48 PHYSIOLOGICAL MORPHOLOGY 



one function only. Growth, respiration, and nutrition are essential general 

 functions of all living substance, while, at the same time, it is of the highest 

 importance that different parts of the organism should have an inherent 

 power of becoming definitely modified to perform special functions. There 

 is no justification for the supposition 1 that only certain parts or layers 

 of the protoplast are concerned re?pectively with metabolism, respiration, 

 or movement, nor is it possible that the nucleus performs a single 

 function only. 



In the protoplast, just as in the entire plant, special organs may be 

 devoted mainly to one particular purpose, as, for example, is the case 

 with chloroplastids. leucoplastids, &c. The power of producing albumen, 

 acids, colouring material, or even oil (Sect. Hi) is not, however, necessarily 

 restricted to particular plastids. 



The functional importance of pyrenoids, karyoids 2 , nematoplasts 3 , pigment 

 spots, &c., is not yet clearly understood. It is besides frequently forgotten, in the 

 hasty creation of new special names \ that generically similar organs may differ 

 markedly in form, as well as in their contents. The various purposes chloroplastids 

 and vacuoles may subserve afford excellent examples of this 5 . Moreover, organs, 

 or the units of which organs are composed, may take on, temporarily, different 

 arrangements, shapes, or groupings, as is exemplified by vacuoles, by mitotic cell- 

 division, and in the changes of position of chromatophores and microsomes which 

 may take place in the living cell. 



From this it is clear that only a morphological nomenclature of the different 

 parts of the protoplast is possible. Hence there is no justification for Strasburger's ' 

 distinction between trophoplasm and kinoplasm, as parts of the cytoplasm with 

 distinct and special physiological properties, for the distinction between the two 

 is merely morphological and is not based upon any known points of physiological 

 difference. 



The distinction drawn between hyaloplasm 7 and granule- 8 or spongioplasm ' 

 refers only to actual visible appearances and differences of structure. 



Hypotheses regarding the ultimate structure of protoplasm. All considerations 

 concerning ultimate protoplasmic structure lead unavoidably to the conclusion that 

 living substance must be built up of excessively minute organs and units, and that 



1 This conclusion has actually been put forward by Brass, Biolog. Studien, 1883, Heft I. 

 a Palla, Ber. d. Bot. Ges., 1894, p. 153. 



3 Zimmermann, Beihefte z. Bot. Centralbl., 1893, Bd. Ill, p. 215. 



4 See for example Schiitt, Die Peridineen, 1895, pp. 41, 81, 87, &c. 



5 Crato, Bot. Zeitung, 1893, p. 158; Cohn's Beitrage, 1896, Bd. vn, p. 407. On gas vacuoles, 

 Klebahn, Flora, 1895, p. 241. 



8 Strasburger, Histologische Beitrage, 1892, Heft 4, p. 60; 1893, Heft 5, p. 101. See also 

 Zacharias, Flora, 1895, Erg.-bd., p. 259 ; Jahrbuch f. wiss. Bot., 1897, Bd. XXX, p. 375. 



7 Pfeffer, Osmot. Untersuch., 1877, p. 123. On the nomenclature, see Pfeffer, Plasmahaut u. 

 Vacuolen, 1890, p. 188. 



8 Strasburger, Zellbildung u. Zelltheilung, 1876, 2. Aufl., p. 286. 

 ' Nageli, Theorie d. Canning, 1879, p. 154. 



