastic nature 

 of their contents. 



Any spaces within the protoplast containing ergastic liquid or (very 

 rarely) gas may be regarded as vacuoles, but the term is ordinarily 

 used with reference to those occupied by the aqueous mixture know^n as 

 cell sap. Vacuoles of this general nature are small and comparatively 

 inconspicuous in animals, but in plants they appear to be almost uni- 

 versally present and clearly play a prominent role in metabolism. In 

 terminal meristems of vascular plants, as shown especially by the recent 

 work of Zirkle (1932), they are usually rather numerous, small, and 

 spherical, although they may be drawn out into other shapes by the 

 streaming cytoplasm. In the apical cells of Osmunda (fern) and Lunu- 



1 For an extensive account of the ergastic materials in plants, see A. Meyer (1920, 

 1926). For the chemistry of plant products, see R. W. Thatcher (1921), Onslow 

 (1923), Czapek (1913, 1920), Molisch (1913), Rigg (1924), Trier (1924), Haas and Hill 

 (1928), Gortner (1929), and Wiesner et al. (1932). Ergastic materials are not to be 

 confused with the ergastoplasm of Gamier, Bouin, Prenant, and others. This term 

 was applied to a supposedly very active or "superior" type of protoplasm; see Faure- 

 Fremiet (1910o) and Wilson (1925). For general accounts of vacuoles, see Meyer 

 (1920-1921; Chap. VI, Sec. 6), Lundegardh (1922; Pt. 2, Chap. VIII), P. Dangeard 

 (1923o) and Guilliermond (1929a). 



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